Debt Obligations (Details 4) (USD $)					0 Months Ended	6 Months Ended	12 Months Ended	0 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Collateralized loan obligation	Dec. 31, 2012 Collateralized loan obligation	Sep. 24, 2012 CLO I - Issued two investment grade tranches September 24, 2012. Replacement period through September 2014. Stated maturity date of October 2022. Interest is variable based on three-month LIBOR; the weighted average note rate was 3.64% and 3.65% at June 30, 2013 and December 31, 2012 respectively item	Jun. 30, 2013 CLO I - Issued two investment grade tranches September 24, 2012. Replacement period through September 2014. Stated maturity date of October 2022. Interest is variable based on three-month LIBOR; the weighted average note rate was 3.64% and 3.65% at June 30, 2013 and December 31, 2012 respectively item	Dec. 31, 2012 CLO I - Issued two investment grade tranches September 24, 2012. Replacement period through September 2014. Stated maturity date of October 2022. Interest is variable based on three-month LIBOR; the weighted average note rate was 3.64% and 3.65% at June 30, 2013 and December 31, 2012 respectively item	Jan. 28, 2013 CLO II - Issued two investment grade tranches January 28, 2013. Replacement period through January 2015. Stated maturity date of February 2023. Interest is variable based on three-month LIBOR; the weighted average note rate was 2.59% item	Jun. 30, 2013 CLO II - Issued two investment grade tranches January 28, 2013. Replacement period through January 2015. Stated maturity date of February 2023. Interest is variable based on three-month LIBOR; the weighted average note rate was 2.59% item	Jan. 28, 2013 CLO II - Issued two investment grade tranches January 28, 2013. Replacement period through January 2015. Stated maturity date of February 2023. Interest is variable based on three-month LIBOR; the weighted average note rate was 2.59% Forecast	Jan. 28, 2013 Class A senior secured floating rate notes	Sep. 24, 2012 Class A senior secured floating rate notes	Jan. 28, 2013 Class B secured floating rate notes	Sep. 24, 2012 Class B secured floating rate notes
Debt Obligations
Debt, Face Value			$ 264,500,000			$ 87,500,000	$ 87,500,000		$ 177,000,000	$ 260,000,000	$ 156,000,000	$ 75,000,000	$ 21,000,000	$ 12,500,000
Debt, Carrying Value	744,105,570	812,452,845	264,500,000			87,500,000	87,500,000		177,000,000
Collateral Loans, Unpaid Principal			370,438,106		125,100,000	125,000,146	125,086,650		245,437,960
Collateral Loans, Carrying Value			369,475,418			124,646,506	124,525,103	210,000,000	244,828,912
Collateral Cash, Restricted Cash	34,147,603	42,535,514	14,286,630			86,504			14,200,126
Number of investment grade tranches issued					2	2	2	2	2
Variable interest rate, description					one-month LIBOR	three-month LIBOR	three-month LIBOR	one-month LIBOR	three-month LIBOR
Weighted average note rate (as a percent)			2.93%	3.65%	3.39%	3.64%	3.65%	2.36%	2.59%
Replacement period					2 years			2 years
Number of classes of secured floating rate notes								2
Notional amount of equity interest retained					37,600,000			83,000,000
Issuance costs					2,400,000			3,200,000
Weighted average note rate including certain fees and costs (as a percent)			3.43%	4.33%	4.35%			3.00%
Proceeds from additional loan obligations								$ 50,000,000
Period of additional loan obligations								90 days