Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Leases [Line Items]
Operating lease expense	$ 3	$ 2
Additional operating leasess, primarily for office leases, that have not yet commenced	$ 3
Maximum
Leases [Line Items]
Operating leases, options to extend leases term	9 years
Finance leases, options to extend leases term	9 years
Additional operating leases that have not yet commenced, lease terms	5 years
Minimum
Leases [Line Items]
Additional operating leases that have not yet commenced, lease terms	3 years