Fixed Assets - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 67,900	$ 71,565
Accumulated depreciation and amortization	32,082	31,885
Depreciation and amortization	6,300	6,900	$ 6,700
Assets Held under Capital Leases
Property, Plant and Equipment [Line Items]
Fixed assets, gross	2,300	3,500
Accumulated depreciation and amortization	$ 1,400	$ 2,100