Stock-Based Compensation - Calculation of Fair Value of Stock Options (Detail)	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Calculation of Fair Value of Stock Option
Expected dividend yield	0.51%	0.94%
Risk-free interest rate	1.24%	0.75%	1.53%
Expected life in years	5 years	5 years 5 months 9 days	5 years
Historical Volatility	0.57%	0.51%	0.51%