Secured Borrowings (Details) (ClearPoint, USD $)			0 Months Ended				3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Feb. 14, 2013 Credit facility	Mar. 31, 2013 Credit facility	Dec. 31, 2012 Credit facility	Dec. 31, 2011 Credit facility	Mar. 31, 2013 Credit facility Subsequent event	Dec. 31, 2011 Credit Facility No. 1	Dec. 31, 2012 Credit Facility No. 2	Dec. 31, 2011 Credit Facility No. 2	Dec. 31, 2012 Credit Facility No. 3	Dec. 31, 2011 Credit Facility No. 3	Dec. 31, 2011 Accelerated Purchase Facility
Secured Borrowings
Facility Limit	$ 90,000,000	$ 300,000,000			$ 90,000,000	$ 250,000,000	$ 10,000,000	$ 75,000,000	$ 45,000,000	$ 75,000,000	$ 45,000,000	$ 100,000,000	$ 50,000,000
Outstanding Balance	64,908,000	213,611,000		0	64,908,000	211,262,000		68,756,000	32,510,000	49,704,000	32,398,000	92,802,000	2,349,000
Committed capacity					$ 0	$ 100,000,000
Period following closing date of transaction, after which any outstanding funded loan becomes immediately due			31 days
Written notice period required for termination							5 days