Investments (Schedule Of Other Investments) (Details) (USD $) In Thousands, unless otherwise specified												6 Months Ended						6 Months Ended						6 Months Ended								6 Months Ended			6 Months Ended										6 Months Ended								6 Months Ended								6 Months Ended				6 Months Ended								6 Months Ended								6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Investments with redemption restrictions [Member]	Jun. 30, 2013 Investments without redemption restrictions [Member]		Jun. 30, 2013 Total Private Equity Structures [Member]	Jun. 30, 2013 Total Private Equity Structures [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Total Private Equity Structures [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Private Equity [Member]	Jun. 30, 2013 Private Equity [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Private Equity [Member] Investments with redemption restrictions [Member] Minimum [Member]	Jun. 30, 2013 Private Equity [Member] Investments with redemption restrictions [Member] Maximum [Member]	Jun. 30, 2013 Private Equity [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Mezzanine Debt [Member]	Jun. 30, 2013 Mezzanine Debt [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Mezzanine Debt [Member] Investments with redemption restrictions [Member] Minimum [Member]	Jun. 30, 2013 Mezzanine Debt [Member] Investments with redemption restrictions [Member] Maximum [Member]	Jun. 30, 2013 Mezzanine Debt [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Distressed [Member]	Jun. 30, 2013 Distressed [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Distressed [Member] Investments with redemption restrictions [Member] Minimum [Member]	Jun. 30, 2013 Distressed [Member] Investments with redemption restrictions [Member] Maximum [Member]	Jun. 30, 2013 Distressed [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Hedge Funds [Member]	Jun. 30, 2013 Hedge Funds [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Hedge Funds [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Hedge Funds [Member] Investments without redemption restrictions [Member] Minimum [Member]	Jun. 30, 2013 Distressed Funds [Member]	Jun. 30, 2013 Distressed Funds [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Distressed Funds [Member] Investments with redemption restrictions [Member] Minimum [Member]	Jun. 30, 2013 Distressed Funds [Member] Investments with redemption restrictions [Member] Maximum [Member]	Jun. 30, 2013 Distressed Funds [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Distressed Funds [Member] Investments without redemption restrictions [Member] Minimum [Member]		Jun. 30, 2013 Distressed Funds [Member] Investments without redemption restrictions [Member] Maximum [Member]		Jun. 30, 2013 Equity Long/Short [Member]	Jun. 30, 2013 Equity Long/Short [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Equity Long/Short [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Equity Long/Short [Member] Investments without redemption restrictions [Member] Minimum [Member]		Jun. 30, 2013 Equity Long/Short [Member] Investments without redemption restrictions [Member] Maximum [Member]		Jun. 30, 2013 Multi-Strategy Funds [Member]	Jun. 30, 2013 Multi-Strategy Funds [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Multi-Strategy Funds [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Multi-Strategy Funds [Member] Investments without redemption restrictions [Member] Minimum [Member]		Jun. 30, 2013 Multi-Strategy Funds [Member] Investments without redemption restrictions [Member] Maximum [Member]		Jun. 30, 2013 Global Macro [Member]	Jun. 30, 2013 Global Macro [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Global Macro [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Event Driven Funds [Member]	Jun. 30, 2013 Event Driven Funds [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Event Driven Funds [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Event Driven Funds [Member] Investments without redemption restrictions [Member] Minimum [Member]		Jun. 30, 2013 Event Driven Funds [Member] Investments without redemption restrictions [Member] Maximum [Member]		Jun. 30, 2013 Relative Value Credit [Member]	Jun. 30, 2013 Relative Value Credit [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Relative Value Credit [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 Other Private Securities [Member]	Jun. 30, 2013 Other Private Securities [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 Other Private Securities [Member] Investments without redemption restrictions [Member]		Jun. 30, 2013 High Yield Loan Fund [Member]	Jun. 30, 2013 High Yield Loan Fund [Member] Investments with redemption restrictions [Member]	Jun. 30, 2013 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	$ 849,100	$ 783,534	$ 302,191	$ 546,909	[1]	$ 190,072	$ 190,072	$ 0	[1]	$ 125,950	$ 125,950			$ 0	[1]	$ 55,232	$ 55,232			$ 0	[1]	$ 8,890	$ 8,890			$ 0	[1]	$ 492,156	$ 112,119	$ 380,037	[1]		$ 136,779	$ 112,119			$ 24,660	[1]					$ 110,889	$ 0	$ 110,889	[1]					$ 127,107	$ 0	$ 127,107	[1]					$ 19,842	$ 0	$ 19,842	[1]	$ 22,430	$ 0	$ 22,430	[1]					$ 75,109	$ 0	$ 75,109	[1]	$ 134,709	$ 0	$ 134,709	[1]	$ 32,163	$ 0	$ 32,163	[1]
Estimated remaining restriction period												3 years	10 years					8 years	10 years					4 years	5 years										1 year	2 years
Redemption frequency																																					Quarterly	[1]							Quarterly	[1]							Quarterly	[1]							Monthly	[1]			Annual	[1]							Quarterly	[1]							Monthly	[1]
Required notification period for redemption																																P30D							P45D	[1]	P65D	[1]					P30D	[1]	P60D	[1]					P45D	[1]	P90D	[1]			P3D	[1]					P60D	[1]		[1]			P60D	[1]							P30D	[1]
Unfunded Commitments	$ 381,287					$ 376,287				$ 160,490						$ 209,623						$ 6,174						$ 0					$ 0										$ 0								$ 0								$ 0				$ 0												$ 5,000				$ 0

[1] The redemption frequency and notice periods only apply to the investments without redemption restrictions. Some or all of these investments may be subject to a gate.