Quarterly report pursuant to Section 13 or 15(d)

Revenue - Narrative (Details)

v3.21.2
Revenue - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Concentration Risk [Line Items]        
Refund liability $ 2,258   $ 2,258  
Revenue from Contract with Customer Benchmark | Geographic Concentration Risk | Two Airports        
Concentration Risk [Line Items]        
Concentration risk, percentage 14.00% 13.00% 14.00% 14.00%