Summary of significant accounting policies (Details 3) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Foreign Currency Translation
Cumulative foreign currency translation adjustments, net of tax in accumulated other comprehensive income	$ 783	$ 443
Income tax expense related to foreign currency translation adjustments	0	0
Recent accounting pronouncements
Short-term debt issuance cost classified as prepaid expenses and other current assets	178	178
Long-term debt issuance cost classified as other assets	$ 425	$ 514
DAS | Minimum
Revenue recognition
Term of the arrangement used to determine revenue recognition	5 years
DAS | Maximum
Revenue recognition
Term of the arrangement used to determine revenue recognition	10 years
Wholesale - Wi-Fi | Minimum
Revenue recognition
Term of the arrangement used to determine revenue recognition	1 year
Wholesale - Wi-Fi | Maximum
Revenue recognition
Term of the arrangement used to determine revenue recognition	5 years