Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Derivative [Line Items]
Foreign currency transactions		$ 4,726		$ (1,564)		$ 6,234		$ (1,499)
Net Realized Gain/Loss on Financial Derivatives		(4,664)	[1]	(21,370)	[2]	(13,638)	[1]	(35,082)	[2]
Unrealized Gain (Loss) on Financial Derivatives		1,653	[3]	7,540	[4]	(3,113)	[3]	(15,574)	[4]
Foreign currency translation		(2,483)		2,190		712		3,108
Derivative [Member]
Derivative [Line Items]
Foreign currency transactions		(56)		400		(68)		300
Foreign currency translation		(59)		(100)		(194)		1,000
Credit Default Swaps On Asset Backed Securities [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		583	[1]	622	[2]	486	[1]	1,007	[2]
Unrealized Gain (Loss) on Financial Derivatives		(577)	[3]	(288)	[4]	(319)	[3]	(518)	[4]
Credit Default Swaps On Asset Backed Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(58)	[1]	983	[2]	(2,514)	[1]	3,790	[2]
Unrealized Gain (Loss) on Financial Derivatives		(522)	[3]	(2,660)	[4]	(3,132)	[3]	(905)	[4]
Credit Default Swaps On Corporate Bond Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(975)	[1]	(21,220)	[2]	(2,147)	[1]	(34,230)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(591)	[3]	12,572	[4]	(573)	[3]	(5,260)	[4]
Credit Default Swaps On Corporate Bonds [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(241)	[1]	110	[2]	218	[1]	237	[2]
Unrealized Gain (Loss) on Financial Derivatives		1,837	[3]	(14)	[4]	842	[3]	47	[4]
Total Return Swaps [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(293)	[1]	(4,408)	[2]	(1,649)	[1]	(11,323)	[2]
Unrealized Gain (Loss) on Financial Derivatives		1	[3]	(917)	[4]	150	[3]	3,466	[4]
Interest Rate Swaps [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		318	[1]	182	[2]	(262)	[1]	(1,167)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(694)	[3]	1,087	[4]	(1,492)	[3]	(11,129)	[4]
Futures [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	(152)				(331)
Unrealized Gain (Loss) on Financial Derivatives	[3]	147				183
Futures [Member] | Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			(89)				(824)
Unrealized Gain (Loss) on Financial Derivatives	[4]			271				417
Forwards [Member] | Currency risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(4,013)	[1]	1,525	[2]	(7,357)	[1]	221	[2]
Unrealized Gain (Loss) on Financial Derivatives		2,026	[3]	(1,855)	[4]	1,162	[3]	(1,402)	[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]	0	[4]	31	[3]	8	[4]
Options [Member] | Credit/Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			925				7,257
Unrealized Gain (Loss) on Financial Derivatives	[4]			(656)				(298)
Options [Member] | Credit/Interest Rates/Equity Market risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	167				18
Unrealized Gain (Loss) on Financial Derivatives	[3]	26				41
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 $(56) thousand and $(68) thousand, for the three and nine month periods ended September 30, 2017, 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 $0.4 million and $0.3 million, for the three and nine month periods ended September 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 $(59) thousand and $(194) thousand, for the three and nine month periods ended September 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 $(0.1) million and $1.0 million, for the three and nine month periods ended September 30, 2016, which is included on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.