Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Derivative [Line Items]
Foreign currency transactions		$ (5,597)		$ (3,073)		$ (1,486)
Net Realized Gain/Loss on Financial Derivatives		(36,321)	[1]	(10,115)	[2],[3]	(11,211)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(6,494)	[4]	8,780	[2],[5]	(8,272)	[2]
Foreign currency translation		3,643		(1,706)		(950)
Reimbursement from third party				1,500
Derivative [Member]
Derivative [Line Items]
Foreign currency transactions		300		200
Foreign currency translation		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		719	[1]	(3,066)	[2],[3]	(4,674)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(703)	[4]	2,133	[2],[5]	4,658	[2]
Credit Default Swaps On Asset Backed Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		3,935	[1]	(714)	[2],[3]	(1,551)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(3,349)	[4]	(285)	[2],[5]	316	[2]
Credit Default Swaps On Corporate Bond Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(36,195)	[1]	(8,059)	[2],[3]	(4,304)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(4,044)	[4]	7,503	[2],[5]	4,337	[2]
Credit Default Swaps On Corporate Bonds [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(14)	[1]	(1,005)	[2],[3]	270	[2]
Unrealized Gain (Loss) on Financial Derivatives		712	[4]	694	[2],[5]	(782)	[2]
Total Return Swaps [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(12,987)	[1]	1,838	[2],[3]
Unrealized Gain (Loss) on Financial Derivatives		4,427	[4]	(4,564)	[2],[5]
Total Return Swaps [Member] | Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]					7,304
Unrealized Gain (Loss) on Financial Derivatives	[2]					49
Interest Rate Swaps [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(2,912)	[1]	(9,603)	[2],[3],[6]	(13,329)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(1,983)	[4]	1,983	[2],[5],[6]	(19,217)	[2]
Futures [Member] | Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(84)	[1]	708	[2],[3]	4,589	[2]
Unrealized Gain (Loss) on Financial Derivatives		456	[4]	(676)	[2],[5]	2,552	[2]
Forwards [Member] | Currency risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		4,093	[1]	4,738	[2],[3]	1,630	[2]
Unrealized Gain (Loss) on Financial Derivatives		(1,580)	[4]	377	[2],[5]	786	[2]
Mortgage Loan Purchase Commitments [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		0	[1]	0	[2],[3]
Unrealized Gain (Loss) on Financial Derivatives		(23)	[4]	(8)	[2],[5]
Options [Member] | Credit/Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		7,174	[1]	5,048	[2],[3]	(1,146)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(413)	[4]	$ 1,623	[2],[5]	$ (971)	[2]
Warrant [Member] | Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	(50)
Unrealized Gain (Loss) on Financial Derivatives	[4]	$ 6

[1] 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.

[2] Conformed to current period presentation.

[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 $1.1 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 a $1.5 million reimbursement from a third party.