Employee Stock Plans (Components Of Stock-Based Compensation Expense Recognized) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, pre-tax	$ 13,399	$ 15,547	$ 17,729
Tax benefit from stock-based compensation expense	(4,701)	(5,675)	(6,471)
Total stock-based compensation expense, net of tax	8,698	9,872	11,258
Restricted Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, pre-tax	12,381	14,090	16,470
Stock Options And SARs [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, pre-tax	933	1,028	853
ESPP [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, pre-tax	$ 85	$ 429	$ 406