REGULATORY ENVIRONMENT - WI 2020 AND 2021 RATES - MARCH APPLICATION (Details) - Public Service Commission of Wisconsin (PSCW) - March 2019 Rate Application $ in Millions	1 Months Ended
Mar. 31, 2019 USD ($)
2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Requested return on equity (as a percent)	10.35%
Requested common equity component average (as a percent)	52.00%
Percentage of first 25 basis points of additional earnings retained by the utility	100.00%
Return on equity in excess of authorized amount (as a percent)	0.25%
Percentage of additional earnings between 25 and 75 basis points refunded to customers	50.00%
Return on equity in excess of first 25 basis points above authorized amount (as a percent)	0.50%
Percentage of earnings in excess of 75 basis points refunded to customers	100.00%
Electric rates \| 2020 rates
Public Utilities, General Disclosures [Line Items]
Requested rate increase	$ 83
Requested rate increase (as a percent)	2.90%
Electric rates \| 2020 rates \| Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 94
Electric rates \| 2021 rates
Public Utilities, General Disclosures [Line Items]
Requested rate increase	$ 83
Requested rate increase (as a percent)	2.90%
Electric rates \| 2021 rates \| Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 17
Natural gas rates \| 2020 rates
Public Utilities, General Disclosures [Line Items]
Requested rate increase	$ 15
Requested rate increase (as a percent)	3.90%
Steam rates \| 2020 rates
Public Utilities, General Disclosures [Line Items]
Requested rate increase	$ 1
Requested rate increase (as a percent)	4.50%

The increase (decrease) during the reporting period in regulated liabilities. Regulated liabilities are created when regulatory agency permits an entity to defer revenues to the balance sheet.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of utility earnings in excess of 25 basis points above the utility’s authorized return on equity (ROE), but not exceeding 75 basis points above the authorized ROE, that will be refunded to customers.

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Percentage of utility earnings in excess of 75 basis points above the utility’s authorized return on equity (ROE) that will be refunded to customers.

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Percentage of first 25 basis points of utility earnings above the utility’s authorized return on equity (ROE) that will be retained by the utility.

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Return on equity (ROE) in excess of authorized amount, for which the additional earnings will be retained by the utility.

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Return on equity (ROE) in excess of the first 25 basis points above the authorized amount, for which a percentage will be returned to customers.

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