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Regulatory Matters (Schedule of COVID-19 Regulatory Impact) (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | $ 2,492.2 | $ 1,930.5
Incremental O&M - COVID | Columbia Of Ohio |  |
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | 2.1 | 2.0
Incremental O&M and Bad Debt-COVID | Columbia Of Pennsylvania |  |
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | 5.2 | 5.4
Incremental Bad Debt - COVID | NIPSCO |  |
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | 2.2 | 9.2
Incremental Bad Debt - COVID | Columbia Of Virginia |  |
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | 1.5 | 0.0
Incremental Bad Debt - COVID | Columbia Of Maryland |  |
Regulated Operations [Line Items] |  |
COVID-19 related regulatory asset | $ 0.9 | $ 0.7

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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