Condensed Consolidated Statement of Changes in Stockholders' Equity - 3 months ended Jul. 31, 2017 - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Treasury stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance, Shares at Apr. 30, 2017		84,488	(200)
Beginning balance at Apr. 30, 2017	$ 186,305	$ 8	$ 0	$ 455,755	$ (1,682)	$ (267,776)
Stock-based expense	4,959			4,959
Issuance of common stock upon exercise of stock options, shares		99
Issuance of common stock upon exercise of stock options	378			378
Vested restricted stock units converted to shares, shares		1,362
Tax withholdings related to net share settlements of stock-based compensation awards, shares		(163)
Tax withholdings related to net share settlements of stock-based compensation awards	(777)			(777)
Change in foreign currency translation adjustment	283				283
Change in unrealized gain on investments	(14)				(14)
Net loss	(2,316)					(2,316)
Ending balance, Shares at Jul. 31, 2017		85,786	(200)
Ending balance at Jul. 31, 2017	$ 188,818	$ 8	$ 0	460,641	$ (1,413)	(270,418)
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 326		$ (326)