Assets - Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets
Allowance for doubtful accounts receivable	$ 300	$ 300
Inventories
Materials	42,165	46,457
Work-in-process	20,992	25,250
Finished goods	1,540	5,356
Total	64,697	77,063
Prepaid expenses and other current assets
Supplier deposits against purchase commitments	$ 7,900	$ 7,800