Revenue Recognition - Schedule of Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 44,247	$ 52,571	$ 88,929	$ 108,232
Point in Time | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	21,786	28,303	44,612	61,220
Point in Time | Restaurant/Retail | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	21,503	27,430	43,880	59,594
Point in Time | Restaurant/Retail | Grocery
Disaggregation of Revenue [Line Items]
Revenue	283	873	732	1,626
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	6,476	6,524	13,210	13,127
Over Time | Restaurant/Retail | Restaurant/Retail
Disaggregation of Revenue [Line Items]
Revenue	5,829	5,742	11,579	11,599
Over Time | Restaurant/Retail | Grocery
Disaggregation of Revenue [Line Items]
Revenue	647	782	1,631	1,528
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	15,985	17,744	31,107	33,885
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	8,192	8,707	16,738	17,041
Over Time | Government | ISR Solutions
Disaggregation of Revenue [Line Items]
Revenue	$ 7,793	$ 9,037	$ 14,369	$ 16,844