Employee Stock Plans (Restricted Stock Activity) (Detail) (Restricted Stock [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Restricted Stock [Member]
Restricted Stock Activity [Line Items]
Shares, Non-vested, beginning of year	2,007	2,480	2,387
Shares, Granted	687	562	1,017
Shares, Vested	(794)	(920)	(754)
Shares, Forfeited/expired	(119)	(115)	(170)
Shares, Non-vested, end of year	1,781	2,007	2,480
Weighted-Average Grant Date Fair Value, Non-vested, beginning of year	$ 8.64	$ 9.93	$ 15.50
Weighted-Average Grant Date Fair Value, Granted	$ 21.46	$ 15.12	$ 10.57
Weighted-Average Grant Date Fair Value, Vested	$ 15.58	$ 15.32	$ 20.43
Weighted-Average Grant Date Fair Value, Forfeited/expired	$ 18.19	$ 14.83	$ 17.91
Weighted-Average Grant Date Fair Value, Non-vested, end of year	$ 9.85	$ 8.64	$ 9.93