Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Current tax benefit (expense)	$ 0	$ (2)	$ 4	$ (7)
Deferred tax benefit (expense)	1	1	(1)	1
Total income tax benefit (expense)	$ 1	$ (1)	$ 3	$ (6)