Debt and Interest Expense - Interest Expense Table (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Debt and other	$ 989	$ 973	$ 949
Capitalized interest	(164)	(201)	(263)
Total interest expense	$ 825	$ 772	$ 686