Financial Derivatives (Schedule Of Gains And Losses On Derivative Contracts) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	$ (38)		$ 1,218
Unrealized Gain (Loss) on Financial Derivatives			(2,439)
Foreign currency translation	(5,063)		(65)	[1]
Unrealized Gain (Loss) on Derivatives, including Foreign Currency Translation Gain (Loss)	(5,148)	[2]
Financial Derivatives - Assets [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	25,306		8,041
Unrealized Gain (Loss) on Financial Derivatives	(7,156)	[2]	(4,560)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	401		1,190
Unrealized Gain (Loss) on Financial Derivatives	(355)	[2]	(1,210)
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	226		(1,302)
Unrealized Gain (Loss) on Financial Derivatives	(1,252)	[2]	145
Financial Derivatives - Assets [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	(3,014)		652
Unrealized Gain (Loss) on Financial Derivatives	828	[2]	(315)
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market/Credit		Equity Market
Net Realized Gain/Loss on Financial Derivatives	1,810		5,925
Unrealized Gain (Loss) on Financial Derivatives	110	[2]	10
Financial Derivatives - Assets [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	19,460		1,472
Unrealized Gain (Loss) on Financial Derivatives	(6,987)	[2]	(6,080)
Financial Derivatives - Assets [Member] | Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	2,398		41
Unrealized Gain (Loss) on Financial Derivatives	824	[2]	2,435
Financial Derivatives - Assets [Member] | Forwards [Member]
Derivative [Line Items]
Primary risk exposure	Currency		Currency
Net Realized Gain/Loss on Financial Derivatives	7,285		10
Unrealized Gain (Loss) on Financial Derivatives	(884)	[2]	167
Financial Derivatives - Assets [Member] | Other Derivatives [Member]
Derivative [Line Items]
Primary risk exposure	Credit/ Interest Rates		Credit/ Interest Rates
Net Realized Gain/Loss on Financial Derivatives	(3,260)		53
Unrealized Gain (Loss) on Financial Derivatives	560	[2]	288
Financial Derivatives - Liabilities [Member]
Derivative [Line Items]
Net Realized Gain/Loss on Financial Derivatives	(25,344)		(6,823)
Unrealized Gain (Loss) on Financial Derivatives	2,008	[2]	2,121
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	(19)		(19)
Unrealized Gain (Loss) on Financial Derivatives	0	[2]	0
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	145		2,603
Unrealized Gain (Loss) on Financial Derivatives	206	[2]	(1,486)
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bond Indices [Member]
Derivative [Line Items]
Primary risk exposure	Credit		Credit
Net Realized Gain/Loss on Financial Derivatives	2,124		(3,804)
Unrealized Gain (Loss) on Financial Derivatives	(2,656)	[2]	4,571
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Corporate Bonds [Member]
Derivative [Line Items]
Primary risk exposure	Credit
Net Realized Gain/Loss on Financial Derivatives	(668)
Unrealized Gain (Loss) on Financial Derivatives	485	[2]
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Equity Market/Credit		Equity Market
Net Realized Gain/Loss on Financial Derivatives	(458)		(1,417)
Unrealized Gain (Loss) on Financial Derivatives	(304)	[2]	36
Financial Derivatives - Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	(25,197)		(3,765)
Unrealized Gain (Loss) on Financial Derivatives	4,321	[2]	(468)
Financial Derivatives - Liabilities [Member] | Futures [Member]
Derivative [Line Items]
Primary risk exposure	Interest Rates/Equity Market		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	(32)		128
Unrealized Gain (Loss) on Financial Derivatives	(411)	[2]	(139)
Financial Derivatives - Liabilities [Member] | Forwards [Member]
Derivative [Line Items]
Primary risk exposure	Currency		Currency
Net Realized Gain/Loss on Financial Derivatives	(1,489)		(492)
Unrealized Gain (Loss) on Financial Derivatives	(581)	[2]	(4)
Financial Derivatives - Liabilities [Member] | Other Derivatives [Member]
Derivative [Line Items]
Primary risk exposure	Credit/ Interest Rates		Interest Rates
Net Realized Gain/Loss on Financial Derivatives	250		(57)
Unrealized Gain (Loss) on Financial Derivatives	948	[2]	(389)
Derivative [Member]
Derivative [Line Items]
Foreign currency translation	$ 1,000

[1] Conformed to current period presentation.

[2] Includes foreign currency translation on derivatives in the amount of $1.0 million which is shown on the Consolidated Statement of Operations in Change in net unrealized gain (loss) on foreign currency translation.