Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal
Current	$ 5	$ 7	$ (576)
Deferred	338	376	734
State
Current	50	15	(22)
Deferred	55	81	52
Foreign
Current	29	35	36
Deferred	(27)	(11)	(54)
Total income tax expense	450	503	170
Income tax expense allocation
Attributable to income	450	503	170
Stockholders' equity:
Tax effect of the change in accumulated other comprehensive loss	$ 17	$ (62)	$ (2)