Property, Equipment, and Leasehold Improvements (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold equipment, gross	$ 83,666	$ 80,842
Less accumulated depreciation and amortization	(62,273)	(57,107)
Property, equipment and leasehold improvements, net	21,393	23,735
Land
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold equipment, gross	1,122	1,122
Building and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold equipment, gross	6,223	6,203
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold equipment, gross	5,706	5,656
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold equipment, gross	$ 70,615	$ 67,861