Property and equipment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Property and equipment
Total property and equipment	$ 147,245		$ 133,855
Less: accumulated depreciation and amortization	(70,800)		(66,295)
Total property and equipment, net	76,445		67,560
Depreciation and amortization allocation of property and equipment
Total depreciation and amortization of property and equipment	5,784	4,133
Network access
Depreciation and amortization allocation of property and equipment
Total depreciation and amortization of property and equipment	3,862	2,877
Network operations
Depreciation and amortization allocation of property and equipment
Total depreciation and amortization of property and equipment	1,187	808
Development and technology
Depreciation and amortization allocation of property and equipment
Total depreciation and amortization of property and equipment	697	416
General and administrative
Depreciation and amortization allocation of property and equipment
Total depreciation and amortization of property and equipment	38	32
Leasehold improvements
Property and equipment
Total property and equipment	108,459		97,462
Construction in progress
Property and equipment
Total property and equipment	17,755		18,157
Computer equipment
Property and equipment
Total property and equipment	7,486		7,372
Software
Property and equipment
Total property and equipment	13,132		10,452
Office equipment
Property and equipment
Total property and equipment	$ 413		$ 412