Consolidated Statement Of Assets, Liabilities And Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Statement Of Assets, Liabilities And Shareholders' Equity [Abstract]
Investments at value, cost	$ 1,232,162	$ 1,234,203
Financial derivatives - assets, cost	105,906	118,281
Repurchase agreements, cost	13,650	15,750
Investments sold short at fair value, proceeds	579,447	459,013
Financial derivatives - liabilities, proceeds	21,088	9,636
Securitized debt proceeds	$ 1,495	$ 0
Common stock, no 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