Leases Lessee, Operating Lease, Liability, Maturity (Details) $ in Millions	Jul. 31, 2019 USD ($)
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2020	$ 1,237
2021	2,462
2022	2,230
2023	2,008
2024	1,820
Thereafter	16,319
Total undiscounted lease obligations	26,076
Less imputed interest	(8,202)
Net lease obligations	17,874
Finance Lease, Liability, Payment, Due [Abstract]
Remainder of 2020	356
2021	707
2022	653
2023	536
2024	470
Thereafter	5,676
Total undiscounted lease obligations	8,398
Less imputed interest	(4,044)
Net lease obligations	$ 4,354