Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Quarterly Financial Information Disclosure [Abstract] | |||||||||||
| Revenue | $ 27,846 | $ 22,135 | $ 21,735 | $ 22,791 | $ 22,075 | $ 21,081 | $ 21,286 | $ 20,587 | $ 94,507 | $ 85,029 | $ 80,736 |
| Operating income | 4,514 | 4,836 | 5,014 | 4,645 | 4,129 | 4,779 | 4,568 | 4,542 | 19,009 | 18,018 | 16,831 |
| Net income attributable to Comcast Corporation | $ 2,511 | $ 2,886 | $ 3,216 | $ 3,118 | $ 14,999 | $ 2,642 | $ 2,521 | $ 2,573 | $ 11,731 | $ 22,735 | $ 8,678 |
| Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) | $ 0.55 | $ 0.63 | $ 0.70 | $ 0.67 | $ 3.22 | $ 0.56 | $ 0.53 | $ 0.54 | $ 2.56 | $ 4.83 | $ 1.80 |
| Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share) | 0.55 | 0.62 | 0.69 | 0.66 | 3.17 | 0.55 | 0.52 | 0.53 | 2.53 | 4.75 | 1.78 |
| Dividends declared per common share (in dollars per share) | $ 0.19 | $ 0.19 | $ 0.19 | $ 0.19 | $ 0.1575 | $ 0.1575 | $ 0.1575 | $ 0.1575 | $ 0.76 | $ 0.63 | $ 0.55 |
| Income tax benefit as a result of the impact of the 2017 tax reform | $ 12,700 | $ 120 | $ 12,682 | $ 0 | |||||||
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to the 2017 tax reform legislation. No definition available.
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- Definition Aggregate dividends declared during the period for each share of common stock outstanding. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The net result for the period of deducting operating expenses from operating revenues. No definition available.
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- References No definition available.
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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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