Stock incentive plans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Recognized stock-based compensation expense
Total stock-based compensation	$ 7,164	$ 4,506	$ 2,735
Stock-based compensation expense capitalized	398
Network operations
Recognized stock-based compensation expense
Total stock-based compensation	1,356	888	352
Development and technology
Recognized stock-based compensation expense
Total stock-based compensation	600	380	352
Selling and marketing
Recognized stock-based compensation expense
Total stock-based compensation	2,017	1,045	571
General and administrative
Recognized stock-based compensation expense
Total stock-based compensation	$ 3,191	$ 2,193	$ 1,460