Supplemental Financial Information - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss)
Net unrealized gain (loss) on short-term investments	$ 354	$ (89)
Cumulative foreign currency translation adjustment	2,621	1,154
Defined benefit pension obligation	(1,117)	(1,117)
Accumulated other comprehensive income (loss)	$ 1,858	$ (52)