Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Support contract timing			12 months
Customer deposits	$ 1,700	$ 1,300	$ 1,700	$ 1,300
Recognition of deferred revenue			15,846	9,922
Revenue	77,860	54,847	201,277	155,270
Service
Disaggregation of Revenue [Line Items]
Revenue	29,530	16,877	74,743	50,952
Restaurant/Retail
Disaggregation of Revenue [Line Items]
Recognition of deferred revenue	2,400	2,200	7,500	9,900
Revenue	59,821	37,347	147,529	102,389
Restaurant/Retail | Hardware, Software And Service
Disaggregation of Revenue [Line Items]
Revenue		37,300		102,400
Government
Disaggregation of Revenue [Line Items]
Funded performance obligations	38,000		38,000		$ 27,800
Revenue	$ 18,039	$ 17,500	$ 53,748	$ 52,881
Minimum
Disaggregation of Revenue [Line Items]
Payment period			30 days
Maximum
Disaggregation of Revenue [Line Items]
Payment period			90 days