Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017
Derivative [Line Items]
Foreign currency transactions		$ (1,110)		$ 531		$ 658		$ 1,509
Net Realized Gain/Loss on Financial Derivatives		177	[1]	(6,588)	[2]	(1,325)	[1]	(8,975)	[2]
Unrealized Gain (Loss) on Financial Derivatives		6,855	[3]	(3,903)	[4]	10,899	[3]	(4,766)	[4]
Foreign currency translation		(1,964)		3,340		(1,863)		3,195
Derivative [Member]
Derivative [Line Items]
Foreign currency transactions		22		(19)		(200)		(3)
Foreign currency translation		200		(90)		300		(126)
Credit Default Swaps On Asset Backed Securities [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		161	[1]	312	[2]	247	[1]	(97)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(477)	[3]	(709)	[4]	(549)	[3]	259	[4]
Credit Default Swaps On Asset Backed Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(204)	[1]	(1,283)	[2]	(2,046)	[1]	(2,456)	[2]
Unrealized Gain (Loss) on Financial Derivatives		1	[3]	(488)	[4]	1,453	[3]	(2,610)	[4]
Credit Default Swaps On Corporate Bond Indices [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(675)	[1]	(886)	[2]	(2,237)	[1]	(1,172)	[2]
Unrealized Gain (Loss) on Financial Derivatives		866	[3]	45	[4]	2,428	[3]	18	[4]
Credit Default Swaps On Corporate Bonds [Member] | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(1,472)	[1]	(548)	[2]	2,996	[1]	458	[2]
Unrealized Gain (Loss) on Financial Derivatives		3,063	[3]	(666)	[4]	(792)	[3]	(995)	[4]
Total Return Swaps [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		257	[1]	(603)	[2]	423	[1]	(1,356)	[2]
Unrealized Gain (Loss) on Financial Derivatives		(331)	[3]	10	[4]	(313)	[3]	148	[4]
Interest Rate Swaps [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		(677)	[1]	(834)	[2]	(1,500)	[1]	(580)	[2]
Unrealized Gain (Loss) on Financial Derivatives		2,091	[3]	(960)	[4]	7,130	[3]	(801)	[4]
Futures [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			(145)				(178)
Unrealized Gain (Loss) on Financial Derivatives	[4]			53				37
Futures [Member] | Interest Rate/Currency Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	1,684				923
Unrealized Gain (Loss) on Financial Derivatives	[3]	1,542				981
Forwards [Member] | Currency risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives		1,104	[1]	(2,523)	[2]	(69)	[1]	(3,345)	[2]
Unrealized Gain (Loss) on Financial Derivatives		100	[3]	(1,194)	[4]	485	[3]	(864)	[4]
Warrant [Member] | Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			0				(100)
Unrealized Gain (Loss) on Financial Derivatives	[4]			0				(6)
Mortgage Loan Purchase Commitments [Member] | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			0				0
Unrealized Gain (Loss) on Financial Derivatives	[4]			0				31
Options [Member] | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[2]			(78)				(149)
Unrealized Gain (Loss) on Financial Derivatives	[4]			$ 6				$ 17
Options [Member] | Interest Rates/Equity Market Risk [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	[1]	(1)				(62)
Unrealized Gain (Loss) on Financial Derivatives	[3]	$ 0				$ 76

[1] Includes gain/(loss) on foreign currency transactions on derivatives in the amount of $22 thousand and $(0.2) million, for the three- and six-month periods ended June 30, 2018, 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 $(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.

[3] Includes foreign currency translation on derivatives in the amount of $0.2 million and $0.3 million, for the three- and six-month periods ended June 30, 2018, 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 $(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.