Loans and Other Lending Investments, net (Details 3) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012 rating	Dec. 31, 2011 rating
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	$ 2,671,735	$ 3,504,861
Senior mortgages
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	2,046,736
Subordinate mortgages
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	151,832
Corporate/Partnership loans
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	473,167
Performing Loans
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	1,541,189	2,176,536
Weighted Average Risk Ratings	3.08	3.29
Performing Loans | Senior mortgages
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	979,560	1,514,016
Weighted Average Risk Ratings	2.84	3.19
Performing Loans | Subordinate mortgages
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	98,572	190,342
Weighted Average Risk Ratings	2.44	3.36
Performing Loans | Corporate/Partnership loans
Recorded Investments in loans, presented by class and by credit quality, as indicated by risk rating
Performing Loans	$ 463,057	$ 472,178
Weighted Average Risk Ratings	3.72	3.61