Debt and Financing Costs - Components of Financing Costs, Net (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]
Interest expense	$ 120	$ 125	$ 371	$ 373
Amortization of deferred loan costs	6	2	10	5
Capitalized interest	(56)	(66)	(173)	(216)
Loss on extinguishment of debt	39		39
Interest income	(2)	(1)	(7)	(5)
Financing costs, net	$ 107	$ 60	$ 240	$ 157