Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 335,402	$ 345,453	$ 364,328	$ 356,657
Amortization expense of intangible assets	6,387	10,114	8,359
Operating Segments [Member] | Financial Advisory Segment [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	270,861	280,912
Operating Segments [Member] | Asset Management Segment [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 64,541	$ 64,541