Stockholders' Equity of the REIT - Schedule of Terms and Conditions Preferred Stock Outstanding (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Class of Stock [Line Items]
Shares Outstanding	21,300,000
Liquidation Preference of Preferred Stock	$ 582,500
Series L [Member]
Class of Stock [Line Items]
Shares Outstanding	2,000,000
Liquidation Preference of Preferred Stock	50,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	6.50%
Series M [Member]
Class of Stock [Line Items]
Shares Outstanding	2,300,000
Liquidation Preference of Preferred Stock	57,500
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	6.75%
Series O [Member]
Class of Stock [Line Items]
Shares Outstanding	3,000,000
Liquidation Preference of Preferred Stock	75,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	7.00%
Series P [Member]
Class of Stock [Line Items]
Shares Outstanding	2,000,000
Liquidation Preference of Preferred Stock	50,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	6.85%
Series Q [Member]
Class of Stock [Line Items]
Shares Outstanding	2,000,000
Liquidation Preference of Preferred Stock	100,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	8.54%
Series R [Member]
Class of Stock [Line Items]
Shares Outstanding	5,000,000
Liquidation Preference of Preferred Stock	125,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	6.75%
Series S [Member]
Class of Stock [Line Items]
Shares Outstanding	5,000,000
Liquidation Preference of Preferred Stock	$ 125,000
Preferred Stock Par Or Stated Value Per Share	$ 0.01
Dividend Rate	6.75%