Income Taxes - Schedule of Significant Components of Provision for Income Taxes Attributable to Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income tax provision:
Federal taxes	$ 210	$ 1,585	$ 2,087
State taxes	234	223	209
International taxes	135	133	104
Total current provision	579	1,941	2,400
Deferred income tax (benefit) provision:
Federal taxes	620	1,509	(621)
State taxes	115	(69)	(63)
International taxes	(21)	(6)	(2)
Total deferred (benefit) provision	714	1,434	(686)
Income tax provision (benefit)	$ 1,293	$ 3,375	$ 1,714