Leases - Maturities of Lease Liabilities (Details) $ in Millions	Jun. 30, 2019 USD ($)
Leases [Abstract]
Operating Leases, 2019	$ 116
Operating Leases, 2020	513
Operating Leases, 2021	439
Operating Leases, 2022	347
Operating Leases, 2023	301
Operating Leases, Thereafter	816
Operating Leases, Total lease payments	2,532
Operating Leases, Less amount representing interest	(334)
Operating Leases, Total	2,198
Finance Lease, 2019	36
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	469
Finance Lease, Less amount representing interest	(73)
Finance Lease, Total	$ 396