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Share-Based Compensation - Fair Value of Stock Options Granted (Detail)
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Risk-Free Interest Rate 1.40% 1.60% 1.60%
Expected Life (years) 5 years 5 years 5 years
Expected Volatility 28.30% 22.70% 26.50%
Expected Dividend Yield 1.90% 2.00% 2.00%