Leases (Finance Lease) (Details) - WPL [Member] - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Leases [Line Items]
Finance lease liabilities, Sheboygan Falls Energy Facility	$ 55.8	$ 55.8	$ 60.0
Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	35.0	35.0
Finance lease liabilities, Other current liabilities	8.0	8.0
Finance lease liabilities, Sheboygan Falls Energy Facility	56.0	56.0
Finance lease liabilities, Total	$ 64.0	$ 64.0
Finance Lease, Weighted Average Remaining Lease Term	6 years	6 years
Finance lease, Discount rate, percent	11.00%	11.00%
Finance lease, Depreciation expense	$ 2.0	$ 3.0
Finance lease, Interest expense	2.0	4.0
Finance lease, Total expense	$ 4.0	$ 7.0

Total Finance Lease Expense

No definition available.

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- Definition

Amount of interest expense on finance lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
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-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

+ Details

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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=77888426&loc=SL77918701-209980

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+ Details

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

+ References

Reference 1: 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=77888419&loc=SL77918627-209977

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

+ References

+ Details

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- Definition

Amount of lessee's right to use underlying asset under finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

+ References

+ Details

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- Definition

Weighted average discount rate for finance lease calculated at point in time.

+ References

+ Details

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- Definition

Weighted average remaining lease term for finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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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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- Details

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