Summary of Significant Accounting Policies - Schedule of Disaggregation of Revenue by Revenue Source (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Total revenue	$ 273,784	$ 255,098	$ 232,780
Systems Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	205,073	191,411	165,601
Software Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	29,168	25,473	29,795
Parts Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	28,658	27,143	25,343
Service Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 10,885	$ 11,071	$ 12,041