CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 185,989	$ 5,541	$ 213,064	$ 7,755
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale marketable securities, net of tax	885	(76)	1,963	67
Comprehensive income	$ 186,874	$ 5,465	$ 215,027	$ 7,822