Income Taxes - Schedule of Significant Components of Provision for Income Taxes Attributable to Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current income tax provision:
Federal taxes									$ 2,087	$ 1,991	$ 1,934
State taxes									209	207	197
International taxes									104	73	91
Total current provision									2,400	2,271	2,222
Deferred income tax (benefit) provision:
Federal taxes									(621)	(368)	(125)
State taxes									(63)	(39)	22
International taxes									(2)	5	27
Total deferred (benefit) provision									(686)	(402)	(76)
Income tax provision (benefit)	$ 342	$ 496	$ 424	$ 452	$ 426	$ 530	$ 384	$ 529	1,714	1,869	2,146
Pre-tax earnings from foreign operations									$ 287	$ 288	$ 466