Summary of Significant Accounting Policies - Summary of Financial Information for Joint Ventures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Total assets	$ 1,749	$ 1,577
Total liabilities	1,444	1,231
Revenues	693	606	$ 491
Net income	$ 80	$ 71	$ 32