Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current - U.S. Federal	$ 8	$ (18)	$ 116
International	0	0	1
Total current	8	(18)	117
Deferred - U.S. Federal	476	286	866
International	(9)	0	2
Total deferred	467	286	868
Total income tax expense (benefit)	$ 475	$ 268	$ 985