Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	$ (6,442)	$ (3,187)	$ (12,774)	$ (31,669)
Unrealized Gain (Loss) on Financial Derivatives	(2,005)	(2,664)	14,578	15,015
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	(2,661)	2,306	(3,857)	(11,765)
Unrealized Gain (Loss) on Financial Derivatives	2,650	(7,847)	17,723	(925)
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 Financial Derivatives	(3,113)	3,963	(404)	(1,514)
Unrealized Gain (Loss) on Financial Derivatives	2,995	(3,823)	(1,497)	4,285
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 Financial Derivatives	(181)	(134)	(4,302)	(7,200)
Unrealized Gain (Loss) on Financial Derivatives	(1,011)	(4,174)	2,503	(6,442)
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 Financial Derivatives	(84)	12	(3)	(1,548)
Unrealized Gain (Loss) on Financial Derivatives	44	(602)	0	570
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market	Equity Market	Equity Market	Equity Market
Net Realized Gain/Loss on Financial Derivatives	907	(1,520)	911	(1,520)
Unrealized Gain (Loss) on Financial Derivatives	(112)	257	15	257
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 Financial Derivatives	(512)	0	(229)	49
Unrealized Gain (Loss) on Financial Derivatives	(195)	495	15,768	417
Financial Derivatives - Assets [Member] | Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/Loss on Financial Derivatives	255	(15)	103	(32)
Unrealized Gain (Loss) on Financial Derivatives	970	0	975	(12)
Financial Derivatives - Assets [Member] | Other Derivatives [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	67		67
Unrealized Gain (Loss) on Financial Derivatives	(41)		(41)
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	(3,781)	(5,493)	(8,917)	(19,904)
Unrealized Gain (Loss) on Financial Derivatives	(4,655)	5,183	(3,145)	15,940
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 Financial Derivatives	(2)		(59)
Unrealized Gain (Loss) on Financial Derivatives	222		(318)
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 Financial Derivatives	339	(190)	539	4,372
Unrealized Gain (Loss) on Financial Derivatives	959	1,543	1,772	650
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 Financial Derivatives	(2,985)	(160)	(7,517)	143
Unrealized Gain (Loss) on Financial Derivatives	(1,959)	11	(1,759)	11
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 Financial Derivatives	(53)	1,066	(448)	(2,262)
Unrealized Gain (Loss) on Financial Derivatives	96	252	43	273
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 Financial Derivatives	(10)	(6,209)	282	(22,157)
Unrealized Gain (Loss) on Financial Derivatives	(4,099)	3,410	(2,997)	15,093
Financial Derivatives - Liabilities [Member] | Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates	Interest Rates	Interest Rates
Net Realized Gain/Loss on Financial Derivatives	(1,029)	0	(1,673)	0
Unrealized Gain (Loss) on Financial Derivatives	82	(33)	70	(87)
Financial Derivatives - Liabilities [Member] | Other Derivatives [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates/Equity Market		Interest Rates/Equity Market
Net Realized Gain/Loss on Financial Derivatives	(41)		(41)
Unrealized Gain (Loss) on Financial Derivatives	$ 44		$ 44