Debt and Preferred Equity Investments (Details 4) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 segment	Mar. 31, 2012	Dec. 31, 2012 segment
Debt and Preferred Equity Investments
Number of portfolio segments of financial receivables	1		1
Additional amount of financing receivables included in other assets	$ 129,000,000		$ 121,300,000
Recorded investment:
Average recorded investment in impaired loans	10,864,000	79,937,000
Investment and preferred equity income (loss) recognized	227,000	1,562,000
Class of financing receivable
Unpaid principal balance:
With an allowance recorded	10,750,000		10,750,000
Unpaid Principal Balance	10,750,000		10,750,000
Recorded investment:
With an allowance recorded	10,750,000		10,750,000
Recorded Investment	10,750,000		10,750,000
Allowance Allocated	$ 7,000,000		$ 7,000,000