Income Taxes - Additional information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Taxes [Line Items]
Effective tax rate of income (loss) before income taxes	36.60%	37.60%	34.40%	36.50%
Reduction in income tax expense	$ 2		$ 34
Equity in net losses of unconsolidated entities	13	$ 16	45	$ 23
Investments Qualifying for Federal Tax Credits [Member]
Income Taxes [Line Items]
Equity in net losses of unconsolidated entities	9	9	15	15
Income tax expense (benefit), including tax credits, from equity method investment	$ 14	$ 14	$ 25	$ 25