Goodwill and Other Intangible Assets - Other Intangible Assets and Amortization Expense Table (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Gross carrying amount	$ 1,013	$ 1,013
Accumulated amortization	(140)	(109)
Net carrying amount	873	904
Amortization expense	$ 31	$ 32