Fair Value Disclosures (Investments Measured At Fair Value Based On Net Asset Value - Footnote) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) fund	Dec. 31, 2014 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments in managed funds	$ 603,720	$ 281,470
Equity Long/Short Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amount redeemable	107,100
Investment in private asset management fund managed by company	$ 52,400	$ 117,200
Equity Long/Short Hedge Funds [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Notice period redemption of investments prior written notice period		30 days
Equity Long/Short Hedge Funds [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Notice period redemption of investments prior written notice period		90 days
Folger Hill Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Number of funds | fund	2
Notice period redemption of investments prior notice period (not less than)	45 days
Investments in managed funds	$ 375,500
Fixed Income and High Yield Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Percentage of funds being liquidated	8.00%	8.00%
Funds Of Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Percentage of investments with no redemption provisions	95.00%	95.00%
Estimated period for the liquidation of the underlying assets	12 months
Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Percentage of investments in certain industries	100.00%	99.00%
Equity Funds [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated period for the liquidation of the underlying assets	1 year
Equity Funds [Member] | Maximum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated period for the liquidation of the underlying assets	8 years
Multi-Strategy Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fee to withdraw from fund	5.00%
Quarterly maximum withdrawal percentage	25.00%