Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Finance Leases
2022	$ 418
2023	290
2024	152
2025	59
2026	14
Thereafter	0
Total lease payments	933
Less: imputed interest	39
Finance lease liabilities	894	$ 1,046
Real Estate
Operating Leases
2022	411
2023	335
2024	260
2025	190
2026	108
Thereafter	207
Total lease payments	1,511
Less: imputed interest	135
Total payments	1,376
Equipment
Operating Leases
2022	41
2023	23
2024	11
2025	5
2026	2
Thereafter	1
Total lease payments	83
Less: imputed interest	3
Total payments	$ 80