Leases - Maturities of Lease Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating Leases, 2019	$ 42
Operating Leases, 2020	510
Operating Leases, 2021	436
Operating Leases, 2022	346
Operating Leases, 2023	301
Operating Leases, Thereafter	818
Operating Leases, Total lease payments	2,453
Operating Leases, Less amount representing interest	(315)
Operating Leases, Total	2,138
Finance Lease, 2019	19
Finance Lease, 2020	69
Finance Lease, 2021	200
Finance Lease, 2022	35
Finance Lease, 2023	28
Finance Lease, Thereafter	101
Finance Lease, Total lease payments	452
Finance Lease, Less amount representing interest	(67)
Finance Lease, Total	$ 385