Leases - Maturities of lease liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finance Leases
2020	$ 21
2021	17
2022	16
2023	15
2024	14
After 2024	55
Total	138
Less: Amounts representing interest	6
Present value of future minimum lease payments	132
Less: Current obligations	21
Long-term obligations	111	$ 75
Operating Leases
2020	267
2021	191
2022	138
2023	97
2024	65
After 2024	173
Total	931
Less: Amounts representing interest	77
Present value of future minimum lease payments	854
Current operating lease liabilities	247
Noncurrent operating lease liabilities	$ 607
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent us-gaap:OperatingLeaseLiabilityNoncurrent