Restructuring Charges - Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 USD ($) employee
Restructuring accruals
Restructuring Charges.	$ 5,640	$ 4,679	$ 4,394
Ft. Collins, Colorado and Camarillo, California facilities (2014 Plan)
Restructuring accruals
Restructuring Charges.		$ 2,700
Hyeongok-ri South Korea facility (2015 Plan)
Restructuring accruals
Number of employees terminated | employee		23
Restructuring Charges.		$ 1,100
2016 Restructuring Plan
Restructuring accruals
Number of employees terminated | employee	50
Restructuring Charges.	$ 4,400
2016 Restructuring Plan | Minimum
Restructuring accruals
Expected additional restructuring costs to be incurred	2,000
2016 Restructuring Plan | Maximum
Restructuring accruals
Expected additional restructuring costs to be incurred	$ 5,000
Personnel severance and related costs | Ft. Collins, Colorado and Camarillo, California facilities (2014 Plan)
Restructuring accruals
Number of employees terminated | employee			93
Restructuring Charges.			$ 4,000
Personnel severance and related costs | ALD technology development
Restructuring accruals
Number of employees terminated | employee	25
Restructuring Charges.	$ 1,200
Personnel severance and related costs | LED Market Restructuring Plan
Restructuring accruals
Number of permanent positions eliminated | employee		16
Number of temporary positions eliminated | employee		12
Restructuring Charges.		$ 900
Personnel severance and related costs | 2016 Restructuring Plan
Restructuring accruals
Restructuring Charges.	3,300
Facility closing costs | Ft. Collins, Colorado and Camarillo, California facilities (2014 Plan)
Restructuring accruals
Restructuring Charges.			$ 400
Facility closing costs | 2016 Restructuring Plan
Restructuring accruals
Restructuring Charges.	$ 1,100