Cash Payments for Interest and Income Taxes Supplemental Cash Flow Information [Abstract] Employee benefit obligations and other, net of deferred taxes of $3, $3, $5 and $6 Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Reclassification Adjustment, After Tax Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Reclassification Adjustment, After Tax Other Industries [Abstract] Other Industries [Abstract] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Net income attributable to Comcast Corporation Net income (loss) Net Income (Loss) Attributable to Parent Consolidated Entities [Axis] Consolidated Entities [Axis] Entity Emerging Growth Company Entity Emerging Growth Company 1.875% Notes Due 2036 [Member] Notes 1.875 percent due 2036 [Member] Notes 1.875% due 2036 [Member] 9.455% Guaranteed Notes Due 2022 [Member] Guaranteed Notes 9.455 Percent Due 2022 [Member] Guaranteed Notes 9.455% Due 2022 [Member] Other intangible assets - accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization 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. Entity Address, Address Line One Entity Address, Address Line One Dividends declared Dividends, Common Stock, Cash Marketable equity securities Equity Securities, FV-NI, Current Currency translation adjustments, deferred taxes Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Entity Filer Category Entity Filer Category Cable Networks [Member] Cable Networks [Member] Cable Networks Member Other noncurrent assets, net Other Assets, Noncurrent Lease Arrangements [Domain] Lease Arrangements [Domain] Lease Arrangements Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Investment, Name [Axis] Investment, Name [Axis] Segments [Axis] Segments [Axis] 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 1.250% Notes Due 2040 [Member] Notes 1.250 percent due 2040 [Member] Notes 1.250% due 2040 [Member] Stock compensation plans APIC, Share-based Payment Arrangement, Increase for Cost Recognition 1.500% Notes Due 2029 [Member] Notes 1.500 percent Due 2029 [Member] Notes 1.500% Due 2029 [Member] Programming and production Total programming and production costs 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. Investment securing collateralized obligation Less: Investment securing collateralized obligation Investment Securing Collateralized Obligation Carrying amount of investment presented separately as investment securing collateralized obligation that is partially securing an obligation. Document Fiscal Year Focus Document Fiscal Year Focus Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Amortization Amortization Amortization of Intangible Assets Long-term debt, less current portion Long-term Debt and Lease Obligation Weighted average discount rate on operating lease Operating Lease, Weighted Average Discount Rate, Percent 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 Award Type [Domain] Award Type [Domain] Credit Facility [Domain] Credit Facility [Domain] Assets Assets [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] Segment Reconciling Items [Member] Segment Reconciling Items [Member] 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 Preferred stock Preferred Stock, Value, Issued Entity Address, City or Town Entity Address, City or Town Retained Earnings [Member] Retained Earnings [Member] Debt Instrument [Axis] Debt Instrument [Axis] Reclassification, Type [Domain] Reclassification, Type [Domain] Supplemental Financial Information [Abstract] Supplemental Financial Information [Abstract] Statement Of Cash Flows Supplemental Information Abstract Advertising, marketing and promotion Marketing and Advertising Expense Ownership percentage in variable interest entity Noncontrolling Interest, Ownership Percentage by Parent Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Repurchases of common stock under repurchase program and employee plans Stock Repurchased and Retired During Period, Value 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. Investments, All Other Investments [Abstract] Operating lease assets and liabilities recognized Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Atairos [Member] Atairos [Member] Atairos [Member] Entity Interactive Data Current Entity Interactive Data Current Film and television costs Film, Monetized On Its Own Capitalized Cost, And Entertainment, License Agreement For Program Material, Including Sports Rights Advances Total amounts of capitalized film cost for film predominantly monetized on its own and capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic Owned Film, Monetized on Its Own, Capitalized Cost Revenue Revenue from Contract with Customer [Text Block] 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. Document Type Document Type Released, less amortization Film, Monetized on Its Own, Capitalized Cost, Released Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Residential, Voice [Member] Residential, Voice [Member] Residential, Voice [Member] Entity Current Reporting Status Entity Current Reporting Status Contract acquisition and fulfillment costs (included in other noncurrent assets, net) Capitalized Contract Cost, Net Other balance sheet accounts Schedule Of Other Balance Sheet Accounts [Table Text Block] Schedule Of Other Balance Sheet Accounts [Table Text Block] Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member] Film and television costs, net Film And Television Costs Net Amount of net increase (decrease) in film and television costs. Investment Summary Summary Investment Holdings [Table Text Block] Foreign currency translation and other Goodwill, Foreign Currency Translation And Other Goodwill, Foreign Currency Translation And Other Goodwill [Roll Forward] Goodwill [Roll Forward] Plan Name [Axis] Plan Name [Axis] Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Document Transition Report Document Transition Report Total liabilities and equity Liabilities and Equity Additional paid-in capital Additional Paid in Capital Other operating and administrative Other Operating And Administrative Other operating and administrative expense recognized in the period not presented separately. Liabilities and Equity Liabilities and Equity [Abstract] Condensed Consolidated Financial Statements Business Description and Basis of Presentation [Text Block] Realized and unrealized gains (losses) on equity securities, net Equity Securities, FV-NI, Gain (Loss) 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] Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Owned Film, Monetized On Its Own, Amortization Expense, Including Participations And Residuals Amount of amortization expense for capitalized film cost for film predominantly monetized on its own and participation and residuals expenses. Financial Data by Business Segment Segment Reporting Information, Profit (Loss) [Abstract] Other operating assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Borrowings outstanding under credit facility Long-term Line of Credit 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 Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] NBCUniversal Segments [Member] NBCUniversal Segments [Member] Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Table] Trading Symbol Trading Symbol Current Liabilities: Liabilities, Current [Abstract] Unrecognized gains (losses) on employee benefit obligations and other Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Tax Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Tax 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. Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Long-Term Debt Debt Disclosure [Text Block] Programming and Production Expense Schedule Of Programming And Production Cost [Table Text Block] Schedule Of Programming And Production Cost Number of reportable segments Number of Reportable Segments Redeemable noncontrolling interests and redeemable subsidiary preferred stock Beginning balance Ending balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Other [Member] Other Geographic Locations [Member] Other Geographic Locations [Member] Common stock Common Stock, Value, Issued Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Investment and other income (loss), net Investment and other income (loss), net Nonoperating Income (Expense) Headquarters and Other [Member] Headquarters And Other [Member] Headquarters And Other [Member] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Commitments and contingencies Commitments and Contingencies Accumulated other comprehensive income (loss) Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Dividends payable (in dollars per share) Dividends Payable, Amount Per Share Supplemental Financial Information [Table] Supplemental Financial Information [Table] Supplemental Financial Information [Table] Programming and Production Costs Entertainment [Text Block] Less: Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Other investments Other Investments Amortization of owned film and television costs Film, Monetized on Its Own, Amortization Expense Ownership [Axis] Ownership [Axis] Document Period End Date Document Period End Date Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Goodwill [Line Items] Goodwill [Line Items] Total costs and expenses Costs and Expenses Class of Stock [Axis] Class of Stock [Axis] Entity Registrant Name Entity Registrant Name Treasury stock (in shares) Treasury Stock, Shares Other Other Programming And Production Expense Other Programming And Production Expense Licensed, including sports rights Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Amortization Expense Amount of amortization expense for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Fair value of collateralized obligation Collateralized Obligation, Fair Value Fair value of obligation presented separately as collateralized obligation that is secured by assets. Cash dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Accrued expenses and other current liabilities Accrued Liabilities, Current Hulu [Member] Hulu [Member] Hulu member. Dividends paid Payments of Dividends Stock Options [Member] Share-based Payment Arrangement, Option [Member] Equity [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] Issuances of common stock under employee plans Stock Issued During Period, Value, Issued for Services 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. Common Stock [Member] Common Stock [Member] Variable Rate [Axis] Variable Rate [Axis] Total Intersegment Eliminations [Member] Total Intersegment Eliminations [Member] Total Intersegment Eliminations Other intangible assets, net of accumulated amortization Other Intangible Assets, Net Segment Information Segment Reporting Disclosure [Text Block] Operating income Operating Income (Loss) Cash payments for the redemption of redeemable subsidiary preferred stock Payments For Repurchase Of Redeemable Subsidiary Preferred Stock Payments For Repurchase Of Redeemable Subsidiary Preferred Stock Less: Other comprehensive income (loss) attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Cumulative translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Share-based compensation Share-based Payment Arrangement, Noncash Expense Variable Rate [Domain] Variable Rate [Domain] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Depreciation Depreciation Depreciation Treasury Stock at Cost [Member] Treasury Stock [Member] Total fair value of debt Long-term Debt, Fair Value Licensed, including sports advances Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Capitalized Cost Amount of capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Other Payments for (Proceeds from) Other Investing Activities Capital expenditures Capital Expenditures Payments to Acquire Property, Plant, and Equipment Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Business Combinations [Abstract] Business Combinations [Abstract] Number of preferred stock series (in series) Number of Preferred Stock Series Number of Preferred Stock Series Franchise rights Indefinite-Lived Franchise Rights Consolidated variable interest entity's liabilities included in condensed consolidated balance sheet Liabilities Legal Entity [Axis] Legal Entity [Axis] Adjusted EBITDA Adjusted EBITDA The measure used to evaluate the profitability of operating segments. Other Temporary Equity, Other Changes Award Type [Axis] Award Type [Axis] Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Video distribution programming Video Distribution Programming Expense Video Distribution Programming Expense Consolidation Items [Axis] Consolidation Items [Axis] Total Comcast Corporation shareholders’ equity Stockholders' Equity Attributable to Parent Studios [Member] Studios [Member] Studios Common stock, shares issued (in shares) Common Stock, Shares, Issued Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Accounts payable and accrued expenses related to trade creditors Increase (Decrease) in Accounts Payable and Accrued Liabilities Segment Change Reclassification Due To Segment Change [Member] Reclassification Due To Segment Change Schedule of cash payments for interest and income taxes Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Goodwill and Intangible Assets Disclosure [Abstract] 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 Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Adjustments Adjustments for Items Excluded from Adjusted EBITDA Adjustments represent the impacts of certain events, gains, losses or other charges that are excluded from Adjusted EBITDA 0.750% Notes Due 2032 [Member] Notes 0.750 percent due 2032 [Member] Notes 0.750% due 2032 [Member] In production and in development Film, Monetized On Its Own, Capitalized Cost, In Production And In Development Amounts of capitalized film cost incurred in production and in development of film predominantly monetized on its own Interest expense Interest expense Interest Expense City Area Code City Area Code Retained earnings Retained Earnings (Accumulated Deficit) Operating Segments [Member] Operating Segments [Member] Lease terms Lessee, Operating Lease, Term of Contract Restricted Share Units (RSUs) [Member] Restricted Stock Units (RSUs) [Member] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Equity method Equity method investment Equity Method Investments Income Statement [Abstract] Income Statement [Abstract] Amendment Flag Amendment Flag Broadcast Television [Member] Broadcast Television [Member] Broadcast Television Member 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. Schedule of Other Investments [Table] Other Investment Not Readily Marketable [Table] Less: Current investments Short-term Investments Filmed Entertainment [Member] Filmed Entertainment [Member] Filmed Entertainment Member Total equity Beginning balance Ending balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Theatrical [Member] Theatrical [Member] Theatrical [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Receivables, net Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current Commitments And Contingencies [Table] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Proceeds from borrowings Proceeds from Issuance of Long-term Debt Equity Components [Axis] Equity Components [Axis] Total current assets Assets, Current Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Other income (loss), net Other Income Loss Net Nonoperating income (losses), net recorded in the income statement that are not separately stated. Realized (gains) losses reclassified to net income, net of deferred taxes of $—, $4, $— and $21 Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Financial Data by Business Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Redemption of subsidiary preferred stock Temporary Equity, Redemption Of Preferred Stock Temporary Equity, Redemption Of Preferred Stock Entity File Number Entity File Number Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Media [Member] Media [Member] Media Product and Service [Axis] Product and Service [Axis] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Small Business Entity Small Business Nonmarketable equity securities Equity Securities without Readily Determinable Fair Value, Amount Content Licensing [Member] Content Licensing [Member] Content Licensing [Member] 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 Equity Component [Domain] Equity Component [Domain] Other Stockholders' Equity, Other Currency translation adjustments, net of deferred taxes of $(17), $(9), $(109) and $(16) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax NBCUniversal Enterprise [Member] NBCUniversal Enterprise [Member] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Investments [Abstract] Investments [Abstract] Statement [Line Items] Statement [Line Items] Deferred gains (losses), net of deferred taxes of $2, $7, $(17) and $17 Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Restricted cash included in other noncurrent assets, net Restricted Cash, Noncurrent Total investments Investments 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. Purchases of investments Payments to Acquire Investments Schedule of recognized share-based compensation expense Share-based Payment Arrangement, Cost by Plan [Table Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Increase to deferred tax liabilities from change in foreign tax rate Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability Entity Address, State or Province Entity Address, State or Province Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Other [Member] Other [Member] Other [Member] Entity [Domain] Entity [Domain] Segment Reporting [Abstract] Segment Reporting [Abstract] Collateralized obligation Collateralized obligation Collateralized Obligation Carrying amount of obligation presented separately as collateralized obligation that is secured by assets. Construction of Universal Beijing Resort Payments For Construction Of Theme Park The cash outflow associated with the construction of a theme park. Number of stock options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Schedule of weighted average common shares outstanding Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Completed, not released Film, Monetized on Its Own, Capitalized Cost, Completed and Not Released Entity Shell Company Entity Shell Company Local Phone Number Local Phone Number Principal amount of term loan outstanding Other Long-term Debt Noncurrent deferred revenue (included in other noncurrent liabilities) Deferred Revenue, Noncurrent Direct To Consumer [Member] Direct To Consumer [Member] Direct To Consumer [Member] Total assets Consolidated variable interest entity's assets included in condensed consolidated balance sheet Assets Investment, Name [Domain] Investment, Name [Domain] Plan Name [Domain] Plan Name [Domain] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Geographical [Domain] Geographical [Domain] Theme Parks [Member] Theme Parks [Member] Theme Parks Member Supplemental Financial Information [Line Items] Supplemental Financial Information [Line Items] Supplemental Financial Information Air Touch [Member] Air Touch [Member] Air Touch [member] Home Entertainment And Other [Member] Home Entertainment And Other [Member] Home Entertainment And Other Product and Service [Domain] Product and Service [Domain] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Management Grant [Member] Management Grant [Member] Management Grant [Member] Depreciation and Amortization Depreciation, Depletion and Amortization, Nonproduction Schedule of receivables, net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] 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 Net income (loss) Net Income (Loss) Attributable to Noncontrolling Interest Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Schedule of cash, cash equivalents and restricted cash ScheduleOfCashCashEquivalentsAndRestrictedCash [Table Text Block] Tabular disclosure of the components of cash, cash equivalents and restricted cash. Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Entity Tax Identification Number Entity Tax Identification Number Geographical [Axis] Geographical [Axis] Weighted average number of common shares outstanding – basic (in shares) Weighted Average Number of Shares Outstanding, Basic Corporate and Other [Member] Corporate and Other [Member] Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Segments [Domain] Segments [Domain] Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Contributions from and distributions to noncontrolling interests Net income (loss) Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Income taxes Income Taxes Paid, Net Cash payments for the redemption of redeemable preferred shares Payments For Repurchase and Redemption of Subsidiary Preferred Stock The cash outflow for repurchase and redemption of subsidiary preferred stock. Document And Entity Information [Line Items] Document And Entity Information [Line Items] [Line Items] for Document And Entity Information [Table] Comprehensive income (loss) attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Proceeds from collateralized obligation Proceeds From Collateralized Obligation The cash inflow from amounts received from the issuance of an obligation that is secured by assets and is presented separately as proceeds from collateralized obligation. Sky Limited [Member] Sky Limited [Member] Sky Limited [Member] Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Treasury stock Treasury Stock, Value Employee benefit obligations and other, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Reclassification Adjustment, Tax Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Reclassification Adjustment, Tax Residential, Video [Member] Residential, Video [Member] Residential, Video [Member] Deferred income taxes Deferred Income Tax Liabilities, Net Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments Lease Arrangements [Axis] Lease Arrangements [Axis] Lease Arrangements Variable Interest Entity, Primary Beneficiary [Member] Variable Interest Entity, Primary Beneficiary [Member] Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current Depreciation and amortization Depreciation, Depletion and Amortization Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Dividends payable Dividends Payable Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Investments Noncurrent investments Long-term Investments Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] 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. Revenues [Abstract] Revenues [Abstract] Distribution [Member] Distribution [Member] Distribution Class B Common Stock [Member] Common Class B [Member] Cash paid for intangible assets Cash Paid for Intangible Assets Payments to Acquire Intangible Assets Consolidated Entities [Domain] Consolidated Entities [Domain] Investments Investment [Text Block] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Schedule of Other Investments [Line Items] Other Investment Not Readily Marketable [Line Items] Reclassification, Type [Axis] Reclassification, Type [Axis] Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Property and equipment, net of accumulated depreciation Property, Plant and Equipment, Net Other noncurrent liabilities Other Liabilities, Noncurrent 5.50% Notes Due 2029 [Member] Notes 5.50 Percent Due 2029 [Member] Notes 5.50% Due 2029 [Member] Potential increased maximum borrowing capacity under the revolving credit facility Line of Credit Facility, Potential Increase To Maximum Borrowing Capacity Line of Credit Facility, Potential Increase To Maximum Borrowing Capacity Residential, Broadband [Member] Residential, Broadband [Member] Residential, Broadband [Member] Unrealized gains (losses) recognized Equity Securities, FV-NI, Unrealized Gain (Loss) Document Quarterly Report Document Quarterly Report Deferred gains (losses) on cash flow hedges AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax Revenue Revenues Film and television content: Film And Television Content [Abstract] Film And Television Content Residential, Wireless [Member] Residential, Wireless [Member] Residential, Wireless [Member] Line of Credit Facility [Table] Line of Credit Facility [Table] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Costs and Expenses: Costs and Expenses [Abstract] Deferred gains (losses) on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Total carrying value of debt Debt and Lease Obligation Schedule of Goodwill [Table] Schedule of Goodwill [Table] Recognized share-based compensation expense Share-based Payment Arrangement, Expense Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Europe [Member] Europe [Member] Film and television costs Film, Monetized On Its Own, And Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Capitalized Costs, Noncurrent Amount of capitalized film cost for film predominantly monetized on its own and capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances, noncurrent. Document Fiscal Period Focus Document Fiscal Period Focus Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Receivables, gross Accounts Receivable, before Allowance for Credit Loss, Current Current portion of long-term debt Debt, Current Restricted cash included in other current assets Restricted Cash, Current Class A Common Stock [Member] Common Class A [Member] Cash, cash equivalents and restricted cash, beginning of period Cash, cash equivalents and restricted cash, end of period Cash, cash equivalents and restricted cash, end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash payments received upon redemption of preferred stock Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities United States [Member] UNITED STATES Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Current Assets: Assets, Current [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Other Proceeds from (Payments for) Other Financing Activities 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. Cash flow hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Entity Central Index Key Entity Central Index Key London Interbank Offered Rate (LIBOR) [Member] London Interbank Offered Rate (LIBOR) [Member] Deferred revenue Deferred Revenue, Current Security Exchange Name Security Exchange Name Weighted-average number of common shares outstanding – diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Current Fiscal Year End Date Current Fiscal Year End Date Spread on variable rate Debt Instrument, Basis Spread on Variable Rate Business Services [Member] Business Services [Member] Business Services [Member] Equity and Share-Based Compensation Stockholders' Equity Note Disclosure [Text Block] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Content [Member] Content [Member] Content [Member] Credit Facility [Axis] Credit Facility [Axis] Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Reconciliation of Adjusted EBITDA from Segments to Consolidated Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Employee stock purchase plans Stock Issued During Period, Value, Employee Stock Purchase Plan Property and equipment - accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Total current liabilities Liabilities, Current Employee Stock Purchase Plans [Member] Employee Stock [Member] Class of Stock [Domain] Class of Stock [Domain] Eliminations [Member] Intersegment Eliminations [Member] Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Capitalized Film and Television Costs and Programming Rights Schedule Of Capitalized Film And Television Costs [Table Text Block] Schedule of capitalized costs for film predominantly monetized on its own and for rights acquired by broadcaster under license agreement for program material, including sports rights advances, recorded at the balance sheet date. Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Ownership [Domain] Ownership [Domain] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Cable Communications [Member] Cable Communications [Member] Cable Communications Member 0.250% Notes Due 2027 [Member] Notes 0.250 percent Due 2027 [Member] Notes 0.250% Due 2027 [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Title of 12(b) Security Title of 12(b) Security Other current assets Other Assets, Current Statement [Table] Statement [Table] Unrecognized pretax compensation expense on nonvested awards Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Cover [Abstract] Cover [Abstract] Goodwill Balance, beginning of period Balance, end of period Goodwill Advertising [Member] Advertising [Member] Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Schedule of Goodwill Schedule of Goodwill [Table Text Block] 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] Noncurrent receivables, net (included in other noncurrent assets, net) Accounts Receivable, after Allowance for Credit Loss, Noncurrent Owned: Film, Capitalized Cost [Abstract] Commitments And Contingencies [Line Items] Commitment And Contingencies [Line Items] [Line Items] for Commitment And Contingencies [Table] Deferred income taxes Deferred Income Tax Expense (Benefit)