Revenue Recognition - Cumulative Effect from Adoption of New Accounting Standard (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets:
Trade and other accounts receivable, net of allowance	$ 19,966	$ 22,939	$ 22,712
Inventories	33,645	23,020	23,450
Liabilities and Stockholders’ Equity:
Accounts payable and accrued liabilities	16,513	27,320	27,283
Deferred revenue and customer deposits	4,279	6,054	6,572
Accumulated deficit	$ (283,503)	(246,955)	$ (247,233)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Assets:
Trade and other accounts receivable, net of allowance		227
Inventories		(430)
Liabilities and Stockholders’ Equity:
Accounts payable and accrued liabilities		37
Deferred revenue and customer deposits		(518)
Accumulated deficit		$ 278