Common Stock and Stock-Based Compensation - Weighted Average Assumptions Used to Estimate Fair Values (Detail)	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Common Stock and Stock-based Compensation [Abstract]
Dividend yield	1.30%	1.50%	1.40%
Expected volatility	27.90%	35.00%	29.50%
Weighted average expected life (in years)	5 years 3 months	5 years 3 months	5 years
Risk-free interest rate	1.30%	0.60%	1.40%