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, 2013	$ 241,349	$ 7	$ 0	$ 370,397	$ (146)	$ (128,909)
Beginning balance, Shares at Apr. 30, 2013		73,925	(250)
Excess tax benefit related to stock-based expense	216			216
Stock-based compensation	14,468			14,468
Issuance of restricted stock awards		76
Exercise of stock options and vested restricted stock units, Shares		3,563
Exercise of stock options and vested restricted stock units	10,855	$ 1		10,854
Shares issued under employee stock plans, shares		324
Shares issued under employee stock plans	2,266			2,266
Change in foreign currency translation adjustment	386				386
Change in unrealized gain on investments	88				88
Net loss applicable to common stockholders	(63,166)					(63,166)
Ending balance, Shares at Apr. 30, 2014		77,888	(250)
Ending balance at Apr. 30, 2014	206,462	$ 8	$ 0	398,201	328	(192,075)
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	1,246	1,851
Exercise of stock options and vested restricted stock units	$ 5,008			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	227	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)