Other Income, Net - Other Income, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Other Income and Expenses [Abstract]
Foreign currency gain (loss)	$ (708)	$ (2,103)	$ 1,177
Accretion (amortization) on investments	3,001	2,492	(1,718)
Interest income	25,185	15,388	8,383
Other income, net	$ 27,478	$ 15,777	$ 7,842