Share Based Compensation Weighted average assumptions by grant year (Details) (USD $)	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Share-based Compensation [Abstract]
Risk-free interest rate	0.86%	0.67%	1.46%
Expected dividend yield	1.33%	1.20%	1.49%
Expected volatility factor	49.62%	51.44%	49.33%
Expected option term (in years)	3 years 9 months	4 years	4 years 6 months
Weighted average grant date fair value	$ 10.92	$ 11.05	$ 7.85