Acquisitions and Divestitures - Components of Assets Held-for-sale (Details) - USD ($) $ in Millions |
Sep. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Business Combinations [Abstract] | ||
| Current assets | $ 19 | |
| Property, plant and equipment | 491 | |
| Regulatory assets | 64 | |
| Goodwill | 39 | |
| Other assets | 5 | |
| Assets held for sale | 618 | $ 566 |
| Current liabilities | 18 | |
| Deferred income taxes | 68 | |
| Regulatory liabilities | 41 | |
| Other liabilities | 11 | |
| Liabilities related to assets held for sale | $ 138 | $ 128 |