Income Taxes - Components of United States and Foreign Tax (Benefit) Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (15)	$ (22)	$ (25)
Foreign	188	166	175
State	(1)	3	2
Current income tax expense (benefit)	172	147	152
Deferred:
Federal	120	389	77
Foreign	6	(8)	(328)
State	5	(15)	22
Deferred income tax expense (benefit)	131	366	(229)
United States and Foreign Tax (Benefit) Expense	$ 303	$ 513	$ (77)