Employee Retirement Benefits The accumulated benefit obligation (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
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
Service cost	187	121	62
Interest cost	335	334	324
Actuarial (gain) loss and assumption changes	433	1,363	237
Retiree benefits paid	(208)	(227)	(166)
Benefit obligation at end of year	$ 8,307	$ 7,560	$ 5,969