Commitments and Contingencies (Details) (USD $)	12 Months Ended			12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2012 Loans	Dec. 31, 2012 Real Estate	Dec. 31, 2012 Strategic Investments	Dec. 31, 2012 Unsecured Debt		Jan. 24, 2013 Subsequent Event
Unfunded Commitments
Proceeds from debt transactions	$ 3,510,000,000
Amount of debt due within the next 12 months	545,254,000	[1]					545,254,000	[1]
Total unencumbered assets	3,007,100,000		4,062,118,000
Real estate, agreement to sell property									220,000,000
Percentage of capital committed to strategic investments that may be drawn down	100.00%
Performance-Based Commitments	81,069,000			44,751,000	36,318,000	0
Discretionary Fundings	102,000			102,000	0	0
Other	47,322,000			0	0	47,322,000
Total	$ 128,493,000			$ 44,853,000	$ 36,318,000	$ 47,322,000

[1] Includes minimum required amortization payments on the March 2012 Secured Credit Facilities and the October 2012 Secured Credit Facility.