Summary of Significant Accounting Policies Effect of adopting new accounting guidance (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 280
Other Postretirement Benefit Plans, Defined Benefit [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service cost	7	$ 22
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	78	$ 94
Other Postretirement Benefit Plans, Defined Benefit [Member] | Operating Income (Loss) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service cost	7
Other Postretirement Benefit Plans, Defined Benefit [Member] | Other Nonoperating Income (Expense) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 71