Debt and Interest Expense - Interest Expense Table (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Disclosure [Abstract]
Debt and other	$ 245	$ 250	$ 743	$ 723
Capitalized interest	(46)	(46)	(127)	(150)
Total interest expense	$ 199	$ 204	$ 616	$ 573