Consolidated Statements of Equity (USD $)	Total	Common Stock	Stockholders' Equity Additional Paid-In Capital	Stockholders' Equity Accumulated Deficit
Beginning balance at Dec. 31, 2010	$ 1,487,246,000	$ 2,026,000	$ 1,795,413,000	$ (310,193,000)
Beginning balance, shares at Dec. 31, 2010		202,643,705
Issuance of common stock, shares		21,713,365
Issuance of common stock	210,210,000	214,000	209,996,000	0
Offering costs	(15,002,000)	0	(15,002,000)	0
Issuance of restricted common stock, shares		286,000
Issuance of restricted common stock	0	0	0	0
Amortization of nonvested share based compensation	897,000	0	897,000	0
Issuance of common stock under the DRIP, shares		1,857,957
Issuance of common stock under the DRIP	17,651,000	19,000	17,632,000	0
Repurchase of common stock, shares		(821,848)
Repurchase of common stock	(7,916,000)	(8,000)	(7,908,000)	0
Distributions	(38,531,000)	0	0	(38,531,000)
Net (loss) income attributable to controlling interest	2,150,000	0	0	2,150,000
Ending balance at Mar. 31, 2011	1,656,705,000	2,251,000	2,001,028,000	(346,574,000)
Ending balance, shares at Mar. 31, 2011		225,679,179
Beginning balance at Dec. 31, 2011	1,567,340,000	2,284,000	2,032,305,000	(467,249,000)
Beginning balance, shares at Dec. 31, 2011		228,491,312
Issuance of restricted common stock, shares		18,000
Issuance of restricted common stock	0	1,000	(1,000)	0
Amortization of nonvested share based compensation	1,002,000	0	1,002,000	0
Issuance of common stock under the DRIP, shares		2,015,580
Issuance of common stock under the DRIP	19,148,000	20,000	19,128,000	0
Repurchase of common stock, shares		(1,010,843)
Repurchase of common stock	(9,916,000)	(10,000)	(9,906,000)	0
Distributions	(41,502,000)	0	0	(41,502,000)
Net (loss) income attributable to controlling interest	(315,000)	0	0	(315,000)
Ending balance at Mar. 31, 2012	$ 1,535,757,000	$ 2,295,000	$ 2,042,528,000	$ (509,066,000)
Ending balance, shares at Mar. 31, 2012		229,514,049