XML 100 R73.htm IDEA: XBRL DOCUMENT v3.7.0.1
Assumptions To Value Stock Options (Detail)
12 Months Ended
May 31, 2017
May 31, 2016
May 31, 2015
Non-Qualified Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 2.59% 2.33% 1.88%
Expected volatility 36.86% 38.40% 50.92%
Risk-free interest rate 1.15% 1.98% 1.88%
Expected life (years) 6 years 6 years 6 years
Market-Based Restricted Common Shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield     1.60%
Expected volatility     44.00%
Risk-free interest rate     1.70%