Stock-Based Compensation (Assumptions Used to Value Options) (Details) (USD $)	12 Months Ended
	Apr. 30, 2011	Apr. 30, 2010		Apr. 30, 2009
Options - Management and Director [Member]
Expected volatility, minimum	28.98%	27.11%		23.41%
Expected volatility, maximum	30.20%	27.27%		25.20%
Expected term (years)	5	5		4
Dividend yield, minimum	4.18%	3.24%		2.35%
Dividend yield, maximum	5.17%	3.55%		3.04%
Risk-free interest rate, minimum	1.26%	2.38%		2.54%
Risk-free interest rate, maximum	1.92%	2.75%		3.26%
Weighted-average fair value	$ 2.25	$ 3.27		$ 3.80
Options - Seasonal [Member]
Expected volatility		33.81%	[1]	25.35%	[1]
Expected term (years)		2	[1]	2	[1]
Weighted-average fair value		$ 2.70	[1]	$ 2.83	[1]
Dividend yield		3.48%	[1]	2.80%	[1]
Risk-free interest rate		0.85%	[1]	2.54%	[1]
ESPP Options [Member]
Expected volatility, minimum	22.75%	23.68%		29.13%
Expected volatility, maximum	23.31%	43.20%		43.82%
Expected term (years)	0.5	0.5		0.5
Dividend yield, minimum	3.86%	2.65%		2.67%
Dividend yield, maximum	4.80%	3.46%		2.78%
Risk-free interest rate, minimum	0.19%	0.20%		0.27%
Risk-free interest rate, maximum	0.23%	0.33%		2.13%
Weighted-average fair value	$ 2.16	$ 3.66		$ 4.38

[1] This plan was terminated in fiscal year 2010, except for outstanding awards thereunder.