Debt and Preferred Equity Investments (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2012 segment	Dec. 31, 2011 receivable segment
Debt and Preferred Equity Investments
Number of portfolio segments of financial receivables	1	1
Additional amount of financing receivables included in other assets	$ 121,300,000	$ 108,700,000
Nonaccrual balance of financing receivables		102,600,000
Recorded investment for financing receivables past due 90 days		17,300,000
Number of financing receivables past due 90 days		2
Recorded investment:
Average recorded investment in impaired loans	50,231,000	191,288,000
Investment and preferred equity income (loss) recognized	3,712,000	9,554,000
Class of financing receivable
Unpaid principal balance:
With no related allowance recorded		106,623,000
With an allowance recorded	10,750,000	86,121,000
Unpaid Principal Balance	10,750,000	192,744,000
Recorded investment:
With no related allowance recorded		83,378,000
With an allowance recorded	10,750,000	81,475,000
Recorded Investment	10,750,000	164,853,000
Allowance Allocated	$ 7,000,000	$ 50,175,000