Common Equity (Details 4) (USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Repurchased During Period, Shares			2,700,000	5,400,000	4,300,000
Common Equity (Textuals)
Common stock shares, Authorized			325,000,000	325,000,000
Common stock shares, Outstanding			225,517,339	225,962,959
Exercise price of non qualified stock options	$ 52.895
Intrinsic value of options exercised			$ 50,500,000	$ 44,500,000	$ 47,500,000
Exercise price of the stock option on the grant date		no less than 100% of the common stock's fair market value
Minimum percentage award based on performance unit			0.00
Maximum percentage award based on performance unit			1.75
Amount paid for Shares Purchased by agents from open market			123,200,000	223,400,000	153,200,000
Exercise of stock options			50,300,000	48,500,000	49,800,000
Maximum period to defer interest payments on the Junior Notes			We have the option to defer interest payments on the Junior Notes, from time to time, for one or more periods of up to 10 consecutive years per period. During any period in which we defer interest payments, we may not declare or pay any dividends or distributions on, or redeem, repurchase or acquire, our common stock.
Ability to declare common dividends limited to Percentage of Net Income by Wisconsin Electric			limited to 75% or 50%
Wisconsin Electric's common stock equity to total capitalization			is less than 25% and 20%
3.60% Serial Preferred Stock			3.60%
Maximum percentage of equity method investment			50.00%
Equity method investment			3,700,000,000
Percentage of equity method investment exceeding consolidated net assets			25.00%
Stock Repurchased During Period, Value			123,200,000	223,400,000	153,200,000
Share Repurchase Plan, 2014 - 2017 [Member] [Domain]
Common Equity (Textuals)
Stock Repurchase Program, Authorized Amount				300,000,000
Share Repurchase Plan, 2011 [Member]
Common Equity (Textuals)
Treasury Stock Acquired, Average Cost Per Share			$ 43.66
Treasury Stock, Value, Acquired, Cost Method			18,600,000
Share Repurchases to Fulfill Exercised Stock Options and Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Repurchased During Period, Shares			2,300,000	2,400,000	2,800,000
Common Equity (Textuals)
Stock Repurchased During Period, Value			104,600,000	97,400,000	101,400,000
Share Repurchase Plan, 2011 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Repurchased During Period, Shares			400,000	3,000,000	1,500,000
Common Equity (Textuals)
Stock Repurchased During Period, Value			$ 18,600,000	$ 126,000,000	$ 51,800,000
Stock Options [Member]
Common Equity (Textuals)
Stock options awarded under long-term incentive compensation			899,500
Mimimum period after grant that stock options can be exercised		6 months
Expiration of options from time of grant		10 years