Industry segment and geographic information - Segment Results (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	$ 40,291	$ 35,065	$ 52,001	$ 42,227	$ 47,754	$ 46,278	$ 45,253	$ 44,061	$ 169,584	$ 183,346	$ 160,239
Cost of revenue									92,335	100,797	78,784
Gross profit	$ 17,826	$ 17,398	$ 23,274	$ 18,751	$ 20,982	$ 20,172	$ 20,721	$ 20,674	$ 77,249	$ 82,549	$ 81,455
Gross margin (as a percent)									46.00%	45.00%	51.00%
Automotive
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue									$ 123,784	$ 135,372	$ 103,100
Cost of revenue									73,923	81,293	56,319
Gross profit									$ 49,861	$ 54,079	$ 46,781
Gross margin (as a percent)									40.00%	40.00%	45.00%
Advertising
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue									$ 26,841	$ 21,744	$ 17,941
Cost of revenue									12,724	12,296	11,710
Gross profit									$ 14,117	$ 9,448	$ 6,231
Gross margin (as a percent)									53.00%	43.00%	35.00%
Mobile Navigation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue									$ 18,959	$ 26,230	$ 39,198
Cost of revenue									5,688	7,208	10,755
Gross profit									$ 13,271	$ 19,022	$ 28,443
Gross margin (as a percent)									70.00%	73.00%	73.00%