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 Entity Public Float hello Entity Current Reporting Status Entity Well-known Seasoned Issuer Entity Voluntary Filers Consolidated Balance Sheet Class A Common Stock [Member] Common Stock A Assets Cash and cash equivalents Cash and cash equivalents, end of year Cash and cash equivalents, beginning of year Cash and Cash Equivalents, at Carrying Value, Total Short Term Investments Less: Current investments Less: Current investments Short-term Investments, Total Investments Accounts receivable, less allowance for doubtful accounts of $196 and $175 Accounts receivable, less allowance for doubtful accounts of $173 and $175 Accounts Receivable, Net, Current, Total Accounts receivable, net Deferred income taxes Deferred Tax Assets, Net, Current, Ending Balance Deferred Tax Assets, Net, Current, Beginning Balance Deferred Tax Assets, Net, Current, Total Deferred income taxes Other current assets Total current assets Current Assets Total current assets Long Term Investments Noncurrent investments Noncurrent investments Investments Property and equipment, net of accumulated depreciation of $31,229 and $27,810 Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property and equipment, net of accumulated depreciation of $32,505 and $27,810 Property and equipment, net Property and equipment, net Franchise rights Cable franchise rights Goodwill Goodwill ending balance Goodwill beginning balance Goodwill Other intangible assets, net of accumulated amortization of $9,518 and $8,711 Other intangible assets, net of accumulated amortization of $9,791 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 salaries and wages Accrued expenses and other current liabilities Accrued Liabilities, Current, Total Current portion of long-term debt Less: current portion Debt, Current, Total Total current liabilities Total current liabilities Long-term debt, less current portion Long-term debt, less current portion Long-term Debt and Capital Lease Obligations, Total Deferred income taxes, total Deferred income taxes Other noncurrent liabilities Other Liabilities, Noncurrent, Total Commitments and contingencies (Note 18) 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 deferred taxes 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 Minority Interest 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 Ending Balance Beginning Balance Total equity Total liabilities and equity Total Liabilities Total liabilities and equity Accounts receivable, less 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 Less: 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 Less: Accumulated depreciation Other intangible assets, accumulated amortization Finite-lived intangible assets, accumulated amortization Other intangible assets Finite-lived 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 Balance Balance Treasury stock common shares Treasury Stock, Shares, Ending Balance Treasury Stock, Shares, Beginning Balance Consolidated Statement of Operations 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 Operating, selling, general and administrative expenses 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 Change in debt component to interest expense Interest Expense, Total Investment income (loss), net ' Investment income (loss), net Investment income (loss), net 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 expense Other Nonoperating Income (Expense), Total Other income (expense) Nonoperating income (Expense), Total Nonoperating income (expense) 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 Income tax expense Income tax expense 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 Dividend per share Consolidated Statement of Cash Flows Operating Activities Adjustments to reconcile net income from consolidated operations to net cash provided by operating activities: Amortization Amortization, Total Share-based compensation expense 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 Noncash interest expense (income), net Gain Loss On Investments And Noncash Other Income Expense Net Gain Loss On Investments And Noncash Other Income Expense Net (Gains) losses on investments and noncash other (income) expense, net (Gains) losses on investments and noncash other (income) expense, net Deferred Income Tax Expense (Benefit) Deferred income taxes Deferred income tax expense (benefit) Deferred Income Tax Expense (Benefit), Total Deferred income taxes Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Change in accounts receivable, net Change in accounts receivable, net Change in accounts payable and accrued expenses related to trade creditors 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 Net cash provided by (used in) 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 Debt Repayments and Repurchases Repurchases of common stock Repurchases of common stock Aggregate consideration Dividends paid Dividends paid Payments of Dividends, Total Issuances of common stock 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 Consolidated Statement of Changes in Equity Statement, Equity Components [Axis] Equity Component [Domain] Redeemable Non-controlling Interests [Member] Redeemable Noncontrolling Interests [Member] Additional Paid-In Capital [Member] Retained Earnings [Member] Treasury Stock at Cost [Member] Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interests [Member] Cumulative effect related to change in accounting principle Cumulative effect related to change in accounting principle on January 1, 2008 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 Amount related to shares issued or received in a share exchange. Share Exchange Issued Received Amount Share exchange Dividends declared Dividends declared Amount 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) Consolidated Statement of Comprehensive Income Holding gains (losses) during the period, net of deferred taxes of $47, $(4) and $7 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, net of deferred taxes of $(19), $(18) and $(10) Employee benefit obligations, net of deferred taxes of $9, $(15) and $30 Other Comprehensive Income, Defined Benefit Plans Adjustment, Net of Tax, Total 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 Legal Entity [Axis] Entity [Domain] Comcast [Member] Holding gains (losses) during the period, deferred taxes Reclassification adjustments for losses (gains) included in net income, deferred taxes Employee benefit obligations, deferred taxes Employee benefit obligations, deferred taxes Other Comprehensive Income, Defined Benefit Plans, Tax, Total Organization And Business Abstract Organization and Business Organization and Business Text Block Organization and Business Summary of Significant Accounting Policies Summary of Significant Accounting Policies Summary of Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Summary of Significant Accounting Policies Recent Accounting Pronouncements Abstract Recent Accounting Pronouncements Schedule Of New Accounting Pronouncements And Changes In Accounting Principles Text Block Recent Accounting Pronouncements Earnings Per Share Earnings Per Share [Text Block] Earnings Per Share Acquisitions And Other Significant Events Abstract Acquisitions and Other Significant Events Business Combination Disclosure Text block Acquisitions and Other Significant Events Investments 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 Property and Equipment Property and Equipment Text Block Property and Equipment Good will Goodwill and Other Intangible Assets Goodwill And Intangible Assets Disclosure Text Block Goodwill and Other Intangible Assets Long-term Debt Long-Term Debt [Text Block] Long-Term Debt Derivative Financial Instruments [Abstract] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Financial Instruments FairValueMeasurementsAndDerivativeFinancialInstrumentsAbstract Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Noncontrolling Interests Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interests Postretirement, Pension and Other Employee Benefit Plans Postretirement, Pension and Other Employee Benefit Plans text block Postretirement, Pension and Other Employee Benefit Plans Equity Equity text block Equity Share-Based Compensation Disclosure of Compensation Related Costs, Share-Based Payments Share-Based Compensation Income Taxes Abstract Income Taxes IncomeTaxDisclosureTextBlock Income Taxes Statement Of Cash Flows Supplemental Information Abstract Statement of Cash Flows - Supplemental Information Cash Flow Supplemental Disclosures Text Block Statement of Cash Flows - Supplemental Information Commitments And Contingencies Abstract Commitments and Contingencies Commitments and Contingencies [Text Block] Commitments and Contingencies Financial Data By Business Segment Abstract Financial Data by Business Segment Segment Reporting Disclosure [Text Block] Financial Data by Business Segment Quarterly Financial Information QuarterlyFinancialInformationTextBlock Quarterly Financial Information Subsequent Events [Abstract] Subsequent Events Schedule of Subsequent Events [Text Block] Subsequent Events Subsequent Events Condensed Consolidating Financial Information Abstract Condensed Consolidating Financial Information