Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2019
Statement of Financial Position [Abstract]
Investments at value, cost	$ 2,970,306
Financial derivatives–assets, net cost	22,526
Repurchase agreements, cost	61,274
Investments sold short at value, proceeds	(844,604)
Financial derivatives-liabilities, at fair value Net proceeds	(19,019)
Other secured borrowings proceeds	(114,100)
Other secured financing, at fair value-Proceeds	$ (298,706)
Common shares		$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	29,796,601	29,745,776
Common stock, shares outstanding	29,796,601	29,745,776