Leases - Lease Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Operating Leases
Remainder of 2019	$ 73
2020	83
2021	47
2022	32
2023	19
2024 and thereafter	67
Total Lease Liabilities, Undiscounted	321
Less: Imputed Interest	41
Total Lease Liabilities	280
Finance Leases
Remainder of 2019	37
2020	47
2021	32
2022	22
2023	20
2024 and Thereafter	105
Total Lease Liabilities, Undiscounted	263
Less: Imputed Interest	48
Total Lease Liabilities	215	$ 223
Total
Remainder of 2019	110
2019		143
2020	130	120
2021	79	90
2022	54	84
2023	39	70
2024 and Thereafter	172	280
Total Lease Liabilities, Undiscounted	584	787
Operating lease liability, current	86
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