Stockholders' Equity of the REIT - Schedule of Preferred Stock (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Total preferred stock	$ 582,200	$ 582,200
Series L [Member]
Class of Stock [Line Items]
Total preferred stock	49,100	49,100
Series M [Member]
Class of Stock [Line Items]
Total preferred stock	57,500	57,500
Series O [Member]
Class of Stock [Line Items]
Total preferred stock	75,300	75,300
Series P [Member]
Class of Stock [Line Items]
Total preferred stock	50,300	50,300
Series Q [Member]
Class of Stock [Line Items]
Total preferred stock	100,000	100,000
Series R [Member]
Class of Stock [Line Items]
Total preferred stock	125,000	125,000
Series S [Member]
Class of Stock [Line Items]
Total preferred stock	$ 125,000	$ 125,000