Income Taxes - Components (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal									$ (3)	$ 68	$ 795
State and local									35	41	109
Foreign									16	6	21
Total current									48	115	925
Deferred									109	151	303
Total income tax expense (benefit)	$ 48	$ 39	$ 35	$ 35	$ 34	$ 58	$ 82	$ 92	157	$ 266	$ 1,228
Decrease in current provision for income taxes in connection with change in accounting method for tax asset disposals									(47)
Increase in deferred provision for income taxes in connection with change in accounting method for tax asset disposals									$ 47