INCOME TAXES - WI 2020 AND 2021 RATES (Details) - Public Service Commission of Wisconsin (PSCW) - 2020 and 2021 rates - Tax Cuts and Jobs Act of 2017	1 Months Ended
Dec. 31, 2019
Electric rates
Income Taxes [Line Items]
Amortization period	2 years
Natural gas rates
Income Taxes [Line Items]
Amortization period	4 years

Amortization period for the recovery of regulatory liability, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_RegulatoryLiabilityAmortizationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration