Investments, Debt and Equity Securities [Abstract] Investment Holdings [Table] Investment Holdings [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Air Touch [Member] Air Touch [Member] Air Touch [member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] Schedule of Other Investments [Line Items] Investment Holdings [Line Items] Number of series of preferred stock Number of Preferred Stock Series Number of Preferred Stock Series Held to maturity investment Debt Securities, Held-to-maturity, Noncurrent Fair value of held to maturity investment redeemable preferred shares Debt Securities, Held-to-maturity, Fair Value Preferred stock aggregate redemption value Preferred Stock Aggregate Redemption Value Preferred stock aggregate redemption value Redeemable subsidiary preferred shares Carrying Amount Of Redeemable Preferred Stock Carrying amount of redeemable preferred stock Fair value of redeemable preferred shares Fair Value Of Redeemable Preferred Shares Fair value of our redeemable subsidiary preferred shares and/or stock Nonredeemable subsidiary preferred shares Nonredeemable Preferred Stock Nonredeemable preferred stock issued by a wholly owned subsidiary of the company. Organization, Consolidation and Presentation of Financial Statements [Abstract] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Line Items] Business And Basis Of Presentation [Line Items] Business And Basis Of Presentation Basis of Presentation and Summary of Significant Accounting Policies Business Description and Basis of Presentation [Text Block] Statement of Comprehensive Income [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Unrealized gains (losses) on marketable securities, net of deferred taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Deferred gains (losses) on cash flow hedges, net of deferred taxes Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Amounts reclassified to net income: Amounts Reclassified To Net Income [Abstract] Realized (gains) losses on marketable securities, net of deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Realized (gains) losses on cash flow hedges, net of deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Employee benefit obligations, net of deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Currency translation adjustments, net of deferred taxes Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: Net income attributable to noncontrolling interests and redeemable subsidiary preferred stock Net Income (Loss) Attributable To Noncontrolling Interests And Redeemable Subsidiary Preferred Stock Amount of net income (loss) attributable to noncontrolling interest and dividends on redeemable subsidiary preferred stock. Less: Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Less: Other comprehensive income (loss) attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Comprehensive income attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information (Unaudited) Quarterly Financial Information [Text Block] Condensed Financial Information Disclosure [Abstract] Condensed Income Statement [Table] Condensed Income Statement [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Service [Member] Service [Member] Management Fee [Member] Management Fee [Member] Management Fee [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Comcast Parent [Member] Parent Company [Member] Subsidiary Issuer [Member] Subsidiary Issuer [Member] Guarantor Subsidiaries [Member] Guarantor Subsidiaries [Member] Non-Guarantor Subsidiaries [Member] Non-Guarantor Subsidiaries [Member] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Reportable Legal Entities [Member] Reportable Legal Entities [Member] Elimination and Consolidation Adjustments [Member] Consolidation, Eliminations [Member] Comcast Holdings [Member] Comcast Holdings [Member] Comcast Holdings CCCL Parent [Member] CCCL Parent [Member] CCCL Parent NBCUniversal Media Parent [Member] NBCUniversal Media Parent [Member] Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Revenue Revenues Costs and Expenses: Costs and Expenses [Abstract] Programming and production Programming And Production Costs The amount of expense recognized in the period for costs associated with video programming and content acquisition and production costs. Programming expenses include the fees paid to license the programming distributed to video customers, such as the programming license fees charged by cable networks and fees charged for retransmission of the signals from local broadcast television stations. Production costs include the amortization of owned and acquired programming, sports rights, direct production costs, residual and participation payments, production overhead, costs associated with the distribution of programming to third-party networks and other distribution platforms, and on-air talent costs. It also includes the amortization of capitalized theatrical film production and acquisition costs and distribution expenses. Other operating and administrative Other Operating And Administrative Other operating and administrative expense recognized in the period not presented separately. Advertising, marketing and promotion Marketing and Advertising Expense Depreciation Depreciation Amortization Amortization of Intangible Assets Other operating gains Gain (Loss) on Disposition of Assets Total costs and expenses Costs and Expenses Operating income Operating Income (Loss) Interest expense Interest Expense Investment and other income (loss), net Nonoperating Income (Expense) Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax (expense) benefit Income Tax Expense (Benefit) Net income Less: Net income attributable to noncontrolling interests and redeemable subsidiary preferred stock Net Income Attributable to Comcast Corporation Net Income (Loss) Attributable to Parent Earnings Per Share [Abstract] Computation of diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Line Items] Goodwill And Intangible Assets [Line Items] [Line Items] for Goodwill And Intangible Assets [Table] Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Cable Distribution System [Member] Cable Distribution System [Member] Cable Distribution System [Member] Customer Premise Equipment [Member] Customer Premise Equipment [Member] Customer premise equipment [Member] Other Equipment [Member] Other Capitalized Property Plant and Equipment [Member] Building and Leasehold Improvements [Member] Building and Building Improvements [Member] Furniture, Fixtures and Equipment [Member] Furniture and Fixtures [Member] Construction in Process [Member] Construction in Progress [Member] Land [Member] Land [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Weighted-Average Original Useful Life Property, Plant and Equipment, Useful Life Property and equipment, at cost Property, Plant and Equipment, Gross Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property and equipment, net Property, Plant and Equipment, Net Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Net transactions with affiliates Net transactions with affiliates Net transactions with affiliates. Capital expenditures Payments to Acquire Property, Plant, and Equipment Cash paid for intangible assets Payments to Acquire Intangible Assets Acquisitions and construction of real estate properties Payments For Acquisitions And Construction Of Real Estate Properties The cash outflow for the acquisition and construction of buildings (properties) whether for investment or use. Construction of Universal Beijing Resort Payments For Construction Of Theme Park The cash outflow associated with the construction of a theme park. Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from sales of businesses and investments Proceeds From Sales Of Businesses And Investments The cash inflow associated with the sale of businesses and investments, if any, during the period. Purchases of investments Payments to Acquire Investments Deposits Deposit Cash paid for deposits Other Payments for (Proceeds from) Other Investing Activities Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from (repayments of) short-term borrowings, net Proceeds from (Repayments of) Short-term Debt Proceeds from borrowings Proceeds from Issuance of Long-term Debt Repurchases and repayments of debt Repayments of Other Debt Repurchases of common stock under repurchase program and employee plans Payments for Repurchase of Common Stock Dividends paid Payments of Dividends Purchase of Universal Studios Japan noncontrolling interests Payments to Acquire Additional Interest in Subsidiaries Issuances of common stock Proceeds from Issuance of Common Stock Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock Distributions To Noncontrolling Interests And Dividends For Redeemable Subsidiary Preferred Stock The cash outflow related to distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock. Other Proceeds from (Payments for) Other Financing Activities Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Impact of foreign currency on cash, cash equivalents and restricted cash Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Increase (decrease) in cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents and restricted cash, beginning of year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash, end of year Other Industries [Abstract] Film And Television Cost [Table] Film And Television Cost [Table] Film And Television Cost [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum [Member] Maximum [Member] Film And Television Cost [Line Items] Film And Television Cost [Line Items] [Line Items] for Film And Television Cost [Table] Amortization of completed film and television production expected to be amortized during the next fiscal year Film Costs, Amortized in Next Operating Cycle Expected amortization percentage of released and unamortized film and television costs during the next three fiscal years Percentage of Unamortized Film Costs Remaining unamortized costs of acquired film and television libraries Film And Television Library Costs Unamortized The remaining amount of costs related to film and television libraries that are expected to be amortized. Amortization period of acquired film and television library costs Acquired Film and Television Library Costs, Amortization Period Acquired Film and Television Library Costs, Amortization Period Expected amortization percentage of unamortized acquired film and television library costs during the next three fiscal years Percentage Of Acquired Film And Television Libraries To Be Amortized In The Next Three Years The percentage of unamortized acquired film and television library costs that are expected to be amortized within three years from the date of the balance sheet. Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2014-09 [Member] Accounting Standards Update 2014-09 [Member] Revenue [Line Items] Disaggregation of Revenue [Line Items] Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Schedule of receivables, net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Other balance sheet accounts Schedule Of Other Balance Sheet Accounts [Table Text Block] Schedule Of Other Balance Sheet Accounts [Table Text Block] Income Tax Disclosure [Abstract] Income Taxes [Table] Income Taxes [Table] Income Taxes [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Sky Limited [Member] Sky Limited [Member] Sky Limited [Member] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Federal Tax Authority [Member] Domestic Tax Authority [Member] Foreign Tax Authority [Member] Foreign Tax Authority [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Uncertain Tax Positions Indemnified by GE [Member] Uncertain Tax Positions Indemnified By Third Party [Member] Income Taxes [Line Items] Income Taxes [Line Items] [Line Items] for Income Taxes [Table] Foreign income before taxes Income (Loss) from Continuing Operations before Income Taxes, Foreign Change in net deferred tax liability related to acquisitions Change In Net Deferred Tax Liability Related To Acquisitions Changes in net deferred tax liability that were not recorded as deferred income tax benefit (expense) related to acquisitions. Increase (decrease) in deferred income taxes Deferred State and Local Income Tax Expense (Benefit) Federal corporate income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Reduction of net deferred tax liabilities Decrease In Deferred Tax Liabilities 2017 Tax Reform Enactment Decrease In net Deferred Tax Liabilities due to rate change along with certain immaterial changes in tax basis resulting from the 2017 tax reform legislation. Net tax benefit related to cumulative undistributed foreign earnings and foreign tax credits Decrease In Deferred Tax Liabilities Foreign Taxes 2017 Tax Reformenactment Decrease in net deferred tax liabilities related to undistributed foreign earnings and net deferred tax assets related to foreign tax credits resulting from the 2017 tax reform legislation. One-time repatriation tax on cumulative undistributed foreign earnings and profits Income tax transition tax 2017 tax reform legislation Amount of one-time deemed repatriation tax on undistributed foreign earnings and profits resulting from the 2017 tax reform legislation. Income tax benefit, 2018 tax reform legislation Income Tax Benefit, 2018 Tax Reform Legislation Income tax benefit as a result of the 2018 tax reform legislation Deferred tax liability attributable to temporary differences in other comprehensive income Changes In Net Deferred Tax Liability Related To Other Comprehensive Income Changes in net deferred tax liability that were not recorded as deferred income tax benefit (expense) associated with items included in other comprehensive income (loss) Deferred tax related to purchase of noncontrolling interest Deferred Tax Related To Purchase Of Noncontrolling Interest Impact on deferred taxes related to the purchase of the remaining noncontrolling interest Net deferred tax liability, franchise rights Deferred Tax Liability Franchise Rights Amount of net deferred tax liabilities related to cable franchise rights that will remain unchanged unless an impairment is recognized or a cable franchise is disposed. Operating loss carryforwards Operating Loss Carryforwards Deferred Tax Assets, Operating Loss Carryforwards Deferred Tax Assets, Operating Loss Carryforwards Liability for Uncertainty in Income Taxes, Noncurrent Liability for Uncertainty in Income Taxes, Noncurrent Unrecognized tax benefits that would impact effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Unrecognized tax benefits, interest on income taxes accrued Unrecognized Tax Benefits, Interest on Income Taxes Accrued Commitments and Contingencies Disclosure [Abstract] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Workforce Subject to Collective Bargaining Arrangements [Member] Workforce Subject to Collective Bargaining Arrangements [Member] Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] NBCUniversal Enterprise [Member] NBCUniversal Enterprise [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Redeemable Subsidiary Preferred Stock [Member] Redeemable Preferred Stock [Member] Commitment And Contingencies [Line Items] Commitment And Contingencies [Line Items] [Line Items] for Commitment And Contingencies [Table] Number of employees covered under collective bargaining agreements Number Of Employees Covered Under Collective Bargaining Agreements Number of employees covered by collective bargaining agreements. Percentage of full-time equivalent employees covered by collective bargaining agreements that have expired or are schedule to expire during the next year Concentration Risk, Percentage Carrying value of contractual obligation Carrying value of contractual obligation Carrying value of future obligation classified as a liability which is no longer recorded at fair value. Contractual value of a potential obligation Contractual Value of a Potential Future Obligation Contractual value of a potential future obligation based on a contractual formula on a specified date. Related party liquidation preference preferred stock not subject to guarantee Related Party Liquidation Preference Preferred Stock Not Subject To Guarantee Represents the related party liquidation preference of preferred stock not subject to guarantee by NBCUniversal. Redeemable subsidiary preferred stock, put period Preferred Stock, Put Period The holders have the right to cause NBCUniversal Enterprise to redeem their shares at a price equal to the liquidation preference plus accrued but unpaid dividends for a 30 day period beginning on March 19, 2020 and thereafter on every third anniversary of such date (each such date, a “put date”). Redeemable subsidiary preferred stock, dividend rate Preferred Stock, Dividend Rate, Percentage Redeemable subsidiary preferred stock, call period Preferred Stock, Call Period Shares of preferred stock can be called for redemption by NBCUniversal Enterprise at a price equal to the liquidation preference plus accrued but unpaid dividends one year following the put date applicable to such shares. Temporary equity, fair value of redeemable subsidiary preferred stock Temporary Equity, Fair Value Of Redeemable Subsidiary Preferred Stock Temporary Equity, Fair Value of our redeemable subsidiary preferred stock. Programming and Talent Commitments Contractual Obligation, Fiscal Year Maturity [Abstract] 2019 Contractual Obligation, Due in Next Fiscal Year 2020 Contractual Obligation, Due in Second Year 2021 Contractual Obligation, Due in Third Year 2022 Contractual Obligation, Due in Fourth Year 2023 Contractual Obligation, Due in Fifth Year Thereafter Contractual Obligation, Due after Fifth Year Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Commercial Paper [Member] Commercial Paper [Member] Revolving Bank Credit Facility [Member] Revolving Bank Credit Facility [Member] Revolving Bank Credit Facility [Member] Term Loans [Member] Term Loans [Member] Term Loans [Member] Senior notes with maturities of 5 years or less, at face value [Member] Senior notes with maturities of 5 years or less, at face value [Member] Senior notes with maturities of 5 years or less [Member] Senior notes with maturities between 5 and 10 years, at face value [Member] Senior notes with maturities between 5 and 10 years, at face value [Member] Senior notes with maturities between 5 and 10 years [Member] Senior notes with maturities greater than 10 years, at face value [Member] Senior notes with maturities greater than 10 years, at face value [Member] Senior notes with maturities greater than 10 years [Member] 4.00% Notes Due 2049 To Comcast [Member] 4.00% Notes Due 2049 To Comcast [Member] 4.00% Notes Due 2049 To Comcast [Member] Other Including Capital Lease Obligations [Member] Other Including Capital Lease Obligations [Member] Other Including Capital Lease Obligations [Member] Sky Transaction Term Loan [Member] Sky Transaction Term Loan [Member] Sky Transaction Term Loan [Member] Universal Studios Japan Term Loans Maturing 2022 [Member] Universal Studios Japan Term Loans Maturing 2022 [Member] Universal Studios Japan Term Loans Maturing 2022 [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Sky Outstanding Indebtedness [Member] Sky Outstanding Indebtedness [Member] Sky Outstanding Indebtedness [Member] Sky Outstanding Indebtedness - U.S. Dollar Denominated [Member] Sky Outstanding Indebtedness - U.S. Dollar Denominated [Member] Sky Outstanding Indebtedness - U.S. Dollar Denominated [Member] Sky Outstanding Indebtedness - Euro Denominated [Member] Sky Outstanding Indebtedness - Euro Denominated [Member] Sky Outstanding Indebtedness - Euro Denominated [Member] Sky Outstanding Indebtedness - Pounds Sterling Denominated [Member] Sky Outstanding Indebtedness - Pounds Sterling Denominated [Member] Sky Outstanding Indebtedness - Pounds Sterling Denominated [Member] Notes 5.50% Due 2029 [Member] Notes 5.50% Due 2029 [Member] Notes 5.50% due 2029 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Commercial paper Commercial Paper Credit facility Long-term Line of Credit Term loans Other Long-term Debt Current Principal Balance Debt Assumed in Acquisition Not Subject to Guarantee Carrying Value Debt Assumed in Acquisition Not Subject to Guarantee Carrying value of debt instruments assumed in acquisition but not guaranteed by Comcast Corporation, the cable guarantors or NBCUniversal Media LLC. Senior notes Senior Notes Notes due 2049 to Comcast Other Notes Payable, Noncurrent Other, including capital lease obligations Other Borrowings Debt issuance costs, premiums and discounts, net Debt issuance costs, premiums, discounts and fair value adjustments for hedged positions The carrying amount as of the balance sheet date for the net impact of debt issuance costs, premiums, discounts and fair value adjustments for hedged positions. Total debt Debt and Capital Lease Obligations Less: Current portion Debt, Current Long-term debt Long-term Debt and Capital Lease Obligations Interest rate Debt, Weighted Average Interest Rate Interest rate Debt Instrument, Interest Rate, Stated Percentage Supplemental Financial Information [Abstract] Statement Of Cash Flows Supplemental Information Abstract Supplemental Financial Information [Table] Supplemental Financial Information [Table] Supplemental Financial Information [Table] Supplemental Financial Information [Line Items] Supplemental Financial Information [Line Items] [Line Items] for Supplemental Financial Information [Table] Schedule of cash payments for interest and income taxes Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of cash, cash equivalents and restricted cash ScheduleOfCashCashEquivalentsAndRestrictedCash [Table Text Block] Tabular disclosure of the components of cash, cash equivalents and restricted cash. Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Condensed Consolidating Financial Information Condensed Financial Information of Parent Company Only Disclosure [Text Block] Accounting Policies [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Accounting Standards Update 2016-01 [Member] Accounting Standards Update 2016-01 [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Member's Capital [Member] Member's Capital [Member] AOCI Attributable to Parent [Member] AOCI Attributable to Parent [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative Effect of New Accounting Principle in Period of Adoption Cumulative Effect of New Accounting Principle in Period of Adoption Schedule of Long-Term Debt Schedule of Debt [Table Text Block] Debt Maturities Schedule of Maturities of Long-term Debt [Table Text Block] Long-term Debt, Fiscal Year Maturity [Abstract] Long-term Debt, Fiscal Year Maturity [Abstract] 2019 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2020 Long-term Debt, Maturities, Repayments of Principal in Year Two 2021 Long-term Debt, Maturities, Repayments of Principal in Year Three 2022 Long-term Debt, Maturities, Repayments of Principal in Year Four 2023 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Cable Communications [Member] Cable Communications [Member] Cable Communications Member NBCUniversal Segments [Member] NBCUniversal Segments [Member] Number of primary businesses Number Of Businesses Number Of Businesses Interest in business acquired in acquisition Business Acquisition, Percentage Of Voting Interests Acquired In Period Business Acquisition, Percentage Of Voting Interests Acquired Cash consideration transferred by Comcast Business Combination, Consideration Transferred Number of reportable segments Number of Reportable Segments SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Allowance for doubtful accounts [Member] SEC Schedule, 12-09, Allowance, Credit Loss [Member] Valuation allowance on deferred tax assets [Member] SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Balance at Beginning of Year SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Additions Charged to Costs and Expenses SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Deductions from Reserves SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Balance at End of Year Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted share units [Member] Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Stock options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Weighted-average exercise price of awards granted during the year (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Stock options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Weighted-average exercise price of shares outstanding (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Awards granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Awards nonvested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Weighted-average fair value at grant date of nonvested awards (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Condensed Consolidating Statement of Income Condensed Income Statement [Table Text Block] Condensed Consolidating Statement of Cash Flows Condensed Cash Flow Statement [Table Text Block] Condensed Consolidating Balance Sheet Condensed Balance Sheet [Table Text Block] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Previous Reported [Member] Previously Reported [Member] Effects of Adoption [Member] Restatement Adjustment [Member] Residential, Video [Member] Residential, Video [Member] Residential, Video [Member] Residential, High-Speed Internet [Member] Residential, High-Speed Internet [Member] Residential, High-Speed Internet [Member] Residential, Voice [Member] Residential, Voice [Member] Residential, Voice [Member] Business Services [Member] Business Services [Member] Business Services [Member] Advertising [Member] Advertising [Member] Other [Member] Other [Member] Other [Member] Operating costs and expenses Operating Expenses Excluding Depreciation And Amortization Operating costs and expenses, which are comprised of total costs and expenses, excluding depreciation and amortization expense and other operating gains. Depreciation and Amortization Depreciation, Depletion and Amortization, Nonproduction Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Debt Conversion Description [Axis] Debt Conversion Description [Axis] Debt Conversion, Name [Domain] Debt Conversion, Name [Domain] Senior Notes Exchange [Member] Senior Notes Exchange [Member] Senior Notes Exchange [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes [Member] Senior Notes [Member] Senior 3.97% Notes Due 2047 [Member] Senior 3.97% Notes Due 2047 [Member] Senior 3.97% Notes Due 2047 [Member] Senior 4.00% Notes Due 2047 [Member] Senior 4.00% Notes Due 2049 [Member] Senior 4.00% Notes Due 2049 [Member] Senior 4.05% Notes Due 2052 [Member] Senior 4.05% Notes Due 2052 [Member] Senior 4.05% Notes Due 2052 [Member] Comcast and NBCUniversal Senior Notes [Member] Comcast and NBCUniversal Senior Notes [Member] Comcast and NBCUniversal Senior Notes [Member] Senior 6.40% Notes Due 2040 [Member] Senior 6.40% Notes Due 2040 [Member] Senior 6.400% Notes Due 2040 [Member] Comcast [Member] Comcast [Member] Comcast [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Carrying Value Of Related Party Contractual Obligation [Member] Carrying Value Of Related Party Contractual Obligation [Member] NBCUniversal Holdings Preferred Stock [Member] NBCUniversal Holdings Preferred Stock [Member] Former Comcast And NBCUniversal Revolving Credit Agreements [Member] FormerComcastAndNBCUniversalRevolvingCreditAgreements [Member] Former Comcast And NBCUniversal Revolving Credit Agreements [Member] Comcast and NBCUniversal Revolving Credit Agreements [Member] Comcast and NBCUniversal Revolving Credit Agreements [Member] Comcast and NBCUniversal Revolving Credit Agreements [Member] Stock options [Member] Employee Stock Option [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Revolving credit agreement capacity Revolving Credit Agreement Capacity The maximum amount of borrowing or lending capacity with respect to the cash management arrangement between Comcast and NBCUniversal under the revolving credit agreement. Borrowing margin for LIBOR based borrowings Debt Instrument, Basis Spread on Variable Rate Other noncurrent liabilities Other Liabilities, Noncurrent Aggregate principal amount Debt Instrument, Face Amount Amount of debt exchanged Debt Exchange, Amount The aggregate principal amount of the debt being exchanged in a debt exchange transaction. Interest expense on extinguishment of debt Preferred stock, dividend rate Preferred stock liquidation preference value Preferred Stock, Liquidation Preference, Value Preferred stock dividend rate, spread on variable rate Preferred Stock Dividend Rate, Spread On Variable Rate Percentage points added to the reference rate to compute the variable rate on dividend payments on preferred stock; the variable rate will reset every 5 years Recognized share-based compensation expense Allocated Share-based Compensation Expense Unrecognized pretax compensation expense on nonvested awards Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Equity [Abstract] Equity [Table] Equity [Table] Equity [Table] Class A Common Stock [Member] Common Class A [Member] Class B Common Stock [Member] Common Class B [Member] Equity [Line Items] Equity [Line Items] [Line Items] for Equity [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding at beginning of period (in shares) Common Stock, Shares, Outstanding Stock compensation plans (in shares) Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Repurchases and retirements of common stock (in shares) Stock Repurchased and Retired During Period, Shares Employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Common stock, shares outstanding at end of period (in shares) Unrealized gains (losses) on marketable securities, deferred taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Deferred gains (losses) on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Realized (gains) losses on marketable securities, deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Employee benefit obligations, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Currency translation adjustments, deferred tax Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Class of Treasury Stock [Table] Class of Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] New Authorization [Member] New Authorization [Member] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Cash consideration Shares repurchased (in shares) Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Atairos [Member] Atairos [Member] Atairos [Member] Hulu [Member] Hulu [Member] Hulu member. The Weather Channel [Member] The Weather Channel [Member] The Weather Channel [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Former CFO [Member] Former CFO [Member] Former CFO [Member] Time Warner, Inc. [Member] Time Warner, Inc. [Member] Time Warner, Inc. [Member] Minimum [Member] Minimum [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Term of agreement Term of agreement Term of agreement for Atairos Funding commitment Equity Method Investment, Funding Commitment Equity Method Investment, Funding Commitment Management fee funding commitment Equity Method Investment, Management Fee Funding Commitment Equity Method Investment, Management Fee Funding Commitment Funding commitment by management company investors Equity Method Investment, Funding Commitment by Management Company Investors Equity Method Investment, Funding Commitment by Management Company Investors Percent of losses Equity Method Investment, Percent of Losses Represents the percentage of any losses in an equity method investment that the Company is obligated to absorb. Percentage of residual returns Percentage of residual returns Represents the percentage of any residual returns that Comcast has the right to receive Equity method investments Equity Method Investments Purchases of investments Capital Contribution To VIE The cash outflow associated with a capital contribution to a VIE accounted for as an equity method investment Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments Pretax gain, sale of business to Atairos Gain (Loss) on Disposition of Business Cash capital contributions for equity method investments Payments to Acquire Equity Method Investments Ownership percentage Equity Method Investment, Ownership Percentage Put/call period Equity Method Investment, Put or Call Period Equity Method Investment, Put or Call Period Deferred gain Equity Method Investment, Deferred Gain This element represents disclosure of the amount of gain which has been deferred as the result of a dilution in our ownership percentage in an equity method investment which deferred gain has been reflected in the accompanying statement of financial position. Pretax gain on sale of investment Equity Method Investment, Realized Gain (Loss) on Disposal Pretax gain on sale of investment Pretax Gain On Sale Of Investment Pretax gain recognized as a result of the sale of The Weather Channel's product and technology business to IBM Schedule of recognized share-based compensation expense Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Schedule of stock option and restricted share units activity Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of stock option and restricted share units fair value and significant assumptions Stock Option Fair Value and Significant Assumptions [Text Block] Stock option fair value and significant assumptions Comcast And Consolidated Subsidiaries [Member] Comcast And Consolidated Subsidiaries [Member] Total costs and expenses Interest expense and investment and other income (loss), net Other Income (Expense) Related Party Represents the intercompany transactions with ultimate parent, which are included in interest expense and investment and other income (loss), net. Employee stock purchase plans [Member] Employee Stock [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Property and equipment and intangible assets accrued but not yet paid Capital Expenditures Incurred but Not yet Paid Dividends payable Dividends Payable Dividends payable (in dollars per share) Dividends Payable, Amount Per Share Aggregate principal amount issued Aggregate principal amount of certain series of outstanding notes Assets contributed to variable interest entity Contribution of Property Capital contribution accrued but not yet paid Capital Contribution Accrued But Not Yet Paid Capital contribution to a VIE recorded in the current period to be paid in a future period. Schedule of common stock outstanding Schedule of Common Stock Outstanding Roll Forward [Table Text Block] Schedule of shares repurchased Class of Treasury Stock [Table Text Block] Film and Television Costs Schedule Of Film And Television Costs [Table Text Block] Schedule Of Film And Television Costs [Table Text Block] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Schedule of Investments [Line Items] Debt and Equity Securities, FV-NI [Line Items] Equity method Marketable equity securities Equity Securities, FV-NI Nonmarketable equity securities Equity Securities without Readily Determinable Fair Value, Amount Other investments Other Investments Total investments Investments Less: Current investments Short-term Investments Long-term Investments Long-term Investments Retirement Benefits [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Deferred Compensation Plans [Member] Deferred Compensation Plans [Member] Deferred Compensation Plans [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Benefit obligation Deferred Compensation Plans Benefit Obligation Deferred compensation plans benefit obligation Interest expense Deferred Compensation Plans interest cost Deferred compensation plans interest cost Deferred Compensation Plans Deferred Compensation Plans [Text Block] Information regarding deferred compensation plans, including benefit obligations and related expense. Postretirement and Pension Benefits Condensed Information On Our Postretirement And Pension Benefit Plans [Table Text Block] Tabular disclosure of the change in the benefit obligation of pension plans and/or other employee benefit plans from the beginning to the end of the period, showing separately, if applicable, the effects of the following: service cost, interest cost, contributions by plan participants, actuarial gains and losses, foreign currency exchange rate changes, benefits paid, plan amendments, business combinations, divestitures, curtailments, settlements, and special and contractual termination benefits. Disclosure also includes the certain accumulated beneift obligations dislcosure and the assumptions used to determine for pension plans and/or other employee benefit plans the benefit obligation and net benefit cost. Investment and Other Income (Loss), Net [Line Items] Equity in net income (losses) of investees, net Realized and unrealized gains (losses) on equity securities, net Equity Securities, FV-NI, Gain (Loss) Other income (loss), net Other Income Loss Net Nonoperating income (losses), net recorded in the income statement that are not separately stated. Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Gross unrecognized tax benefits, January 1 Unrecognized Tax Benefits Additions based on tax positions related to the current year Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Additions based on tax positions related to prior years Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Additions from acquired subsidiaries Unrecognized Tax Benefits Increases Resulting From Acquired Subsidiaries Unrecognized Tax Benefits Increases Resulting From Acquired Subsidiaries Reductions for tax positions of prior years Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Reductions due to expiration of statutes of limitations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Settlements with tax authorities Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Gross unrecognized tax benefits, December 31 Positions paid Unrecognized Tax Benefits Positions Paid Unrecognized tax benefits associated with positions for which tax has been assessed and paid. Liability for uncertain tax positions Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Business Acquisition [Line Items] Transaction expenses Business Combination, Acquisition Related Costs Interest expense Interest Expenses Financing costs associated with debt facilities and the borrowings related to acquisition. Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Postretirement Benefit Plan [Member] Other Postretirement Benefits Plan [Member] Benefit obligation Defined Benefit Plan, Funded (Unfunded) Status of Plan Amounts in accumulated other comprehensive income not yet recognized in benefits expense Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Programming and Production Costs Film And Television Costs Disclosure [Text Block] Film and Television costs Disclosure [Text Block] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Operating Segments [Member] Operating Segments [Member] Corporate, Non-Segment [Member] Corporate, Non-Segment [Member] Cable Networks [Member] Cable Networks [Member] Cable Networks Member Broadcast Television [Member] Broadcast Television [Member] Broadcast Television Member Filmed Entertainment [Member] Filmed Entertainment [Member] Filmed Entertainment Member Theme Parks [Member] Theme Parks [Member] Theme Parks Member Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Balance, beginning of period Goodwill Goodwill, Acquired During Period Goodwill, Acquired During Period Dispositions Goodwill, Written off Related to Sale of Business Unit Adjustments Goodwill, Other Increase (Decrease) Foreign currency translation Goodwill, Foreign Currency Translation Gain (Loss) Balance, end of period Total costs and expenses Operating income Consideration transferred Cash Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Accounts receivable and other current assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Accounts Receivable And Other Current Assets Amount of accounts receivable and other current assets recognized as of the acquisition date. Film and television costs (See Note 4) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Film And Television Costs Amount of Film And Television Costs recognized as of the acquisition date Property and equipment (See Note 11) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Intangible assets (See Note 12) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill Accounts payable, accrued liabilities and other current liabilities Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Accounts Payable, Accrued Liabilities, And Other Current Liabilities Amount of accounts payable, accrued liabilities, and other current liabilities recognized as of the acquisition date. Long-term debt (See Note 7) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Deferred tax assets (liabilities), net (See Note 5) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets (Liabilities), Net Amount of Deferred Tax Assets (Liabilities), Net recognized as of the acquisition date Other noncurrent assets and (liabilities), net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets And Liabilities, Net Amount of Other Noncurrent Assets And Liabilities, Net recognized as of the acquisition date Fair value of identifiable net assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Unrealized gains (losses) on marketable securities Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax Deferred gains (losses) on cash flow hedges Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Unrecognized gains (losses) on employee benefit obligations Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Cumulative translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Film Costs: Theatrical Film Costs [Abstract] Released, less amortization Theatrical Film Costs, Released Completed, not released Theatrical Film Costs, Completed and Not Released In production and in development Theatrical Film Costs, In Production And In Development The amount of direct negative costs incurred in the production and development of a theatrical film, as well as allocations of production overhead and capitalized interest. Examples of direct negative costs include costs of story and scenario; compensation of cast, directors, producers, extras, and miscellaneous staff; costs of set construction and operations, wardrobe, and accessories; costs of sound synchronization; rental facilities on location; and postproduction costs such as music, special effects, and editing. Total film costs Theatrical Film Costs Television Costs: Direct-to-television Film Costs [Abstract] Released, less amortization Direct-to-television Film Costs, Released In production and in development Direct-to-Television Film Costs, In Production and In Development The amount of direct negative costs incurred in the production and development of a direct-to-television film, as well as allocations of production overhead and capitalized interest. Examples of direct negative costs include costs of story and scenario; compensation of cast, directors, producers, extras, and miscellaneous staff; costs of set construction and operations, wardrobe, and accessories; costs of sound synchronization; rental facilities on location; and postproduction costs such as music, special effects, and editing. Total television costs Direct-to-television Film Costs Programming rights, less amortization Programming Rights Less Amortization The carrying amount of total acquired programming rights, less amortization Total film costs, television costs and programming rights Total Film And Television Costs And Programming Rights After Amortization The carrying amount of owned films, television series and other television productions and the current and noncurrent portion of acquired television and cable networks programming rights recorded on the balance sheet. Owned films, television series and other television production costs include capitalizable production costs, production overhead, interest, development costs and acquired production costs. Film and television rights include multi-year programming arrangements, acquired movies, series and other programs. The carrying amount is stated at the lower of cost, less accumulated amortization, or net realizable/fair value at the balance sheet date. Less: Current portion of programming rights Programming Rights, Current The current portion of acquired television and cable networks programming rights recorded on the balance sheet. Includes multi-year programming arrangements, acquired movies, series and other programs. Carrying amount is stated at the lower of cost, less accumulated amortization, or net realizable value at the balance sheet date. Film and television costs Film And Television Costs The carrying amount of owned films, television series and other television productions and noncurrent acquired television and cable networks programming rights recorded on the balance sheet. Owned films, television series and other television production costs include capitalizable production costs, including direct costs, production overhead, print costs, development costs and interest. Film and television rights include multi-year programming arrangements, acquired movies, series and other programs. The carrying amount is stated at the lower of cost, less accumulated amortization, or net realizable/fair value at the balance sheet date. Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Segment Information Segment Reporting Disclosure [Text Block] Total current assets Assets, Current Other intangible assets, net Other Intangible Assets, Net Other noncurrent assets, net Other Assets, Noncurrent Total assets Assets Total current liabilities Liabilities, Current Deferred income taxes Deferred Income Tax Liabilities, Net Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total equity Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Receivables, net Accounts Receivable, Net, Current Note receivable from Comcast Note Receivable From Ultimate Parent Total amount due from Parent with respect to cash management arrangements under the matching revolving credit notes as of the balance sheet date Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current Accrued expenses and other current liabilities Accrued Liabilities, Current Note payable to Comcast Note Payable To Ultimate Parent The total amount due to Parent, with respect to cash management arrangements under the matching revolving credit notes, as of the balance sheet date. Long-term debt, less current portion Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Software [Member] Computer Software, Intangible Asset [Member] Finite-lived intangible asset amortization period Finite-Lived Intangible Asset, Useful Life Number of divisions Number of Divisions Number of Divisions Revenue Business Acquisition, Pro Forma Revenue Net income attributable to Comcast Corporation Business Acquisition, Pro Forma Net Income (Loss) Attributable To Parent The Pro Forma Net Income (Loss) Attributable To Parent for the period as if the business combination had been completed at the beginning of the period Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Tax Adjustments [Axis] Tax Adjustments [Axis] Tax Adjustments [Axis] Tax Adjustments [Domain] Tax Adjustments [Domain] Tax Adjustments [Domain] Adjustments to uncertain and effectively settled tax positions, net [Member] Uncertain And Effectively Settled Tax Positions, Net [Member] Uncertain And Effectively Settled Tax Positions, Net Member Accrued interest on uncertain and effectively settled tax positions, net [Member] Accrued Interest On Uncertain And Effectively Settled Tax Positions Net [Member] Accrued Interest On Uncertain And Effectively Settled Tax Positions Net [Member] Federal tax at statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount State income taxes, net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Foreign income taxed at different rates Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Nontaxable income attributable to noncontrolling interests Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Amount Other adjustments Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Excess tax benefits recognized on share-based compensation Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Federal tax legislation Effective Income Tax Rate Reconciliation 2017 tax reform legislation Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to the 2017 tax reform legislation. Income tax expense (benefit) Statement of Financial Position [Abstract] Assets Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Programming rights Other current assets Other Assets, Current Total current assets Investments Property and equipment, net Franchise rights Indefinite-Lived Franchise Rights Goodwill Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Total assets Liabilities and Equity Liabilities and Equity [Abstract] Current Liabilities: Liabilities, Current [Abstract] Accrued participations and residuals Accrued Participations And Residuals, Current The total amount of participations, residual and royalty expenses due to another party in less than one year. Royalty expenses are due to content creators, including artists, authors and other talent; participations includes amounts to financial participants in films, including actors, directors, and producers, for contractually defined participations in a film's net profit or gross receipts; residuals include amounts due to unions and guilds. Program obligations Program Rights Obligations, Current Deferred revenue Deferred Revenue, Current Current portion of long-term debt Total current liabilities Accrued participations, residuals and program obligations Accrued Participations Residuals And Program Obligations, Noncurrent The noncurrent amount of participations, residual, royalty expenses and program obligations due to another party. Royalty expenses are due to content creators, including artists, authors and other talent; participations includes amounts to financial participants in films, including actors, directors, and producers, for contractually defined participations in a film's net profit or gross receipts; residuals include amounts due to unions and guilds. Deferred income taxes Commitments and contingencies Commitments and Contingencies Redeemable noncontrolling interests Redeemable Noncontrolling Interest, Equity, Carrying Amount Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred stock—authorized, 20,000,000 shares; issued, zero Preferred Stock, Value, Issued Member’s capital Members' Capital Common stock Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Treasury stock, 872,791,028 Class A common shares Treasury Stock, Value Accumulated other comprehensive income (loss) Total NBCUniversal member’s equity Members' Equity Total Comcast Corporation shareholders’ equity Stockholders' Equity Attributable to Parent Noncontrolling interests Members' Equity Attributable to Noncontrolling Interest Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Total equity Total liabilities and equity Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Deferred gains (losses) on cash flow hedges Unrecognized gains (losses) on employee benefit obligations Cumulative translation adjustments Accumulated other comprehensive income (loss) Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Hedging [Member] Cash Flow Hedging [Member] Net Investment Hedging [Member] Net Investment Hedging [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Currency Swap [Member] Currency Swap [Member] Unsecured Debt [Member] Unsecured Debt [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Senior Unsecured Fixed And Floating Rate Notes Issued October 2018 [Member] Senior Unsecured Fixed And Floating Rate Notes Issued October 2018 [Member] Senior Unsecured Fixed And Floating Rate Notes Issued October 2018 [Member] Comcast Unsecured Sterling-Denominated Term Loan Credit Agreement [Member] Unsecured Sterling-Denominated Term Loan Credit Agreement [Member] Unsecured Sterling-Denominated Term Loan Credit Agreement [Member] Unsecured Dollar-Denominated Term Loan Credit Agreement [Member] Unsecured Dollar-Denominated Term Loan Credit Agreement [Member] Unsecured Dollar-Denominated Term Loan Credit Agreement [Member] Senior Unsecured Fixed Rate Notes Issued February 2018 [Member] Senior Unsecured Fixed Rate Notes Issued February 2018 [Member] Senior Unsecured Fixed Rate Notes Issued February 2018 [Member] Comcast Revolving Credit Facility [Member] Comcast Revolving Credit Facility [Member] NBCUniversal Enterprise Credit Facility [Member] NBCUniversal Enterprise Credit Facility [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] NBCUniversal Enterprise Commercial Paper [Member] NBCUniversal Enterprise Commercial Paper [Member] Maturing In Next Five Years [Member] Maturing In Next Five Years [Member] Comcast And Comcast Cable Debt Securities [Member] Comcast And Comcast Cable Debt Securities [Member] Sky Revolving Credit Facility [Member] Sky Revolving Credit Facility [Member] Sky Revolving Credit Facility [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] London Interbank Offered Rate (LIBOR) [Member] London Interbank Offered Rate (LIBOR) [Member] Fair value of debt Long-term Debt, Fair Value Aggregate notional amount Derivative, Notional Amount Aggregate liability fair value Derivative Liability Borrowings Repayments of debt Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Potential increase of maximum borrowing capacity Line of Credit facility, Potential increase to Maximum Borrowing Capacity Potential increased maximum borrowing capacity under the revolving credit facility, subject to approval of the lenders. Amount outstanding under credit facility Amounts available under revolving credit facilities Line of Credit Facility, Remaining Borrowing Capacity Commercial paper capacity Commercial Paper Capacity Amount represents the maximum borrowing capacity under the commercial paper program. Commercial paper outstanding Unused irrevocable standby letters of credit Letters Of Credit And Bank Guarantees, Outstanding Amount The total amount of the contingent obligation under letters of credit outstanding and our bank guarantees as of the reporting date. Ownership in cable holding company subsidiaries Ownership In Cable Holding Company Subsidiaries Represents the Company's ownership in its cable holding company subsidiaries. Guarantee obligations, maximum capacity of credit facility Guarantee Obligations Maximum Capacity Of Credit Facility Maximum capacity of credit facility subject to cross-guarantee Principal amount of debt securities subject to guarantee Guarantee Obligations, Current Principal Balance Principal amount of debt securities subject to guarantee. Related party aggregate principal amount senior notes not subject to guarantee Related Party Aggregate Principal Amount Senior Notes Not Subject To Guarantee Represents the related party aggregate principal amount of senior notes not subject to guarantee by NBCUniversal. Guarantee obligations, term loans Guarantee Obligations, Term Loans Guarantee Obligations, Term Loans Principal amount of debt securities not subject to guarantee Non Guarantee Obligations Current Principal Balance Principal amount of debt instruments not guaranteed by Comcast Corporation, the cable guarantors nor NBCUniversal Media, LLC. Share-based compensation arrangement by share-based payment award, award vesting period in years Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Period from grant date that an equity-based award expires Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Weighted average fair value of RSUs (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Adjustments to additional paid in capital, income tax benefit from share-based compensation Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation DreamWorks Animation [Member] DreamWorks Animation [Member] Allocation of Purchase Price Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Amounts Related to Expenses Included in Consolidated Statement of Operations Schedule of Business Acquisitions, by Acquisition [Table Text Block] Unaudited Actual and Pro Forma Information Business Acquisition, Pro Forma Information [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Estimated Amortization Expense of Finite-Lived Intangible Assets Finite-Lived Intangible Assets [Line Items] 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Five Deferred Tax Assets: Deferred Tax Assets, Net [Abstract] Net operating loss carryforwards Nondeductible accruals and other Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other Less: Valuation allowance Deferred Tax Assets, Valuation Allowance Total deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred Tax Liabilities: Deferred Tax Liabilities, Net [Abstract] Differences between book and tax basis of property and equipment and intangible assets Deferred Tax Liabilities, Property, Plant And Equipment And Intangible Assets Amount before allocation of valuation allowances of deferred tax liability attributable to deductible temporary differences from property and equipment and intangible assets. Differences between book and tax basis of investments DeferredTaxLiabilityInvestments Amount of deferred tax liability attributable to taxable temporary differences from investments. Differences between book and tax basis of long-term debt Deferred Tax Liabilities, Long-Term Debt Amount before allocation of valuation allowances of deferred tax liability attributable to deductible temporary differences from long-term debt. Differences between book and tax basis of foreign subsidiaries and undistributed foreign earnings Deferred Tax Liabilities, Undistributed Foreign Earnings Total deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax liability Deferred Tax Liabilities, Net Revenue From Contract With Customer Financial Statement Impact Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Recent Accounting Pronouncements and Tax Reform New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Long-Term Debt Debt Disclosure [Text Block] Earnings Per Share Earnings Per Share [Text Block] Investments [Table] Investments [Table] Investments [Table] Investments [Line Items] Investments [Line Items] [Line Items] for Investments [Table] Investment Summary Summary Investment Holdings [Table Text Block] Investment and other income (loss), net Components Of Investment and Other Income Loss Net [Table Text Block] Tabular disclosure of investment and other income (loss), net, including, but not limited to, equity in net income (losses) of investees, net, realized and unrealized gains (losses) on equity securities, net, and other income (loss), net. Schedule for the components of income tax expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of items that effect income tax expense Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of the components of net deferred tax liability Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Reconciliation of unrecognized tax benefits Summary of Income Tax Contingencies [Table Text Block] Basic EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Basic Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Assumed exercise or issuance of shares relating to stock plans (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Schedule of minimum annual programming and talent commitments and operating leases Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block] Schedule of rental expenses charged to operations Rental Expense [Table Text Block] Tabular disclosure of rental expense from operating leases for each period for which an income statement is presented. Rental expense Operating Leases, Rent Expense Equity Stockholders' Equity Note Disclosure [Text Block] Schedule of quarterly financial information Quarterly Financial Information [Table Text Block] Cash Payments for Interest and Income Taxes Supplemental Cash Flow Information [Abstract] Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Income taxes Income Taxes Paid, Net Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] Property and Equipment Property, Plant and Equipment [Table Text Block] Eliminations [Member] Segment Reconciling Items [Member] Financial Data by Business Segment Segment Reporting Information, Profit (Loss) [Abstract] Adjusted EBITDA Adjusted EBITDA The measure used to evaluate the profitability of operating segments. Depreciation and Amortization Capital Expenditures Cash Paid for Intangible Assets Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Condensed Consolidated Balance Sheet [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Receivables, gross Accounts Receivable, Gross, Current Less: Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Receivables, net Noncurrent receivables (included in other noncurrent assets, net) Accounts Receivable, Net, Noncurrent Contract acquisition and fulfillment costs (included in other noncurrent assets, net) Capitalized Contract Cost, Net Noncurrent deferred revenue (included in other noncurrent liabilities) Deferred Revenue, Noncurrent Schedule of Goodwill Schedule of Goodwill [Table Text Block] Other Intangible Assets Intangible Assets Disclosure [Text Block] Amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Document and Entity Information [Abstract] DocumentAndEntityInformationAbstract Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Line Items] Document And Entity Information [Line Items] [Line Items] for Document And Entity Information [Table] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Public Float Entity Public Float Entity Current Reporting Status Entity Current Reporting Status Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Statement of Stockholders' Equity [Abstract] Redeemable Noncontrolling Interests And Redeemable Subsidiary Preferred Stock [Member] Redeemable Noncontrolling Interests And Redeemable Subsidiary Preferred Stock [Member] Redeemable Noncontrolling Interests and Redeemable Subsidiary Preferred Stock [Member] Redeemable Noncontrolling Interest [Member] Redeemable Noncontrolling Interest [Member] Common Stock [Member] Common Stock [Member] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Treasury Stock at Cost [Member] Treasury Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Beginning Balance Beginning Balance Cumulative effects of adoption of accounting standards Stock compensation plans Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Repurchases of common stock under repurchase program and employee plans Stock Repurchased and Retired During Period, Value Employee stock purchase plans Stock Issued During Period, Value, Employee Stock Purchase Plan Dividends declared / Distributions to member Dividends, Common Stock, Cash Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Contributions from and distributions to noncontrolling interests Contribution from member Member Contribution Contribution from member including, but not limited to, a business, investment or asset. Purchase of Universal Studios Japan noncontrolling interests Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Other Stockholders' Equity, Other Net income Equity Profit Loss Profit or loss as represented on the statement of changes in equity. Ending Balance Ending Balance Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Beginning Balance Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Attributable To Temporary Equity Contributions from and (distributions to) noncontrolling interests attributable to temporary equity. Other Temporary Equity, Other Changes Net income Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Ending Balance Revenue Revenue from Contract with Customer [Text Block] Related Party Transactions Condensed Financial Statements Schedule of Related Party Transactions [Table Text Block] Related Party Transactions Related Party Transactions Disclosure [Text Block] Current Expense (Benefit): Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Foreign Current Foreign Tax Expense (Benefit) Current income tax expense (benefit) Current Income Tax Expense (Benefit) Deferred Expense (Benefit): Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Foreign Deferred Foreign Income Tax Expense (Benefit) Deferred income tax expense (benefit) Deferred Income Tax Expense (Benefit) Withholding tax expense Foreign Withholding Tax Expense The amount of tax liability incurred by the Company in licensing its content to non-US territories. U.S. domestic tax expense Domestic Tax Expense Benefit Amount of current and deferred income tax expense (benefit) attributable to income (loss) from continuing domestic operations within the country of domicile of the entity. Net income attributable to Comcast Corporation Dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Income tax benefit as a result of the impact of the 2017 tax reform Schedule Of Intangible Assets [Table] Schedule Of Intangible Assets [Table] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] FCC Spectrum [Member] Licensing Agreements [Member] FCC Spectrum Auction [Line Items] FCC Spectrum Auction [Line Items] FCC Spectrum Auction [Line Items] Proceeds from FCC spectrum auction Proceeds from Sale of Intangible Assets Gain on sale of spectrum rights Gain (Loss) on Disposition of Intangible Assets Amount of spectrum acquired Indefinite-lived Intangible Assets (Excluding Goodwill) Deposit to acquire intangible asset Deposit To Acquire Intangible Asset Deposit paid in a prior period for the right to an intangible asset in a future period. Comcast Senior Notes, Fixed and Floating Rates [Member] Senior Notes, Fixed And Floating Rates With Maturities Between 2020 and 2058 [Member] Senior Notes, Fixed And Floating Rates With Maturities Between 2020 and 2058 [Member] Comcast Unsecured Dollar-Denominated Term Loan Credit Agreement [Member] Customer Relationships [Member] Customer Relationships [Member] Customer Contracts [Member] Developed Technology [Member] Developed Technology [Member] Trade Names [Member] Trade Names [Member] Shares acquired, share price (in gbp per share) Business Acquisition, Share Price Percentage of voting interests acquired in period Cash consideration Debt issued to finance cash consideration Maximum borrowing capacity under term loans Debt Instrument, Term Loan, Maximum Borrowing Capacity Debt Instrument, Term Loan, Maximum Borrowing Capacity Amount outstanding Finite-lived intangible assets acquired Finite-lived Intangible Assets Acquired Estimated weighted average useful life Indefinite-lived intangible assets acquired Indefinite-lived Intangible Assets Acquired Revenue attributable to Comcast Corporation since acquisition date Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Net income (loss) attributable to Comcast Corporation since acquisition date Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Adjustment for legal settlement Gain (Loss) Related to Litigation Settlement Adjustment for Sky transaction-related costs Acquisition-Related Expenses Acquisition related expenses directly related to the transaction, including the U.K. share acquisition tax and success-based investment banker fees, and legal, accounting and valuation services. Depreciation Amortization Other operating gains Interest expense Investment and other income (loss), net Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Income Statement [Abstract] Investment and other income (loss), net Income tax (expense) benefit Less: Net income attributable to noncontrolling interests Net income attributable to Comcast Corporation Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Axis] Cash Consideration Transferred By Comcast [Domain] Cash Consideration Transferred By Comcast [Domain] [Domain] for Cash Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Member] Consideration Transferred By Comcast [Member] Consideration Transferred By Comcast [Member] Business acquisition, price paid per share (in dollars per share) Film and television costs Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Film and Television Costs Amount of film and television costs acquired at the acquisition date. Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Snap [Member] Snap [Member] Snap [Member] Schedule of Marketable Equity Securities [Line Items] Schedule of Fair Value Method Investments [Line Items] [Line Items] for Schedule of Fair Value Method Investments [Table] Payments to acquire marketable securities Payments to Acquire Marketable Securities Marketable equity securities Marketable securities, recognized unrealized gains (losses) Equity Securities, FV-NI, Unrealized Gain (Loss) Stock option fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Stock Option Valuation Assumptions: Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected option life Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Investments in and amounts due from subsidiaries eliminated upon consolidation Investments in and amounts due from subsidiaries eliminated upon consolidation Investments in and amounts due from subsidiaries eliminated upon consolidation Common stock Other shareholders’ equity Other stockholders equity Other stockholders equity. Distribution [Member] Distribution [Member] Distribution Content Licensing And Other [Member] Content Licensing And Other [Member] Content Licensing And Other [Member] Content Licensing [Member] Content Licensing [Member] Content Licensing [Member] Direct To Consumer [Member] Direct To Consumer [Member] Direct To Consumer [Member] Theatrical [Member] Theatrical [Member] Theatrical [Member] Content [Member] Content [Member] Content [Member] Distribution And Other [Member] Distribution And Other [Member] Distribution And Other [Member] Home Entertainment [Member] Home Entertainment [Member] Home Entertainment [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Disaggregation of Revenue [Line Items] Cable segment revenue types as percentage of total cable revenue Cable Segment Revenue Types As Percentage Of Total Cable Revenue Cable segment revenue types as percentage of total cable revenue Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States [Member] UNITED STATES Foreign [Member] Non-US [Member] Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Universal Studios Japan [Member] Universal Studios Japan [Member] Payments to acquire additional interest in noncontrolling interest Restricted cash included in other current assets Restricted Cash, Current Restricted cash included in other noncurrent assets, net Restricted Cash, Noncurrent Cash, cash equivalents and restricted cash, end of year Pension Plans [Member] Pension Plan [Member] Multiemployer Plan Type [Axis] Multiemployer Plan Type [Axis] Multiemployer Plans Type [Domain] Multiemployer Plans Type [Domain] Multiemployer Plans, Pension [Member] Multiemployer Plans, Pension [Member] Multiemployer Plans, Postretirement Benefit [Member] Multiemployer Plans, Postretirement Benefit [Member] Cash surrender value of life insurance policies Cash Surrender Value of Life Insurance Benefit obligation Expenses related to retirement investment plans Defined Contribution Plan, Cost Multiemployer plan contributions Multiemployer Plan, Contributions by Employer Severance costs Other Restructuring Costs Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Share-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Voting power Common Stock Voting Power Common Stock Voting Power Number of votes entitled of each class B common stock Number Of Votes Entitled Of Each Class B Common Stock Number of votes entitled to vote for each share of Class B common stock share. Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Schedule II - Valuation and Qualifying Accounts SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Statement of Cash Flows [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation, amortization and other operating gains Depreciation And Amortization And Gain (Loss) On Disposition Of Assets Depreciation And Amortization Expense And (Gain) Loss On Disposition Of Assets Share-based compensation Share-based Compensation Noncash interest expense (income), net Noncash Interest Expense (Income) Net Represents noncash interest expense (income) items as adjustments to reconcile net income (loss) to cash provided by (used in) operating activities. Net (gain) loss on investment activity and other Gain (Loss) On Investments And Other Noncash Income (Loss) Net Net (gain) loss on investment activity, including cash received from investees, and other noncash income (loss), net. Deferred income taxes Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Current and noncurrent receivables, net Change In Current And Noncurrent Receivables Net The increase (decrease) during the reporting period in the amount of current and noncurrent receivables. Film and television costs, net Film And Television Costs Net Amount of net increase (decrease) in film and television costs. Accounts payable and accrued expenses related to trade creditors Increase (Decrease) in Accounts Payable and Accrued Liabilities Other operating assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Note receivable from Comcast Note Receivable Issued From Ultimate Parent Cash flow from note receivable issued from and repayments from Ultimate Parent. Deposits Proceeds from (repayments of) borrowings from Comcast, net Proceeds From Note Receivable Issued To And Borrowings From Ultimate Parent Proceeds From Note Receivable Issued To And Borrowings From Ultimate Parent Distributions to member Payments of Capital Distribution Distributions to noncontrolling interests Distributions To Noncontrolling Interest Holders The cash outflow related to distributions to noncontrolling interests. Issuances of common stock Increase (decrease) in cash, cash equivalents and restricted cash Schedule of Indefinite and Finite-Lived Intangible Assets [Table] Schedule of Indefinite and Finite-Lived Intangible Assets [Table] Schedule of assets, excluding financial assets and goodwill, lacking physical substance. Schedule of Indefinite and Finite-Lived Intangible Assets [Line Items] Schedule of Indefinite and Finite-Lived Intangible Assets [Line Items] [Line Items] for Schedule of assets, excluding financial assets and goodwill, lacking physical substance. Total Intangible Assets, Gross (Excluding Goodwill) Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-Lived Intangible Assets [Table] Franchise Rights [Member] Franchise Rights [Member] FCC Licenses [Member] Indefinite-lived Intangible Assets [Line Items] Indefinite-lived Intangible Assets [Line Items] Gross Carrying Amount Patents and other technology rights [Member] Patents and other technology rights [Member] Other agreements and rights [Member] Other Intangible Assets [Member] Weighted-Average Original Useful Life Gross Carrying Amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Ownership percentage in variable interest entity Noncontrolling Interest, Ownership Percentage by Parent Maximum borrowing capacity of variable interest entity Variable Interest Entity, Maximum Borrowing Capacity Variable interest entity, maximum borrowing capacity under financing agreements. Other Long-term Debt Consolidated variable interest entity's assets included in condensed consolidated balance sheet Variable Interest Entity, Consolidated, Carrying Amount, Assets Consolidated variable interest entity's liabilities included in condensed consolidated balance sheet Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Residential [Member] Residential Customers [Member] Residential Customers [Member] Business Customers [Member] Business Customers [Member] Business Customers [Member] High-speed Internet Customers [Member] High-speed Internet Customers [Member] High-speed Internet Customers [Member] Video Customers [Member] Video Customers [Member] Video Customers [Member] Voice Customers [Member] Voice Customers [Member] Voice Customers [Member] Security And Automation Customers [Member] Security And Automation Customers [Member] Security And Automation Customers [Member] Total customer relationships Total Customer Relationships Represents the number of residential and business customers that subscribe to at least one of our four primary services of video, high-speed Internet, voice, and security and automation. Number of customers Number Of Customers Represents the number of customers that subscribe to our services. Retail customer relationships Total Retail Customer Relationships Represents the number of retail customers that subscribe to at least one of Sky's primary services of video, high-speed internet, voice, and wireless phone services Financial Data by Business Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Reconciliation of Adjusted EBITDA from Segments to Consolidated Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Line Items] Recent Accounting Pronouncements [Line Items] [Line Items] for Recent Accounting Pronouncements [Table] Basis of Presentation Consolidation, Policy [Policy Text Block] Foreign Currency Translation Foreign Currency Transactions and Translations Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Advertising Cost Advertising Cost, Policy, Expensed Advertising Cost [Policy Text Block] Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Derivative Financial Instruments Derivatives, Policy [Policy Text Block] Fair Value Measurements Fair Value Measurement, Policy [Policy Text Block] Asset Retirement Obligations Asset Retirement Obligation and Environmental Cost [Policy Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Film And Television Costs Film And Television Costs [Policy Text Block] Describes an entity's accounting policy for film and television costs. This accounting policy also may address how an entity assesses and measures impairment of film and television costs. Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Investments Investment, Policy [Policy Text Block] Impairment Testing of Investments Investments Impairment [Policy Text Block] Disclosure of accounting policy for recognizing and measuring the impairment of long-lived assets. Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Indefinite-Lived Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived, Policy [Policy Text Block] Finite-Lived Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Share-Based Compensation Compensation Related Costs, Policy [Policy Text Block] Postretirement and Pension Benefits Pension and Other Postretirement Plans, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Residential [Member] Residential [Member] Residential [Member] Revenue [Line Items] Term of contract Revenue, Performance Obligation, Description Of Timing, Term Of Contract Revenue, Performance Obligation, Description Of Timing, Term Of Contract Annual revenue that estimates remaining performance obligations Annual Revenue That Estimates Remaining Performance Obligations Years of annual revenue that estimate revenue for performance obligations that have not been recognized as revenue Timing period of recognition Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Expected payment terms Revenue, Performance Obligation, Description Of Payment Terms, Period Revenue, Performance Obligation, Description Of Payment Terms, Period Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Treasury stock (in shares) Treasury Stock, Shares