Quarterly report pursuant to Section 13 or 15(d)

Concentrations (Details)

v3.19.1
Concentrations (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Concentration Risk [Line Items]      
Cash and cash equivalents $ 20,813   $ 39,154
Sales Revenue Segment | Customer Concentration Risk      
Concentration Risk [Line Items]      
Southwest Airlines, concentration risk, percent 21.00% 18.00%  
Sales Revenue Segment | Customer Concentration Risk | Connectivity      
Concentration Risk [Line Items]      
Southwest Airlines, concentration risk, percent 39.00% 33.00%  
Accounts Receivable | Customer Concentration Risk      
Concentration Risk [Line Items]      
Southwest Airlines, concentration risk, percent 16.00%   16.00%
Foreign Subsidiaries      
Concentration Risk [Line Items]      
Cash and cash equivalents $ 11,800