Dividends and Treasury Stock Dividends paid (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Stockholders' Equity Note [Abstract]
Payments of Ordinary Dividends, Common Stock		$ 4,671	$ 4,668	$ 9,353	$ 9,326
Cash dividends paid per common share (in dollars per share)	[1]	$ 0.130	$ 0.130	$ 0.260	$ 0.260
Dividends Payable		$ 0	$ 0	$ 0	$ 0

[1] There were no declared and unpaid shareholder dividends at July 31, 2019 or 2018.