Debt - Schedule of Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Debt Disclosure [Abstract]
Contractual interest expense	$ 24	$ 26	$ 72	$ 82
Amortization of debt issuance costs	1	1	3	3
Debt interest expense	$ 25	$ 27	$ 75	$ 85