v3.8.0.1
Summary of significant accounting policies - Non controlling interests (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Non-controlling interests      
Distributions to non-controlling interest holders $ 125 $ 286 $ 500
Chicago Concourse Development Group, LLC      
Non-controlling interests      
Percentage of net profits less capital expenditures of the preceding year allocated to non-controlling interest holders 30.00%    
Distributions to non-controlling interest holders $ 125 286 500
Boingo Holding Participacoes Ltda.      
Non-controlling interests      
Distributions to non-controlling interest holders $ 0 $ 0 $ 0