Revenue Recognition - Performance Obligation (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	$ 11,082	$ 12,486	$ 12,813
Current under one year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	9,506	12,084
Current under one year | Restaurant/Retail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	9,506	12,084
Current under one year | Government
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	0	0
Non-current over one year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	3,082	3,916
Non-current over one year | Restaurant/Retail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	3,082	3,916
Non-current over one year | Government
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations	$ 0	$ 0