Employee Benefit Plan (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Postemployment Benefits [Abstract]
Percentage of participant's contribution matched by employer	50.00%
Employer matching contribution, maximum percentage of participant's base salary	6.00%
Defined contribution plan expense		$ 11,000,000.0	$ 1,700,000	$ 0	$ 0