Condensed Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
INVESTMENT INCOME
Interest income	$ 18,265	$ 16,662	$ 18,990	$ 20,427	$ 23,091	$ 26,440	$ 25,739	$ 26,513	$ 74,344	$ 101,783	$ 93,533
Other income	2,342	807	1,024	1,668	932	565	1,023	293	5,841	2,813	318
Total investment income	20,607	17,469	20,014	22,095	24,023	27,005	26,762	26,806	80,185	104,596	93,851
EXPENSES
Base management fee	2,416	2,485	2,553	2,611	2,772	2,849	2,920	2,952	10,065	11,493	10,751
Interest expense	4,461	4,143	4,234	3,468	3,186	3,073	2,867	2,986	16,306	12,112	9,927
Other investment related expenses	2,062	2,068	2,191	1,749	1,774	1,473	1,163	1,202	8,070	5,612	4,689
Other Operating Expense	2,640	2,379	2,515	2,445	2,835	2,087	2,082	2,199
Total expenses	11,579	11,075	11,493	10,273	10,567	9,482	9,032	9,339	44,420	38,420	35,100
Net investment income	9,028	6,394	8,521	11,822	13,456	17,523	17,730	17,467	35,765	66,176	58,751
NET REALIZED AND CHANGE IN NET UNREALIZED GAIN (LOSS) ON INVESTMENTS, FINANCIAL DERIVATIVES, AND FOREIGN CURRENCY TRANSACTIONS/TRANSLATION
Realized Investment Gains (Losses)	(2,242)	(23,020)	(2,331)	(11,940)	1,483	8,280	761	10,429	(39,533)	20,953	4,162
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation	(4,854)	17,176	(1,188)	(23,068)	(13,077)	(21,876)	(5,268)	(8,479)	(11,934)	(48,700)	(2,964)
Net Realized And Unrealized Gain Loss On Investments And Financial Derivatives	(7,096)	(5,844)	(3,519)	(35,008)	(11,594)	(13,596)	(4,507)	1,950	(51,467)	(27,747)	1,198
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	1,932	550	5,002	(23,186)	1,862	3,927	13,223	19,417	(15,702)	38,429	59,949
Net Income (Loss) Attributable to Noncontrolling Interest	240	34	17	14	82	31	71	156	305	340	782
Net Income (Loss) Attributable to Parent	$ 1,692	$ 516	$ 4,985	$ (23,200)	$ 1,780	$ 3,896	$ 13,152	$ 19,261	$ (16,007)	$ 38,089	$ 59,167
NET INCREASE (DECREASE) IN SHAREHOLDERS' EQUITY RESULTING FROM OPERATIONS PER SHARE:
Basic and Diluted (in usd per share)	$ 0.05	$ 0.02	$ 0.15	$ (0.69)	$ 0.05	$ 0.12	$ 0.39	$ 0.57	$ (0.48)	$ 1.13	$ 2.09