Restructuring - Summary of Expenditures Incurred to Date and Future Expenditures Associated with Restructuring (Details) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,598	$ 3,507	$ 800	$ 5,900
Edgewood Facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	300	100	400
Piedmont Facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(200)	900	100	800
Monona Facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,100	400	200	1,700
Shadyside Facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	700	1,700	200	2,600
Other Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	200	200	400
Separation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	196	2,668
Separation costs | Edgewood Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	200	100	300
Separation costs | Piedmont Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(200)	500	100	400
Separation costs | Monona Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(200)	300	200	300
Separation costs | Shadyside Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	500	1,500	200	2,200
Separation costs | Other Restructuring | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	100	0	100
Separation costs | Other Restructuring | Selling, general and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	100	200	300
Facility and other costs | Edgewood Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	100	0	100
Facility and other costs | Piedmont Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	400	0	400
Facility and other costs | Monona Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,300	100	0	1,400
Facility and other costs | Shadyside Facility | Cost of Revenues
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 200	$ 200	$ 0	$ 400