Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Treasury stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance at Apr. 30, 2014	$ 206,462	$ 8	$ 0	$ 398,201	$ 328	$ (192,075)
Beginning balance, Shares at Apr. 30, 2014		77,888	(250)
Stock Issued During Period, Shares, New Issues			50
Excess tax benefit related to stock-based expense	6			6
Stock-based compensation	12,802			12,802
Issuance of restricted stock awards		166
Exercise of stock options and vested restricted stock units, Shares		1,851
Exercise of stock options and vested restricted stock units	5,008	$ 0		5,008
Shares issued under employee stock plans, shares		441
Shares issued under employee stock plans	2,492			2,492
Change in foreign currency translation adjustment	(934)				(934)
Change in unrealized gain on investments	(32)				(32)
Net loss applicable to common stockholders	(34,421)					(34,421)
Ending balance, Shares at Apr. 30, 2015		80,346	(200)
Ending balance at Apr. 30, 2015	191,383	$ 8	$ 0	418,509	(638)	(226,496)
Excess tax benefit related to stock-based expense	(38)			(38)
Stock-based compensation	15,574			15,574
Issuance of restricted stock awards		242
Exercise of stock options and vested restricted stock units, Shares		1,022
Exercise of stock options and vested restricted stock units	849			849
Shares issued under employee stock plans, shares		660
Shares issued under employee stock plans	2,345			2,345
Change in foreign currency translation adjustment	(255)				(255)
Change in unrealized gain on investments	15				15
Net loss applicable to common stockholders	(25,339)					(25,339)
Ending balance, Shares at Apr. 30, 2016		82,270	(200)
Ending balance at Apr. 30, 2016	184,534	$ 8	$ 0	437,239	(878)	(251,835)
Excess tax benefit related to stock-based expense	(155)			(155)
Stock-based compensation	16,777			16,777
Issuance of restricted stock awards		185
Exercise of stock options and vested restricted stock units, Shares		1,419
Exercise of stock options and vested restricted stock units	(115)			(115)
Shares issued under employee stock plans, shares		614
Shares issued under employee stock plans	2,009			2,009
Change in foreign currency translation adjustment	(784)				(784)
Change in unrealized gain on investments	(20)				(20)
Net loss applicable to common stockholders	(15,941)					(15,941)
Ending balance, Shares at Apr. 30, 2017		84,488	(200)
Ending balance at Apr. 30, 2017	$ 186,305	$ 8	$ 0	$ 455,755	$ (1,682)	$ (267,776)