Change in Accumulated Depreciation and Amortization of Real Estate Assets (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Real Estate And Accumulated Depreciation [Line Items]
Beginning Balance	$ 4,768	$ 4,306	$ 3,834
Depreciation and amortization	550	537	496
Dispositions and other	(270)	(75)	(24)
Ending Balance	$ 5,048	$ 4,768	$ 4,306