DocumentAndEntityInformationAbstract Document and Entity Information [Abstract] Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Class B common stock [Member] Common Stock B Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Trading Symbol Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Statement of Financial Position [Abstract] Legal Entity [Axis] Entity [Domain] Parent Company [Member] Class A common stock [Member] Common Stock A Assets Cash and cash equivalents Cash and cash equivalents, end of period Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value, Total Short Term Investments Less: Current investments Short-term Investments, Total Investments Accounts receivable, less allowance for doubtful accounts of $185 and $175 Accounts Receivable, Net, Current, Total Accounts receivable, net Other current assets Total current assets Total current assets Long Term Investments Noncurrent investments Long-term Investments, Total Investments Property and equipment, net of accumulated depreciation of $30,188 and $27,810 Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property, Plant and Equipment, Net, Total Property and equipment, net Franchise rights Goodwill Goodwill ending balance Goodwill beginning balance Other intangible assets, net of accumulated amortization of $9,222 and $8,711 Finite-Lived Intangible Assets, Net, Total Other intangible assets, net Other noncurrent assets, net Other Assets, Noncurrent, Total Total assets Total assets Liabilities and Equity Accounts payable and accrued expenses related to trade creditors Accounts Payable, Current, Total Accrued expenses and other current liabilities Accrued Liabilities, Current, Total Current portion of long-term debt Debt, Current, Total Total current liabilities Total current liabilities Long-term debt, less current portion Long-term Debt and Capital Lease Obligations, Total Deferred income taxes Deferred income taxes Other noncurrent liabilities Other Liabilities, Noncurrent, Total Commitments and contingencies (Note 12) Redeemable noncontrolling interests Equity: Preferred stock - authorized, 20,000,000 shares; issued, zero Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred Stock, Value, Issued, Total Common stock Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common Stock, Value, Issued, Total Additional Paid In Capital Additional Paid in Capital, Ending Balance Additional Paid in Capital, Beginning Balance Additional Paid in Capital, Total Additional paid-in capital Retained Earnings Accumulated Deficit Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Total Retained earnings Treasury stock, 365,460,750 Class A common shares and 70,934,764 Class A Special common shares Treasury stock, 365,460,750 Class A common shares and 70,934,764 Class A Special common shares Treasury Stock, Value, Ending Balance Treasury Stock, Value, Beginning Balance Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated other comprehensive income (loss), net of deferred taxes Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive income (loss) Total Comcast Corporation shareholders' equity Stockholders' Equity Attributable to Parent, Ending Balance Stockholders' Equity Attributable to Parent, Beginning Balance Total Comcast Corporation shareholders' equity Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Stockholders' Equity Attributable to Noncontrolling Interest, Total Noncontrolling interests Total equity Balance Balance Total equity Total liabilities and equity Total liabilities and equity Accounts receivable, allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current, Ending Balance Allowance for Doubtful Accounts Receivable, Current, Beginning Balance Property and equipment, accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Other intangible assets, accumulated amortization Preferred stock, authorized Preferred stock, issued Preferred Stock, Shares Issued, Total Common stock, par value Common stock, authorized Common stock, issued Common Stock, Shares, Issued, Total Common stock, outstanding Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Treasury stock common shares Treasury Stock, Shares, Ending Balance Treasury Stock, Shares, Beginning Balance Income Statement [Abstract] Revenue Revenues, Total Costs and Expenses: Operating expenses less depreciation and amortization. Operating Expenses Excluding Depreciation And Amortization Operating (excluding depreciation and amortization) Operating (excluding depreciation and amortization) Selling, general and administrative Selling, General and Administrative Expense, Total Depreciation Depreciation, Total Adjustment for Amortization Amortization Amortization of Intangible Assets, Total Amortization Costs and Expenses, Total Costs and expenses, total Costs and expenses, total Operating income Operating income (loss) Operating income Operating income (loss) Other Income (Expense): Interest expense Interest expense Interest Expense, Total Investment income (loss), net Investment Income, Net, Total Equity in net income (losses) of affiliates, net Equity in net (income) losses of affiliates, net Income (Loss) from Equity Method Investments, Total Other income (expense) Other Nonoperating Income (Expense), Total Nonoperating Income (Expense), Total Nonoperating income (expense), total Sum of operating profit and nonoperating income (expense) before income taxes, extraordinary items, cumulative effects of changes in accounting principles, and noncontrolling interest. Income Loss From Continuing Operations Before Income Taxes Income before income taxes Income before income taxes Income (loss) before income taxes Income tax expense Income tax expense Income Tax Expense (Benefit), Total Net income from consolidated operations Net income from consolidated operations Net income (loss) from consolidated operations Net (income) loss attributable to noncontrolling interests Net (income) loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest, Total Net income attributable to Comcast Corporation Net income attributable to Comcast Corporation Net income (loss) attributable to Comcast Corporation Basic earnings per common share attributable to Comcast Corporation shareholders Earnings Per Share, Basic, Total Diluted earnings per common share attributable to Comcast Corporation shareholders Earnings Per Share, Diluted, Total Dividends declared per common share attributable to Comcast Corporation shareholders Statement of Cash Flows [Abstract] Net cash provided by operating activities Net cash provided by (used in) operating activities Net cash provided by operating activities Investing Activities Capital expenditures Capital expenditures Payments to Acquire Property, Plant, and Equipment, Total Cash paid for intangible assets Cash paid for intangible assets Acquisitions, net of cash acquired Acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired, Total Proceeds from sales of investments Proceeds from Sale, Maturity and Collections of Investments, Total Purchases of investments Purchases of investments Payments to Acquire Investments, Total Other Other Net cash provided by (used in) investing activities Net cash provided by (used in) investing activities Financing Activities Proceeds from borrowings Repurchases and repayments of debt Repurchases and repayments of debt Repurchases of common stock Repurchases of common stock Dividends paid Dividends paid Payments of Dividends, Total Proceeds From Payments For Other Financing Activities Other Other Net cash provided by (used in) financing activities Net cash provided by (used in) financing activities Increase (decrease) in cash and cash equivalents Increase (decrease) in cash and cash equivalents Statement of Stockholders' Equity [Abstract] Statement, Equity Components [Axis] Equity Component [Domain] Redeemable Non-controlling Interests [Member] Redeemable Non-controlling Interests [Member] Additional Paid-In Capital [Member] Retained Earnings [Member] Treasury Stock at Cost [Member] Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interests [Member] Stock compensation plans Repurchase and retirement of common stock Repurchase and retirement of common stock Repurchase and retirement of common stock Employee stock purchase plan Dividends declared Dividends declared Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Total Sale (purchase) of subsidiary shares to (from) noncontrolling interests, net Noncontrolling Interest, Period Increase (Decrease), Total Contributions from and (distributions to) noncontrolling interests. Contributions From And Distributions To Noncontrolling Interests Contributions from (distributions to) noncontrolling interests Profit or loss as represented on the statement of changes in equity. Equity Profit Loss Net income (loss) Statement of Income and Comprehensive Income [Abstract] Holding gains (losses) during the period, net of deferred taxes of $24, $(2), $24 and $(1) Reclassification adjustments for losses (gains) included in net income, net of deferred taxes of $(1) and $(12) Reclassification adjustments for losses (gains) included in net income attributable to Comcast Corporation, net of deferred taxes of $(2), $(2), $(3) and $(14) Cumulative translation adjustments Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Comprehensive income Comprehensive income Comprehensive income attributable to Comcast Corporation Comprehensive income attributable to Comcast Corporation Holding gains (losses) during the period, deferred taxes Reclassification adjustments for losses (gains) included in net income attributable to Comcast Corporation, deferred taxes CondensedConsolidatedFinancialStatementsAbstract Condensed Consolidated Financial Statements [Abstract] Condensed Consolidated Financial Statements RecentAccountingPronouncementsAbstract Recent Accounting Pronouncements [Abstract] Recent Accounting Guidance Earnings Per Share [Abstract] Earnings Per Share AcquisitionsAndOtherSignificantEventsAbstract Acquisitions and Other Significant Events [Abstract] Acquisitions and Other Significant Events Investments [Abstract] Includes all investments held by the company under the equity, cost and the fair value methods. Represents total on the balance sheet. Includes the components of investment income (loss), net. Investments [Text Block] Investments GoodwillAbstract Goodwill [Abstract] Goodwill And Intangible Assets Disclosure Text Block Goodwill Long-term Debt [Abstract] Long-Term Debt FairValueMeasurementsAndDerivativeFinancialInstrumentsAbstract Fair Value Measurements and Derivative Financial Instruments [Abstract] Description of risk management strategies, derivatives in hedging activities and nonhedging derivative instruments, the assets, obligations, liabilities, revenues and expenses arising therefrom, and the amounts of and methodologies and assumptions used in determining the amounts of such items. This disclosure also contains the fair value amounts and methods used to estimate the fair values of all financial instruments. Fair Value Measurements And Derivative Financial Instruments Text Block Fair Value Measurements and Derivative Financial Instruments NoncontrollingInterestsAbstract Noncontrolling Interests [Abstract] Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interests Equity [Abstract] Represents the company's share-based compensation and equity disclosure Share Based Compensation and Equity (Text Block) Equity StatementOfCashFlowsSupplementalInformationAbstract Statement of Cash Flows - Supplemental Information [Abstract] Statement of Cash Flows - Supplemental Information CommitmentsAndContingenciesAbstract Commitments and Contingencies [Abstract] Commitments and Contingencies FinancialDataByBusinessSegmentAbstract Financial Data by Business Segment [Abstract] Financial Data by Business Segment CondensedConsolidatingFinancialInformationAbstract Condensed Consolidating Financial Information [Abstract] Condensed Consolidating Financial Information Derivatives, Policy Computation of Diluted EPS Investment summary. Investment Summary Text Block Investment Summary Components of Investment Income (Loss), Net Components Of Investment Income Loss Net Text Block Components of Investment Income (Loss), Net Schedule of Goodwill This element represents the disclosure related to assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). Fair Value Assets and Liabilities Measured On Recurring Basis [Text Block] Fair Value Assets and Liabilities Measured On Recurring Basis Schedule of the location and amount of gains and losses reported in the statement of financial performance (or when applicable, the statement of financial position, for example, gains and losses initially recognized in other comprehensive income) on derivative instruments designated and nondesignated qualifying as hedging instruments in fair value hedges and related hedged items designated and nondesignated and qualifying in fair value hedges Amount Of Gain Loss Recognized In Income On Derivative Instruments Text Block Amount of Gain (Loss) Recognized in Income on Derivative Instruments Schedule Summarizing Changes In Equity Resulting From Net Income Attributable To Parent And Transfers To Or From Noncontrolling Interests [Text Block] Changes in equity resulting from net income attributable to parent and transfers to or from noncontrolling interests [Text Block] Schedule Summarizing Changes in Equity Resulting from Net Income Attributable to Parent and Transfers to or from Noncontrolling Interests Disclosure of Compensation Related Costs, Share-Based Payments Share-Based Compensation Components Of Accumulated Other Comprehensive Income Components Of Accumulated Other Comprehensive Income Text Block Components of Accumulated Other Comprehensive Income Statement of Cash Flows - Supplemental Information (Tables) Statement of Cash Flows - Supplemental Information (Tables) [Abstract] Adjustments To Reconcile Net Income From Consolidated Operations To Net Cash Provided By Operating Activities Adjustments To Reconcile Net Income From Consolidated Operations To Net Cash Provided By Operating Activities Text Block Adjustments to Reconcile Net Income from Consolidated Operations to Net Cash Provided by Operating Activities Cash Payments For Interest And Income Taxes Cash Payments For Interest And Income Taxes Text Block Cash Payments for Interest and Income Taxes Schedule of Segment Reporting Information, by Segment [Text Block] Financial Data by Business Segment Cable segment revenue sources Cable segment revenue sources [Text Block] Cable Segment Revenue Sources Cable segment and Corporate and Other Reclassification Cable segment and corporate and other reclassification [Text Block] Cable Segment and Corporate and Other Reclassification Condensed Consolidating Financial Information (Tables) Condensed Consolidating Financial Information (Tables) [Abstract] Schedule of condensed consolidating balance sheet. Schedule Of Condensed Consolidating Balance Sheet Text Block Schedule of Condensed Consolidating Balance Sheets Schedule of condensed consolidating statement of operations Schedule Of Condensed Consolidating Statement Of Operations Text Block Schedule of Condensed Consolidating Statement of Operations Schedule of condensed consolidating statement of cash flows Schedule Of Condensed Consolidating Statement Of Cash Flows Text Block Schedule of Condensed Consolidating Statement of Cash Flows Shares to corporate shareholders [Member] Shares to corporate shareholders [Member] Shares relating to stock plans [Member] Shares relating to stock plans [Member] Excluded shares from diluted EPS because their inclusion would have an antidilutive effect Assumed exercise or issuance of shares relating to stock plans Incremental Common Shares Attributable to Share-based Payment Arrangements, Total Weighted Average Number of Shares Outstanding, Basic Weighted Average Number of Shares Outstanding, Basic, Total Weighted Average Number of Shares Outstanding, Diluted Weighted Average Number of Shares Outstanding, Diluted, Total Weighted Average Number of Shares Outstanding, Diluted Acquisition and Other Significant Events (Details) Acquisition and Other Significant Events (Details) [Abstract] Date registrant and unaffiliated company entered into an agreement to form new company. Agreement Date To Form New Company Date we and GE entered into an agreement to form new company Expected ownership percentage in new company Expected ownership percentage in new company Comcast expected ownership percentage in new company to be formed in connection with the NBC Universal transaction Noncontrolling investors expected ownership percentage in new company. Noncontrolling Investors Expected Ownership Percentage In New Company GE's expected ownership percentage in new company to be formed in connection with the NBC Universal transaction Collective value of assets to be contributed to new company. Collective value of assets to be contributed to new company Collective value of assets to be contributed by Comcast to new company to be formed in connection with the NBC Universal transaction Amount of cash payable to the noncontrolling investor of the new company to be formed subject to certain adjustments primarily based on the free cash flow generated by the company to be contributed to the new company by the noncontrolling investor. Cash Payable To The Noncontrolling Investor In New Company Subject To Certain Adjustments Based On Free Cash Flow By Company To Be Contributed to The New Company by The Noncontrolling Investor Amount of cash payable by Comcast to GE subject to certain adjustments primarily based on the free cash flow generated by NBC Universal Period of time for redemption of one half of the Noncontrolling investor's interest (first redemption right) in new company. Period Of Time For Redemption Of One Half Of Noncontrolling Investors Interest First Redemption Right in new company Number of years after the closing of the NBC Universal transaction in which GE can redeem half of its interest in the new company (first redemption right) Period of time for redemption of the noncontrolling investor's remaining interest (remaining redemption right) in new company. Period Of Time For Redemption Of Noncontrolling Investors Remaining Interest in new company Number of years after the closing of the NBC Universal transaction in which GE can redeem its remaining interest in the new company Period of time for redemption of one half of the Noncontrolling Investor's interest in new company. Period Of Time For Redemption Of Half Of Noncontrolling Investors Interest in new company Number of years after the closing of the NBC Universal transaction in which we can purchase half of GE's interest in the new company if GE does not exercise their first redemption right Period of time for redemption of remaining Noncontrolling Investor's interest in new company. Period Of Time For Redemption Of Remaining Noncontrolling Investors Interest in new company Number of years after the closing of the NBC Universal transaction in which we can purchase GE's remaining interest, if any, in the new company Percentage adjustment factor to determine redemption and purchase price for noncontrolling investors interest. Percentage Adjustment Factor To Determine Redemption And Purchase Price For Noncontrolling Investors Interest The redemption and purchase price will equal the ownership percentage being acquired multiplied by 120% of the fully distributed public market trading value of the new company, less half of the excess of 120% of that value over $28.15 billion Amount used for determining redemption and purchase price for future potential redemptions by the noncontrolling investor and/or purchase of additional interest by the controlling parent. Amount Used For Determining Redemption And Purchase Price Amount used for determining redemption and purchase price Parent's cash or common stock funding commitment for each of the noncontrolling investor's two redemption rights. Parents Cash or CommonStock Funding Commitment For Each Of The Noncontrolling Investors Two Redemption Rights Our cash or common stock funding commitment for each of the two GE redemption rights Aggregate cash or common stock funding commitment for the noncontrolling investor's two redemption rights. AggregateCashOrCommonStockFundingCommitmentForNoncontrollingInvestorsTwoRedemptionRights Our aggregate cash or common stock funding commitment for the two GE redemption rights Represents the aggregated purchase price of combined amounts of individually immaterial business combinations that were completed during the period. Aggregate purchase price of series of business acquisitions Expected closing date of transaction subject to various regulatory approvals Expected Closing Date Of Transaction Subject To Various Regulatory Approvals Expected closing date for NBC Universal transaction, subject to various regulatory approvals Amount borrowed from third party lenders by company to be contributed by the noncontrolling investor Amount Borrowed From Third Party Lenders By Company To Be Contributed By The Noncontrolling Investor Amount borrowed by NBC Universal from third party lenders Potential additional borrowings from third party lenders by company to be contributed by the noncontrolling investor Potential Additional Borrowings From Third Party Lenders By Company To Be Contributed By The Noncontrolling Investor Potential additional borrowing by NBC Universal from third party lenders Percentage Adjustment Factor To Determine Redemption And Purchase Price For Noncontrolling Investor Interest in the new company. Percentage Adjustment Factor To Determine Redemption And Purchase Price For Noncontrolling Investor Interest Percentage adjustment factor to determine redemption and purchase price for GE's interest Schedule of Equity Method Investment, Equity Method Investee, Name [Axis] Equity Method Investee, Name [Domain] Air Touch [Member] Air Touch [Member] Fair value method Marketable Securities, Total This item represents the carrying amount on the entity's balance sheet of its investment in equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment losses recognized. Equity Method Investments in Stock and Other Equity method, primarily SpectrumCo and Clearwire Cost method, primarily AirTouch redeemable preferred shares Total investments Investments, Total Cost Method Investments, Fair Value Disclosure This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity. Gains on sales and exchanges of investments,net Investment impairment losses Marketable Securities Unrealized Gain Loss Marketable Securities, Unrealized Gain (Loss), Total Unrealized gains (losses) on securities underlying prepaid forward sale agreements Mark To Market Adjustment on Derivative Component Of Prepaid Forward Sale Agreements Mark To Market Adjustment on Derivative Component Of Prepaid Forward Sale Agreements Mark to market adjustment on derivative component of prepaid forward sale agreements Mark to market adjustments on derivative component of ZONES Mark to market adjustment on derivative component of ZONES Mark to market adjustments on derivative component of ZONES Interest and dividend income Investment Income, Interest and Dividend, Total Other Investment Income (Loss), net Other Investment Income Loss Net Other, net Investment Income Nonoperating ' Investment Income, Nonoperating, Total Investment income (loss), net Segment Reporting Information, by Segment [Axis] Reporting Segment [Domain] Cable Cable [Member] Programming Programming [Member] Corporate and Other Corporate and Other [Member] Goodwill, Acquired During Period Acquisitions Goodwill settlements and adjustments Goodwill settlements and adjustments Settlements and adjustments Long-term Debt, Unclassified [Abstract] Debt Instrument [Axis] Debt Instrument, Name [Domain] Principal amount issued of 5.15% notes due 2020 [Member] Principal amount issued of 5.15% notes due 2020 [Member] Principal amount issued of 6.4% notes due 2040 [Member] Principal amount issued of 6.4% notes due 2040 [Member] Schedule of Trading Securities and Other Trading Assets, Major Types of Trading Securities and Assets [Axis] Major Types of Trading Securities and Assets [Domain] Securities (Assets) [Member] Debt Securities [Member] Corporate Debt Securities [Member] Other Corporate Debt Securities [Member] Other Corporate Debt Securities [Member] Trading Assets, Excluding Debt and Equity Securities [Member] Derivative [Member] Swap [Member] Interest Rate Swap Agreements, Derivative Portion [Member] Prepaid Forward Sale Agreements, Derivative Portion [Member] Principal amount Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Maturity Date Derivative Instruments, Gain (Loss) by Hedging Relationship [Axis] Hedging Relationship [Domain] Fair Value Hedging [Member] Nondesignated [Member] Interest Rate Swap Agreements, Long-Term Debt Portion [Member] Interest Rate Swap Agreements, Long-Term Debt Portion [Member] Prepaid Forward Sale Agreements, Liability Portion [Member] Prepaid Forward Sale Agreements, Liability Portion [Member] Defined Benefit Plan, Fair Value of Plan Assets by Measurement [Axis] Fair Value Plan Asset Measurement [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Trading securities Available-for-sale securities Equity Warrants, Fair Value Disclosure Equity Warrants Fair Value Disclosure Equity warrants Interest Rate Derivative Liabilities At Fair Value ' Interest rate swap agreements This element represents the disclosure related to assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). Fair Value, Assets Measured on Recurring Basis, Total Fair Value Assets and Liabilities Measured On Recurring Basis TextBlock Derivative component of ZONES Fair Value Of Embedded Derivative Liability Component of ZONES Debt Derivative component of ZONES Derivative component of prepaid forward sale agreements Derivative Fair Value Of Embedded Derivative Liability Component Of Prepaid Forward Sale Agreements Derivative component of prepaid forward sale agreements Interest rate swap agreements Fair value derivative liability interest rate collars Fair Value Derivative Liability Interest Rate Collars Interest rate collars Fair Value Liabilities Measured On Recurring Basis Fair Value Liabilities Measured On Recurring Basis Interest rate swap agreements (fixed to variable) Derivative, Gain (Loss) on Derivative, Net, Total Unrealized gains (losses) on securities underlying prepaid forward sale agreements Embedded Derivative, Gain (Loss) on Embedded Derivative, Net, Total Mark to market adjustments on derivative component of prepaid forward sale agreements. Mark to market adjustments on derivative component of prepaid forward sale agreements Mark to market adjustments on derivative component of prepaid forward sale agreements Gain (loss) on fair value hedging relationships Mark to market adjustments on derivative component of ZONES. Mark To Market Adjustments On Derivative Component Of Zones Mark to market adjustments on derivative component of ZONES Total gain (loss) Derivative Instruments, Gain (Loss) Recognized in Income, Net, Total Debt outstanding fair value Total Debt, Fair Value Disclosure Difference between variable and fixed rates received under interest rate swap agreements Difference between variable and fixed rates received under interest rate swap agreements Difference between variable and fixed rates received under interest rate swap agreements Percentage of effectiveness for interest rate swaps Percentage of effectiveness for interest rate swaps Carrying value of noncontrolling interest acquired Carrying value of noncontrolling interest acquired Purchase price to acquire noncontrolling interest. Purchase price to acquire noncontrolling interest Purchase price to acquire noncontrolling interest Increase In Additional Paid In Capital Resulting From Purchase Of Noncontrolling Interest. Increase in Additional Paid in Capital Resulting From Purchase of Noncontrolling Interest Increase in Comcast Corporation additional paid-in capital resulting from the purchase of noncontrolling interest Changes From Net Income Attributable to Parent Changes From Net Income Attributable To Parent Changes From Net Income Attributable to Parent Changes from net income attributable to Comcast Corporation and transfers from (to) noncontrolling interests Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Stock Options [Member] Restricted Share Units [Member] ESPP [Member] ESPP [Member] Annual management grant program-Share-based compensation Annual management grant program-Share-based compensation [Member] Number of stock options granted related to our annual management program. Stock Options Granted Number of stock options granted related to our annual management program Number of restricted share units granted related to our annual management program Restricted Share Units Granted Number of restricted share units granted related to our annual management program Fair Value of stock options granted related to our annual management program. Fair Value of Stock Options Granted Fair Value of stock options granted related to our annual management program Fair value of restricted share units granted related to our annual management grant program. Fair Value Of Restricted Share Units Granted Fair value of restricted share units granted related to our annual management grant program Allocated Share Based Compensation Expense Allocated Share-based Compensation Expense, Total Allocated Share-Based Compensation Expense Amount of unrecognized pretax compensation cost Employee Cost Associated With Participation In Employee Stock Purchase Plan Satisfied With Payroll Deductions Employee Cost Associated With Participation In Employee Stock Purchase Plan Satisfied With Payroll Deductions Unrealized gains (losses) on marketable securities Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Beginning Balance Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Deferred gains (losses) on cash flow hedges Unrealized gains (losses) on employee benefit obligations Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Total Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Beginning Balance Cumulative translation adjustments Amount of deferred losses on cash flow hedges expected to be reclassified as adjustment to interest expense over next 12 months, gross InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNetOfDeferredTaxes Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next 12 Months Net Of Deferred Taxes Amount of deferred losses on cash flow hedges expected to be reclassified as adjustment to interest expense over next 12 months, net of deferred taxes Statement of Cash Flows - Supplemental Information (Details) Statement of Cash Flows - Supplemental Information (Details) [Abstract] Amortization Amortization, Total Share-based compensation Share-based Compensation, Total Gains and other income producing transactions that result in no cash inflows or outflows in the period in which they occur, but increase net income and thus are subtracted (removed) when calculating net cash flow from operating activities using the indirect method. Also other expenses included in net income that result in no cash inflows or outflows in the period. This element is used when there is not a more specific and appropriate element. Other Non Cash Income Expense Noncash interest expense (income), net This item represents (i) the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain or loss of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain or loss which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period; additionally, this item would include any gains or losses realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments of the subject investments, (ii) Gains and other income producing transactions that result in no cash inflows or outflows in the period in which they occur, but increase net income and thus are subtracted (removed) when calculating net cash flow from operating activities using the indirect method, and (iii) Other expenses included in net income that result in no cash inflows or outflows in the period which are not otherwise defined in the taxonomy. (Gains) losses on investments and noncash other (income) expense, net Deferred Income Tax Expense (Benefit) Deferred Income Tax Expense (Benefit), Total Deferred income taxes Change in accounts receivable, net Change in accounts receivable, net Change in accounts payable and accrued expenses related to trade creditors Increase (Decrease) in Accounts Payable and Accrued Liabilities, Total Change in other operating assets and liabilities Change in other operating assets and liabilities Interest Interest Paid, Net, Total Income taxes Income Taxes Paid, Net, Total Dividends payable, amount Dividends payable, amount per share Capital expenditures incurred but not yet paid Guarantor Obligations, Maximum Exposure, Undiscounted Aggregate Notional Amount Of Commitment ERISA litigation settlement Eliminations Eliminations [Member] Cable Segment Revenue Percentage-Video Cable Segment Revenue Percentage-Video [Member] Cable Segment Revenue Percentage - High-speed Internet Cable Segment Revenue Percentage - High-speed Internet [Member] Cable Segment Revenue Percentage- Phone Cable Segment Revenue Percentage- Phone [Member] Cable Segment Revenue Percentage- Advertising Cable Segment Revenue Percentage- Advertising [Member] Cable Segment Revenue Percentage- Franchise fees Cable Segment Revenue Percentage- Franchise fees [Member] Cable Segment Revenue Percentage- Other Cable Segment Revenue Percentage- Other [Member] OperatingIncomeExcludingDepreciationAndAmortization Operating Income Excluding Depreciation And Amortization Operating income (loss) before depreciation and amortization Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction, Total Cable segment revenue types as percentage of total cable revenue Cable segment revenue types as percentage of total cable revenue Percentage of assets attributed to segment Percentage of total assets attributed to reportable segment Condensed Consolidating Financial Information (Details) Condensed Consolidating Financial Information (Details) [Abstract] Comcast Parent Comcast Parent [Member] CCCL Parent CCCL Parent [Member] Combined CCHMO Parents Combined CCHMO Parents [Member] Comcast Holdings Comcast Holdings [Member] Non-Guarantor Subsidiaries Comcast Non-Guarantor Subsidiaries [Member] Elimination and Consolidation Adjustments Elimination and Consolidation Adjustments [Member] Derivative, by Nature [Axis] Derivative, Name [Domain] Debt [Member] Comcast Holdings' ZONES due October 2029 [Member] Comcast Holdings' ZONES due October 2029 [Member] Comcast Holdings' 10 5/8% senior subordinated debentures due 2012 Comcast Holdings' 10 5/8% senior subordinated debentures due 2012 [Member] Comcast Holdings' ZONES due November 2029 Comcast Holdings' ZONES due November 2029 [Member] Guarantee Obligations Current Principle Balance Guarantee Obligations Current Principle Balance Amount of unconditional subordinated guarantee on principal amount outstanding debt instruments Amount of unconditional guarantee of principal amount outstanding of Comcast Holdings Investments in and amounts due from subsidiaries eliminated upon consolidation Investments in and amounts due from subsidiaries eliminated upon consolidation Other stockholders equity. Other stockholders equity Other shareholders' equity Sales Revenue Sales Revenue, Services, Net, Total Service revenue Management fees revenue Management fee revenue, Total Management fee revenue Net transactions with affiliates. Net transactions with affiliates Class A Special Common Stock [Member] Class A Special Common Stock [Member] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Actual [Member] Cable segment and corporate and other reclassification [Member] Cable segment and corporate and other reclassification [Member]