Leases Schedule of Minimum Lease Payments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating leases
2019	$ 381	$ 709
2020	650	619
2021	562	553
2022	383	389
2023	273	295
2024 and thereafter	837	858
Gross lease payments	3,086	3,423
Less: imputed interest	403
Total operating lease liabilities	2,683
Finance leases
2019	39	70
2020	78	71
2021	70	66
2022	77	75
2023	83	82
2024 and thereafter	600	586
Gross lease payments	947	950
Less: imputed interest	292	301
Total finance lease liabilities	$ 655	$ 649