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		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 47	$ 30	$ 94	$ 60
Interest cost	84	84	168	168
Amortization of actuarial losses	58	31	116	63
Net periodic benefit cost	$ 189	$ 145	$ 378	$ 291