Leases - Reconciliation of Operating and Finance Lease Liabilities Recorded on the Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating Leases
Remainder of 2019	$ 134
2020	191
2021	70
2022	49
2023	35
Thereafter	155
Total lease payments	634
Less portion representing imputed interest	77
Total lease liabilities	557
Finance Leases
Remainder of 2019	35
2020	62
2021	52
2022	48
2023	44
Thereafter	322
Total lease payments	563
Less portion representing imputed interest	302
Total lease liabilities	261
Operating Leases
2019		$ 264
2020		139
2021		57
2022		35
2023		24
Thereafter		135
Total lease payments		654
Finance Leases
2019		58
2020		50
2021		48
2022		45
2023		43
Thereafter		323
Total lease payments		567
Capital Leases, Future Minimum Payments, Interest Included in Payments		319
Capital Lease Obligations	$ 261	$ 248