Debt and Financing Costs - Financing Costs, Net (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Debt Disclosure [Abstract]
Interest expense	$ 146	$ 132	$ 437	$ 371
Amortization of deferred loan costs	2	2	6	5
Capitalized interest	(93)	(90)	(276)	(241)
Interest income	(4)	(4)	(12)	(10)
Financing costs, net	$ 51	$ 40	$ 155	$ 125