Leases (Details) $ in Millions	12 Months Ended
	Jan. 31, 2020 USD ($)
Leases
Weighted-average remaining lease term	10 years 1 month 6 days
Weighed average discount rate	4.20%
Cash paid for operating leases	$ 1,280
Operating lease cost	1,270
Variable lease cost	$ 230
Maximum
Leases
Typical period of primary lease term for operating lease, build-to-suit, maximum	15 years