Goodwill and Other Intangible Assets - Gross Cost and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	$ 68,987	$ 63,776
Goodwill and other intangible assets, accumulated amortization	60,080	57,561
Other intangible assets, Net Carrying Amount	8,907	6,215
Success/Performance Fees [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	35,259	30,740
Goodwill and other intangible assets, accumulated amortization	26,984	25,192
Other intangible assets, Net Carrying Amount	8,275	5,548
Management Fees, Customer Relationships and Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	33,728	33,036
Goodwill and other intangible assets, accumulated amortization	33,096	32,369
Other intangible assets, Net Carrying Amount	$ 632	$ 667