Summary of Significant Accounting Policies - Schedule of Changes in Warranty and After-Sale Costs Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warranty and After-Sale Costs
Balance at beginning of year	$ 2,779	$ 3,133	$ 1,739
Net additions charged to earnings	4,520	3,559	1,559
Adjustments to pre-existing warranties	(439)	(554)	1,278
Costs incurred	(3,493)	(3,359)	(1,443)
Balance at end of year	$ 3,367	$ 2,779	$ 3,133