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, 2012	Jan. 31, 2011	Jan. 31, 2010
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employer expense	$ 1,556	$ 1,254	$ 1,085
Long-term portion in other liabilities	7,348	5,757	5,283
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	5,969	5,512	4,840
Employer expense	582	552	515
Other comprehensive (income) loss	1,236	71	348
Total recognized in net and other comprehensive income	1,818	623	863
Retiree benefits paid	(227)	(166)	(191)
Benefit obligation at end of year	7,560	5,969	5,512
Current portion in accrued liabilities	212	212	229
Long-term portion in other liabilities	$ 7,348	$ 5,757	$ 5,283
Assumptions used:
Discount rate	4.50%	5.75%	6.00%
Wage inflation rate	4.00%	4.00%	3.00%