Summary of business and significant accounting policies - Concentration of Risk and Significant Customers (Details)	12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2012
Sprint Nextel Corporation
Concentration Risk [Line Items]
Concentration risk, percentage of revenue	10.00%	16.00%	36.00%
AT&T Mobility LLC
Concentration Risk [Line Items]
Concentration risk, percentage of revenue	24.00%	28.00%	35.00%
AT&T Mobility LLC | Accounts receivable
Concentration Risk [Line Items]
Concentration risk, percentage of revenue	19.00%	23.00%
Ford Motor Company
Concentration Risk [Line Items]
Concentration risk, percentage of revenue	46.00%	36.00%	13.00%
Ford Motor Company | Accounts receivable
Concentration Risk [Line Items]
Concentration risk, percentage of revenue	47.00%	45.00%