Fair Value Measurements - Schedule of Classification of Investments and Certain Other Assets and Liabilities Measured at Fair Value on Recurring Basis and Investments Measured at NAV (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 458,744	$ 478,109
Total Derivative Assets	1,993	1,048
Total investments measured at fair value	460,737	479,157
Securities sold, not yet purchased	4,482	3,239
Contingent consideration liability	22,608
Total Derivative Liabilities	182,223	195,689
Total of Liabilities Measured at Fair Value	209,313	198,928
Fair Value, Measurements, Nonrecurring [Member] | NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments measured at fair value	129,591	122,732
Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		535
Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	41,017	44,834
Alternative Investment Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	32,441	67,600
Alternative Investment Funds [Member] | Fair Value, Measurements, Nonrecurring [Member] | NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	7,125	22,465
Debt Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	74,597	67,134
Debt Funds [Member] | Fair Value, Measurements, Nonrecurring [Member] | NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	6	6
Equity Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	188,268	197,787
Equity Funds [Member] | Fair Value, Measurements, Nonrecurring [Member] | NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	39	42
Private Equity Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	122,421	100,219
Private Equity Funds [Member] | Fair Value, Measurements, Nonrecurring [Member] | NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	122,421	100,219
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments measured at fair value	327,645	354,101
Securities sold, not yet purchased	4,482	3,239
Total of Liabilities Measured at Fair Value	4,482	3,239
Level 1 [Member] | Debt [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		535
Level 1 [Member] | Equities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	39,509	43,558
Level 1 [Member] | Alternative Investment Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	25,316	45,135
Level 1 [Member] | Debt Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	74,591	67,128
Level 1 [Member] | Equity Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	188,229	197,745
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Derivative Assets	1,993	1,048
Total investments measured at fair value	1,993	1,048
Total Derivative Liabilities	182,223	195,689
Total of Liabilities Measured at Fair Value	182,223	195,689
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments measured at fair value	1,508	1,276
Contingent consideration liability	22,608
Total of Liabilities Measured at Fair Value	22,608
Level 3 [Member] | Equities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 1,508	$ 1,276