Debt and Financing Costs - Components of Financing Costs, Net (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Debt Disclosure [Abstract]
Interest expense	$ 116	$ 123	$ 232	$ 251
Amortization of deferred loan costs	2	2	3	4
Capitalized interest	(12)	(5)	(23)	(9)
Interest income	(2)	(3)	(3)	(5)
Financing costs, net	$ 104	$ 117	$ 209	$ 241