Debt Obligations, Collateralized Loan Obligations (Details)	1 Months Ended					12 Months Ended
	Dec. 31, 2016 USD ($)	Aug. 31, 2016 USD ($) item	Aug. 31, 2015 USD ($) item	Mar. 31, 2015 USD ($)	Feb. 28, 2015 USD ($) item	Dec. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)
Debt Obligations
Debt, Carrying Value	$ 728,441,109					$ 728,441,109		$ 758,899,661
Collateral Cash, Restricted Cash	$ 29,314,929					$ 29,314,929		48,301,244
Weighted average note rate (as a percent)	2.25%					2.25%
CLOs
Debt Obligations
Debt, Face Value	$ 737,000,000					$ 737,000,000		768,000,000
Debt, Carrying Value	728,441,109					728,441,109		758,899,661
Collateral Loans, Unpaid Principal	960,567,514					960,567,514		971,162,690
Collateral Loans, Carrying Value	957,527,517					957,527,517		968,970,064
Collateral Cash, Restricted Cash	14,432,488					14,432,488		42,992,023
Collateral-At-Risk	$ 0					$ 0		$ 0
Weighted average note rate (as a percent)	3.21%					3.21%		2.84%
Weighted average note rate including certain fees and costs (as a percent)	3.71%					3.71%		3.24%
Deferred financing fees	$ 8,600,000					$ 8,600,000		$ 9,100,000
CLO VI
Debt Obligations
Debt, Face Value	250,250,000	$ 275,400,000				250,250,000	$ 325,000,000
Debt, Carrying Value	246,442,883	$ 250,300,000				246,442,883
Collateral Loans, Unpaid Principal	324,569,105					324,569,105
Collateral Loans, Carrying Value	323,350,928					323,350,928
Collateral Cash, Restricted Cash	$ 430,895					$ 430,895
Number of investment grade tranches issued | item		3
Number of newly-formed wholly-owned subsidiaries | item		2
Replacement period		3 years
Proceeds from additional loan obligations		$ 49,600,000
Maximum period of additional loan obligations		120 days
Notional amount of equity interest retained		$ 74,800,000
Weighted average note rate (as a percent)	3.30%	2.48%				3.30%
Variable interest rate, description		one-month LIBOR				one-month LIBOR
Weighted average note rate including certain fees and costs (as a percent)		3.44%
CLO V
Debt Obligations
Debt, Face Value	$ 267,750,000		$ 302,600,000			$ 267,750,000		267,750,000	$ 350,000,000
Debt, Carrying Value	264,864,114		$ 267,800,000			264,864,114		263,784,723
Collateral Loans, Unpaid Principal	344,679,286					344,679,286		343,561,696
Collateral Loans, Carrying Value	343,747,570					343,747,570		342,988,734
Collateral Cash, Restricted Cash	$ 5,320,715					$ 5,320,715		$ 6,438,304
Number of investment grade tranches issued | item			3
Number of newly-formed wholly-owned subsidiaries | item			2
Replacement period			3 years
Proceeds from additional loan obligations			$ 47,400,000
Maximum period of additional loan obligations			120 days
Notional amount of equity interest retained			$ 82,300,000
Weighted average note rate (as a percent)	3.26%		2.44%			3.26%		2.91%
Variable interest rate, description			one-month LIBOR			one-month LIBOR
Weighted average note rate including certain fees and costs (as a percent)			3.07%
CLO IV
Debt Obligations
Debt, Face Value	$ 219,000,000					$ 219,000,000		$ 219,000,000
Debt, Carrying Value	217,134,112				$ 219,000,000	217,134,112		215,985,420
Collateral Loans, Unpaid Principal	291,319,123					291,319,123		288,581,773
Collateral Loans, Carrying Value	290,429,019				$ 250,000,000	290,429,019		287,946,641
Collateral Cash, Restricted Cash	$ 8,680,878					$ 8,680,878		$ 11,418,227
Number of investment grade tranches issued | item					3
Number of newly-formed wholly-owned subsidiaries | item					2
Replacement period					2 years 6 months
Proceeds from additional loan obligations					$ 50,000,000
Notional amount of equity interest retained					$ 81,000,000
Weighted average note rate (as a percent)	3.06%				2.24%	3.06%		2.71%
Variable interest rate, description					one-month LIBOR	one-month LIBOR
Weighted average note rate including certain fees and costs (as a percent)					2.96%
CLO III
Debt Obligations
Debt, Face Value								$ 281,250,000
Debt, Carrying Value								279,129,518
Collateral Loans, Unpaid Principal								339,019,221
Collateral Loans, Carrying Value								338,034,689
Collateral Cash, Restricted Cash								$ 25,135,492
Weighted average note rate (as a percent)								2.86%
Debt instrument redemption value	$ 281,300,000					$ 281,300,000
Deferred fees expensed as interest expense	$ 1,000,000
CLO II
Debt Obligations
Debt instrument redemption value				$ 177,000,000
Deferred fees expensed as interest expense				$ 1,500,000
Class C secured floating rate notes
Debt Obligations
Notes acquired			$ 12,500,000
Net proceeds			$ 12,500,000