Common Stock and Stock-Based Compensation - Weighted Average Assumptions Used to Estimate Fair Values (Detail)	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Common Stock and Stock-based Compensation [Abstract]
Dividend yield	1.50%	1.40%	1.60%
Expected volatility	35.00%	29.50%	31.50%
Weighted average expected life (in years)	5 years 3 months	5 years	5 years
Risk-free interest rate	0.60%	1.40%	1.70%