Leases - Lease Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating Leases
Remainder of 2019	$ 50
2020	85
2021	48
2022	33
2023	21
2024 and thereafter	80
Total Lease Liabilities, Undiscounted	317
Less: Imputed Interest	39
Total Lease Liabilities	278
Finance Leases
Remainder of 2019	25
2020	48
2021	33
2022	23
2023	21
2024 and Thereafter	105
Total Lease Liabilities, Undiscounted	255
Less: Imputed Interest	44
Total Lease Liabilities	211
Liabilities	11,445	$ 10,526
Total
Remainder of 2019	75
2019		143
2020	133	120
2021	81	90
2022	56	84
2023	42	70
2024 and Thereafter	185	280
Total Lease Liabilities, Undiscounted	572	787
Liabilities, Undiscounted Excess Amount	83
Lease Liability	489
Operating lease liability, current	88	0
Finance lease liability, current	$ 41	41
Operating Leases
2019		91
2020		74
2021		59
2022		62
2023		50
2024 and Thereafter		176
Total Lease Liabilities, Undiscounted		512
Finance Leases
2019		52
2020		46
2021		31
2022		22
2023		20
2024 and Thereafter		104
Total Lease Liabilities, Undiscounted		$ 275