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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	$ (4,927)	$ (8,546)	$ (6,332)	$ (28,481)
Unrealized Gain (Loss) on Derivatives	21,837	2,926	16,582	17,679
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	(2,705)	(2,279)	(1,196)	(14,071)
Unrealized Gain (Loss) on Derivatives	20,206	3,363	15,072	6,922
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/Loss on Derivatives	(542)	(734)	2,709	(5,477)
Unrealized Gain (Loss) on Derivatives	1,107	1,308	(4,492)	8,107
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/Loss on Derivatives	(2,634)	(1,573)	(4,121)	(7,066)
Unrealized Gain (Loss) on Derivatives	3,489	1,522	3,514	(2,268)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/Loss on Derivatives	82	(12)	82	(1,560)
Unrealized Gain (Loss) on Derivatives	(44)	602	(44)	1,173
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market		Equity Market
Net Realized Gain/Loss on Derivatives	42		4
Unrealized Gain (Loss) on Derivatives	66		127
Financial Derivatives - Assets [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	500	49	283	49
Unrealized Gain (Loss) on Derivatives	15,583	(69)	15,962	(78)
Financial Derivatives - Assets [Member] | U.S. Treasury Note Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Derivatives	(153)		(153)
Unrealized Gain (Loss) on Derivatives	5		5
Financial Derivatives - Assets [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure		Interest Rates		Interest Rates
Net Realized Gain/Loss on Derivatives		(9)		(17)
Unrealized Gain (Loss) on Derivatives		0		(12)
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	(2,222)	(6,267)	(5,136)	(14,410)
Unrealized Gain (Loss) on Derivatives	1,631	(437)	1,510	10,757
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Derivatives	(29)		(57)
Unrealized Gain (Loss) on Derivatives	(540)		(540)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/Loss on Derivatives	22	253	200	4,562
Unrealized Gain (Loss) on Derivatives	455	(927)	814	(893)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit	Credit	Credit
Net Realized Gain/Loss on Derivatives	(905)	301	(4,532)	304
Unrealized Gain (Loss) on Derivatives	378	(66)	200	0
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market	Equity Market	Equity Market	Equity Market
Net Realized Gain/Loss on Derivatives	(363)	(1,273)	(395)	(3,328)
Unrealized Gain (Loss) on Derivatives	(90)	(4)	(53)	21
Financial Derivatives - Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	(325)	(5,548)	292	(15,948)
Unrealized Gain (Loss) on Derivatives	1,462	562	1,101	11,683
Financial Derivatives - Liabilities [Member] | U.S. Treasury Note Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Derivatives	(597)		(597)
Unrealized Gain (Loss) on Derivatives	(54)		(54)
Financial Derivatives - Liabilities [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	(25)	0	(47)	0
Unrealized Gain (Loss) on Derivatives	$ 20	$ (2)	$ 42	$ (54)