Income Taxes - Summary of Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Income Tax Disclosure [Abstract]
Income before income taxes	$ 5,529	$ 9,433	$ 8,299	$ 10,808
Provision for income taxes	$ 2,226	$ 801	$ 2,432	$ 393
Effective tax rate	40.30%	8.50%	29.30%	3.60%