Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Income Tax Disclosure [Abstract]
Net income before provision for income taxes	$ 190,185	$ 6,757	$ 219,360	$ 9,287
Provision for income taxes	$ 4,196	$ 1,216	$ 6,296	$ 1,532
Effective tax rate	2.20%	18.00%	2.90%	16.50%