Goodwill and Other Intangible Assets - Gross Cost and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	$ 69,009	$ 68,987
Other intangible assets, accumulated amortization	60,909	60,080
Other intangible assets, Net Carrying Amount	8,100	8,907
Success/Performance Fees [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	35,279	35,259
Other intangible assets, accumulated amortization	27,744	26,984
Other intangible assets, Net Carrying Amount	7,535	8,275
Management Fees, Customer Relationships and Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	33,730	33,728
Other intangible assets, accumulated amortization	33,165	33,096
Other intangible assets, Net Carrying Amount	$ 565	$ 632