Condensed Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
INVESTMENT INCOME
Interest income	$ 23,810		$ 21,145		$ 21,788		$ 22,886		$ 18,265	$ 16,662	$ 18,990	$ 20,427	$ 89,629		$ 74,344		$ 101,783
Other income	1,288		1,232		872		939		2,342	807	1,024	1,668	4,331		5,841		2,813
Total investment income	25,098		22,377		22,660		23,825		20,607	17,469	20,014	22,095	93,960		80,185		104,596
EXPENSES
Base management fee to affiliate	2,113	[1]	2,161	[1]	2,372	[1]	2,410	[1]	2,416	2,485	2,553	2,611	9,056	[2]	10,065	[2]	11,493	[2]
Interest expense	9,326		8,166		7,625		6,003		4,461	4,143	4,234	3,468	31,120		16,306		12,112
Other investment related expenses	4,267		1,908		2,058		1,521		2,062	2,068	2,191	1,749
Other operating expenses	2,333		2,240		2,173		2,116		2,640	2,379	2,515	2,445
Total expenses	18,039		14,475		14,228		12,050		11,579	11,075	11,493	10,273	58,792		44,420		38,420
NET INVESTMENT INCOME	7,059		7,902		8,432		11,775		9,028	6,394	8,521	11,822	35,168		35,765		66,176
NET REALIZED AND CHANGE IN NET UNREALIZED GAIN (LOSS) ON INVESTMENTS, FINANCIAL DERIVATIVES, AND FOREIGN CURRENCY TRANSACTIONS/TRANSLATION
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions	(5,831)		1,205		(5,347)		(831)		(2,242)	(23,020)	(2,331)	(11,940)	(10,804)		(39,533)		20,953
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation	6,970		(2,512)		2,356		4,786		(4,854)	17,176	(1,188)	(23,068)	11,600		(11,934)		(48,700)
Total Change in Net Unrealized Gain Loss On Investments, Financial derivatives, and Foreign currency translation	1,139		(1,307)		(2,991)		3,955		(7,096)	(5,844)	(3,519)	(35,008)	796		(51,467)		(27,747)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	8,198		6,595		5,441		15,730		1,932	550	5,002	(23,186)	35,964		(15,702)		38,429
Net Income (Loss) Attributable to Noncontrolling Interest	754		400		377		452		240	34	17	14	1,983		305		340
Net Income (Loss) Attributable to Parent	$ 7,444		$ 6,195		$ 5,064		$ 15,278		$ 1,692	$ 516	$ 4,985	$ (23,200)	$ 33,981		$ (16,007)		$ 38,089
NET INCREASE (DECREASE) IN SHAREHOLDERS' EQUITY RESULTING FROM OPERATIONS PER SHARE:
Basic and Diluted (in usd per share)	$ 0.23	[3]	$ 0.19	[3]	$ 0.16	[3]	$ 0.47	[3]	$ 0.05	$ 0.02	$ 0.15	$ (0.69)	$ 1.04		$ (0.48)		$ 1.13
Management fee rebate	$ 160		$ 172		$ 0		$ 0						$ 332	[2]	$ 0	[2]	$ 0	[2]

[1] Net of management fee rebate of $0.2 million for the each of the three month periods ended September 30, 2017 and December 31, 2017, respectively. See Note 9 for further details on management fee rebates.(2)For th

[2] See Note 9 for further details on management fee rebates.

[3] For the year ended December 31, 2017 the sum of EPS for the four quarters of the year does not equal EPS as calculated for the entire year (see Note 13) as a result of changes in shares during the year due to repurchases of common share, as EPS is calculated using average shares outstanding during the period.