Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Investments at value, cost	$ 1,672,400	$ 2,122,326
Financial derivatives–assets, at fair value Net cost	163,943	61,560
Repurchase agreements, cost	105,329	172,001
Investments sold short at value, proceeds	(731,048)	(1,290,091)
Financial derivatives-liabilities, at fair value Net proceeds	(56,200)	(33,555)
Securitized debt proceeds	$ 0	$ (749)
Common stock, par value
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	33,126,012	33,449,678
Common stock, shares outstanding	33,126,012	33,449,678