Net income (loss) per share - Calculation of basic and diluted net income (loss) per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Net income applicable to common stockholders:
Net loss	$ (26,605)	$ (30,763)	$ (15,652)	$ (16,098)	$ (12,810)	$ (13,694)	$ (11,423)	$ (9,335)	$ (89,118)	$ (47,262)	$ (35,321)
Weighted average common shares used in computing net loss per share, basic and diluted (in shares)									44,498	43,343	41,567
Net loss per share, basic and diluted (in dollars per share)									$ (2.00)	$ (1.09)	$ (0.85)