Fixed Assets - Additional information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 73,025	$ 66,235
Accumulated depreciation and amortization	29,880	28,759
Depreciation and amortization	6,700	6,700	$ 6,300
Assets Held under Capital Leases
Property, Plant and Equipment [Line Items]
Fixed assets, gross	4,000	4,700
Accumulated depreciation and amortization	$ 2,300	$ 2,900