Leases Supplemental balance sheet information (Details) - USD ($) $ in Millions |
Jun. 30, 2019 |
Dec. 31, 2018 |
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|---|---|---|---|---|---|---|---|---|---|
| Property, Plant and Equipment, Gross | $ 18,300 | $ 18,187 | |||||||
| Accumulated Depreciation | (6,860) | (6,832) | |||||||
| Property, plant and equipment, net | 12,051 | $ 12,442 | |||||||
| Operating Lease, Right-of-Use Asset | [1],[2] | $ 184 | |||||||
| Operating Lease, Weighted Average Remaining Lease Term | [1] | 15 years 9 months 18 days | |||||||
| Finance Lease, Weighted Average Remaining Lease Term | [1] | 7 years 4 months 24 days | |||||||
| Operating Lease, Weighted Average Discount Rate, Percent | [1] | 5.10% | |||||||
| Finance Lease, Weighted Average Discount Rate, Percent | [1] | 8.00% | |||||||
| Property Subject to Finance Lease [Member] | |||||||||
| Property, Plant and Equipment, Gross | [1],[3] | $ 213 | |||||||
| Accumulated Depreciation | [1],[3] | (104) | |||||||
| Property, plant and equipment, net | [1],[3] | $ 109 | |||||||
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