CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 198,642	$ 2,211	$ 411,706	$ 9,966
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale marketable securities, net of tax	(1,455)	719	508	786
Comprehensive income	$ 197,187	$ 2,930	$ 412,214	$ 10,752