Pension plan (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended												3 Months Ended		9 Months Ended
	Oct. 31, 2012	Jan. 31, 2012	Oct. 31, 2012 Equity Securities [Member]	Jan. 31, 2012 Equity Securities [Member]	Oct. 31, 2012 Bonds [Member]	Jan. 31, 2012 Bonds [Member]	Oct. 31, 2012 US Treasury and Government [Member]	Jan. 31, 2012 US Treasury and Government [Member]	Oct. 31, 2012 Real Estate Funds [Member]	Jan. 31, 2012 Real Estate Funds [Member]	Oct. 31, 2012 Money Market Funds [Member]	Jan. 31, 2012 Money Market Funds [Member]	Oct. 31, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Oct. 31, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]	Oct. 31, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Oct. 31, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]
Pension plan [Line Items]
Service cost													$ 43	$ 31	$ 128	$ 94
Interest cost													75	79	224	235
Expected return on plan assets													(111)	(101)	(333)	(304)
Amortization of prior service cost													12	31	37	95
Recognized actuarial loss													43	16	130	47
Net periodic benefit costs													62	56	186	167
Equity securities			3,175	3,018
Available-for-sale Securities, Fair Value Disclosure	5,715	5,364			2,141	1,968	281	268
Real Estate									118	110
Money market Fund											252	138
Defined Benefit Plan, Fair Value of Plan Assets	5,967	5,502
Pension Contributions	$ 292