Other Significant Transactions (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Jun. 30, 2011
Class of Stock [Line Items]
Total number of Common Stock sold	120,477,521		117,642,872	120,477,521
Proceeds from issuance of Common Stock				$ 60,973,000
Other Significant Transactions (Textuals) [Abstract]
Principal amount of debt scheduled to maturity between 2012 and 2016 repaid through a series of financing transactions completed during the period	625,700,000
Total amount of new loans	673,800,000			673,800,000
Proceeds from series of financing transactions that repaid non-recourse property loans scheduled to mature between 2012 and 2016		120,600,000	218,600,000	334,600,000
Total purchase under securitization transaction	51,500,000			51,534,000
Face value of investments in debt securities classified as available for sale	100,900,000			100,900,000
Term of new loan				10 years
Term of new loan scheduled to amortize				30 years
Losses on extinguishment of debt	23,000,000
Prepayment penalties associated with loans	20,700,000
Write off of deferred loan cost	2,300,000
Total cost of noncontrolling limited partnership interests				13,600,000
Accrued settlement included in total cost of noncontrolling limited partnership interests				7,500,000
Sales of common stock initiated but settled in the subsequent period				325,000
Net proceeds from sales of common stock that will be recognized in the subsequent period				8,200,000
Common Class A [Member]
Class of Stock [Line Items]
Total number of Common Stock sold	2,800,000			2,800,000
Gross proceeds from sale of Common Stock				70,600,000
Proceeds from issuance of Common Stock				$ 69,200,000