Common Stock and Other Equity Related Transactions - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended			1 Months Ended	3 Months Ended					3 Months Ended			1 Months Ended	3 Months Ended		1 Months Ended		3 Months Ended
	Sep. 30, 2011	Mar. 04, 2011	Dec. 31, 2010	Mar. 31, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Sep. 30, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Jun. 30, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Mar. 31, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Mar. 04, 2011 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Dec. 31, 2010 8.034% Series A Cumulative Redeemable Perpetual Preferred Stock	Sep. 30, 2011 Common Stock	Jun. 30, 2011 Common Stock	Mar. 31, 2011 Common Stock	Oct. 31, 2011 Common Stock Dividend Paid	Sep. 30, 2011 Series B Subordinated Non-Voting Cumulative Redeemable Preferred Stock	Dec. 31, 2010 Series B Subordinated Non-Voting Cumulative Redeemable Preferred Stock	Oct. 31, 2011 Series B Subordinated Non-Voting Cumulative Redeemable Preferred Stock Dividend Paid	Oct. 31, 2011 Series B Subordinated Non-Voting Cumulative Redeemable Preferred Stock Stock Issued	Mar. 31, 2011 Series D 8.0625 % Units	Mar. 31, 2011 Series F 7.95% Units
Class of Stock [Line Items]
Cumulative Redeemable Preferred Stock, shares issued					8,000,000			8,000,000	0					1,242,462	0
Cumulative Redeemable Preferred Stock, par value per share					$ 0.01			$ 0.01	$ 0.01					$ 0.01	$ 0.01
Stock issued for the Acquisition Properties, share										1,708,276				1,242,462			497,538
Cumulative Redeemable Preferred Stock, liquidation preference per share								$ 25
Cumulative Redeemable Preferred Stock, conversion price per share								$ 24.75
Cumulative Redeemable Preferred Stock, redemption price								$ 25
Perpetual Preferred OP Units conversion	$ 200,000
Common stock issued in equity offering	6,000,000
Net proceeds from issuance of Common Stock	344,049
Dividend distribution to Preferred Stock holders					$ 0.502125	$ 0.502125	$ 0.156217									$ 0.375
Dividend record date					Sep. 09, 2011	Jun. 10, 2011	Mar. 21, 2011			Sep. 30, 2011	Jun. 24, 2011	Mar. 25, 2011		Sep. 30, 2011
Dividend payment date					Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011			Oct. 14, 2011	Jul. 08, 2011	Apr. 08, 2011		Oct. 14, 2011
Dividend distribution to common stock holders											$ 0.375	$ 0.375	$ 0.375
Preferred stock, dividend rate				8.034%														8.0625%	7.95%
Non-controlling interests - Perpetual Preferred OP Units		$ 200,000	$ 200,000															$ 150,000	$ 50,000