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 Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Number of stock options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Treasury Stock at Cost [Member] Treasury Stock [Member] Accounts payable and accrued expenses related to trade creditors Increase (Decrease) in Accounts Payable and Accrued Liabilities Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] 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] Segments [Axis] Segments [Axis] Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] 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. Completed, not released Direct-to-television Film Costs, Completed and Not Released Liabilities and Equity Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Cable Networks [Member] Cable Networks [Member] Cable Networks Member Deferred income taxes Deferred Income Tax Liabilities, Net Current Fiscal Year End Date Current Fiscal Year End Date Number of series of preferred stock Number of Preferred Stock Series Number of Preferred Stock Series Deferred revenue Deferred Revenue, Current Proceeds from borrowings Proceeds from Issuance of Long-term Debt Operating income Operating Income (Loss) Entity Address, Postal Zip Code Entity Address, Postal Zip Code 1.250% Notes Due 2040 [Member] Notes 1.250 percent due 2040 [Member] Notes 1.250% due 2040 [Member] Total current liabilities Liabilities, Current 1.500% Notes Due 2029 [Member] Notes 1.500 percent Due 2029 [Member] Notes 1.500% Due 2029 [Member] 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. 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. 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. Other investments Other Investments Commitments and contingencies (Note 12) Commitments and Contingencies Assets Assets [Abstract] Repurchases of common stock under employee plans Payments for Repurchase of Common Stock Investment, Name [Axis] Investment, Name [Axis] Accounting Policies [Abstract] Accounting Policies [Abstract] Programming and Production Costs Entertainment [Text Block] Entity Shell Company Entity Shell Company Cover [Abstract] Cover [Abstract] Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current Document Type Document Type Retained earnings Retained Earnings (Accumulated Deficit) Deferred gains (losses) on cash flow hedges, net of deferred taxes of $6, $(35), $23 and $(24) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Remaining three months of 2020 Film, Monetized On Its Own, Completed And Not Released, Expected Amortization In Remainder Of Fiscal Year Amount of amortization for completed and not released film predominantly monetized on its own and expected to be recognized for the remainder of fiscal year following latest fiscal year Class B Common Stock [Member] Common Class B [Member] Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Other Temporary Equity, Other Changes Unrecognized pretax compensation expense on nonvested awards Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Long-term debt, less current portion Long-term Debt and Lease Obligation New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] 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] Preferred stock—authorized, 20,000,000 shares; issued, zero Preferred Stock, Value, Issued Cash capital contributions for equity method investments Payments to Acquire Equity Method Investments Document Quarterly Report Document Quarterly Report FCC Licenses [Member] Operating and Broadcast Rights [Member] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Other noncurrent liabilities Other Liabilities, Noncurrent Other Payments for (Proceeds from) Other Investing Activities Total film and 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. Released, less amortization Film, Monetized on Its Own, Capitalized Cost, Released Stock compensation plans APIC, Share-based Payment Arrangement, Increase for Cost Recognition Advertising, marketing and promotion Marketing and Advertising Expense Supplemental Financial Information [Abstract] Supplemental Financial Information [Abstract] Statement Of Cash Flows Supplemental Information Abstract 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 Entity File Number Entity File Number Geographical [Domain] Geographical [Domain] Dividends payable (in dollars per share) Dividends Payable, Amount Per Share 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. Statement [Line Items] Statement [Line Items] Class of Stock [Domain] Class of Stock [Domain] Document Fiscal Period Focus Document Fiscal Period Focus Atairos [Member] Atairos [Member] Atairos [Member] Statement [Table] Statement [Table] Total film and television costs and programming rights 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. Amounts reclassified to net income: Amounts Reclassified To Net Income [Abstract] Completed, not released Theatrical Film Costs And Direct-To-Television Costs, Completed And Not Released Theatrical Film Costs And Direct-To-Television Costs, Completed And Not Released Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued 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. 2022 Entertainment, License Agreement For Program Material, Including Sports Rights Advances,Expected Amortization, Year Three Amount of amortization for right acquired by broadcaster under license agreement for program material, including sports rights advances, expected to be recognized within third operating cycle following most recent annual statement of financial position. Business Combinations [Abstract] Business Combinations [Abstract] Advertising [Member] Advertising [Member] Film and Television Costs Owned Film and Television Costs Film, Capitalized Cost [Abstract] Residential, Voice [Member] Residential, Voice [Member] Residential, Voice [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Long-Term Debt Debt Disclosure [Text Block] Other balance sheet accounts Schedule Of Other Balance Sheet Accounts [Table Text Block] Schedule Of Other Balance Sheet Accounts [Table Text Block] Film and television costs, net Film And Television Costs Net Amount of net increase (decrease) in film and television costs. Computation of diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] 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. Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Amendment Flag Amendment Flag Employee benefit obligations, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Deferred gains (losses) on cash flow hedges AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax 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 Realized (gains) losses on cash flow hedges, net of deferred taxes of $8, $11, $29 and $7 Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax In production and in development Theatrical Film Costs And Direct-to-Television Costs, In Production And In Development Theatrical Film Costs And Direct-to-Television Costs, In Production And In Development Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Television Costs Direct-to-television Film Costs [Abstract] Software [Member] Computer Software, Intangible Asset [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Geographical [Axis] Geographical [Axis] Local Phone Number Local Phone Number Recognition of previously deferred gain Deferred Gain Recognized On Dilution Of Equity Method Investment Deferred Gain Recognized On Dilution Of Equity Method Investment Segments [Domain] Segments [Domain] Other operating and administrative Other Operating And Administrative Other operating and administrative expense recognized in the period not presented separately. Completed, not released Theatrical Film Costs, Completed and Not Released Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Employee stock purchase plans [Member] Employee Stock [Member] Less: Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Indefinite-lived Intangible Assets [Line Items] Indefinite-lived Intangible Assets [Line Items] 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] Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Amortization Amortization Amortization of Intangible Assets Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Schedule of Fair Value Method Investments [Table] Entity Current Reporting Status Entity Current Reporting Status Other noncurrent assets, net Other Assets, Noncurrent Plan Name [Axis] Plan Name [Axis] Segment Information Segment Reporting Disclosure [Text Block] Total assets Consolidated variable interest entity's assets included in condensed consolidated balance sheet Assets NBCUniversal Segments [Member] NBCUniversal Segments [Member] Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Table] Realized and unrealized gains (losses) on equity securities, net Equity Securities, FV-NI, Gain (Loss) 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 Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Unrealized gains (losses) on marketable securities, net of deferred taxes of $—, $—, $1 and $— OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Owned film and television costs Film, Monetized on Its Own, Amortization Expense Condensed Consolidated Financial Statements Business Description and Basis of Presentation [Text Block] Entity Small Business Entity Small Business 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. Unrealized gains (losses) on marketable securities, deferred taxes OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Film Costs Theatrical Film Costs [Abstract] Interest expense Interest expense Interest Expense Other Stockholders' Equity, Other Depreciation and amortization Depreciation, Depletion and Amortization Entity Filer Category Entity Filer Category Other Agreements and Rights [Member] Other Intangible Assets [Member] Marketable equity securities, recognized unrealized gains (losses) Equity Securities, FV-NI, Unrealized Gain (Loss) Product and Service [Axis] Product and Service [Axis] Consolidated variable interest entity's liabilities included in condensed consolidated balance sheet Liabilities Entity Address, City or Town Entity Address, City or Town Principal amount of term loan outstanding Other Long-term Debt Other [Member] Other Geographic Locations [Member] Other Geographic Locations [Member] Headquarters and Other [Member] Headquarters And Other [Member] Headquarters And Other [Member] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Total Film Costs Under Previous Guidance [Abstract] Film Costs Under Previous Guidance [Abstract] [Abstract] Document Fiscal Year Focus Document Fiscal Year Focus Noncurrent deferred revenue (included in other noncurrent liabilities) Deferred Revenue, Noncurrent Other operating assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Debt Instrument [Axis] Debt Instrument [Axis] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Operating Segments [Member] Operating Segments [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] 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] Receivables, gross Accounts Receivable, before Allowance for Credit Loss, Current Programming 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. Equity method Equity method investment Equity Method Investments Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Fair value of collateralized obligation Collateralized Obligation, Fair Value Fair value of obligation presented separately as collateralized obligation that is secured by assets. Estimated Future Amortization Expense for Capitalized Film and Television Costs and Programming Rights Schedule Of Estimated Future Amortization Expense For Capitalized Film And Television Cost [Table Text Block] Schedule of estimated future amortization 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. Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Common stock, shares authorized (in shares) Common Stock, Shares Authorized Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Hulu [Member] Hulu [Member] Hulu member. Assumed exercise or issuance of shares relating to stock plans (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Released, less amortization Direct-to-television Film Costs, Released Financial Data by Business Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Document Period End Date Document Period End Date Entity Registrant Name Entity Registrant Name Income Statement [Abstract] Income Statement [Abstract] Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Less: Net income (loss) attributable to noncontrolling interests and redeemable subsidiary preferred stock 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. 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Four Employee benefit obligations, net of deferred taxes of $2, $3, $7 and $8 Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Variable Interest Entity, Primary Beneficiary [Member] Variable Interest Entity, Primary Beneficiary [Member] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Current Assets: Assets, Current [Abstract] Franchise Rights [Member] Franchise Rights [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Comprehensive income (loss) attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Programming rights, less amortization Programming Rights Less Amortization The carrying amount of total acquired programming rights, less amortization Contract acquisition and fulfillment costs (included in other noncurrent assets, net) Capitalized Contract Cost, Net Counterparty Name [Domain] Counterparty Name [Domain] Capital expenditures Capital Expenditures Payments to Acquire Property, Plant, and Equipment Consolidation Items [Domain] Consolidation Items [Domain] Programming rights, less amortization 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. Entity Tax Identification Number Entity Tax Identification Number Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Completed, not released: Film, Disclosures [Abstract] Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments Other intangible assets, net of accumulated amortization of $18,405 and $17,217 Other Intangible Assets, Net Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Adjusted EBITDA Adjusted EBITDA The measure used to evaluate the profitability of operating segments. Trading Symbol Trading Symbol Distribution And Other [Member] Distribution And Other [Member] Distribution And Other [Member] Schedule of Other Investments [Line Items] Schedule of Held-to-maturity Securities [Line Items] Snap [Member] Snap [Member] Snap [Member] Remaining three months of 2020 Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Expected Amortization, Remainder Of Fiscal Year Entertainment, license agreement for program material, including sports rights advances, expected amortization to be recognized in the remainder of fiscal year following latest fiscal year Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Schedule of recognized share-based compensation expense Share-based Payment Arrangement, Cost by Plan [Table Text Block] Cash payments received upon redemption of preferred stock Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Share-based compensation Share-based Payment Arrangement, Noncash Expense Proceeds from (repayments of) short-term borrowings, net Proceeds from (Repayments of) Short-term Debt Legal Entity [Axis] Legal Entity [Axis] Marketable equity securities Equity Securities, FV-NI Other Proceeds from (Payments for) Other Financing Activities Intangible Assets, Net (Excluding Goodwill) [Abstract] Intangible Assets, Net (Excluding Goodwill) [Abstract] Less: Other comprehensive income (loss) attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Entity [Domain] Entity [Domain] Intangible Assets Intangible Assets Disclosure [Text Block] 0.750% Notes Due 2032 [Member] Notes 0.750 percent due 2032 [Member] Notes 0.750% due 2032 [Member] Investment Summary Summary Investment Holdings [Table Text Block] Total investments Investments Residential, High-Speed Internet [Member] Residential, High-Speed Internet [Member] Residential, High-Speed Internet [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 Total carrying value of debt Debt and Lease Obligation City Area Code City Area Code Customer Relationships [Member] Customer Relationships [Member] Total costs and expenses Costs and Expenses Equity Components [Axis] Equity Components [Axis] Title of 12(b) Security Title of 12(b) Security Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Released and programming rights: Film, Monetized on Its Own, Released Film, Expected Amortization [Abstract] Consolidated Entities [Domain] Consolidated Entities [Domain] Europe [Member] Europe [Member] Schedule of cash payments for interest and income taxes Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Net income (loss) Net Income (Loss) Attributable to Noncontrolling Interest Broadcast Television [Member] Broadcast Television [Member] Broadcast Television Member United States [Member] UNITED STATES Revenues [Abstract] Revenues [Abstract] 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. Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Filmed Entertainment [Member] Filmed Entertainment [Member] Filmed Entertainment Member Remaining three months of 2020 Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year Theatrical [Member] Theatrical [Member] Theatrical [Member] Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Commitments And Contingencies [Table] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Cumulative translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Eliminations [Member] Intersegment Eliminations [Member] Other income (loss), net Other Income Loss Net Nonoperating income (losses), net recorded in the income statement that are not separately stated. 2022 Film, Monetized on Its Own, Released Film, Expected Amortization, Year Three Reconciliation of Adjusted EBITDA from Segments to Consolidated Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Total Intangible Assets, Gross (Excluding Goodwill) Number of reportable segments Number of Reportable Segments Released, less amortization Theatrical Film Costs, Released Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] 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. Consolidation Items [Axis] Consolidation Items [Axis] Investments [Abstract] Investments [Abstract] Receivables, net Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current Unrecognized gains (losses) on employee benefit obligations Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Ownership percentage in variable interest entity Noncontrolling Interest, Ownership Percentage by Parent Content Licensing [Member] Content Licensing [Member] Content Licensing [Member] Depreciation and Amortization Depreciation, Depletion and Amortization, Nonproduction Unrealized gains (losses) on marketable securities AOCI, Debt Securities, Available-for-sale, Adjustment, after Tax Accounting Standards Update [Axis] Accounting Standards Update [Axis] Restricted cash included in other noncurrent assets, net Restricted Cash, Noncurrent NBCUniversal Enterprise [Member] NBCUniversal Enterprise [Member] Goodwill Goodwill Redeemable subsidiary preferred shares Carrying Amount Of Redeemable Preferred Stock Carrying amount of redeemable preferred stock 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. Programming Rights Entertainment, License Agreement for Program Material [Abstract] Programming rights Less: Current portion of programming rights Programming Rights, Current The current portion of acquired television and cable networks programming rights recorded on the balance sheet. Includes multi-year programming arrangements, acquired movies, series and other programs. Carrying amount is stated at the lower of cost, less accumulated amortization, or net realizable value at the balance sheet date. Repurchases of common stock under employee plans Stock Repurchased and Retired During Period, Value Cash dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Marketable equity securities, recognized realized gains (losses) Equity Securities, FV-NI, Realized Gain (Loss) Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Other current assets Other Assets, Current Summary of Intangible Assets Schedule Of Finite-Lived And Indefinite-Lived Intangible Assets [Table Text Block] Schedule Of Finite-Lived And Indefinite-Lived Intangible Assets [Table Text Block] Peloton [Member] Peloton [Member] Peloton Released and programming rights: Entertainment, License Agreement for Program Material, Expected Amortization [Abstract] Other [Member] Other [Member] Other [Member] Entity Central Index Key Entity Central Index Key Accounting Standards Update 2016-13 [Member] Accounting Standards Update 2016-13 [Member] Collateralized obligation Collateralized obligation Collateralized Obligation Carrying amount of obligation presented separately as collateralized obligation that is secured by assets. Entity Emerging Growth Company Entity Emerging Growth Company Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Recent Accounting Pronouncements Accounting Standards Update and Change in Accounting Principle [Text Block] Amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Diluted EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Diluted Construction of Universal Beijing Resort Payments For Construction Of Theme Park The cash outflow associated with the construction of a theme park. Completed, not released Film, Monetized on Its Own, Capitalized Cost, Completed and Not Released Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-Lived Intangible Assets [Table] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Direct To Consumer [Member] Direct To Consumer [Member] Direct To Consumer [Member] Film Costs and Entertainment Entities Film Costs And Entertainment Entities, Policy [Policy Text Block] Disclosure of accounting policy for film costs related to film libraries and for entertainment entities. 2021 Film, Monetized on Its Own, Released Film, Expected Amortization, Year Two Held to maturity investment Debt Securities, Held-to-maturity, Current Amortization of Film and Television Costs Amortization Of Film And TV Costs [Table Text Block] Total amount of amortization expense for both capitalized cost of owned film and television costs and for rights acquired by broadcaster under license agreement for program material, including sports rights advances, recorded in programming and production costs Theme Parks [Member] Theme Parks [Member] Theme Parks Member Investment Holdings [Table] Investment Holdings [Table] Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities AirTouch [Member] Air Touch [Member] Air Touch [Member] Air Touch [member] Recognized share-based compensation expense Share-based Payment Arrangement, Expense Released, less amortization Theatrical Film Costs And Direct-To-Television Costs, Released Theatrical Film Costs And Direct-To-Television Costs, Released Management Grant [Member] Management Grant [Member] Management Grant [Member] Employee stock purchase plans Stock Issued During Period, Value, Employee Stock Purchase Plan Counterparty Name [Axis] Counterparty Name [Axis] Common stock Common Stock, Value, Issued Investments Noncurrent investments Long-term Investments 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 Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] 2022 Finite-Lived Intangible Asset, Expected Amortization, Year Two Restricted cash included in other current assets Restricted Cash, Current Schedule of receivables, net Schedule of Accounts, Notes, Loans and Financing Receivable [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. Current portion of long-term debt Debt, Current 2021 Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Expected Amortization, Year Two Amount of amortization for right acquired by broadcaster under license agreement for program material, including sports rights advances, expected to be recognized within second operating cycle following most recent annual statement of financial position. Total Film, Capitalized Cost Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest 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 Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Contributions from and distributions to noncontrolling interests Common stock, shares issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] 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] Segment Reporting [Abstract] Segment Reporting [Abstract] 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] Residential, Video [Member] Residential, Video [Member] Residential, Video [Member] Total Comcast Corporation shareholders’ equity Stockholders' Equity Attributable to Parent Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Total liabilities and equity Liabilities and Equity Accumulated other comprehensive income (loss) Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Cash paid for intangible assets Cash Paid for Intangible Assets Payments to Acquire Intangible Assets Restricted share units [Member] Restricted Stock Units (RSUs) [Member] Entertainment Entities Entertainment Entities, Policy [Policy Text Block] Accounting Standards Update [Domain] Accounting Standards Update [Domain] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Weighted-Average Original Useful Life Finite-Lived Intangible Asset, Useful Life Equity Component [Domain] Equity Component [Domain] Dividends paid Payments of Dividends 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. Entity Address, Address Line One Entity Address, Address Line One Property and equipment, net of accumulated depreciation of $53,959 and $53,239 Property, Plant and Equipment, Net 2023 Finite-Lived Intangible Asset, Expected Amortization, Year Three Distribution [Member] Distribution [Member] Distribution Net income attributable to Comcast Corporation Net income (loss) Net Income Attributable to Comcast Corporation Net Income (Loss) Attributable to Parent Entity Address, State or Province Entity Address, State or Province Film and television costs 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. Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Franchise rights Indefinite-Lived Franchise Rights Investment, Name [Domain] Investment, Name [Domain] Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Trade Names [Member] Trade Names [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Universal Beijing Resort [Member] Programming rights Less: Current portion of programming rights Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Capitalized Cost, Current Amount of capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances, current. Total current assets Assets, Current Corporate and Other [Member] Corporate and Other [Member] Earnings Per Share [Abstract] Earnings Per Share [Abstract] 5.50% Notes Due 2029 [Member] Notes 5.50 Percent Due 2029 [Member] Notes 5.50% Due 2029 [Member] Entity Interactive Data Current Entity Interactive Data Current Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Adjustment for potential legal settlement Gain (Loss) Related to Litigation Settlement Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Residential, Wireless [Member] Residential, Wireless [Member] Residential, Wireless [Member] Cash Payments for Interest and Income Taxes Supplemental Cash Flow Information [Abstract] Film and Television Costs Film Costs, Policy [Policy Text Block] Common Stock [Member] Common Stock [Member] Product and Service [Domain] Product and Service [Domain] Net income (loss) Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Film and television costs 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. Film and Television Costs Film, Monetized on Its Own, Capitalized Cost Gross Carrying Amount Finite-Lived Intangible Assets, Gross Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Currency translation adjustments, deferred taxes Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Property and equipment - accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Class A Common Stock [Member] Common Class A [Member] Home Entertainment [Member] Home Entertainment [Member] Home Entertainment [Member] Film Costs Theatrical Film Costs 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 Investment and other income (loss), net Investment and other income (loss), net Nonoperating Income (Expense) Investment and Other Income (Loss), Net Components Of Investment And Other Income (Loss), Net [Table Text Block] Tabular disclosure of investment and other income (loss), net, including, but not limited to, equity in net income (losses) of investees, net, realized and unrealized gains (losses) on equity securities, net, and other income (loss), net. Schedule of Marketable Equity Securities [Line Items] Schedule of Fair Value Method Investments [Line Items] [Line Items] for Schedule of Fair Value Method Investments [Table] Stock options [Member] Share-based Payment Arrangement, Option [Member] Television Costs Direct-to-television Film Costs Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Basic EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Basic Costs and Expenses: Costs and Expenses [Abstract] Ownership [Axis] Ownership [Axis] Content Licensing And Other [Member] Content Licensing And Other [Member] Content Licensing And Other [Member] Treasury stock (in shares) Treasury Stock, Shares Currency translation adjustments, net of deferred taxes of $40, $(80), $24 and $(98) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Ownership [Domain] Ownership [Domain] Plan Name [Domain] Plan Name [Domain] Dividends payable Dividends Payable Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Ownership percentage Equity Method Investment, Ownership Percentage Revenue Revenue from Contract with Customer [Text Block] Business Services [Member] Business Services [Member] Business Services [Member] Nonmarketable equity securities Equity Securities without Readily Determinable Fair Value, Amount Total equity Beginning balance Ending balance Cumulative effects of adoption of accounting standards Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Additional paid-in capital Additional Paid in Capital 2021 Finite-Lived Intangible Asset, Expected Amortization, Year One Total fair value of debt Long-term Debt, Fair Value Revenue Revenues Class of Stock [Axis] Class of Stock [Axis] Income tax expense Income Tax Expense (Benefit) Income taxes Income Taxes Paid, Net 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 Content [Member] Content [Member] Content [Member] Accounting Standards Update and Change in Accounting Principle [Table] Accounting Standards Update and Change in Accounting Principle [Table] Deferred gains (losses) on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Accrued expenses and other current liabilities Accrued Liabilities, Current Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Other Industries [Abstract] Other Industries [Abstract] Noncurrent receivables, net (included in other noncurrent assets, net) Accounts Receivable, after Allowance for Credit Loss, Noncurrent Remaining three months of 2020 Film, Monetized On Its Own, Released, Expected Amortization, Remainder Of Fiscal Year Amount of amortization for released film predominantly monetized on its own and expected to be recognized in the remainder of fiscal year following latest fiscal year Depreciation Depreciation Depreciation 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. Gross Carrying Amount Indefinite-lived Intangible Assets (Excluding Goodwill) Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Deferred income taxes Deferred Income Tax Expense (Benefit) Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Cable Communications [Member] Cable Communications [Member] Cable Communications Member Award Type [Axis] Award Type [Axis] 0.250% Notes Due 2027 [Member] Notes 0.250 percent Due 2027 [Member] Notes 0.250% Due 2027 [Member] Other intangible assets - accumulated amortization Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Security Exchange Name Security Exchange Name Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Financial Data by Business Segment Segment Reporting Information, Profit (Loss) [Abstract] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Repurchases and repayments of debt Repayments of Other Debt Dividends declared Dividends, Common Stock, Cash Retained Earnings [Member] Retained Earnings [Member] Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Purchases of investments Payments to Acquire Investments Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Payment Arrangement, Noncash Expense [Abstract] Share-based Payment Arrangement, Noncash Expense [Abstract] Award Type [Domain] Award Type [Domain] Document Transition Report Document Transition Report AT&T, Inc. [Member] AT&T, Inc. [Member] AT&T, Inc. [Member] Redeemable Subsidiary Preferred Stock [Member] Redeemable Preferred Stock [Member] Treasury stock, 872,791,028 Class A common shares Treasury Stock, Value Earnings Per Share Earnings Per Share [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Redeemable noncontrolling interests Beginning balance Ending balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Current Liabilities: Liabilities, Current [Abstract] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Commitments And Contingencies [Line Items] Commitment And Contingencies [Line Items] [Line Items] for Commitment And Contingencies [Table] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] 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. Less: Current investments Short-term Investments