Income Taxes - Components of Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
United States - Federal, Current income tax expense (benefit)	$ (4)	$ (1)	$ 1
United States - Federal, Deferred income taxes and other accruals expense (benefit)	6	72	(74)
United States - State, Current & Deferred income taxes and other accruals expense (benefit)	(1)	16	(45)
United States - Current & Deferred income taxes, and other accruals expense (benefit)	1	87	(118)
Foreign - Current income tax expense (benefit)	48	447	455
Foreign - Deferred income taxes and other accruals expense (benefit)	(60)	(73)	(2)
Foreign - Current & Deferred income taxes and other accruals expense (benefit)	(12)	374	453
Provision (Benefit) For Income Taxes	$ (11)	$ 461	$ 335