Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative [Line Items]
Net Realized Gain/(Loss)	$ (8,546)	$ 7,105	$ (28,481)	$ 10,473
Change in Net Unrealized Gain/(Loss)	2,926	(5,178)	17,679	(7,022)
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/(Loss)	(2,279)	6,063	(14,071)	3,430
Change in Net Unrealized Gain/(Loss)	3,363	(2,031)	6,922	(3,601)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure			Credit	Credit
Net Realized Gain/(Loss)	(734)	2,628	(5,477)	5,308
Change in Net Unrealized Gain/(Loss)	1,308	(1,490)	8,107	(4,740)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure			Credit	Credit
Net Realized Gain/(Loss)	(1,573)	3,820	(7,066)	(1,226)
Change in Net Unrealized Gain/(Loss)	1,522	1,096	(2,268)	1,974
Financial Derivatives - Assets [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure			Credit
Net Realized Gain/(Loss)	(12)		(1,560)
Change in Net Unrealized Gain/(Loss)	602		1,173
Financial Derivatives - Assets [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure			Interest Rates	Interest Rates
Net Realized Gain/(Loss)	49	(385)	49	(652)
Change in Net Unrealized Gain/(Loss)	(69)	(1,637)	(78)	(835)
Financial Derivatives - Assets [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure			Interest Rates
Net Realized Gain/(Loss)	(9)		(17)
Change in Net Unrealized Gain/(Loss)	0		(12)
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/(Loss)	(6,267)	1,042	(14,410)	7,043
Change in Net Unrealized Gain/(Loss)	(437)	(3,147)	10,757	(3,421)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure			Credit	Credit
Net Realized Gain/(Loss)	253	2,442	4,562	8,863
Change in Net Unrealized Gain/(Loss)	(927)	(208)	(893)	(217)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure			Credit	Credit
Net Realized Gain/(Loss)	301	(50)	304	(100)
Change in Net Unrealized Gain/(Loss)	(66)	0	0	(34)
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure			Equity Market
Net Realized Gain/(Loss)	(1,273)		(3,328)
Change in Net Unrealized Gain/(Loss)	(4)		21
Financial Derivatives - Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure			Interest Rates	Interest Rates
Net Realized Gain/(Loss)	(5,548)	(1,002)	(15,948)	(1,001)
Change in Net Unrealized Gain/(Loss)	562	(3,141)	11,683	(3,691)
Financial Derivatives - Liabilities [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure			Interest Rates	Interest Rates
Net Realized Gain/(Loss)	0	(348)	0	(719)
Change in Net Unrealized Gain/(Loss)	$ (2)	$ 202	$ (54)	$ 521