Leases - Operating Lease Maturities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Abstract]
Remainder of fiscal year ending March 31, 2020	$ 1,111
Fiscal year ending March 31, 2021	2,173
Fiscal year ending March 31, 2022	1,665
Fiscal year ending March 31, 2023	1,158
Fiscal year ending March 31, 2024	799
Thereafter	2,024
Total lease payments	8,930
Less imputed interest	(1,428)
Total	$ 7,502