Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
| Balance, January 1 | $ 1,136 | $ 1,171 | $ 1,701 |
| Additions based on tax positions related to the current year | 74 | 67 | 63 |
| Additions based on tax positions related to prior years | 67 | 98 | 111 |
| Additions from acquired subsidiaries | 13 | 0 | 0 |
| Reductions for tax positions of prior years | (62) | (84) | (220) |
| Reductions due to expiration of statutes of limitations | (44) | (41) | (448) |
| Settlements with tax authorities | (81) | (75) | (36) |
| Balance, December 31 | $ 1,103 | $ 1,136 | $ 1,171 |