Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Derivative [Line Items]
Foreign currency transactions		$ 3,845		$ (5,597)		$ (3,073)
Net Realized Gain/Loss on Financial Derivatives		(18,704)	[1]	(36,321)	[2]	(10,115)	[3]
Unrealized Gain (Loss) on Financial Derivatives		(317)	[4]	(6,494)	[5]	8,780	[6]
Foreign currency translation		4,326		3,643		(1,706)
Reimbursement from third party						1,500
Derivative [Member]
Derivative [Line Items]
Foreign currency transactions		(100)		300		200
Foreign currency translation		(200)		1,100		(1,100)
Credit Default Swaps On Asset Backed Securities [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(601)	[1]	719	[2]	(3,066)	[3]
Unrealized Gain (Loss) on Financial Derivatives		(263)	[4]	(703)	[5]	2,133	[6]
Credit Default Swaps On Asset Backed Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(5,291)	[1]	3,935	[2]	(714)	[3]
Unrealized Gain (Loss) on Financial Derivatives		(817)	[4]	(3,349)	[5]	(285)	[6]
Credit Default Swaps On Corporate Bond Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(3,336)	[1]	(36,195)	[2]	(8,059)	[3]
Unrealized Gain (Loss) on Financial Derivatives		(459)	[4]	(4,044)	[5]	7,503	[6]
Credit Default Swaps On Corporate Bonds [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		205	[1]	(14)	[2]	(1,005)	[3]
Unrealized Gain (Loss) on Financial Derivatives		907	[4]	712	[5]	694	[6]
Total Return Swaps [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(1,825)	[1]	(12,987)	[2]	1,838	[3]
Unrealized Gain (Loss) on Financial Derivatives		149	[4]	4,427	[5]	(4,564)	[6]
Interest Rate Swaps [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(1,171)	[1]	(2,912)	[2]	(9,603)	[3],[7]
Unrealized Gain (Loss) on Financial Derivatives		571	[4]	(1,983)	[5]	1,983	[6],[7]
Futures [Member] | Interest Rate/Currency Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	(195)
Unrealized Gain (Loss) on Financial Derivatives	[4]	(423)
Futures [Member] | Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives				(84)	[2]	708	[3]
Unrealized Gain (Loss) on Financial Derivatives				456	[5]	(676)	[6]
Forwards [Member] | Currency risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(6,390)	[1]	4,093	[2]	4,738	[3]
Unrealized Gain (Loss) on Financial Derivatives		(18)	[4]	(1,580)	[5]	377	[6]
Mortgage Loan Purchase Commitments [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		0	[1]	0	[2]	0	[3]
Unrealized Gain (Loss) on Financial Derivatives		31	[4]	(23)	[5]	(8)	[6]
Options [Member] | Credit/Interest Rates/Equity Market risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		0	[1]	7,174	[2]	5,048	[3]
Unrealized Gain (Loss) on Financial Derivatives		10	[4]	(413)	[5]	$ 1,623	[6]
Warrant [Member] | Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(100)	[1]	(50)	[2]
Unrealized Gain (Loss) on Financial Derivatives		$ (5)	[4]	$ 6	[5]

[1] Includes gain/(loss) on foreign currency transactions on derivatives in the amount of $(0.1) million, which is included on the Consolidated Statement of Operations in Realized gain (loss) on foreign currency transactions.

[2] Includes gain/(loss) on foreign currency transactions on derivatives in the amount of $0.3 million, which is included on the Consolidated Statement of Operations in Realized gain (loss) on foreign currency transactions.

[3] Includes foreign currency translation on derivatives in the amount of $0.2 million, which is included on the Consolidated Statement of Operations in Realized gain (loss) on foreign currency transactions.

[4] Includes foreign currency translation on derivatives in the amount of $(0.2) million, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.

[5] Includes foreign currency translation on derivatives in the amount of $1.1 million, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.

[6] Includes foreign currency translation on derivatives in the amount of $(1.1) million, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.

[7] Includes a $1.5 million reimbursement from a third party.