Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
| Gross unrecognized tax benefits, January 1 | $ 1,543 | $ 1,497 | $ 1,443 |
| Additions based on tax positions related to the current year | 230 | 229 | 121 |
| Additions based on tax positions related to prior years | 133 | 125 | 319 |
| Additions from acquired subsidiaries | 1 | 130 | 0 |
| Reductions for tax positions of prior years | (344) | (346) | (251) |
| Reductions due to expiration of statutes of limitations | (117) | (75) | (70) |
| Settlements with tax authorities | (24) | (17) | (65) |
| Gross unrecognized tax benefits, December 31 | 1,422 | 1,543 | 1,497 |
| Positions paid | (409) | (531) | (688) |
| Liability for uncertain tax positions | $ 1,013 | $ 1,012 | $ 809 |