Income Taxes - Components (Details) - USD ($) $ 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
Current:
Federal									$ 68	$ 795	$ 191
State and local									41	109	27
Foreign									6	21	11
Total current									115	925	229
Deferred									151	303	(140)
Total income tax expense (benefit)	$ 34	$ 58	$ 82	$ 92	$ 907	$ 61	$ 108	$ 152	$ 266	$ 1,228	$ 89