Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Derivative [Line Items]
Foreign currency transactions		$ 531		$ (354)		$ 1,509		$ 66
Net Realized Gain/Loss on Financial Derivatives		(6,588)	[1]	(3,355)	[2]	(8,975)	[1]	(13,714)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(3,903)	[3]	(2,805)	[4]	(4,766)	[3]	(23,113)	[4]
Foreign currency translation		3,340		(2,301)		3,195		918
Derivative [Member]
Derivative [Line Items]
Foreign currency transactions		(19)		(150)		(3)		(532)
Foreign currency translation		(90)		(122)		(126)		1,000
Credit Default Swaps On Asset Backed Securities [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		312	[1]	310	[2]	(97)	[1]	385	[2]
Unrealized Gain (Loss) on Financial Derivatives		(709)	[3]	(125)	[4]	259	[3]	(231)	[4]
Credit Default Swaps On Asset Backed Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(1,283)	[1]	222	[2]	(2,456)	[1]	2,808	[2]
Unrealized Gain (Loss) on Financial Derivatives		(488)	[3]	2,685	[4]	(2,610)	[3]	1,755	[4]
Credit Default Swaps On Corporate Bond Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(886)	[1]	(5,911)	[2]	(1,172)	[1]	(13,010)	[2]
Unrealized Gain (Loss) on Financial Derivatives		45	[3]	(7,434)	[4]	18	[3]	(17,831)	[4]
Credit Default Swaps On Corporate Bonds [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(548)	[1]	154	[2]	458	[1]	126	[2]
Unrealized Gain (Loss) on Financial Derivatives		(666)	[3]	(62)	[4]	(995)	[3]	61	[4]
Total Return Swaps [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(603)	[1]	(1,248)	[2]	(1,356)	[1]	(6,914)	[2]
Unrealized Gain (Loss) on Financial Derivatives		10	[3]	(465)	[4]	148	[3]	4,382	[4]
Interest Rate Swaps [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(834)	[1]	2,434	[2]	(580)	[1]	(1,349)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(960)	[3]	(6,273)	[4]	(801)	[3]	(12,217)	[4]
Futures [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	(145)				(178)
Unrealized Gain (Loss) on Financial Derivatives	[3]	53				37
Futures [Member] | Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			(201)				(736)
Unrealized Gain (Loss) on Financial Derivatives	[4]			20				146
Forwards [Member] | Currency risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(2,523)	[1]	(972)	[2]	(3,345)	[1]	(1,305)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(1,194)	[3]	3,500	[4]	(864)	[3]	454	[4]
Mortgage Loan Purchase Commitments [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		0	[1]	0	[2]	0	[1]	0	[2]
Unrealized Gain (Loss) on Financial Derivatives		0	[3]	(35)	[4]	31	[3]	8	[4]
Options [Member] | Credit/Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(78)	[1]	1,857	[2]	(149)	[1]	6,331	[2]
Unrealized Gain (Loss) on Financial Derivatives		6	[3]	5,384	[4]	17	[3]	360	[4]
Warrant [Member] | Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		0	[1]	0	[2]	(100)	[1]	(50)	[2]
Unrealized Gain (Loss) on Financial Derivatives		$ 0	[3]	$ 0	[4]	$ (6)	[3]	$ 0	[4]

[1] Includes gain/(loss) on foreign currency transactions on derivatives in the amount of $(19) thousand and $(3) thousand, for the three and six month periods ended June 30, 2017, which is included on the Consolidated Statement of Operations in Realized gain (loss) on foreign currency transactions.

[2] on derivatives in the amount of $(150) thousand and $(532) thousand, for the three and six month periods ended June 30, 2016, 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 $(90) thousand and $(126) thousand, for the three and six month periods ended June 30, 2017, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.

[4] Includes foreign currency translation on derivatives in the amount of $(122) thousand and $1.0 million, for the three and six month periods ended June 30, 2016, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.