Investments (Schedule Of Other Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	$ 911,392		$ 783,534
Unfunded Commitments	467,524		266,416
Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	368,052		253,097
Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	543,340		530,437
Hedge Funds [Member] | Investments without redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P30D
Portion at Fair Value, Fair Value Disclosure [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	764,081		655,888
Unfunded Commitments	467,524		266,416
Portion at Fair Value, Fair Value Disclosure [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	368,052		253,097
Portion at Fair Value, Fair Value Disclosure [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	396,029		402,791
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	216,825		151,009
Unfunded Commitments	467,524		266,416
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity Funds [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	216,825		151,009
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity Funds [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity (Primary And Secondary) [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	144,422		111,879
Unfunded Commitments	263,519		174,772
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity (Primary And Secondary) [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	144,422		111,879
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity (Primary And Secondary) [Member] | Investments with redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	2 years		3 years
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity (Primary And Secondary) [Member] | Investments with redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	9 years		10 years
Portion at Fair Value, Fair Value Disclosure [Member] | Private Equity (Primary And Secondary) [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Mezzanine Debt [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	64,627		29,834
Unfunded Commitments	198,756		85,850
Portion at Fair Value, Fair Value Disclosure [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	64,627		29,834
Portion at Fair Value, Fair Value Disclosure [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	8 years		8 years
Portion at Fair Value, Fair Value Disclosure [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	9 years		9 years
Portion at Fair Value, Fair Value Disclosure [Member] | Mezzanine Debt [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	7,776		9,296
Unfunded Commitments	5,249		5,794
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	7,776		9,296
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed [Member] | Investments with redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	4 years		4 years
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed [Member] | Investments with redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	4 years		6 years
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	515,298		504,879
Unfunded Commitments	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	151,227		102,088
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	364,071		402,791
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	151,227		138,213
Unfunded Commitments	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	151,227		102,088
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	1 year		1 year
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period	2 years		2 years
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		36,125
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency			Quarterly	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments without redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period			P45D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Distressed Funds [Member] | Investments without redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period			P65D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Equity Long/Short [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	99,365		169,845
Unfunded Commitments	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Equity Long/Short [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	99,365		169,845
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Quarterly	[1]	Quarterly	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P30D	[1]	P30D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P60D	[1]	P60D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Multi-Strategy Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	136,958		131,713
Unfunded Commitments	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Multi-Strategy Funds [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	136,958		131,713
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Quarterly	[1]	Quarterly	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P45D	[1]	P45D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P90D	[1]	P90D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds, Global Opportunity [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			19,117
Unfunded Commitments			0
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds, Global Opportunity [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			0
Portion at Fair Value, Fair Value Disclosure [Member] | Hedge Funds, Global Opportunity [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			19,117
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency			Monthly	[1]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period			P3D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Event Driven Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	14,018		45,991
Unfunded Commitments	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Event Driven Funds [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Portion at Fair Value, Fair Value Disclosure [Member] | Event Driven Funds [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	14,018		45,991
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Annual	[1]	Quarterly	[1]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P60D	[1]	P60D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | Relative Value Credit [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	113,730
Unfunded Commitments	0
Portion at Fair Value, Fair Value Disclosure [Member] | Relative Value Credit [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0
Portion at Fair Value, Fair Value Disclosure [Member] | Relative Value Credit [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	113,730
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Quarterly	[1]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P60D	[1]
Portion at Fair Value, Fair Value Disclosure [Member] | High Yield Loan Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	31,958
Unfunded Commitments	0
Portion at Fair Value, Fair Value Disclosure [Member] | High Yield Loan Fund [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0
Portion at Fair Value, Fair Value Disclosure [Member] | High Yield Loan Fund [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	31,958
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Monthly	[1]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	P30D	[1]
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other Private Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	147,311		127,646
Unfunded Commitments	0		0
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other Private Securities [Member] | Investments with redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	0		0
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Other Private Securities [Member] | Investments without redemption restrictions [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets	$ 147,311		$ 127,646

[1] The redemption frequency and notice periods only apply to the investments without redemption restrictions.