Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount, beginning balance	$ 68,114	$ 68,116
Accumulated Amortization	(27,729)	(24,404)
Accumulated Impairment Loss	(19,258)	(19,258)
Net Carrying Value, ending balance	$ 21,127	$ 24,454
Trademarks
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	15 years	15 years
Gross Carrying Amount, beginning balance	$ 7,100	$ 7,100
Accumulated Amortization	(1,838)	(1,769)
Accumulated Impairment Loss	(4,179)	(4,179)
Net Carrying Value, ending balance	$ 1,083	$ 1,152
Existing technology
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	13 years	13 years
Gross Carrying Amount, beginning balance	$ 12,600	$ 12,600
Accumulated Amortization	(4,986)	(4,704)
Accumulated Impairment Loss	(4,328)	(4,328)
Net Carrying Value, ending balance	$ 3,286	$ 3,568
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	11 years	11 years
Gross Carrying Amount, beginning balance	$ 33,500	$ 33,500
Accumulated Amortization	(15,612)	(14,681)
Accumulated Impairment Loss	(10,751)	(10,751)
Net Carrying Value, ending balance	$ 7,137	$ 8,068
Reacquired rights
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	3 years	3 years
Gross Carrying Amount, beginning balance	$ 7,500	$ 7,500
Accumulated Amortization	(2,894)	(1,356)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 4,606	$ 6,144
Patents
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	8 years	8 years
Gross Carrying Amount, beginning balance	$ 6,796	$ 6,798
Accumulated Amortization	(1,919)	(1,504)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 4,877	$ 5,294
Other
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	2 years	2 years
Gross Carrying Amount, beginning balance	$ 618	$ 618
Accumulated Amortization	(480)	(390)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 138	$ 228