Revenue Recognition - Schedule of Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 45,380	$ 46,362	$ 134,309	$ 154,594
Point in Time | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	23,934	22,452	66,916	83,673
Point in Time | Restaurant/Retail | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	23,599	21,761	65,849	81,422
Point in Time | Restaurant/Retail | Grocery
Disaggregation of Revenue [Line Items]
Revenue	335	691	1,067	2,251
Point in Time | Restaurant/Retail | Mission Systems
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Point in Time | Restaurant/Retail | ISR Solutions
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Over Time | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	5,907	6,474	20,747	19,600
Over Time | Restaurant/Retail | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	5,508	5,727	18,718	17,258
Over Time | Restaurant/Retail | Grocery
Disaggregation of Revenue [Line Items]
Revenue	399	747	2,029	2,342
Over Time | Restaurant/Retail | Mission Systems
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Over Time | Restaurant/Retail | ISR Solutions
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Over Time | Government
Disaggregation of Revenue [Line Items]
Revenue	15,539	17,436	46,646	51,321
Over Time | Government | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Over Time | Government | Grocery
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Over Time | Government | Mission Systems
Disaggregation of Revenue [Line Items]
Revenue	8,420	8,283	25,161	25,324
Over Time | Government | ISR Solutions
Disaggregation of Revenue [Line Items]
Revenue	$ 7,119	$ 9,153	$ 21,485	$ 25,997