CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 27,075	$ 2,214
Other comprehensive income:
Unrealized gain on available-for-sale marketable securities, net of tax	1,078	143
Comprehensive income	$ 28,153	$ 2,357