Income Taxes - Components of 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	$ 76	$ 116	$ 104
Deferred	52	(99)	(382)
Total income tax expense (benefit)	$ 128	$ 17	$ (278)