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Regulatory Matters (Schedule of COVID-19 Regulatory Impact) (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Incremental O&M - COVID | Columbia Of Ohio |  |
Regulated Operations |  |
Regulatory Assets | $ 2.1 | $ 2.0
Incremental Bad Debt - COVID | Columbia Of Pennsylvania |  |
Regulated Operations |  |
Regulatory Assets | 6.5 | 5.4
Incremental O&M and Bad Debt - COVID | NIPSCO |  |
Regulated Operations |  |
Regulatory Assets | 2.2 | 9.2
Incremental O&M and Bad Debt - COVID | Columbia Of Virginia |  |
Regulated Operations |  |
Regulatory Assets | 1.4 | 0.0
Incremental O&M and Bad Debt - COVID | Columbia Of Maryland |  |
Regulated Operations |  |
Regulatory Assets | $ 0.9 | $ 0.7

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