Stockholders' Equity - Additional Information (Detail) (USD $)	6 Months Ended			3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended															6 Months Ended
	Oct. 31, 2014 OptionPlan	Oct. 31, 2013	Oct. 31, 2014 2004 Incentive Stock Plan	Oct. 31, 2014 2011 ESPP	Oct. 31, 2014 2011 ESPP	Oct. 31, 2013 2011 ESPP	Oct. 31, 2013 Employee Stock Option	Oct. 31, 2014 Employee Stock Option	Oct. 31, 2013 Employee Stock Option	Oct. 31, 2014 RSUs	Oct. 31, 2013 RSUs	Oct. 31, 2014 RSUs Executive Officer	Oct. 31, 2013 RSUs Executive Officer	Oct. 31, 2014 RSUs Non-Executive Employees	Oct. 31, 2014 RSUs Director	Oct. 31, 2013 RSUs Director	Oct. 31, 2013 RSUs Non-Executive Officer	Oct. 31, 2014 PSUs Executive Officer	Oct. 31, 2013 PSUs Executive Officer	Oct. 31, 2014 RSUs and PSUs	Oct. 31, 2013 RSUs and PSUs	Apr. 30, 2014 Maximum	Oct. 31, 2014 Maximum PSUs Executive Officer	Oct. 31, 2013 Maximum PSUs Executive Officer	Oct. 31, 2014 Open Market
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase authorization																						$ 30,000,000
Repurchasing shares																									2,100,000
Repurchase shares value																									30,000,000
Number of common stock issuable with antidilutive effect				107,081	54,037		88,839		124,930
Number of stock option plans	2
Period to award vested and calculate volatility rate			3 years
Period of award vested exercisable			10 years
Intrinsic value of stock outstanding	9,300,000	14,000,000
Intrinsic value of stock exercisable	9,100,000	11,100,000
Intrinsic value of stock exercised	1,300,000	3,900,000
Unrecognized compensation cost of outstanding options	81,000
Weighted average remaining contractual term								5 months 5 days												1 year 4 months 24 days
Shares purchase under Employee Stock Purchase Plan					79,291	84,081
Stock-based compensation expense	2,801,000	4,774,000
Performance period	3 years
Percentage of maximum aggregate award granted	200.00%
Percentage of stock outperform in order for target award to be earned	10.00%
Stock Units, Awarded										237,100	450,656	20,000	250,000	166,600	50,500	42,238				283,700	480,656		93,200	60,000
Stock Units, Vested																		46,600	30,000	312,670	210,230
Stock-based compensation expense																				2,400,000	3,700,000
Market value of Vested shares																				3,600,000	2,400,000
Stock Units, Forfeited																	153,418			69,371	12,518
Unrecognized compensation cost related to unvested RSUs and PSUs																				$ 5,600,000