Dividends and Treasury Stock (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017	Jan. 31, 2015
Stockholders' Equity Note [Abstract]
Stock Repurchase Program, Authorized Amount	$ 75,000	$ 50,000	$ 75,000	$ 50,000	$ 40,000
Shares repurchased, Treasury Stock	0	0	0	0
Payments for Repurchase of Common Stock	$ 0	$ 0	$ 0	$ 0
Unpaid repurchases of common stock	0	$ 0	0	$ 0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 27,959		$ 27,959