Financing Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 15, 2015
Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Letters of credit issued, amount	$ 650	$ 850
Borrowing outstanding under line of credit	$ 0	0
JPMorgan Chase Bank [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date	Apr. 15, 2015
Borrowing capacity under line of credit			$ 125,000
Maturity date of the line of credit	Apr. 15, 2020
Unamortized Debt Issuance Expense	$ 434	548
Letters of credit issued, amount	464	0
Borrowing outstanding under line of credit	0	0
Remaining borrowing capacity under the line of credit	124,536	$ 125,000
All lenders [Member]
Line of Credit Facility [Line Items]
Letters of credit issued, amount	$ 1,114