Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Percentage of total revenue accounted for percentage-of-completion revenue, less than									0.10%	0.10%	0.10%
Product sales as a percentage of total revenue									95.00%	95.00%	95.00%
Revenue	$ 43,449	$ 53,709	$ 39,546	$ 41,069	$ 55,299	$ 61,167	$ 65,875	$ 60,765	$ 177,773	$ 243,106	$ 188,233
Operating expenses (excluding depreciation and amortization)									159,808	188,744	143,983
Products
Disaggregation of Revenue [Line Items]
Revenue									172,412	237,211	182,294
Operating expenses (excluding depreciation and amortization)									152,846	182,330	140,108
Services
Disaggregation of Revenue [Line Items]
Revenue									5,361	5,895	5,939
Operating expenses (excluding depreciation and amortization)									$ 6,962	$ 6,414	$ 3,875