Income Taxes - Summary of Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Income Tax Disclosure [Abstract]
Income before income taxes	$ 15,437	$ 29,802	$ 23,736	$ 40,610
Provision for income taxes	$ 3,713	$ 757	$ 6,145	$ 1,150
Effective tax rate	24.10%	2.50%	25.90%	2.80%