Summary of significant accounting policies - Revenue recognition - Terms of contracts (Details)	9 Months Ended
	Sep. 30, 2020 item
Minimum
Revenue recognition
Payment terms	30 days
Maximum
Revenue recognition
Payment terms	60 days
DAS | Maximum
Revenue recognition
Initial term of the arrangement	20 years
Wholesale-Wi-Fi | Maximum
Revenue recognition
Initial term of the arrangement	3 years
Military and retail
Revenue recognition
Cancellation period of renewal option prior to end of current contract period	5 days
Multifamily
Revenue recognition
Number of performance obligations	2
Multifamily | Maximum
Revenue recognition
Initial term of the arrangement	10 years