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Shareholders Equity of the REIT (Details Textual) (USD $)
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1 Months Ended | 3 Months Ended | 12 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | ||||||||||||||||
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Jun. 30, 2011
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Mar. 31, 2012
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Jun. 30, 2011
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Dec. 31, 2011
Stock
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Dec. 31, 2011
Stock
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Dec. 31, 2010
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Dec. 31, 2009
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Jun. 03, 2011
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Jun. 02, 2011
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Dec. 31, 2011
6.5% Series L Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
6.75% series M Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
7.00% series O Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
6.85% series P Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
8.54% series Q Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
6.75% series R Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
6.75% series S Cumulative Redeemable Preferred Units [Member]
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Dec. 31, 2011
Employee Share Purchase Plan
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Mar. 31, 2010
Controlled Offering Program [Member]
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Dec. 31, 2011
Common Stock
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Dec. 31, 2010
Common Stock
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Dec. 31, 2009
Common Stock
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Dec. 31, 2008
Common Stock
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| Class of Stock [Line Items] | ||||||||||||||||||||||
| Common stock, shares issued | 459,401,000 | 459,401,000 | 254,482,000 | 0 | ||||||||||||||||||
| Common shares issued to public | 34,500,000 | 34,500,000 | 41,069,000 | 78,031,000 | ||||||||||||||||||
| Percentage of fee earn from gross proceeds | 2.00% | |||||||||||||||||||||
| Discounted price of market price of common shares | 85.00% | |||||||||||||||||||||
| Aggregate fair value of common shares under employee purchase plan | $ 25,000 | |||||||||||||||||||||
| Number of common shares issued under employee purchase plan | 76,000 | 87,000 | ||||||||||||||||||||
| Number of common stock shares available under Employee Share plan | 4,900,000 | 4,900,000 | ||||||||||||||||||||
| Cumulative redeemable preferred units, issued | 21,300,000 | 21,300,000 | 2,000,000 | 2,300,000 | 3,000,000 | 2,000,000 | 2,000,000 | 5,000,000 | 5,000,000 | |||||||||||||
| Common stock shares authorized to be issued | 500,000,000 | |||||||||||||||||||||
| Stockholders' Equity of the REIT and Partners' Capital of the Operating Partnership (Textual) [Abstract] | ||||||||||||||||||||||
| Conversion basis of common stock | 0.4464 | 0.4464 | 0.4464 | 0.4464 | ||||||||||||||||||
| Restated number of shares post merger | 254,500,000 | |||||||||||||||||||||
| Common shares added to reflect outstanding stock of acquired entity | 169,600,000 | |||||||||||||||||||||
| Net proceeds from shares added to reflect outstanding shares of common stock of acquired entity | 1,100,000,000 | |||||||||||||||||||||
| Gross proceeds from the issue of common stock under share based compensation plans | 700,000 | 30,800,000 | 337,400,000 | |||||||||||||||||||
| Number of units redeemed under Limited Partnership | 0 | 0 | 100,000 | 200,000 | ||||||||||||||||||
| REIT Description | five or fewer individuals may not own more than 50% of the value of our outstanding stock at any time during the last half of our taxable year. Therefore, our charter restricts beneficial ownership (or ownership generally attributed to a person under the REIT tax rules) by a person or persons acting as a group, of each of our issued and outstanding common, series L preferred stock, series M preferred stock, series O preferred stock and series P preferred stock, or (ii) series Q preferred stock, series R preferred stock or series S preferred stock that, together with all other capital stock owned or deemed owned by that person, would cause that person to own or be deemed to own more than 9.8% (by value or number of shares, whichever is more restrictive) or our issued and outstanding capital stock. | five or fewer individuals may not own more than 50% of the value of our outstanding stock at any time during the last half of our taxable year. Therefore, our charter restricts beneficial ownership (or ownership generally attributed to a person under the REIT tax rules) by a person or persons acting as a group, of each of our issued and outstanding common, series L preferred stock, series M preferred stock, series O preferred stock and series P preferred stock, or (ii) series Q preferred stock, series R preferred stock or series S preferred stock that, together with all other capital stock owned or deemed owned by that person, would cause that person to own or be deemed to own more than 9.8% (by value or number of shares, whichever is more restrictive) or our issued and outstanding capital stock. | ||||||||||||||||||||
| Beneficial interest of outstanding shares | 50.00% | 50.00% | ||||||||||||||||||||
| Number of Individuals need to own the beneficial interest of outstanding shares under REIT code | five or fewer individuals | five or fewer individuals | ||||||||||||||||||||
| Beneficial interest of outstanding shares by a single person or acting as group | 9.80% | 9.80% | ||||||||||||||||||||
| Real Estate Investment Trust Requirements Code Description | generally required to make common stock distributions (other than capital gain distributions) to our shareholders at least equal to (i) the sum of (a) 90% of our “REIT taxable income” computed without regard to the dividends paid deduction and net capital gains and (b) 90% of the net income (after tax), if any, from foreclosure property, minus (ii) certain excess non-cash income | generally required to make common stock distributions (other than capital gain distributions) to our shareholders at least equal to (i) the sum of (a) 90% of our “REIT taxable income” computed without regard to the dividends paid deduction and net capital gains and (b) 90% of the net income (after tax), if any, from foreclosure property, minus (ii) certain excess non-cash income | ||||||||||||||||||||
| Percentage of REIT taxable income computed without regard to the dividends paid deduction and net capital gains | 90.00% | 90.00% | ||||||||||||||||||||
| Percentage of net income after tax from foreclosure property | 90.00% | 90.00% | ||||||||||||||||||||
| Shares authorized to be issued | 600,000,000 | 600,000,000 | ||||||||||||||||||||
| Cash distributions declared | $ 0.28 | |||||||||||||||||||||
| Common stock, shares outstanding | 458,597,000 | 458,597,000 | 254,482,000 | 571,400,000 | 459,401,000 | 254,482,000 | 211,666,000 | 119,191,000 | ||||||||||||||
| Common limited partnership units, outstanding | 2,100,000 | 2,100,000 | ||||||||||||||||||||
| Third party ownership interest of common partnership units | 0.45% | 0.45% | ||||||||||||||||||||
| Number of series of preferred stock | 7 | 7 | ||||||||||||||||||||
| Percentage of ownership restrictions | 25.00% | 25.00% | ||||||||||||||||||||