Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Current tax expense	$ (2)		$ (7)	$ (1)
Deferred tax benefit (expense)	1	$ (2)	1
Total income tax expense	$ (1)	$ (2)	$ (6)	$ (1)