Debt and Financing Costs - Financing Costs, Net (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Debt Disclosure [Abstract]
Interest expense	$ 143	$ 131	$ 291	$ 239
Amortization of deferred loan costs	2	2	4	3
Capitalized interest	(90)	(85)	(183)	(151)
Interest income	(4)	(3)	(8)	(6)
Financing costs, net	$ 51	$ 45	$ 104	$ 85