Statement of Financial Position [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] Class B Common Stock [Member] Common Class B [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] NBCUniversal Media LLC [Member] Statement [Line Items] Statement [Line Items] 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 Debt Disclosure [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Letter of Credit [Member] Letter of Credit [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] NBCUniversal Enterprise Credit Facility [Member] NBCUniversal Enterprise Credit Facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Amounts available under revolving credit facilities Line of Credit Facility, Remaining Borrowing Capacity 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] Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-Term Debt Debt Disclosure [Text Block] Share-based Compensation [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] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Schedule of recognized share-based compensation expense Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Receivables, gross Accounts Receivable, Gross, Current Less: Allowance for returns and customer incentives Returns And Incentives Allowance, Current A valuation allowance for sales returns and other incentives. Less: Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Receivables, net Accounts Receivable, Net, Current 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] Equity Award [Domain] Equity Award [Domain] Restricted Share Units [Member] Restricted Stock Units (RSUs) [Member] Stock Options [Member] Employee Stock Option [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 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 Unrecognized pretax compensation expense on nonvested awards Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Condensed Financial Information of Parent Company Only 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] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Reportable Legal Entities [Member] Reportable Legal Entities [Member] Elimination and Consolidation Adjustments [Member] Consolidation, Eliminations [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Net Cash Provided by (Used in) Operating Activities [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Net transactions with affiliates Net transactions with affiliates Net transactions with affiliates. Capital expenditures Payments to Acquire Property, Plant, and Equipment Cash paid for intangible assets Payments to Acquire Intangible Assets Acquisitions and construction of real estate properties Payments For Acquisitions And Construction Of Real Estate Properties The cash outflow for the acquisition and construction of buildings (properties) whether for investment or use. Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from sales of 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 Proceeds from Issuance of Long-term Debt Repurchases and repayments of debt Repayments of Other Debt Repurchases of common stock under repurchase program and employee plans Payments for Repurchase of Common Stock Dividends paid Payments of Dividends Purchase of Universal Studios Japan noncontrolling interests Payments to Acquire Additional Interest in Subsidiaries Issuances of common stock Proceeds from Issuance of Common Stock Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock Distributions To Noncontrolling Interests And Dividends For Redeemable Subsidiary Preferred Stock The cash outflow related to distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock. Other Proceeds from (Payments for) Other Financing Activities Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents, end of period 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 Fair Value Method Investments [Line Items] Schedule of Fair Value Method Investments [Line Items] [Line Items] for Schedule of Fair Value Method Investments [Table] Payments to acquire available-for-sale securities Payments to Acquire Available-for-sale Securities Contributed investment from Comcast Member Contribution Contribution of a business from member Capital expenditures incurred but not yet paid Capital Expenditures Incurred but Not yet Paid Dividends payable Dividends Payable Dividends payable (in dollars per share) Dividends Payable, Amount Per Share Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] DreamWorks Animation [Member] DreamWorks Animation [Member] Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Axis] Cash Consideration Transferred By Comcast [Domain] Cash Consideration Transferred By Comcast [Domain] [Domain] for Cash Consideration Transferred By Comcast [Axis] Consideration Transferred By Comcast [Member] Consideration Transferred By Comcast [Member] Consideration Transferred By Comcast [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Cash consideration transferred Business Combination, Consideration Transferred Business acquisition, price paid per share (in dollars per share) Business Acquisition, Share Price Statement of Comprehensive Income [Abstract] Unrealized gains (losses) on marketable securities, deferred taxes Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Deferred gains (losses) on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Realized (gains) losses on marketable securities, deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Employee benefit obligations, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Currency translation adjustments, deferred taxes Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Commercial Paper [Member] Commercial Paper [Member] NBCUniversal Enterprise Commercial Paper [Member] NBCUniversal Enterprise Commercial Paper [Member] Short-term Debt [Line Items] Short-term Debt [Line Items] Maximum borrowing under commercial paper programs Line of Credit Facility, Maximum Borrowing Capacity Commercial paper outstanding Commercial Paper Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Carrying Value Of Related Party Contractual Obligation [Member] Carrying Value Of Related Party Contractual Obligation [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Other noncurrent liabilities Other Liabilities, Noncurrent Commitments and Contingencies Disclosure [Abstract] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Commitment And Contingencies [Table] Redeemable Preferred Stock [Member] Redeemable Preferred Stock [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Pending Litigation [Member] Pending Litigation [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Sprint Communications Company L.P. Lawsuit [Member] Sprint Communications Company L.P. Lawsuit [Member] Sprint Communications Company L.P. Lawsuit [Member] Commitment And Contingencies [Line Items] Commitment And Contingencies [Line Items] [Line Items] for Commitment And Contingencies [Table] 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. Damages sought Loss Contingency, Damages Sought, Value Earnings Per Share [Abstract] Net income attributable to parent Net Income (Loss) Attributable to Parent Basic EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Basic Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Assumed exercise or issuance of shares relating to stock plans (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted EPS attributable to Comcast Corporation shareholders (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Document and Entity Information [Abstract] DocumentAndEntityInformationAbstract Document And Entity Information [Table] Document And Entity Information [Table] Document And Entity Information [Table] Comcast Corp Comcast Corporation [Member] Comcast Corporation [Member] Document And Entity Information [Line Items] Document And Entity Information [Line Items] [Line Items] for Document And Entity Information [Table] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Trading Symbol Trading Symbol Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Employee Stock Purchase Plans [Member] Employee Stock [Member] Recognized share-based compensation expense Allocated Share-based Compensation Expense Equity And Cost Method Investments [Table] Equity And Cost Method Investments [Table] Equity And Cost Method Investments [Table] Fair Value, Equity And Cost Method Investments [Line Items] Fair Value, Equity And Cost Method Investments [Line Items] [Line Items] for Fair Value, Equity And Cost Method Investments [Table] Investment Summary Summary Investment Holdings [Table Text Block] Investment Income (Loss), Net Components Of Investment Income Loss Net [Table Text Block] Tabular disclosure of investment income (loss), including, but not limited to gains on sales and exchanges of investments, other than temporary impairment losses and interest and dividend income. Income Statement [Abstract] Revenue Revenues Costs and Expenses: Costs and Expenses [Abstract] Programming and production Programming And Production Costs The amount of expense recognized in the period for costs associated with video programming and content acquisition and production costs. Programming expenses include the fees paid to license the programming distributed to video customers, such as the programming license fees charged by cable networks and fees charged for retransmission of the signals from local broadcast television stations. Production costs include the amortization of owned and acquired programming, sports rights, direct production costs, residual and participation payments, production overhead, costs associated with the distribution of programming to third-party networks and other distribution platforms, and on-air talent costs. It also includes the amortization of capitalized theatrical film production and acquisition costs and distribution expenses. Other operating and administrative Other Operating And Administrative Other operating and administrative expense recognized in the period not presented separately. Advertising, marketing and promotion Marketing and Advertising Expense Depreciation Depreciation Amortization Amortization of Intangible Assets Total costs and expenses Costs and Expenses Operating income Operating Income (Loss) Other Income (Expense): Nonoperating Income (Expense) [Abstract] Interest expense Interest Expense Investment income (loss), net Investment Income, Nonoperating Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments Other income (expense), net Other Nonoperating Income (Expense) Total other income (expense) Nonoperating Income (Expense) Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net (income) loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest 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 Basic 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) Dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Universal Studios Japan Term Loan Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Universal Studios Japan Term Loan Maturing March 2022 [Member] Former Universal Studios Japan Term Loans [Member] Former Universal Studios Japan Term Loans [Member] Former Universal Studios Japan Term Loans [Member] Total debt Debt and Capital Lease Obligations Fair value of debt Long-term Debt, Fair Value Debt face amount Debt Instrument, Face Amount Repayments of debt Repayments of Debt Assets Assets [Abstract] Cash and cash equivalents Receivables, net 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. 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 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 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 Other noncurrent assets, net Other Assets, Noncurrent Total assets Assets Liabilities and Equity Liabilities and Equity [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. Accrued expenses and other current liabilities Accrued Expenses And Other Current Liabilities Including Deferred Revenue Accrued Expenses And Other Current Liabilities Including Deferred Revenue Current portion of long-term debt Debt, Current Total current liabilities Liabilities, Current Long-term debt, less current portion Long-term Debt and Capital Lease Obligations Deferred income taxes Deferred Income Tax Liabilities, Net Redeemable noncontrolling interests Redeemable Noncontrolling Interest, Equity, Carrying Amount Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock Common Stock, Value, Issued Other shareholders’ equity Other stockholders equity Other stockholders equity. Total Comcast Corporation shareholders’ equity Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Comcast And Consolidated Subsidiaries [Member] Comcast And Consolidated Subsidiaries [Member] Accrued expenses and other current liabilities Accrued Liabilities, Current Note payable to Comcast Note Payable To 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. Tax Receivable Agreement [Axis] Tax Receivable Agreement [Axis] Tax Receivable Agreement Tax receivable agreement [Domain] Tax receivable agreement [Domain] Tax receivable agreement [Domain] Tax Receivable Agreement [Member] Tax Receivable Agreement [Member] Tax Receivable Agreement [Member] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Axis] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Axis] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Axis] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Domain] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Domain] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Domain] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member] Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member] Allocation of Purchase Price Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract] Film and television costs Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Film and Television Costs Amount of film and television costs acquired at the acquisition date. Intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill Working capital Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital The amount of working capital (current assets less current liabilities, including cash if any) acquired as of the acquisition date. Debt Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Tax receivable agreement Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Tax Receivable Agreement Amount of liability for a tax receivable agreement acquired at the acquisition date. Deferred income taxes Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Other noncurrent assets and liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets and Liabilities The amount of acquisition cost of a business combination allocated to other noncurrent assets and liabilities of the acquired entity not otherwise disclosed separately. Identifiable net assets (liabilities) acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Noncontrolling interests Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value Cash consideration transferred by Comcast Contribution from member Revenue: Revenues [Abstract] Service revenue Sales Revenue, Services, Net Management fee revenue Management Fees Revenue Revenue Comprehensive income (loss) attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Statement of Stockholders' Equity [Abstract] 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] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Beginning balance Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest Stock compensation plans Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Repurchases of common stock under repurchase program and employee plans Stock Repurchased and Retired During Period, Value Employee stock purchase plans Stock Issued During Period, Value, Employee Stock Purchase Plan Dividends declared 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 Purchase of Universal Studios Japan noncontrolling interests Noncontrolling Interest, Decrease from Redemptions or Purchase of 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 Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Beginning balance Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Attributable To Temporary Equity Contributions from and (distributions to) noncontrolling interests attributable to temporary equity. Other Temporary Equity, Other Changes Net income (loss) Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Ending balance Organization, Consolidation and Presentation of Financial Statements [Abstract] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] Business And Basis Of Presentation [Table] 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] 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 Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Deferred gains (losses) on cash flow hedges Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Unrecognized gains (losses) on employee benefit obligations Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Cumulative translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Earnings Per Share Earnings Per Share [Text Block] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Atairos [Member] Atairos [Member] Atairos [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] Purchases of investments Capital Contribution To VIE The cash outflow associated with a capital contribution to a VIE accounted for as an equity method investment Equity in net income (losses) of investees Pretax gain on sale of investment Pretax Gain On Sale Of Investment Pretax gain recognized as a result of the sale of The Weather Channel's product and technology business to IBM Operating costs and expenses Other income (expense) Other Income (Expense) Related Party Represents all of the intercompany transactions with Comcast Corporation which are included in other income (expense) captions. Floating Rate Notes Due 2021 [Member] Floating Rate Notes Due 2021 [Member] Floating Rate Notes Due 2021 [Member] Senior 4.45% Notes Due 2047 [Member] Senior 4.45% Notes Due 2047 [Member] Senior 4.45% Notes Due 2047 [Member] Senior 3.0% Notes Due 2024 [Member] Senior 3.0% Notes Due 2024 [Member] Senior 3.0% Notes Due 2024 [Member] Senior 3.3% Notes Due 2027 [Member] Senior 3.3% Notes Due 2027 [Member] Senior 3.3% Notes Due 2027 [Member] Interest rate Debt Instrument, Interest Rate, Stated Percentage Stock split, conversion ratio Stockholders' Equity Note, Stock Split, Conversion Ratio Related Party Transactions Condensed Financial Statements Schedule of Related Party Transactions [Table Text Block] Accounting Changes and Error Corrections [Abstract] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements [Line Items] Recent Accounting Pronouncements [Line Items] [Line Items] for Recent Accounting Pronouncements [Table] Recent Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Schedule of Cost-method Investments [Table] Schedule of Cost-method Investments [Table] AirTouch [Member] Air Touch [Member] Air Touch [Member] AirTouch [Member] Schedule of Cost-method Investments [Line Items] Schedule of Cost-method Investments [Line Items] Number of series of preferred stock Number of Preferred Stock Series Number of Preferred Stock Series Fair value of redeemable preferred shares Fair Value Of Redeemable Preferred Shares Fair value of our redeemable subsidiary preferred shares and/or stock Fair value of cost method investment redeemable preferred shares Fair Value Of Cost Method Investment Redeemable Preferred Shares The fair value of a cost method investment related to redeemable preferred shares. Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Computation of diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Share-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Condensed Consolidating Financial Information Condensed Financial Information of Parent Company Only Disclosure [Text Block] Gains (losses) on sales and exchanges of investments, net Realized Investment Gains (Losses) Investment impairment losses Other than Temporary Impairment Losses, Investments Interest and dividend income Investment Income, Interest and Dividend Other, net Other Investment Income Loss Net Nonoperating income (losses), net from investment holdings recorded in the income statement that are not separately stated. Investment income (loss), net Other Industries [Abstract] Film And Television Cost [Table] Film And Television Cost [Table] Film And Television Cost [Table] Film And Television Cost [Line Items] Film And Television Cost [Line Items] [Line Items] for Film And Television Cost [Table] Film And Television Costs Film And Television Costs Disclosure [Text Block] Film and Television costs Disclosure [Text Block] Universal Studios Japan [Member] Universal Studios Japan [Member] Payments to acquire additional interest in noncontrolling interest Statement of Cash Flows [Abstract] Operating Activities Acquisitions of real estate properties Payments to Acquire Buildings Proceeds from (repayments of) borrowings from Comcast, net Proceeds From Note Receivable Issued To And Borrowings From Comcast Represents the cash inflow from borrowings from Comcast for a note receivable issued to Comcast. 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. Senior 8.875% Notes Due 2017 [Member] Senior 8.875% Notes Due 2017 [Member] Senior 8.875% Notes Due 2017 [Member] Senior 6.50% Notes Due 2017 [Member] Senior 6.5% Notes Due 2017 [Member] Senior 6.5% Notes Due 2017 [Member] Repurchases and repayments of debt Net income Unrealized gains (losses) on marketable securities, net of deferred taxes Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Deferred gains (losses) on cash flow hedges, net of deferred taxes Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Amounts reclassified to net income: Amounts Reclassified To Net Income [Abstract] Realized (gains) losses on marketable securities, net of deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Realized (gains) losses on cash flow hedges, net of deferred taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Employee benefit obligations, net of deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Currency translation adjustments, net of deferred taxes Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Net (income) loss attributable to noncontrolling interests Other comprehensive (income) loss attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Comprehensive income attributable to Parent Comcast Revolving Credit Facility [Member] Comcast Revolving Credit Facility [Member] Comcast and Comcast Cable Debt Securities [Member] Comcast And Comcast Cable Debt Securities [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] 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. Related party aggregate principal amount senior notes not subject to guarantee Related Party Aggregate Principal Amount Senior Notes Not Subject To Guarantee Represents the related party aggregate principal amount of senior notes not subject to guarantee by NBCUniversal. Related party credit facility not subject to guarantee Related Party Credit Facility Not Subject To Guarantee Represents the related party credit facility 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. Guarantee obligations, maximum capacity Guarantee Obligations Maximum Capacity Of Credit Facility Maximum capacity of credit facility subject to cross-guarantee Guarantee Obligations Current Principal Balance Guarantee Obligations Current Principal Balance Principal amount of debt securities subject to guarantee. Condensed Consolidating Financial Statements Condensed Financial Statements [Table Text Block] Schedule of receivables, net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of adjustments to reconcile net income to net cash provided by operating activities Schedule Of Adjustments To Reconcile Net Income To Net Cash Provided By Operating Activities [Table Text Block] Schedule Of Adjustments To Reconcile Net Income To Net Cash Provided By Operating Activities Schedule of cash payments for interest and income taxes Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Cash Payments for Interest and Income Taxes Supplemental Cash Flow Information [Abstract] Interest Interest Paid, Net Income taxes Income Taxes Paid, Net Current Assets: Assets, Current [Abstract] Other intangible assets, net Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Current Liabilities: Liabilities, Current [Abstract] Program obligations Program Rights Obligations, Current Deferred revenue Deferred Revenue, Current 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. Commitments and contingencies (Note 10) Commitments and Contingencies Preferred stock—authorized, 20,000,000 shares; issued, zero Preferred 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) Total NBCUniversal member’s equity Members' Equity Noncontrolling interests Members' Equity Attributable to Noncontrolling Interest Total equity Other Fair Value Method Investments [Member] Other Fair Value Method Investments [Member] Other Fair Value Method Investments [Member] Hulu [Member] Hulu [Member] Hulu member. Other Equity Method Investments [Member] Other Equity Method Investments [Member] Other Equity Method Investments [Member] BuzzFeed [Member] BuzzFeed [Member] Other Cost Method Investments [Member] Other Cost Method Investments [Member] Other Cost Method Investments [Member] Fair value method Marketable Securities Equity method Equity Method Investments Cost method Cost Method Investments Total Investments Investments Less: Current investments Short-term Investments Noncurrent Investments 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] Financial Data by Business Segment Segment Reporting Disclosure [Text Block] Film Costs: Theatrical Film Costs [Abstract] Released, less amortization Theatrical Film Costs, Released Completed, not released Theatrical Film Costs, Completed and Not Released In production and in development Theatrical Film Costs, In Production And In Development The amount of direct negative costs incurred in the production and development of a theatrical film, as well as allocations of production overhead and capitalized interest. Examples of direct negative costs include costs of story and scenario; compensation of cast, directors, producers, extras, and miscellaneous staff; costs of set construction and operations, wardrobe, and accessories; costs of sound synchronization; rental facilities on location; and postproduction costs such as music, special effects, and editing. Total film costs Theatrical Film Costs Television Costs: Direct-to-television Film Costs [Abstract] Released, less amortization Direct-to-television Film Costs, Released In production and in development Direct-to-Television Film Costs, In Production and In Development The amount of direct negative costs incurred in the production and development of a direct-to-television film, as well as allocations of production overhead and capitalized interest. Examples of direct negative costs include costs of story and scenario; compensation of cast, directors, producers, extras, and miscellaneous staff; costs of set construction and operations, wardrobe, and accessories; costs of sound synchronization; rental facilities on location; and postproduction costs such as music, special effects, and editing. Total television costs Direct-to-television Film Costs Programming rights, less amortization Programming Rights Less Amortization The carrying amount of total acquired programming rights, less amortization Total film costs, television costs and programming rights Total Film And Television Costs And Programming Rights After Amortization The carrying amount of owned films, television series and other television productions and the current and noncurrent portion of acquired television and cable networks programming rights recorded on the balance sheet. Owned films, television series and other television production costs include capitalizable production costs, production overhead, interest, development costs and acquired production costs. Film and television rights include multi-year programming arrangements, acquired movies, series and other programs. The carrying amount is stated at the lower of cost, less accumulated amortization, or net realizable/fair value at the balance sheet date. Less: Current portion of programming rights 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, Policy [Policy Text Block] Film and Television Costs Schedule Of Film And Television Costs [Table Text Block] Schedule Of Film And Television Costs [Table Text Block] Schedule Of Intangible Assets [Table] Schedule Of Intangible Assets [Table] FCC Spectrum Auction [Axis] FCC Spectrum Auction [Axis] FCC Spectrum Auction [Axis] FCC Spectrum Auction [Domain] FCC Spectrum Auction [Domain] [Domain] for FCC Spectrum Auction [Axis] FCC Spectrum Auction [Member] FCC Spectrum Auction [Member] FCC Spectrum Auction [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] FCC Spectrum Auction [Line Items] FCC Spectrum Auction [Line Items] FCC Spectrum Auction [Line Items] Proceeds from FCC Spectrum Auction Proceeds From Spectrum Auction Amount represents the proceeds received for the sale of spectrum in connection with the FCC spectrum auction. Deposit to acquire intangible asset Deposit To Acquire Intangible Asset Deposit paid in a prior period for the right to an intangible asset in a future period. Amount of spectrum acquired Indefinite-Lived Intangible Assets (Excluding Goodwill) Schedule of Business Acquisitions, by Acquisition Schedule of Business Acquisitions, by Acquisition [Table 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] Adjusted EBITDA Adjusted EBITDA Adjusted EBITDA is defined as net income attributable to Parent before net (income) loss attributable to noncontrolling interests, income tax expense, other income (expense) items, net, and depreciation and amortization, and excluding impairment charges related to fixed and intangible assets and gains or losses on the sale of long-lived assets, if any. Depreciation Amortization Other income (expense) items, net Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Residential Video Products And Services [Member] Residential Video Products And Services [Member] Residential Video Products And Services [Member] Residential High-speed Internet Products And Services [Member] Residential High-speed Internet Products And Services [Member] Residential High-speed Internet Products And Services [Member] Residential Voice Products And Services [Member] Residential Voice Products And Services [Member] Residential Voice Products And Services [Member] Business Products And Services [Member] Business Products And Services [Member] Business Products And Services [Member] Advertising Products And Services [Member] Advertising Products And Services [Member] Advertising Products And Services [Member] Other Products And Services [Member] Other Products And Services [Member] Other Products And Services [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Franchise And Other Regulatory Fees [Member] Operating Segments [Member] Operating Segments [Member] 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] Number of reportable segments Number of Reportable Segments Financial Data by Business Segment Segment Reporting Information, Profit (Loss) [Abstract] Depreciation and Amortization Depreciation, Depletion and Amortization, Nonproduction Operating Income (Loss) Capital Expenditures Cash Paid for Intangible Assets 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 Disclosure of major customers Segment Reporting, Disclosure of Major Customers Related Party Transactions Related Party Transactions Disclosure [Text Block] NBCUniversal Enterprise Senior Debt Securities [Member] Senior Notes [Member] Comcast Holdings' ZONES due October 2029 [Member] Comcast Holdings' ZONES due October 2029 [Member] Comcast Holdings' ZONES due October 2029 [Member] Comcast Holdings' ZONES due November 2029 [Member] Comcast Holdings' ZONES due November 2029 [Member] Comcast Holdings' ZONES due November 2029 Universal Studios Japan Term Loan Maturing March 2022 [Member] Principal amount of debt securities subject to guarantee Revolving credit facility subject to guarantee Guarantee Obligations, Line Of Credit Facility Guarantee Obligations, Line Of Credit Facility Principal amount of debt securities not subject to guarantee Non Guarantee Obligations Current Principal Balance Principal amount of debt instruments not guaranteed by Comcast Corporation, the cable guarantors nor NBCUniversal Media, LLC. Term loans subject to guarantee Guarantee Obligations, Term Loans Guarantee Obligations, Term Loans Financial Data by Business Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Cable Communications Segment Revenue Sources Revenue from External Customers by Products and Services [Table Text Block] Reconciliation of Adjusted EBITDA from Segments to Consolidated Reconciliation of Operating Profit (Loss) from Segments to Consolidated [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] Depreciation and amortization Share-based compensation Share-based Compensation Noncash interest expense (income), net Noncash Interest Expense (Income) Net Represents noncash interest expense (income) items as adjustments to reconcile net income (loss) to cash provided by (used in) operating activities. Equity in net (income) losses of investees, net Cash received from investees Proceeds from Equity Method Investment, Distribution Net (gain) loss on investment activity and other Gain (Loss) On Investments And Noncash Other Income (Expense) Net The net realized gain or loss on investments sold during the period and other income (expense), net, which, for cash flow reporting, is a component of proceeds from continuing operations. 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 Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Financial Assets and Financial Liabilities New Accounting Pronouncement [Member] Financial Assets and Financial Liabilities New Accounting Pronouncement [Member] Financial Assets and Financial Liabilities New Accounting Pronouncement [Member] Share Based Compensation New Accounting Pronouncement [Member] Share Based Compensation New Accounting Pronouncement [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Effect of Adoption [Member] Effect of Adoption [Member] Effect of Adoption [Member] New accounting pronouncement impact on net income if adopted New Accounting Pronouncement Impact On Income Statement If Adopted Represents the amount that would have increased (decreased) our net income attributable to the parent if the new accounting standard was adopted Decrease in income tax expense New Accounting Pronouncement Or Change In Accounting Principle Effect On Income Tax Expense Amount Amount of the effect of the adoption of a new accounting pronouncement on income tax expense. Increase in diluted earnings per share (in dollars per share) New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Diluted Earnings Per Share Net cash provided by operating activities Net cash provided by (used in) financing activities