Income Taxes - Significant components of the company's income tax provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Currently payable	$ 18,754	$ 7,354	$ 5,272
Deferred expense (benefit)	(787)	307	(6,039)
Income tax expense (benefit)	$ 17,967	$ 7,661	$ (767)