Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, plant and equipment
Total cost	$ 43,746	$ 38,835
Less accumulated depreciation and amortization	34,800	30,417
Equipment and leasehold improvements, net	8,946	8,418
Depreciation and amortization	4,382	3,907	$ 4,133
Software
Property, plant and equipment
Total cost	29,167	25,292
Computer equipment
Property, plant and equipment
Total cost	8,218	7,260
Leasehold improvements
Property, plant and equipment
Total cost	2,524	2,524
Other equipment
Property, plant and equipment
Total cost	2,499	2,428
Furniture and fixtures
Property, plant and equipment
Total cost	$ 1,338	$ 1,331