Common Equity - Dividend Restrictions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) period	Dec. 31, 2017
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	$ 6,800
Undistributed earnings of investees accounted for by the equity method	$ 383
WE
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
WE | $100 par value, Serial Preferred Stock, 3.60% series
Dividend Payment Restrictions [Line Items]
Dividend rate (as a percent)	3.60%	3.60%
WE | $100 par value, Serial Preferred Stock, 3.60% series | Common stock equity to total capitalization is less than 25%
Dividend Payment Restrictions [Line Items]
Percentage of common equity to total capitalization required to be maintained	25.00%
WE | $100 par value, Serial Preferred Stock, 3.60% series | Common stock equity to total capitalization is less than 20%
Dividend Payment Restrictions [Line Items]
Percentage of common equity to total capitalization required to be maintained	20.00%
WE | Minimum | Public Service Commission of Wisconsin
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	51.00%
WE | Maximum | $100 par value, Serial Preferred Stock, 3.60% series | Common stock equity to total capitalization is less than 25%
Dividend Payment Restrictions [Line Items]
Percentage of net income for which dividends can be declared	75.00%
WE | Maximum | $100 par value, Serial Preferred Stock, 3.60% series | 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%
WG | Minimum | Public Service Commission of Wisconsin
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	49.50%
WPS
Dividend Payment Restrictions [Line Items]
Maximum debt to capitalization ratio	65.00%
WPS | Minimum | Public Service Commission of Wisconsin
Dividend Payment Restrictions [Line Items]
Common equity ratio required to be maintained (as a percent)	51.00%
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%