Leases - Power Purchase Commitment (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) MW	Dec. 31, 2020 USD ($)
Whitewater \| Wisconsin Electric Power Company & Wisconsin Public Service
Leases
Acquisition purchase price, expected	$ 72.7
Power purchase commitment
Leases
Power purchase contract period	25 years
Firm capacity from power purchase contract (in megawatts) \| MW	236.5
Minimum energy requirements over remaining term of power purchase contract (in megawatts) \| MW	0
Finance lease obligation	$ 78.4	$ 12.1
Finance lease obligation at end of life of power purchase contract	$ 0.0

Purchase price of expected asset acquisition prior to consideration being transferred.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 15
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6911878&loc=d3e8732-128492

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The finance lease obligation for a power purchase contract remaining at the end of the life of the contract.

+ References

No definition available.

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- Definition

Firm capacity, in megawatts, from a power purchase agreement accounted for as a finance lease.

+ References

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- Definition

The minimum energy requirements, in megawatts, over the remaining term of a power purchase agreement accounted for as a finance lease.

+ References

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- Definition

Power purchase contract period.

+ References

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