Summary of significant accounting policies (Details 2) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Primary revenue source
Number of reportable segments | segment			1
Revenue	$ 37,186	$ 30,822	$ 100,855	$ 85,670
Marketable securities
Short-term marketable securities	0		0		$ 1,614
Unrealized gains or losses in accumulated other comprehensive loss	0		0		$ 0
Retail
Primary revenue source
Revenue	7,754	10,144	24,608	30,865
DAS
Primary revenue source
Revenue	13,142	10,429	34,863	27,656
Wholesale - Wi-Fi
Primary revenue source
Revenue	5,454	4,709	15,096	11,477
Military
Primary revenue source
Revenue	5,257	943	13,003	2,043
Advertising and other
Primary revenue source
Revenue	$ 5,579	$ 4,597	$ 13,285	$ 13,629