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Regulatory Matters (Narrative) (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2020 USD ($) | Aug. 31, 2020 customer | Jun. 30, 2020 USD ($) | Sep. 30, 2020 USD ($) | Sep. 30, 2019 USD ($) | Dec. 31, 2020 USD ($)
Regulatory Matters [Line Items] |  |  |  |  |  |
Credits issued to customers |  |  |  | $ (72) | $ (12) |
Electric transmission cost recovery [Member] | IPL [Member] |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Credits issued to customers |  |  | $ 42 |  |  |
DAEC PPA [Member] |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Buyout payment | $ 110 |  |  |  |  |
PPA term amendment | 5 years |  |  |  |  |
Derecho windstorm [Member] |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Net regulatory liability, derecho windstorm | $ 7 |  |  | 7 |  |
Derecho windstorm [Member] | IPL [Member] |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Number of customers without power, derecho windstorm (number of customers) | customer |  | 250,000 |  |  |  |
Derecho windstorm repair and rebuilding costs | $ 130 |  |  | $ 130 |  |
Derecho windstorm [Member] | Forecast [Member] | IPL [Member] |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Derecho windstorm repair and rebuilding costs |  |  |  |  |  | $ 140

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- Definition Carrying amount as of the balance sheet date of capitalized storm costs of a regulated entity that are expected to be recoverable through rate adjustments after one year or beyond the normal operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=77907324&loc=d3e43603-110378 + Details
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