Reconciliation of Income Amounts and Weighted Average Number of Common and Common Equivalent Shares Used to Determine Basic and Diluted Earnings per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Oct. 31, 2013		Oct. 31, 2012		Oct. 31, 2013		Oct. 31, 2012
Net income/(loss)
Income from continuing operations	$ 17,145		$ 16,401		$ 43,671		$ 35,272
Income/(loss) from discontinued operations, net of tax	(158)		4,784		(208)		3,699
Net income/(loss)	$ 16,987		$ 21,185		$ 43,463		$ 38,971
Weighted average shares outstanding - Basic	59,620		65,871		61,931		65,611
Dilutive effect of stock option and award plans	1,364		1,403		1,820		1,303
Diluted shares outstanding	60,984		67,274		63,751		66,914
Earnings per share - Basic
Income from continuing operations	$ 0.29	[1]	$ 0.25	[1]	$ 0.71	[1]	$ 0.54	[1]
Income/(loss) from discontinued operations	$ 0.00	[1]	$ 0.07	[1]	$ 0.00	[1]	$ 0.06	[1]
Net income/(loss)	$ 0.28	[1]	$ 0.32	[1]	$ 0.70	[1]	$ 0.59	[1]
Earnings per share - Diluted
Income from continuing operations	$ 0.28	[1]	$ 0.24	[1]	$ 0.69	[1]	$ 0.53	[1]
Income/(loss) from discontinued operations	$ 0.00	[1]	$ 0.07	[1]	$ 0.00	[1]	$ 0.06	[1]
Net income/(loss)	$ 0.28	[1]	$ 0.31	[1]	$ 0.68	[1]	$ 0.58	[1]

[1] Net income per share may not equal earnings per share from continuing plus discontinued operations due to rounding.