Summary of significant accounting policies (Details 3)	6 Months Ended
	Jun. 30, 2014
Platform service arrangements | Minimum
Revenue recognition
Term of the arrangement used to determine revenue recognition	1 year
Platform service arrangements | Maximum
Revenue recognition
Term of the arrangement used to determine revenue recognition	5 years
Telecom operations and wholesale partner arrangements | Minimum
Revenue recognition
Term of the arrangement used to determine revenue recognition	3 years
Telecom operations and wholesale partner arrangements | Maximum
Revenue recognition
Term of the arrangement used to determine revenue recognition	15 years