DocumentAndEntityInformationAbstract Document and Entity Information [Abstract] Statement [Table] Class of Stock [Axis] Class of Stock [Domain] A classification of Special Class A common stock. Class A Special common stock Common Stock A Special Class B common stock Common Stock B Statement [Line Items] Document Type Amendment Flag Document Period End Date Trading Symbol Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus 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 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 Short-term Investments, Total Investments Accounts receivable, less allowance for doubtful accounts of $161 and $175 Accounts Receivable, Net, Current, Total Other current assets Total current assets Total current assets Investments Long-term Investments, Total Investments Property and equipment, net of accumulated depreciation of $29,010 and $27,810 Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property, Plant and Equipment, Net, Total Franchise rights Goodwill Goodwill, Ending Balance Goodwill, Beginning Balance Other intangible assets, net of accumulated amortization of $8,964 and $8,711 Finite-Lived Intangible Assets, Net, Total 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 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 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 Common stock Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common Stock, Value, Issued, Total 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) Selling, general and administrative Selling, General and Administrative Expense, Total Depreciation Depreciation, Total Amortization Of Intangible Assets Amortization of Intangible Assets, Total Amortization Costs and Expenses, Total Costs and expenses, total Operating income Operating income 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 tax expense Income tax expense Income Tax Expense (Benefit), Total Net income from consolidated operations Net income 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 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 (used in) operating activities Net cash provided by (used in) 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 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 Noncontrolling Interests Redeemable Non-controlling Interests Additional Paid-In Capital Retained Earnings Treasury Stock at Cost Accumulated Other Comprehensive Income (Loss) Non-controlling Interests Stock compensation plans Repurchase and retirement of common stock Repurchase 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 $- 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 $(1) and $(12) 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 Pronouncements 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. Derivative Instruments And Hedging Activities And Other Financial Instruments Disclosure Text Block Fair Value Measurements and Derivative Financial Instruments NoncontrollingInterestsAbstract Noncontrolling Interests [Abstract] Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interests Equity [Abstract] 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 Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Actual [Member]