Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and equipment
Total property and equipment	$ 583,067	$ 502,646
Less: accumulated depreciation and amortization	(268,888)	(240,287)
Total property and equipment, net	314,179	262,359
Depreciation and amortization expense
Total depreciation and amortization of property and equipment	78,837	69,097	$ 49,202
Asset impairment charge
Losses on disposals of property and equipment	90	276
Construction in progress projects
Asset impairment charge
Impairment losses	148	882	54
Network access
Depreciation and amortization expense
Total depreciation and amortization of property and equipment	49,766	42,435	27,013
Network operations
Depreciation and amortization expense
Total depreciation and amortization of property and equipment	17,590	16,382	13,966
Development and technology
Depreciation and amortization expense
Total depreciation and amortization of property and equipment	10,443	9,247	7,207
General and administrative
Depreciation and amortization expense
Total depreciation and amortization of property and equipment	1,038	1,033	$ 1,016
Leasehold improvements
Property and equipment
Total property and equipment	474,808	418,023
Software
Property and equipment
Total property and equipment	51,534	42,281
Construction in progress
Property and equipment
Total property and equipment	40,369	27,291
Computer equipment
Property and equipment
Total property and equipment	14,215	13,245
Furniture, fixtures and office equipment
Property and equipment
Total property and equipment	2,141	1,806
Equipment acquired under capital leases
Property and equipment
Total property and equipment	16,284	12,714
Less: accumulated depreciation and amortization	$ (6,245)	$ (3,744)