Fair Values of Assets and Liabilities NAV Investments (Details 4) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017		Mar. 31, 2017
Funds-Of-Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
PercentageDailyRedemption	1.00%
Percentage of Monthly Redemption	20.00%
Percentage of Quarterly Redemption	11.00%
Percentage Not Subject to Redemption	68.00%
Other Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Percentage of Redemption, Investment Funds	34.00%
Percentage of Investment of 20 Year Redemption	66.00%
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	$ 44,156		$ 52,772
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	26,589
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] | Funds-Of-Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	11,024	[1]	18,537
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] | Hedge Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	9,760		10,107
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	20,000
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] | Private Equity Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	14,231	[2]	17,612
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 6,589
Investments Remaining Term, High End of Range	11 years
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] | Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	$ 9,009		6,292
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member] | Other Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investment, Fair Value Disclosure	$ 132	[3]	$ 224
Investments Remaining Term, Category One	1 year
Investments Remaining Term, Category Two	14 years

[1] Liquidation restrictions: 1% daily redemption, 20% monthly redemption, 11% quarterly redemption, and 68% are not subject to redemption or are not currently redeemable.

[2] Liquidations are expected over the remaining term.

[3] Of this balance, 34% has a remaining term of less than one year and 66% has a remaining term of 14 years.