Income Taxes - Provisions for Current and Deferred Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.K.
Current	$ 0	$ 2	$ 0
Deferred	0	0	0
Non-U.K.
Current	7	9	30
Deferred	143	(19)	20
Total income tax expense (benefit)	$ 150	$ (8)	$ 50