Summary of business and significant accounting policies - Accumulated Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	[2]	Dec. 31, 2018	Dec. 31, 2017	[2]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, net of tax as of June 30, 2018	[1]				$ 108,883
Other comprehensive income (loss) before reclassifications, net of tax					(162)
Amount reclassified from accumulated other comprehensive loss, net of tax					7
Other comprehensive income (loss), net of tax		$ (29)	$ (26)		(155)	$ 361
Balance, net of tax as of December 31, 2018		99,431			99,431
AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, net of tax as of June 30, 2018					(1,855)
Balance, net of tax as of December 31, 2018		(2,010)			(2,010)
Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, net of tax as of June 30, 2018					(692)
Other comprehensive income (loss) before reclassifications, net of tax					186
Amount reclassified from accumulated other comprehensive loss, net of tax					7
Other comprehensive income (loss), net of tax					193
Balance, net of tax as of December 31, 2018		(499)			(499)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, net of tax as of June 30, 2018					(1,163)
Other comprehensive income (loss) before reclassifications, net of tax					(348)
Amount reclassified from accumulated other comprehensive loss, net of tax					0
Other comprehensive income (loss), net of tax					(348)
Balance, net of tax as of December 31, 2018		$ (1,511)			$ (1,511)

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

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