Goodwill and Intangibles - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2008
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill allocated	$ 2,708	$ 2,706	$ 2,751	$ 3,500
Impairment loss recognized	$ 2,102	$ 2,102	$ 2,134	$ 2,700