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Stockholders' Equity (Details) (USD $)
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0 Months Ended | 3 Months Ended | 0 Months Ended | 1 Months Ended | 3 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jan. 27, 2012
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Mar. 31, 2012
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Mar. 31, 2011
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Mar. 16, 2012
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Dec. 31, 2011
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May 08, 2012
Atm Program [Member]
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May 08, 2012
Atm Program [Member]
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Mar. 31, 2012
Atm Program [Member]
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Mar. 31, 2012
Quarter 4 [Member]
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Mar. 31, 2012
Quarter 4 [Member]
OP Units [Member]
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Mar. 31, 2012
Quarter 1 [Member]
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Mar. 31, 2012
Quarter 1 [Member]
OP Units [Member]
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| Class of Stock [Line Items] | ||||||||||||
| Common stock, shares outstanding | 149,384,341 | 148,107,611 | ||||||||||
| Dividend paid on common stock | $ 0.55 | |||||||||||
| Dividend shareholder of record date | Dec. 31, 2011 | Mar. 30, 2012 | ||||||||||
| Dividends payable, date declared | Mar. 16, 2012 | Mar. 16, 2012 | ||||||||||
| Dividends payable, amount per share | $ 0.55 | |||||||||||
| Dividend payable date | Jan. 27, 2012 | Apr. 30, 2012 | ||||||||||
| At the market stock offering program, shares issued | 149,463,241 | 148,186,511 | 643,600 | 643,600 | 1,048,800 | |||||||
| At the market stock offering program remaining amount available for issuance | $ 376,200,000 | $ 444,600,000 | ||||||||||
| At the market stock offering program, aggregate value of common stock | 600,000,000 | |||||||||||
| At the market stock offering program, gross proceeds | 68,400,000 | 110,500,000 | ||||||||||
| At the market stock offering program, net proceeds | $ 109,330,000 | $ 345,369,000 | $ 67,700,000 | $ 109,300,000 | ||||||||
| Shares of its Common Stock in connection with the redemption of an equal number of OP Units | 199,526 | |||||||||||
| Shares of Common Stock upon the exercise of options to purchase Common Stock by certain employees | 17,706 | |||||||||||