Stockholders' Equity of REIT and Partners' Capital of Operating Partnership - Schedule of Preferred Stock (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Total preferred stock	$ 582,200	$ 582,200
Series L Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	49,100	49,100
Series M Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	57,500	57,500
Series O Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	75,300	75,300
Series P Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	50,300	50,300
Series Q Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	100,000	100,000
Series R Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	125,000	125,000
Series S Preferred Stock [Member]
Class of Stock [Line Items]
Total preferred stock	$ 125,000	$ 125,000