XML 59 R46.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Weighted Average Grant-Date Fair Values And Weighted Average Assumptions Used to Calculate Fair Value of Options Granted (Detail) - Stock Options - $ / shares
3 Months Ended 6 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted average grant-date fair value $ 57.38 $ 46.50 $ 50.26 $ 41.60
Valuation assumptions:        
Risk-free interest rate 1.88% 1.11% 1.85% 1.32%
Expected option life (years) 4 years 22 days 4 years 1 month 21 days 4 years 26 days 4 years 1 month 17 days
Expected volatility 43.40% 49.00% 43.60% 49.60%