Employee Benefits and Stock-based Compensation - Classification of Stock-based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Stock-based compensation:
Total stock-based compensation	$ 66,871	$ 60,812	$ 56,861
Cost of revenue [Member]
Stock-based compensation:
Total stock-based compensation	1,184	1,261	1,306
Research and development [Member]
Stock-based compensation:
Total stock-based compensation	41,842	37,432	34,575
Selling, general and administrative [Member]
Stock-based compensation:
Total stock-based compensation	$ 23,845	$ 22,119	$ 20,980