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Regulatory Matters (Rate Case Action) (Details) - USD ($) $ in Millions	May 15, 2020	Apr. 24, 2020	Oct. 31, 2018
NIPSCO - Electric
Rate Case Action [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 21.4
Public Utilities, Approved Rate Increase (Decrease), Amount			$ (53.5)
Columbia Of Maryland
Rate Case Action [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 5.0
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 2.0
Columbia Of Pennsylvania
Rate Case Action [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 100.4

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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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