Property and equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property and equipment
Total property and equipment	$ 133,855	$ 93,837
Less: accumulated depreciation and amortization	(66,295)	(51,426)
Total property and equipment, net	67,560	42,411
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	18,940	15,958	12,301
Network access
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	12,651	11,948	8,867
Network operations
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	4,091	2,844	2,444
Development and technology
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	1,992	1,049	873
General and administrative
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	206	117	117
Leasehold improvements
Property and equipment
Total property and equipment	97,462	72,119
Construction in progress
Property and equipment
Total property and equipment	18,157	6,295
Computer equipment
Property and equipment
Total property and equipment	7,372	7,493
Software
Property and equipment
Total property and equipment	10,452	7,519
Office equipment
Property and equipment
Total property and equipment	$ 412	$ 411