Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 213,786	$ 187,232	$ 201,246
Restaurant/Retail | Point in Time
Disaggregation of Revenue [Line Items]
Revenue	73,228	93,857	101,260
Restaurant/Retail | Over Time
Disaggregation of Revenue [Line Items]
Revenue	69,284	29,450	32,809
Restaurant/Retail | Restaurant | Point in Time
Disaggregation of Revenue [Line Items]
Revenue	73,228	92,702	98,353
Restaurant/Retail | Restaurant | Over Time
Disaggregation of Revenue [Line Items]
Revenue	69,284	27,224	29,713
Restaurant/Retail | Grocery | Point in Time
Disaggregation of Revenue [Line Items]
Revenue		1,155	2,907
Restaurant/Retail | Grocery | Over Time
Disaggregation of Revenue [Line Items]
Revenue		2,226	3,096
Restaurant/Retail | ISR Solutions | Point in Time
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Restaurant/Retail | ISR Solutions | Over Time
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Restaurant/Retail | Mission Systems | Point in Time
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Restaurant/Retail | Mission Systems | Over Time
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Government | Over Time
Disaggregation of Revenue [Line Items]
Revenue	71,274	63,925	67,177
Government | Restaurant | Over Time
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Government | Grocery | Over Time
Disaggregation of Revenue [Line Items]
Revenue		0	0
Government | ISR Solutions | Over Time
Disaggregation of Revenue [Line Items]
Revenue	38,327	30,413	32,381
Government | Mission Systems | Over Time
Disaggregation of Revenue [Line Items]
Revenue	$ 32,947	$ 33,512	$ 34,796