Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 450
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-Section 25
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-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

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The capacity, in megawatts, of coal generation expected to be retired by 2020.

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The percentage by which the company plans to reduce carbon dioxide emissions below 2005 levels by 2050

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The capital and operating costs needed to achieve the required level of reduction in emissions.

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Global temperature increases limit

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Number of compliance options available to meet impingement mortality reduction standard of the Clean Water Act under Section 316(b).

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The percentage by which the company plans to reduce carbon dioxide emissions below 2005 levels by 2030.

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The amount of the expected recovery of deferred expenditures and estimated future expenditures, net of insurance recoveries and recoveries from potentially responsible parties, for remediation which the entity has recorded as regulatory assets.

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The renewal period for facility permits authorized by the Wisconsin Department of Natural Resources.

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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) $ in Millions	1 Months Ended	6 Months Ended
	Oct. 31, 2014 compliance_option	Jun. 30, 2018 USD ($) degreecelsius MW	Dec. 31, 2017 USD ($)
Climate Change \| Electric
Air quality
Company goal for percentage of carbon dioxide emissions reduction		40.00%
Long-term company goal for percentage of carbon dioxide emissions reduction by 2050		80.00%
Capacity of coal generation expected to be retired by 2020 \| MW		1,800
Climate Change \| Electric \| Maximum
Air quality
Global temperature increases limit \| degreecelsius		2
Clean Water Act Cooling Water Intake Structure Rule \| Electric
Water quality
Number of compliance options available to meet standard \| compliance_option	7
Renewal period for facility permits		5 years
Steam Electric Effluent Limitation Guidelines \| Electric
Water quality
Renewal period for facility permits		5 years
Expected cost to achieve required emissions reductions		$ 70.0
Manufactured Gas Plant Remediation \| Natural gas
Manufactured gas plant remediation
Regulatory assets recorded for remediation of manufactured gas plant sites		669.9	$ 676.6
Reserves recorded for remediation of manufactured gas plant sites		$ 617.2	$ 617.2