Property and equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property and equipment
Total property and equipment	$ 93,837	$ 79,981
Less: accumulated depreciation and amortization	(51,426)	(40,264)
Total property and equipment, net	42,411	39,717
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	15,958	12,301	7,511
Network access
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	11,948	8,867	4,392
Network operations
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	2,844	2,444	1,747
Development and technology
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	1,049	873	1,024
General and administrative
Depreciation and amortization allocation
Total depreciation and amortization of property and equipment	117	117	348
Leasehold improvements
Property and equipment
Total property and equipment	72,119	60,030
Construction in progress
Property and equipment
Total property and equipment	6,295	7,059
Computer equipment
Property and equipment
Total property and equipment	7,493	6,674
Software
Property and equipment
Total property and equipment	7,519	5,818
Office equipment
Property and equipment
Total property and equipment	411	400
Software and equipment
Property and equipment
Total property and equipment	402	402
Less: accumulated depreciation and amortization	$ (224)	$ 0