Income Taxes - Components of Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
United States - Federal, Current income tax expense (benefit)	$ (1)	$ 1	$ (23)
United States - Federal, Deferred income taxes and other accruals expense (benefit)	72	(74)	(6)
United States - State, Current & Deferred income taxes and other accruals expense (benefit)	16	(45)	0
United States, Current & Deferred income taxes and other accruals expense (benefit)	87	(118)	(29)
Current (a)	447	455	179
Foreign, Deferred income taxes and other accruals expense (benefit)	(73)	(2)	(1,987)
Foreign, Current & Deferred income taxes and other accruals expense (benefit)	374	453	(1,808)
Total Provision (Benefit) For Income Taxes	$ 461	$ 335	$ (1,837)