Stock-Based Compensation (Stock Options and SSARs Fair Value Assumptions) (Details)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Assumptions used for fair value estimation
Risk-free interest rate	1.90%	0.90%	1.90%
Expected volatility	22.50%	22.90%	23.60%
Expected dividend yield	1.80%	1.90%	1.90%
Expected term (years)	6 years 9 months	6 years 6 months	6 years