Consolidated Statement Of Assets, Liabilities And Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Consolidated Statement Of Assets, Liabilities And Shareholders' Equity [Abstract]
Investments at value, cost	$ 1,126,541	$ 1,234,203
Financial derivatives - assets, cost	82,791	118,281
Repurchase agreements, cost	36,748	15,750
Investments sold short at value, proceeds	493,130	459,013
Financial derivatives - liabilities, proceeds	22,033	9,636
Securitized debt proceeds	$ 1,436	$ 0
Common stock, par value
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	16,447,651	16,447,651
Common stock, shares outstanding	16,447,651	16,447,651