Weighted Average Assumptions Used to Estimate Fair Value Each Option (Detail)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	5.20%	5.40%	5.60%
Expected volatility	55.10%	56.00%	55.40%
Risk-free interest rate	2.30%	2.40%	2.70%
Expected term	4 years 4 months 24 days	4 years 3 months 18 days	4 years 3 months 18 days