Accounts payable and accrued expenses related to trade creditors Accounts receivable, less allowance for doubtful accounts of $175 and $190 Accrued expenses and other current liabilities Property and equipment, accumulated depreciation Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss) Additional Paid in Capital Additional paid-in capital Additional Paid-In Capital Amortization Adjustments to reconcile net income from consolidated operations to net cash provided by operating activities: Accounts receivable, allowance for doubtful accounts Amendment Flag Amortization of Intangible Assets Amortization Total assets Total assets Assets Total current assets Total current assets Current Assets: Acquisitions and Other Significant Events Cash and cash equivalents Cash and cash equivalents, end of year Cash and cash equivalents, beginning of year Increase (decrease) in cash and cash equivalents Increase (decrease) in cash and cash equivalents Statement of Cash Flows - Supplemental Information Class of Stock [Domain] Commitments and contingencies (Note 17) Commitments and Contingencies Class A common stock Common Stock A A classification of Special Class A common stock. Class A Special common stock Common Stock A Special Class B common stock Common Stock B Dividends declared per common share attributable to Comcast Corporation shareholders Common stock, par value Common stock, authorized Common stock, issued Common stock, outstanding Common stock Comprehensive income attributable to Comcast Corporation Comprehensive income attributable to Comcast Corporation Comprehensive income Comprehensive income Contributions from and (distributions to) noncontrolling interests. Contributions from (distributions to) noncontrolling interests Costs and Expenses Costs and Expenses, Total Costs and Expenses: Cumulative effect related to change in accounting principle Current Fiscal Year End Date Current portion of long-term debt Deferred Income Tax Expense (Benefit) Deferred income taxes Deferred Tax Assets, Net, Current Deferred income taxes Deferred Tax Liabilities, Noncurrent Deferred income taxes Depreciation 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 Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Share-Based Compensation Dividends declared Dividends declared Document Information [Text Block] Document Period End Date Document Type Basic earnings per common share attributable to Comcast Corporation shareholders Diluted earnings per common share attributable to Comcast Corporation shareholders Earnings Per Share Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Current Reporting Status Entity [Domain] Entity Filer Category Entity Public Float Entity Registrant Name Entity [Text Block] Entity Voluntary Filers Entity Well-known Seasoned Issuer Equity Component [Domain] Profit or loss as represented on the statement of changes in equity. Net income (loss) Other intangible assets, accumulated amortization Other intangible assets, net of accumulated amortization of $8,711 and $8,160 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) Gai ns 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 (Gains) losses on investments and noncash other (income) expense, net Goodwill Goodwill and Other Intangible Assets Sum of operating profit and nonoperating income (expense) before income taxes, extraordinary items, cumulative effects of changes in accounting principles, and noncontrolling interest. Income before income taxes Income before income taxes Equity in net income (losses) of affiliates, net Equity in net (income) losses of affiliates, net Income Statement [Abstract] Income Taxes Income tax expense Income tax expense Change in accounts payable and accrued expenses related to trade creditors Change in accounts receivable, net Change in accounts receivable, net Changes in operating assets and liabilities, net of effects of acquisitions and divestitures: Change in other operating assets and liabilities Change in other operating assets and liabilities Franchise rights Interest Expense Interest expense Investment income (loss), net 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 Legal Entity [Axis] Total liabilities and equity Total liabilities and equity Liabilities and Equity Total current liabilities Total current liabilities Current Liabilities: Long-term debt, less current portion Long-Term Debt Long-term Investments Investments Stockholders' Equity Attributable to Noncontrolling Interest Noncontrolling interests Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interests Sale (purchase) of subsidiary shares to (from) noncontrolling interests, net Organization and Business Net Cash Provided by (Used in) Financing Activities Net cash provided by (used in) financing activities Financing Activities Net Cash Provided by (Used in) Investing Activities Net cash provided by (used in) investing activities Investing Activities Net Cash Provided by (Used in) Operating Activities Net cash provided by (used in) operating activities Operating Activities Net income attributable to Comcast Corporation Net income attributable to Comcast Corporation Net (income) loss attributable to noncontrolling interests Net (income) loss attributable to noncontrolling interests Noncash contribution expense Non-controlling Interests Nonoperating Income (Expense) Nonoperating Income (Expense), Total Other Income (Expense): Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Operating expenses less depreciation and amortization. Operating (excluding depreciation and amortization) Operating income Operating income Other current assets Other noncurrent assets, net Employee benefit obligations, net of deferred taxes of $(15), $30 and $(16) Employee benefit obligations, deferred taxes Cumulative translation adjustments Other comprehensive income (loss) Reclassification adjustments for losses (gains) included in net income, net of deferred taxes of $(18), $(10) and $46 Reclassification adjustments for losses (gains) included in net income, net of deferred taxes of $(18), $(10) and $46 Reclassification adjustments for losses (gains) included in net income, deferred taxes Holding gains (losses) during the period, net of deferred taxes of $(4), $7 and $23 Holding gains (losses) during the period, deferred taxes Other noncurrent liabilities Other noncash income (expense). Noncash interest expense (income), net Noncash interest expense (income), net Other income (expense) Parent Company [Member] Payments for (Proceeds from) Other Investing Activities Other Repurchases of common stock Repurchases of common stock Dividends paid Dividends paid Acquisitions, net of cash acquired Acquisitions, net of cash acquired Cash paid for intangible assets Cash paid for intangible assets Purchases of investments Purchases of investments Capital expenditures Capital expenditures Postretirement, Pension and Other Employee Benefit Plans Preferred stock, authorized Preferred stock, issued Preferred stock - authorized, 20,000,000 shares; issued, zero Issuances of common stock Proceeds from borrowings Other Proceeds from sales of investments Net income from consolidated operations Net income from consolidated operations Property and Equipment Property and equipment, net of accumulated depreciation of $27,810 and $23,235 Quarterly Financial Information (Unaudited) Redeemable Noncontrolling Interests Redeemable Non-controlling Interests Repurchases and repayments of debt Repurchases and repayments of debt Retained Earnings (Accumulated Deficit) Retained earnings Retained Earnings Revenue Condensed Consolidating Financial Information Recent Accounting Pronouncements Schedule II - Valuation and Qualifying Accounts Financial Data by Business Segment Selling, general and administrative Share-based compensation Short-term Investments Investments Summary of Significant Accounting Policies Class of Stock [Axis] Statement, Equity Components [Axis] Statement [Line Items] Statement of Cash Flows [Abstract] Statement of Financial Position [Abstract] Statement of Income and Comprehensive Income [Abstract] Statement of Stockholders' Equity [Abstract] Statement [Table] Total Comcast Corporation shareholders' equity Total Comcast Corporation shareholders' equity Total equity Ending Balance Beginning Balance Total equity Equity: Equity Share exchange Employee stock purchase plan Stock compensation plans Repurchase and retirement of common stock Repurchase and retirement of common stock Redeemable noncontrolling interests Trading Symbol Treasury Stock at Cost Treasury stock common shares 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