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Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Nov. 30, 2019 | Sep. 30, 2020 | Mar. 31, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Common Equity [Line Items] |  |  |  |  |  |
Proceeds from issuance of common stock, net |  | $ 6 |  | $ 125 | $ 241 | $ 185
Equity Forward Agreements [Member] |  |  |  |  |  |
Common Equity [Line Items] |  |  |  |  |  |
Common stock to be issued, equity forward agreements (in shares) | 4,275,127 |  |  |  |  |
Forward sales price (in dollars per share) | $ 52.235 |  | $ 51.98 |  |  |
Proceeds from issuance of common stock, net |  |  | $ 222 |  |  |
Common stock issued during the period, equity forward agreements (in shares) |  |  | 4,275,127 |  | 4,275,127 |

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