Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current - U.S. Federal	$ 410	$ 8	$ (18)
International	0	0	0
Total current	410	8	(18)
Deferred - U.S. Federal	(20)	476	286
International	(7)	(9)	0
Total deferred	(27)	467	286
Total income tax expense (benefit)	$ 383	$ 475	$ 268