Employee Retirement Benefits The components of net periodic benefit cost for postretirement benefits (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 46	$ 30	$ 140	$ 90
Interest cost	84	83	252	251
Amortization of actuarial losses	59	32	175	95
Net periodic benefit cost	$ 189	$ 145	$ 567	$ 436