Dividends and Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Mar. 21, 2016	Jan. 31, 2016
Stockholders' Equity Note [Abstract]
Dividends paid	$ 4,693	$ 4,687	$ 9,384	$ 9,388
Cash dividends paid per common share (in dollars per share)	$ 0.13	$ 0.13	$ 0.26	$ 0.26
Dividends Payable	$ 0	$ 0	$ 0	$ 0
Stock Repurchase Program, Authorized Amount	$ 50,000	$ 50,000	$ 50,000	$ 50,000		$ 40,000
Stock repurchase program, additional amount authorized					$ 10,000
Shares repurchased, Treasury Stock	0	102,187	0	484,252
Payments for Repurchase of Common Stock	$ 0	$ 2,000	$ 0	$ 7,702
Unpaid repurchases of common stock		$ 0		$ 0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 12,959		$ 12,959