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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulated Operations [Line Items]
Regulatory Liabilities	$ 1,980.0	$ 2,065.5
Regulatory Liability, Current	137.4	161.3
Regulatory Liability, Noncurrent	1,842.6	1,904.2
Deferred Derivative Gain (Loss)
Regulated Operations [Line Items]
Regulatory Liabilities	34.2	14.0
Overrecovered Gas And Fuel Costs
Regulated Operations [Line Items]
Regulatory Liabilities	5.4	47.8
Cost Of Removal
Regulated Operations [Line Items]
Regulatory Liabilities	749.5	775.2
Regulatory Effects Of Accounting For Income Taxes
Regulated Operations [Line Items]
Regulatory Liabilities	1,040.8	1,105.1
Other Postretirement Costs
Regulated Operations [Line Items]
Regulatory Liabilities	75.9	69.5
Other Liabilities
Regulated Operations [Line Items]
Regulatory Liabilities	$ 74.2	$ 53.9

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Regulated Operations [Line Items]

+ References

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities 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 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities 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 405
-Section 25
-Paragraph 1
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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities 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 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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