Treasury stock (in shares) Treasury Stock, Shares 0.750% Notes due 2032 Notes 0.750 percent due 2032 [Member] Notes 0.750% due 2032 [Member] Business Acquisition [Axis] Business Acquisition [Axis] Released, less amortization Film, Monetized on Its Own, Capitalized Cost, Released 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 Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] 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] Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Deferred income taxes Deferred Income Tax Liabilities, Net Income Statement [Abstract] Income Statement [Abstract] Number of stock options granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Entity Address, Postal Zip Code Entity Address, Postal Zip Code 1.875% Notes due 2036 Notes 1.875 percent due 2036 [Member] Notes 1.875% due 2036 [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] 9.455% Guaranteed Notes due 2022 Guaranteed Notes 9.455 Percent Due 2022 [Member] Guaranteed Notes 9.455% Due 2022 [Member] Document Fiscal Period Focus Document Fiscal Period Focus Restricted cash included in other noncurrent assets, net Restricted Cash, Noncurrent 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. Weighted-average number of common shares outstanding – diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Property and equipment - accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Debt Instrument [Axis] Debt Instrument [Axis] Marketable equity securities Equity Securities, FV-NI Total investments Investments Sky Sky Limited Segments [Member] Sky Limited [Member] Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Attributable To Temporary Equity Contributions from and (distributions to) noncontrolling interests attributable to temporary equity. Common stock Common Stock, Value, Issued Investments and Variable Interest Entities Investment [Text Block] Additional paid-in capital Additional Paid in Capital Lease Arrangements [Domain] Lease Arrangements [Domain] Lease Arrangements Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Investment Summary Summary Investment Holdings [Table Text Block] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Financial Instruments [Domain] Financial Instruments [Domain] Other Payments for (Proceeds from) Other Investing Activities 1.250% Notes due 2040 Notes 1.250 percent due 2040 [Member] Notes 1.250% due 2040 [Member] 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 Theatrical Theatrical [Member] Theatrical [Member] Universal Beijing Resort Term Loans Universal Beijing Resort Term Loans [Member] Universal Beijing Resort Term Loans [Member] Depreciation Depreciation Depreciation 1.500% Notes due 2029 Notes 1.500 percent Due 2029 [Member] Notes 1.500% Due 2029 [Member] Studios Studios Segments [Member] Studios Segments Operating Segments Operating Segments [Member] Programming and production Total programming and production costs Programming And Production Costs The amount of expense recognized in the period for costs associated with video programming and content acquisition and production costs. Programming expenses include the fees paid to license the programming distributed to video customers, such as the programming license fees charged by cable networks and fees charged for retransmission of the signals from local broadcast television stations. Production costs include the amortization of owned and acquired programming, sports rights, direct production costs, residual and participation payments, production overhead, costs associated with the distribution of programming to third-party networks and other distribution platforms, and on-air talent costs. It also includes the amortization of capitalized theatrical film production and acquisition costs and distribution expenses. Masergy Masergy [Member] Masergy 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. Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized 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 Other income (loss), net Other Income Loss Net Nonoperating income (losses), net recorded in the income statement that are not separately stated. Currency translation adjustments, net of deferred taxes of $42, $(17), $289 and $(109) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Redemption of subsidiary preferred stock Temporary Equity, Redemption Of Preferred Stock Temporary Equity, Redemption Of Preferred Stock Less: Net income (loss) attributable to noncontrolling interests Net income (loss) Net Income (Loss) Attributable to Noncontrolling Interest Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Current Liabilities: Liabilities, Current [Abstract] Dividends payable Dividends Payable Proceeds from borrowings Proceeds from Issuance of Long-Term Debt Common stock, shares issued (in shares) Common Stock, Shares, Issued Equity method Equity Method Investments Net income attributable to Comcast Corporation Net income (loss) Net Income (Loss) Attributable to Parent Financial Data by Business Segment Segment Reporting Information, Profit (Loss) [Abstract] Document And Entity Information [Line Items] Document Information [Line Items] Receivables, gross Accounts Receivable, before Allowance for Credit Loss, Current Content licensing Content Licensing [Member] Content Licensing [Member] Equity Component [Domain] Equity Component [Domain] Amendment Flag Amendment Flag Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Ownership [Axis] Ownership [Axis] Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Employee stock purchase plans Stock Issued During Period, Value, Employee Stock Purchase Plan Comprehensive income attributable to Comcast Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Investment, Name [Domain] Investment, Name [Domain] Total carrying value of debt Debt and Lease Obligation Cumulative translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Financial Data by Business Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Plan Name [Axis] Plan Name [Axis] Employee benefit obligations, deferred taxes Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Entity Current Reporting Status Entity Current Reporting Status Other noncurrent assets, net Other Assets, Noncurrent Cash Payments for Interest and Income Taxes Supplemental Cash Flow Information [Abstract] Programming and Production Costs Entertainment [Text Block] Depreciation and amortization Depreciation, Depletion and Amortization 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. Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Plan Name [Domain] Plan Name [Domain] Contract acquisition and fulfillment costs (included in other noncurrent assets, net) Capitalized Contract Cost, Net Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Dividends payable (in dollars per share) Dividends Payable, Amount Per Share Entity Address, State or Province Entity Address, State or Province Employee Stock Purchase Plans Employee Stock [Member] NBCUniversal NBCUniversal Business Unit [Member] NBCUniversal Business Unit Award Type [Axis] Award Type [Axis] Other Other [Member] Other [Member] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Equity method investments and certain retained distributions Equity Method Investments and Certain Retained Distributions Equity Method Investments and Certain Retained Distributions Other Stockholders' Equity, Other Collateralized obligation Collateralized obligation Collateralized Obligation Carrying amount of obligation presented separately as collateralized obligation that is secured by assets. Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Issuances (repurchases) of common stock under repurchase program and employee plans Stock Issued (Repurchased) During Period, Value Stock Issued (Repurchased) During Period, Value Property and equipment, net of accumulated depreciation of $56,537 and $55,611 Property, Plant and Equipment, Net 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, Continuing Operations 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. Construction of Universal Beijing Resort Payments For Construction Of Theme Park The cash outflow associated with the construction of a theme park. Stock Options Share-Based Payment Arrangement, Option [Member] Costs and Expenses: Costs and Expenses [Abstract] Treasury stock, 872,791,028 Class A common shares Treasury Stock, Value #REF! Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Less: Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Direct-to-consumer Direct To Consumer [Member] Direct To Consumer [Member] Atairos Atairos [Member] Atairos [Member] Short-Term Instruments Short-Term Instruments [Member] Short-Term Instruments Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Film and television costs Film, Monetized On Its Own Capitalized Cost, And Entertainment, License Agreement For Program Material, Including Sports Rights Advances Total amounts of capitalized film cost for film predominantly monetized on its own and capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Common stock, shares authorized (in shares) Common Stock, Shares Authorized Consolidated variable interest entity's liabilities included in condensed consolidated balance sheet Liabilities Business Combination, Separately Recognized Transactions [Table] Business Combination, Separately Recognized Transactions [Table] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Supplemental Financial Information [Line Items] Supplemental Financial Information [Line Items] Supplemental Financial Information Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Accumulated other comprehensive income (loss) Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Home entertainment and other Home Entertainment And Other [Member] Home Entertainment And Other 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. Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Class A Common Stock, $0.01 par value Common Class A [Member] Management Grant Management Grant [Member] Management Grant [Member] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Repurchases of common stock under repurchase program and employee plans Stock Repurchased and Retired During Period, Value Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Realized and unrealized gains (losses) on equity securities, net Equity Securities, FV-NI, Gain (Loss) Franchise rights Indefinite-Lived Franchise Rights Total current assets Assets, Current 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 Income taxes Income Taxes Paid, Net Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Document Type Document Type Deferred gains (losses) on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Voice Residential, Voice [Member] Residential, Voice [Member] Entity Small Business Entity Small Business Equity and Share-Based Compensation Stockholders' Equity Note Disclosure [Text Block] Revenues [Abstract] Revenues [Abstract] Cash dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared 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. Long-Term Debt Debt Disclosure [Text Block] Segments [Axis] Segments [Axis] Product and Service [Domain] Product and Service [Domain] Unrecognized pretax compensation expense on nonvested awards Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Entity Shell Company Entity Shell Company Class B Common Stock Common Class B [Member] Investments [Abstract] Investments [Abstract] Deferred income taxes Deferred Income Tax Expense (Benefit) Schedule of cash payments for interest and income taxes Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Contributions from (distributions to) noncontrolling interests, net Contributions From And Distributions To Noncontrolling Interests Contributions from and distributions to noncontrolling interests Principal amount of term loan outstanding Other Long-Term Debt Financial Instrument [Axis] Financial Instrument [Axis] Title of 12(b) Security Title of 12(b) Security Other investments Other Investments Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Document Period End Date Document Period End Date Less: Current investments Short-Term Investments Cash distribution received from equity method investments Proceeds from Equity Method Investment, Distribution Media Media Segments [Member] Media Segments Total costs and expenses Costs and Expenses Business Unit [Domain] Business Unit [Domain] Business Unit [Domain] 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. Business Combination and Asset Acquisition [Abstract] Video Residential, Video [Member] Residential, Video [Member] Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Total assets Assets Assets Segment Information Segment Reporting Disclosure [Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Noncurrent receivables, net (included in other noncurrent assets, net) Accounts Receivable, after Allowance for Credit Loss, Noncurrent Lease Arrangements [Axis] Lease Arrangements [Axis] Lease Arrangements Liabilities and Equity Liabilities and Equity [Abstract] Accrued expenses and other current liabilities Accrued Liabilities, Current Cash paid for intangible assets Cash Paid for Intangible Assets Payments to Acquire Intangible Assets Other operating and administrative Other Operating And Administrative Other operating and administrative expense recognized in the period not presented separately. Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Total fair value of debt Long-Term Debt, Fair Value Investments Noncurrent investments Long-Term Investments Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Segments [Domain] Segments [Domain] Cable Communications Cable Communications Business Unit [Member] Cable Communications Business Unit 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. 2.0% Exchangeable Subordinated Debentures due 2029 Exchangeable Subordinated Debentures 2.0 Percent Due 2029 [Member] Exchangeable Subordinated Debentures 2.0% Due 2029 [Member] Corporate and Other Corporate, Non-Segment, Intersegment Revenue [Member] Corporate, Non-Segment, Intersegment Revenue Other Temporary Equity, Other Changes 0.250% Notes due 2029 Notes 0.250 percent Due 2029 [Member] Notes 0.250 percent Due 2029 Distribution Distribution [Member] Distribution Owned Film, Monetized On Its Own, Amortization Expense, Including Participations And Residuals Amount of amortization expense for capitalized film cost for film predominantly monetized on its own and participation and residuals expenses. Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Entity Filer Category Entity Filer Category Weighted average number of common shares outstanding – basic (in shares) Weighted Average Number of Shares Outstanding, Basic Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Award Type [Domain] Award Type [Domain] Acquisition, cash consideration Payments to Acquire Businesses, Gross Recognized share-based compensation expense Share-Based Payment Arrangement, Expense Commitments and contingencies Commitments and Contingencies Security Exchange Name Security Exchange Name Entity Registrant Name Entity Registrant Name Universal Beijing Resort Universal Beijing Resort [Member] Universal Beijing Resort [Member] Deferred gains (losses) on cash flow hedges AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax Preferred stock—authorized, 20,000,000 shares; issued, zero Preferred Stock, Value, Issued Remaining unfunded capital commitment Variable Interest Entity, Reporting Entity Involvement, Unfunded Capital Commitment Variable Interest Entity, Reporting Entity Involvement, Unfunded Capital Commitment Redeemable noncontrolling interests Beginning balance Ending balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Realized (gains) losses reclassified to net income, net of deferred taxes of $(11), $—, $(16) and $— Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Restricted cash included in other current assets Restricted Cash, Current Segment Reconciling Items Segment Reconciling Items [Member] Entity Address, City or Town Entity Address, City or Town Business Unit [Axis] Business Unit [Axis] Business Unit Current portion of long-term debt Debt, Current Cash flow hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Repurchases and repayments of debt Repayments of Other Debt Cover [Abstract] Cover [Abstract] Total equity Beginning balance Ending balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest 5.50% Notes due 2029 Notes 5.50 Percent Due 2029 [Member] Notes 5.50% Due 2029 [Member] Unrecognized gains (losses) on employee benefit obligations and other Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Tax Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan And Other, After Tax Eliminations Intersegment Eliminations [Member] 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. Schedule of recognized share-based compensation expense Share-Based Payment Arrangement, Cost by Plan [Table Text Block] Broadband Residential, Broadband [Member] Residential, Broadband [Member] Revenue Revenue from Contract with Customer [Text Block] Segment Reporting [Abstract] Segment Reporting [Abstract] Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Programming and Production Expense Schedule Of Programming And Production Cost [Table Text Block] Schedule Of Programming And Production Cost Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Deferred gains (losses), net of deferred taxes of $(1), $2, $(38) and $(17) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Noncontrolling Interests Noncontrolling Interest [Member] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Investment, Name [Axis] Investment, Name [Axis] Film and television content: Film And Television Content [Abstract] Film And Television Content Wireless Residential, Wireless [Member] Residential, Wireless [Member] Total liabilities and equity Liabilities and Equity Trading Symbol Trading Symbol Entity File Number Entity File Number Cable Communications Cable Communications Segments [Member] Cable Communications Member Net income (loss) Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements 0.000% Notes due 2026 Notes 0.000 percent Due 2026 [Member] Notes 0.000 percent Due 2026 Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Deferred revenue Deferred Revenue, Current Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Reconciliation of Adjusted EBITDA from Segments to Consolidated Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] 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 Restricted Share Units (RSUs) Restricted Stock Units (RSUs) [Member] Amortization of owned film and television costs Film, Monetized on Its Own, Amortization Expense Purchases of investments Payments to Acquire Investments Current Fiscal Year End Date Current Fiscal Year End Date Supplemental Financial Information [Table] Supplemental Financial Information [Table] Supplemental Financial Information [Table] 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. Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Diluted Ownership percentage in variable interest entity Noncontrolling Interest, Ownership Percentage by Parent Stock compensation plans APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Consolidation Items [Axis] Consolidation Items [Axis] Advertising, marketing and promotion Marketing and Advertising Expense Revenue Revenues Total current liabilities Liabilities, Current Other current assets Other Assets, Current Accounts payable and accrued expenses related to trade creditors Increase (Decrease) in Accounts Payable and Accrued Liabilities Schedule of receivables, net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Completed, not released Film, Monetized on Its Own, Capitalized Cost, Completed and Not Released Other Other Programming And Production Expense Other Programming And Production Expense Amortization Amortization Amortization of Intangible Assets Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Licensed, including sports rights Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Amortization Expense Amount of amortization expense for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) Earnings Per Share, Basic 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. Realized (gains) losses on cash flow hedges, deferred taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Fair value of collateralized obligation Collateralized Obligation, Fair Value Fair value of obligation presented separately as collateralized obligation that is secured by assets. Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Unrealized gains (losses) recognized Equity Securities, FV-NI, Unrealized Gain (Loss) Corporate and Other Corporate, Non-Segment [Member] Entity Address, Address Line One Entity Address, Address Line One Restricted Cash Restrictions on Cash and Cash Equivalents [Table Text Block] Other Proceeds from (Payments for) Other Financing Activities Treasury Stock at Cost Treasury Stock [Member] Total Comcast Corporation shareholders’ equity Stockholders' Equity Attributable to Parent Product and Service [Axis] Product and Service [Axis] Hulu Hulu [Member] Hulu member. Class of Stock [Domain] Class of Stock [Domain] Ownership [Domain] Ownership [Domain] Business services Business Services [Member] Business Services [Member] Noncurrent deferred revenue (included in other noncurrent liabilities) Deferred Revenue, Noncurrent Interest expense Interest expense Interest Expense Entity Interactive Data Current Entity Interactive Data Current Inter-Business Unit Eliminations Inter-Business Unit Eliminations [Member] Inter-Business Unit Eliminations Other intangible assets - accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Long-term debt, less current portion Long-Term Debt and Lease Obligation Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Equity [Abstract] Retained Earnings Retained Earnings [Member] Dividends paid Payments of Dividends Content Content [Member] Content [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Dividends declared Dividends, Common Stock, Cash Entity Tax Identification Number Entity Tax Identification Number Class A Common Stock Common Stock [Member] Owned Film, Monetized on Its Own, Capitalized Cost Business Combination, Separately Recognized Transactions [Line Items] Business Combination, Separately Recognized Transactions [Line Items] Number of reportable segments Number of Reportable Segments Repurchases of common stock under repurchase program and employee plans Payments for Repurchase of Common Stock Class of Stock [Axis] Class of Stock [Axis] Cash payments for the redemption of redeemable subsidiary preferred stock Payments For Repurchase Of Redeemable Subsidiary Preferred Stock Payments For Repurchase Of Redeemable Subsidiary Preferred Stock Statement [Table] Statement [Table] Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Document Quarterly Report Document Quarterly Report Consolidated Entities [Domain] Consolidated Entities [Domain] 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. Current Assets: Assets, Current [Abstract] 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 Supplemental Financial Information Additional Financial Information Disclosure [Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Receivables, net Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current Other intangible assets, net of accumulated amortization of $24,946 and $23,545 Other Intangible Assets, Net Entity Central Index Key Entity Central Index Key Equity Components [Axis] Equity Components [Axis] 0.250% Notes due 2027 Notes 0.250 percent Due 2027 [Member] Notes 0.250% Due 2027 [Member] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Licensed, including sports advances Entertainment, License Agreement For Program Material, Including Sports Rights Advances, Capitalized Cost Amount of capitalized cost for rights acquired by broadcaster under license agreement for program material, including sports rights advances. Document Fiscal Year Focus Document Fiscal Year Focus Significant Transactions Significant Transactions [Text Block] The disclosure of significant transactions entered into or completed during the period. Sky Sky Limited Business Unit [Member] Sky Limited Business Unit Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] City Area Code City Area Code Assets Assets [Abstract] Statement [Line Items] Statement [Line Items] Other operating assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Investment and other income (loss), net Investment and other income (loss), net Nonoperating Income (Expense) Adjusted EBITDA Adjusted EBITDA The measure used to evaluate the profitability of operating segments. Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Less: Other comprehensive income (loss) attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Video distribution programming Video Distribution Programming Expense Video Distribution Programming Expense Other Industries [Abstract] Other Industries [Abstract] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Advertising Advertising [Member] Share-based compensation Share-Based Payment Arrangement, Noncash Expense 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 Other noncurrent liabilities Other Liabilities, Noncurrent Equity in net income (losses) of investees, net Income (Loss) from Equity Method Investments Document Transition Report Document Transition Report Local Phone Number Local Phone Number Capital expenditures Capital Expenditures Payments to Acquire Property, Plant, and Equipment Operating income Operating Income (Loss) Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Theme Parks Theme Parks Segments [Member] Theme Parks Member Schedule of weighted average common shares outstanding Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Currency translation adjustments, deferred taxes Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Operating lease assets and liabilities recognized Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Nonmarketable equity securities Equity Securities without Readily Determinable Fair Value, Amount Document And Entity Information [Table] Document Information [Table] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Condensed Consolidated Financial Statements Business Description and Basis of Presentation [Text Block] Adjustments Adjustments for Items Excluded from Adjusted EBITDA Adjustments represent the impacts of certain events, gains, losses or other charges that are excluded from Adjusted EBITDA Goodwill Goodwill Owned: Film, Capitalized Cost [Abstract]