Employee Retirement Benefits The liability and expense reflected in the balance sheet and income statement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employer expense	$ 2,021	$ 1,556	$ 1,254
Long-term portion in other liabilities	8,072	7,348	5,757
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	7,560	5,969	5,512
Employer expense	755	582	552
Other comprehensive (income) loss	200	1,236	71
Total recognized in net and other comprehensive income	955	1,818	623
Retiree benefits paid	(208)	(227)	(166)
Benefit obligation at end of year	8,307	7,560	5,969
Current portion in accrued liabilities	235	212	212
Long-term portion in other liabilities	8,072	7,348	5,757
Assumptions used:
Discount rate	4.25%	4.50%	5.75%
Wage inflation rate	4.00%	4.00%	4.00%
Assumed health care cost trend rate	8.10%	8.60%	9.00%
Ultimate health care cost trend rate	5.00%	5.00%	5.00%
Amounts that will be amortized from accumulated other comprehensive income in next fiscal year	182
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates
Effect on total of service and interest cost components, one percentage point increase	75
Effect on total of service and interest cost components, one percentage point decrease	(53)
Effect on accumulated postretirement benefit obligation, one percenatge point increase	1,588
Effect on accumulated postretirement benefit obligation, one percenatge point decrease	$ (1,288)