Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	$ (1,405)	$ (19,936)
Unrealized Gain (Loss) on Derivatives	(5,254)	14,754
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	1,509	(11,793)
Unrealized Gain (Loss) on Derivatives	(5,133)	3,560
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit
Net Realized Gain/Loss on Derivatives	3,251	(4,744)
Unrealized Gain (Loss) on Derivatives	(5,599)	6,799
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit
Net Realized Gain/Loss on Derivatives	(1,487)	(5,493)
Unrealized Gain (Loss) on Derivatives	25	(3,790)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure		Credit
Net Realized Gain/Loss on Derivatives		(1,548)
Unrealized Gain (Loss) on Derivatives		570
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market
Net Realized Gain/Loss on Derivatives	(38)
Unrealized Gain (Loss) on Derivatives	61
Financial Derivatives - Assets [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	(217)	0
Unrealized Gain (Loss) on Derivatives	380	(8)
Financial Derivatives - Assets [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure		Interest Rates
Net Realized Gain/Loss on Derivatives		(8)
Unrealized Gain (Loss) on Derivatives		(11)
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Derivatives	(2,914)	(8,143)
Unrealized Gain (Loss) on Derivatives	(121)	11,194
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit
Net Realized Gain/Loss on Derivatives	(28)
Unrealized Gain (Loss) on Derivatives	(1)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit
Net Realized Gain/Loss on Derivatives	178	4,309
Unrealized Gain (Loss) on Derivatives	359	34
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit	Credit
Net Realized Gain/Loss on Derivatives	(3,627)	3
Unrealized Gain (Loss) on Derivatives	(178)	66
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market	Equity Market
Net Realized Gain/Loss on Derivatives	(32)	(2,056)
Unrealized Gain (Loss) on Derivatives	37	25
Financial Derivatives - Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	617	(10,399)
Unrealized Gain (Loss) on Derivatives	(360)	11,121
Financial Derivatives - Liabilities [Member] | Eurodollar Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates	Interest Rates
Net Realized Gain/Loss on Derivatives	(22)	0
Unrealized Gain (Loss) on Derivatives	$ 22	$ (52)