Consolidated Statement Of Assets, Liabilities And Equity (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Investments at value, cost	$ 1,806,749	$ 1,328,153
Financial derivatives - cost	43,199	65,860
Repurchase agreements, cost	40,994	13,650
Investments sold short at value, proceeds	(850,801)	(621,048)
Financial derivatives - proceeds	(28,271)	(13,171)
Securitized debt proceeds	$ (1,050)	$ (1,311)
Common stock, par value
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	25,418,937	20,370,469
Common stock, shares outstanding	25,418,937	20,370,469