Share Based Compensation (Details) (2010 Stock Incentive Plan [Member], USD $)	6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	194,900	198,900
Stock options vesting period, years	4 years
Years to expiration	5 years
Time-vested RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period, years	3 years
Weighted average grant date fair value (in dollars per share)	$ 32.75	$ 32.85
Grants in period (in shares)	19,040	25,540
Performance-based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period, years	3 years
Share Based Compensation Arrangement, By Share Based Payment Award, Number Of Shares Granted Based On Target Award Percenatge	100.00%
Weighted average grant date fair value (in dollars per share)	$ 32.75	$ 32.85
Grants in period (in shares)	54,490	56,222
Performance-based RSUs [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Perfromance shares target award	0.00%
Performance-based RSUs [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Perfromance shares target award	150.00%