Dividends and Treasury Stock Dividends paid (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Stockholders' Equity Note [Abstract]
Payments of Ordinary Dividends, Common Stock	[1]	$ 4,668	$ 4,693	$ 9,326	$ 9,384
Cash dividends paid per common share (in dollars per share)	[1]	$ 0.13	$ 0.13	$ 0.26	$ 0.26
Dividends Payable		$ 0	$ 0	$ 0	$ 0

[1] There were no declared and unpaid shareholder dividends at July 31, 2018 or 2017.