Commitments and Contingencies (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Outstanding purchase commitments	$ 5,800
2018	209
2019	1,085
2020	834
2021	478
2022	360
Thereafter	401
Total future lease payments	3,367
Long-term Purchase Commitment [Line Items]
Property, plant and equipment, net	277,978	$ 272,388
Assets Held under Capital Leases
Long-term Purchase Commitment [Line Items]
Property, plant and equipment, net	1,300	1,300
Accumulated depreciation	$ 600	$ 500