Common Equity - Dividend Restrictions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) period	Dec. 31, 2019
Dividend Payment Restrictions [Line Items]
Junior notes minimum interest deferral payment period (in periods) | period	1
Junior notes maximum interest payment deferral period (in years)	10 years
Restricted net assets of consolidated subsidiaries	$ 8,600
Undistributed earnings of investees accounted for by the equity method	$ 386
WE
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
WE | 3.60% Serial Preferred Stock
Dividend Payment Restrictions [Line Items]
Dividend rate (as a percent)	3.60%	3.60%
WE | 3.60% Serial Preferred Stock | Minimum | Common stock equity to total capitalization is between 25% and 20%
Dividend Payment Restrictions [Line Items]
Percentage of common equity to total capitalization required to be maintained	20.00%
WE | 3.60% Serial Preferred Stock | Maximum | Common stock equity to total capitalization is between 25% and 20%
Dividend Payment Restrictions [Line Items]
Percentage of net income for which dividends can be declared	75.00%
Percentage of common equity to total capitalization required to be maintained	25.00%
WE | 3.60% Serial Preferred Stock | Maximum | Common stock equity to total capitalization is less than 20%
Dividend Payment Restrictions [Line Items]
Percentage of net income for which dividends can be declared	50.00%
Percentage of common equity to total capitalization required to be maintained	20.00%
WE | Public Service Commission of Wisconsin | Minimum
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	52.50%
WPS
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
WPS | Public Service Commission of Wisconsin | Minimum
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	52.50%
WG | Public Service Commission of Wisconsin | Minimum
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	52.50%
UMERC
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
ATC Holding LLC
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
Bluewater Gas Storage, LLC
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
WECI Wind Holding I
Dividend Payment Restrictions [Line Items]
Minimum debt service ratio to be maintained for 12-months prior to distribution	1.2
Period needed to maintain minimum debt service coverage ratio	12 months