Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 6,071	$ 6,015
Less accumulated amortization	(5,020)	(4,532)
Intangible assets, net	1,051	1,483
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	1,208	1,204
Patents and know-how
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	4,113	4,090
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 750	$ 721
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	4 years
Minimum | Trade name
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years
Minimum | Patents and know-how
Finite-Lived Intangible Assets [Line Items]
Useful life	5 years
Minimum | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful life	4 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	20 years
Maximum | Trade name
Finite-Lived Intangible Assets [Line Items]
Useful life	20 years
Maximum | Patents and know-how
Finite-Lived Intangible Assets [Line Items]
Useful life	12 years
Maximum | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful life	8 years