Summary of business and significant accounting policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 58,452	$ 53,069	$ 57,176	$ 52,199	$ 55,987	$ 46,382	$ 61,399	$ 54,695	$ 220,896	$ 218,463	[1]	$ 209,715	[1]
Product
Disaggregation of Revenue [Line Items]
Total revenue									168,619	163,599	[1]	155,025	[1]
Services
Disaggregation of Revenue [Line Items]
Total revenue									52,277	54,864	[1]	54,690	[1]
Transferred at point in time | On-board automotive navigation solutions
Disaggregation of Revenue [Line Items]
Total revenue									168,619	163,599		155,025
Transferred at point in time | Advertising services
Disaggregation of Revenue [Line Items]
Total revenue									24,241	27,229		26,841
Transferred over time | Brought-in automotive navigation solutions
Disaggregation of Revenue [Line Items]
Total revenue									17,161	14,209		8,872
Transferred over time | Automotive maintenance and support
Disaggregation of Revenue [Line Items]
Total revenue									1,055	34		18
Transferred over time | Mobile navigation services
Disaggregation of Revenue [Line Items]
Total revenue									$ 9,820	$ 13,392		$ 18,959

[1] See Note 1 for a summary of adjustments.