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Share-Based Compensation - Fair Value of Stock Options Granted (Detail)
12 Months Ended
Jan. 31, 2019
Jan. 31, 2018
Jan. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Risk-Free Interest Rate 2.60% 1.90% 1.40%
Expected Life (years) 9 years 9 years 5 years
Expected Volatility 39.40% 39.00% 28.30%
Expected Dividend Yield 1.50% 2.00% 1.90%