Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulated Operations [Line Items]
Total Assets	$ 2,492.2	$ 1,930.5
Regulatory Assets, Current	206.2	135.7
Regulatory Assets, Noncurrent	2,286.0	1,794.8
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Regulated Operations [Line Items]
Total Assets	512.1	583.3
Other Postretirement Costs
Regulated Operations [Line Items]
Total Assets	74.8	72.4
Environmental Costs
Regulated Operations [Line Items]
Total Assets	45.8	56.6
Regulatory Effects Of Accounting For Income Taxes
Regulated Operations [Line Items]
Total Assets	194.8	194.5
Underrecovered Gas And Fuel Costs
Regulated Operations [Line Items]
Total Assets	73.6	8.0
Depreciation
Regulated Operations [Line Items]
Total Assets	177.5	192.6
Post-In Service Carrying Charges
Regulated Operations [Line Items]
Total Assets	237.9	228.6
Safety Activity Costs
Regulated Operations [Line Items]
Total Assets	171.9	146.0
DSM Program
Regulated Operations [Line Items]
Total Assets	39.2	37.8
Retired coal generating stations
Regulated Operations [Line Items]
Total Assets	803.9	204.7
Deferred Derivative Gain (Loss)
Regulated Operations [Line Items]
Total Assets	9.6	54.7
Deferred Property Taxes
Regulated Operations [Line Items]
Total Assets	65.1	62.9
Renewable Energy Program
Regulated Operations [Line Items]
Total Assets	18.5	0.0
Other Assets
Regulated Operations [Line Items]
Total Assets	$ 67.5	$ 88.4

Regulated Operations [Line Items]

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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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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

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