Interest Cost Components - Schedule of Interest Cost Components (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Amount charged to expense	$ 498	$ 473	$ 453
Amount capitalized	57	56	99
Interest costs, total	$ 555	$ 529	$ 552