Goodwill and Other Intangible Assets - Gross Cost and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	$ 63,776	$ 63,790
Other intangible assets, Accumulated Amortization	57,561	51,754
Other intangible assets, Net Carrying Amount	6,215	12,036
Performance Fees [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	30,740	30,740
Other intangible assets, Accumulated Amortization	25,192	21,116
Other intangible assets, Net Carrying Amount	5,548	9,624
Management Fees, Customer Relationships and Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, Gross Cost	33,036	33,050
Other intangible assets, Accumulated Amortization	32,369	30,638
Other intangible assets, Net Carrying Amount	$ 667	$ 2,412