Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A Common Stock [Member] Common Class A [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] 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] Member's Capital [Member] Member's Capital [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] AOCI Attributable to Parent [Member] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Beginning balance Redeemable Noncontrolling Interest, Equity, Carrying Amount 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 (loss) Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Ending balance Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Beginning balance Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest Cumulative effects of adoption of accounting standards Cumulative Effect of New Accounting Principle in Period of Adoption Distributions to member Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared Stock compensation plans APIC, Share-based Payment Arrangement, Increase for Cost 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 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 Other Stockholders' Equity, Other Net income (loss) Equity Profit Loss Profit or loss as represented on the statement of changes in equity. Ending balance Ending balance Cash dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Statement of Financial Position [Abstract] Class B Common Stock [Member] Common Class B [Member] Assets Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current 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. 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 Other current assets Other Assets, Current Total current assets Assets, Current 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. Investments Long-term Investments Property and equipment, net Property, Plant and Equipment, Net Franchise rights Indefinite-Lived Franchise Rights Goodwill Goodwill Other intangible assets, net Other Intangible Assets, Net Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Other noncurrent assets, net Other Assets, Noncurrent Total assets Assets Liabilities and Equity Liabilities and Equity [Abstract] Current Liabilities: Liabilities, Current [Abstract] Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current 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 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. Current portion of long-term debt Debt, Current Total current liabilities Liabilities, Current Long-term debt, less current portion Long-term Debt and Lease Obligation 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 Deferred Income Tax Liabilities, Net Other noncurrent liabilities Other Liabilities, Noncurrent Commitments and contingencies (Note 11) Commitments and Contingencies Redeemable noncontrolling interests Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred stock—authorized, 20,000,000 shares; issued, zero Preferred Stock, Value, Issued 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 Member’s capital Members' Capital Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax 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 Liabilities and Equity Other Industries [Abstract] Film And Television Costs [Table] Film And Television Cost [Table] Film And Television Cost [Table] Film And Television Costs [Line Items] Film And Television Cost [Line Items] [Line Items] for Film And Television Cost [Table] Film and Television Costs Schedule Of Film And Television Costs [Table Text Block] Schedule Of Film And Television Costs [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Sky Limited [Member] Sky Limited [Member] Sky Limited [Member] Redeemable Subsidiary Preferred Stock [Member] Redeemable Preferred Stock [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] Commitment And Contingencies [Line Items] Commitment And Contingencies [Line Items] [Line Items] for Commitment And Contingencies [Table] Operating lease expense inclusive of short-term and variable lease expenses Operating Lease Expense Inclusive Of Short Term And Variable Lease Expenses Amount of operating lease expense, inclusive of short-term and variable lease expenses, recognized in our consolidated statement of income. Excludes lease costs associated with production activities or other amounts capitalized in our consolidated balance sheet. Weighted average remaining lease term for operating leases Operating Lease, Weighted Average Remaining Lease Term Weighted average discount rate used to calculate operating lease liabilities Operating Lease, Weighted Average Discount Rate, Percent Cash payments for operating leases Operating Lease, Payments Rental expense Operating Leases, Rent Expense Future cash payments related to additional contracts determined to be operating leases Additional Operating Leases, Future Minimum Payments Due Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year related to additional contracts determined to be operating leases in connection with the Sky transaction. 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. Investments [Abstract] Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] 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] Marketable equity securities, recognized unrealized gains (losses) Equity Securities, FV-NI, Unrealized Gain (Loss) Marketable equity securities Equity Securities, FV-NI 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] Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Corporate, Non-Segment [Member] Corporate, Non-Segment [Member] Eliminations [Member] Segment Reconciling Items [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Cable Communications [Member] Cable Communications [Member] Cable Communications 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 NBCUniversal Segments [Member] NBCUniversal Segments [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Residential, High-Speed Internet [Member] Residential, High-Speed Internet [Member] Residential, High-Speed Internet [Member] Residential, Video [Member] Residential, Video [Member] Residential, Video [Member] Residential, Voice [Member] Residential, Voice [Member] Residential, Voice [Member] Residential, Wireless [Member] Residential, Wireless [Member] Residential, Wireless [Member] Business Services [Member] Business Services [Member] Business Services [Member] Distribution [Member] Distribution [Member] Distribution Advertising [Member] Advertising [Member] 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] Content [Member] Content [Member] Content [Member] Theatrical [Member] Theatrical [Member] Theatrical [Member] Distribution And Other [Member] Distribution And Other [Member] Distribution And Other [Member] Home Entertainment [Member] Home Entertainment [Member] Home Entertainment [Member] Other [Member] Other [Member] Other [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue Revenues 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 Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-02 [Member] Accounting Standards Update 2016-02 [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Noncurrent Assets, Net [Member] Other Noncurrent Assets [Member] Accrued Expenses and Other Current Liabilities [Member] Accrued Liabilities [Member] Other Noncurrent Liabilities [Member] Other Noncurrent Liabilities [Member] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Operating lease assets Operating Lease, Right-of-Use Asset Operating lease liabilities, current Operating Lease, Liability, Current Operating lease liabilities, noncurrent Operating Lease, Liability, Noncurrent 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] 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] 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] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Sky Revolving Credit Facility [Member] Sky Revolving Credit Facility [Member] Sky Revolving Credit Facility [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] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Total carrying value of debt Debt and Lease Obligation Total fair value of debt Long-term Debt, Fair Value Borrowings Proceeds from Issuance of Long-term Debt Repayments of debt Repayments of Other Debt Condensed Financial Information Disclosure [Abstract] Condensed Financial Statements [Table] Condensed Financial Statements [Table] Comcast Holdings [Member] Comcast Holdings [Member] Comcast Holdings CCCL Parent [Member] CCCL Parent [Member] CCCL Parent NBCUniversal Media Parent [Member] NBCUniversal Media Parent [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] Reportable Legal Entities [Member] Reportable Legal Entities [Member] Elimination and Consolidation Adjustments [Member] Consolidation, Eliminations [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Cash and cash equivalents 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 Other intangible assets, net Total current liabilities Other shareholders’ equity Other stockholders equity Other stockholders equity. Business Combinations [Abstract] 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] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Universal Beijing Resort term loans [Member] 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. Proceeds from borrowings 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 Statement of Comprehensive Income [Abstract] 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), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Employee benefit obligations, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Currency translation adjustments, deferred taxes Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Line of Credit Facility [Table] Line of Credit Facility [Table] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Net repayments of credit facility Proceeds from (Repayments of) Lines of Credit Credit facility terminated Line Of Credit Facility, Borrowing Capacity Of Credit Facility Terminated Line Of Credit Facility, Borrowing Capacity Of Credit Facility Terminated Amount outstanding under credit facility Long-term Line of Credit Amounts available under revolving credit facilities Line of Credit Facility, Remaining Borrowing Capacity Condensed Consolidating Financial Information Condensed Financial Information of Parent Company Only Disclosure [Text Block] 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] Property and equipment and intangible assets accrued but not yet paid Capital Costs Incurred But Not Yet Paid Future cash outflow to pay for purchases of property and equipment and intangible assets that have occurred. Dividends payable Dividends Payable Dividends payable (in dollars per share) Dividends Payable, Amount Per Share Remaining six months of 2019 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five Total future minimum lease payments Lessee, Operating Lease, Liability, Payments, Due Less: imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Total liability Operating Lease, Liability Schedule of operating lease assets and liabilities Schedule of future minimum rental commitments for operating leases under new accounting guidance Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of future minimum rental commitments and rent expense for operating leases under previous accounting guidance Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of recognized share-based compensation expense Share-based Payment Arrangement, Cost by Plan [Table Text Block] 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] Film And Television Costs Film And Television Costs Disclosure [Text Block] Film and Television costs Disclosure [Text Block] Investment Holdings [Table] Investment Holdings [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Atairos [Member] Atairos [Member] Atairos [Member] Air Touch [Member] Air Touch [Member] Air Touch [member] AirTouch [Member] Schedule of Other Investments [Line Items] Schedule of Held-to-maturity Securities [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 Fair value of redeemable preferred shares Fair Value Of Redeemable Preferred Shares Fair value of our redeemable subsidiary preferred shares and/or stock Leases [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 Rental expense 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 Revenue Revenue from Contract with Customer [Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Related Party Transactions Condensed Financial Statements Schedule of Related Party Transactions [Table Text Block] 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] Service [Member] Service [Member] Management Fee [Member] Management Fee [Member] Management Fee [Member] Revenue: Revenues [Abstract] 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 Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Less: Net income (loss) 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. Net income attributable to Comcast Corporation Net Income (Loss) Attributable to Parent Comprehensive income (loss) attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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] Unrealized gains (losses) on marketable securities AOCI, Debt Securities, Available-for-sale, Adjustment, after Tax Deferred gains (losses) on cash flow hedges AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after 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 Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Statement of Cash Flows [Abstract] Operating Activities Net Cash Provided by (Used in) Operating Activities [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 Depreciation and amortization Depreciation, Depletion and Amortization Share-based compensation Share-based Payment Arrangement, Noncash Expense 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 Deferred Income Tax Expense (Benefit) 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 Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] 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. Note receivable from Comcast Note Receivable Issued From Ultimate Parent Cash flow from note receivable issued from and repayments from Ultimate Parent. 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 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 Repurchases and repayments of debt 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 Repurchases of common stock under repurchase program and employee plans Payments for Repurchase of Common Stock Dividends paid Payments of Dividends 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. 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, 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 period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash, end of period 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 Pro Forma Information Business Acquisition, Pro Forma Information [Table Text Block] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Investment and Other Income (Loss), Net [Line Items] Debt and Equity Securities, FV-NI [Line Items] Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments 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. Investment and other income (loss), net Earnings Per Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [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] Customer Premise Equipment [Member] Customer Premise Equipment [Member] Customer premise equipment [Member] 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] Customer Relationships [Member] Customer Relationships [Member] Developed Technology and Software [Member] Developed Technology and Software [Member] Developed Technology and Software [Member] 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] Trade Names [Member] Trade Names [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Shares acquired, share price (in gbp per share) Business Acquisition, Share Price Percentage of voting interests acquired in period Business Acquisition, Percentage Of Voting Interests Acquired In Period Business Acquisition, Percentage Of Voting Interests Acquired Cash consideration Business Combination, Consideration Transferred Deferred tax assets related to net operating losses Operating Loss Carryforwards, Valuation Allowance Goodwill purchase accounting adjustment Goodwill, Purchase Accounting Adjustments Incremental depreciation and amortization Business Combination, Measurement Period Adjustment, Depreciation And Amortization Business combination measurement period adjustment for depreciation and amortization which was recorded in the current period and related to prior period Property and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Estimated useful lives Property, Plant and Equipment, Useful Life Finite-lived intangible assets acquired Finite-lived Intangible Assets Acquired Estimated weighted average useful life Finite-Lived Intangible Asset, Useful Life Indefinite-lived intangible assets acquired Indefinite-lived Intangible Assets Acquired Document and Entity Information [Abstract] DocumentAndEntityInformationAbstract Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Table] 2.0% Exchangeable Subordinated Debentures Due 2029 [Member] Exchangeable Subordinated Debentures 2.0 Percent Due 2029 [Member] Exchangeable Subordinated Debentures 2.0% Due 2029 [Member] 5.50% Notes Due 2029 [Member] Notes 5.50 Percent Due 2029 [Member] Notes 5.50% Due 2029 [Member] 9.455% Guaranteed Notes Due 2022 [Member] Guaranteed Notes 9.455 Percent Due 2022 [Member] Guaranteed Notes 9.455% Due 2022 [Member] Document And Entity Information [Line Items] Document And Entity Information [Line Items] [Line Items] for Document And Entity Information [Table] Document Type Document Type Document Fiscal Period Focus Document Fiscal Period Focus Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Entity Tax Identification Number Entity Tax Identification Number Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Recent Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Long-Term Debt Debt Disclosure [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Interest in business acquired in acquisition Cash consideration transferred by Comcast Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Comcast and Consolidated Subsidiaries [Member] Comcast And Consolidated Subsidiaries [Member] Film and television costs Direct-to-television Film Costs Schedule of Investments [Line Items] Equity method Equity Method Investments Nonmarketable equity securities Equity Securities without Readily Determinable Fair Value, Amount Other investments Other Investments Total investments Investments Less: Current investments Short-term Investments Noncurrent investments Share-based Payment Arrangement, Noncash Expense [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] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Management Grant [Member] Management Grant [Member] Management Grant [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Restricted share units [Member] Restricted Stock Units (RSUs) [Member] Stock options [Member] Share-based Payment Arrangement, Option [Member] Employee stock purchase plans [Member] Employee Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of restricted share units granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Number of stock options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Weighted-average fair value of restricted share units granted (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 Weighted-average fair value of stock options granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Recognized share-based compensation expense Share-based Payment Arrangement, Expense Unrecognized pretax compensation expense on nonvested awards Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount 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 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 Carrying Value of Related Party Contractual Obligation [Member] Carrying Value Of Related Party Contractual Obligation [Member] Rental expense Property and equipment - accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Other intangible assets - accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization 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) Common Stock, Shares, Outstanding Treasury stock (in shares) Treasury Stock, Shares Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States [Member] UNITED STATES Europe [Member] Europe [Member] Other [Member] Other Geographic Locations [Member] Other Geographic Locations [Member] Foreign [Member] Non-US [Member] 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 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 Intangible assets 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 Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Deferred tax assets (liabilities), net 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 Goodwill Goodwill, Acquired During Period 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 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. Income Statement [Abstract] Income tax expense Net income Less: Net income (loss) attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Investments [Table] Investments [Table] Investments [Table] Investments [Line Items] Investments [Line Items] [Line Items] for Investments [Table] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] 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), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Amounts reclassified to net income: Amounts Reclassified To Net Income [Abstract] Realized (gains) losses on cash flow hedges, net of deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after 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: Other comprehensive income (loss) attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 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. Investment Summary Summary Investment Holdings [Table Text Block] 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 period Computation of diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Accounting Policies [Line Items] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Operating lease liabilities Finance lease liabilities Finance Lease, Liability Additional finance lease liability Additional Finance Lease Liability Present value of lessee's discounted obligation for lease payments from finance lease for additional contracts determined to be leases in connection with Sky transaction. 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, before Allowance for Credit Loss, Current Less: Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Receivables, net Noncurrent receivables, net (included in other noncurrent assets, net) Accounts Receivable, after Allowance for Credit Loss, 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 Net Cash Provided by (Used in) Operating Activities [Abstract] Net cash provided by operating activities Net transactions with affiliates Net transactions with affiliates Net transactions with affiliates. Operating Segments [Member] Operating Segments [Member] Number of reportable segments Number of Reportable Segments 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 Depreciation, Depletion and Amortization, Nonproduction Capital Expenditures Cash Paid for Intangible Assets Comcast and Comcast Cable Debt Securities [Member] Comcast And Comcast Cable Debt Securities [Member] NBCUniversal Enterprise Debt Securities [Member] NBCUniversal Enterprise Debt Securities [Member] NBCUniversal Enterprise Debt Securities [Member] Universal Studios Japan Term Loans Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Sky Senior Notes [Member] Sky Senior Notes [Member] Sky Senior Notes [Member] NBCUniversal Enterprise [Member] NBCUniversal Enterprise [Member] 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, Debt Securities Principal amount of debt securities subject to guarantee. Principal amount of debt securities not subject to guarantee Non Guarantee Obligations Debt Securities Principal amount of debt securities not guaranteed by Comcast Corporation, the cable guarantors nor NBCUniversal Media, LLC. Related party aggregate principal amount debt securities not subject to guarantee Related Party, Aggregate Debt Securities, Not Subject To Guarantee Represents the related party aggregate principal amount of debt securities not subject to guarantee by NBCUniversal. 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. Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Commercial Paper [Member] Commercial Paper [Member] Short-term Debt [Line Items] Short-term Debt [Line Items] Net repayments of commercial paper Proceeds from (Repayments of) Commercial Paper Commercial paper outstanding Commercial Paper Related Party Transactions Related Party Transactions Disclosure [Text Block] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] Condensed Consolidated Financial Statements [Line Items] Business And Basis Of Presentation [Line Items] Business And Basis Of Presentation Condensed Consolidated Financial Statements Business Description and Basis of Presentation [Text Block] Reconciliation of Adjusted EBITDA 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 Sky transaction-related costs Transaction Related Costs Acquisition related and integration costs which have been expensed during the period. Such costs could include costs directly related to the transaction, including the U.K. share acquisition tax and success-based investment banker fees, and legal, accounting and valuation services, and costs incurred to effect a business combination, such as business integration costs, systems integration and conversion costs, and severance and other employee-related costs. Depreciation Amortization Other operating gains Interest expense Net Income Attributable to Comcast Corporation 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) 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) Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Time Warner, Inc. [Member] Time Warner, Inc. [Member] Time Warner, Inc. [Member] AT&T Inc. [Member] AT&T Inc. [Member] AT&T Inc. [Member] Hulu [Member] Hulu [Member] Hulu member. The Weather Channel [Member] The Weather Channel [Member] The Weather Channel [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Ownership percentage Equity Method Investment, Ownership Percentage Cash capital contributions for equity method investments Payments to Acquire Equity Method Investments Maximum total capital call in annual period Equity Method Investment, Maximum Total Capital Call In Annual Period Equity Method Investment, Maximum Total Capital Call In Annual Period Ownership percentage floor Equity Method Investment, Ownership Percentage, Floor Equity Method Investment, Ownership Percentage, Floor Fair market value assessment floor for put and call option Equity Method Investment, Fair Market Value, Floor For Put And Call Option Fair market value floor representing minimum total equity value of investment for put and call option. Ownership percentage representing fair market value floor for put and call option Equity Method Investment, Ownership Percentage Representing Fair Market Value Floor For Put And Call Option Equity Method Investment, Ownership Percentage Representing Fair Market Value Floor For Put And Call Option Minimum guaranteed proceeds floor for put and call option Equity Method Investment, Minimum Guaranteed Proceeds Floor For Put And Call Option Equity Method Investment, Minimum Guaranteed Proceeds Floor Recognition of previously deferred gain Deferred Gain Recognized On Dilution Of Equity Method Investment Deferred Gain Recognized On Dilution Of Equity Method Investment Equity in net income (losses) of investees, net Cash capital contributions for equity method investments Capital Contribution To VIE The cash outflow associated with a capital contribution to a VIE accounted for as an equity method investment Equity method investments Pretax gain, sale of business to Atairos Gain (Loss) on Disposition of Business Pretax gain on sale of investment Equity Method Investment, Realized Gain (Loss) on Disposal Other operating and administrative expenses Business Combination, Acquisition Related Costs Interest expense Interest Expenses Financing costs associated with debt facilities and the borrowings related to acquisition.