Regulatory Environment - WI 2020 and 2021 Rates (Details) - Public Service Commission of Wisconsin (PSCW) - USD ($)	1 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2017	Dec. 31, 2020
2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Number of utilities with earnings sharing mechanism	3
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%
2020 and 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization period	2 years		2 years
2020 and 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization period	4 years		4 years
Number of gas utilities amortizing unprotected deferred tax expense over 4 years	3
WE | 2020 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ 15,300,000
Approved rate increase (as a percent)	0.50%
WE | 2020 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 65,000,000
WE | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ 10,400,000
Approved rate increase (as a percent)	2.80%
WE | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ (5,000,000)
WE | 2020 rates | Steam rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ 1,900,000
Approved rate increase (as a percent)	8.60%
WE | 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 65,000,000
WE | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ (5,000,000)
WE | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)	10.00%
Approved common equity component average (as a percent)	52.50%
WE | 2020 and 2021 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Pleasant Prairie power plant's book value to be securitized	$ 100,000,000
WPS | 2020 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ 15,800,000
Approved rate increase (as a percent)	1.60%
WPS | 2020 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 11,000,000
WPS | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ 4,300,000
Approved rate increase (as a percent)	1.40%
WPS | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 5,000,000
WPS | 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	39,000,000
WPS | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 5,000,000
WPS | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)	10.00%
Approved common equity component average (as a percent)	52.50%
WPS | 2020 and 2021 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Authorized Revenue Requirement For ReACT		$ 275,000,000.0
Cost of the ReACT project, excluding AFUDC	$ 342,000,000
Collection of ReACT Regulatory Asset in Years	8 years
WPS | 2020 and 2021 rates | Electric rates | Earnings sharing mechanisms
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 21,000,000
Amortization period	2 years
WG | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase	$ (1,500,000)
Approved rate increase (as a percent)	(0.20%)
WG | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 3,000,000
WG | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities	$ 3,000,000
WG | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)	10.20%
Approved common equity component average (as a percent)	52.50%