Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Percentage of total revenue accounted for percentage-of-completion revenue, less than	0.10%	0.10%	0.10%	0.10%
Product sales as a percentage of total revenue	95.00%	95.00%	95.00%	95.00%
Disaggregation of Revenue [Line Items]
Revenue	$ 34,692	$ 39,546	$ 77,949	$ 80,615
Operating expenses (excluding depreciation and amortization):	38,306	35,544	82,904	72,199
Products
Disaggregation of Revenue [Line Items]
Revenue	33,632	38,213	75,703	78,142
Operating expenses (excluding depreciation and amortization):	37,798	34,062	81,877	69,247
Services
Disaggregation of Revenue [Line Items]
Revenue	1,060	1,333	2,246	2,473
Operating expenses (excluding depreciation and amortization):	$ 508	$ 1,482	$ 1,027	$ 2,952