Leases Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Lease Liability, 2019	$ 184
Operating Lease Liability, 2020	171
Operating Lease Liability, 2021	132
Operating Lease Liability, 2022	107
Operating Lease Liability, 2023	55
Operating Lease Liability, 2024 and thereafter	129
Operating Lease Liability, Total Payments Due	778
Operating Lease, Interest	71
Total Operating Lease Liabilities	707
Finance Lease Liability, 2019	36
Finance Lease Liability, 2020	30
Finance Lease Liability, 2021	27
Finance Lease Liability, 2022	27
Finance Lease Liability, 2023	9
Finance Lease Liability, 2024 and thereafter	6
Finance Lease Liability, Total Payments Due	135
Finance Lease, Interest	9
Finance Lease, Liability	$ 126
Future Minimum Lease Payments 2019		$ 242
Future Minimum Lease Payments 2020		128
Future Minimum Lease Payments 2021		90
Future Minimum Lease Payments 2022		66
Future Minimum Lease Payments 2023		44
Future Minimum Lease Payments 2024 and thereafter		85
Total Future Minimum Lease Payments		$ 655