Common Equity - Stock Options (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options Activity [Roll Forward]
Outstanding, shares, beginning balance	1,285,806	5,687,714
Granted, shares		92,880	495,550	864,860
Exercised, shares		(439,043)
Transferred, shares		(4,055,745)
Outstanding, shares, ending balance		1,285,806	5,687,714
Options - Weighted Average Exercise Price
Outstanding, Weighted-Average Exercise Price, Beginning	$ 33.41	$ 33.58
Granted, Weighted-Average Exercise Price		50.93
Exercised, Weighted-Average Exercise Price		27.57
Transferred, Weighted-Average Exercise Price		34.68
Outstanding, Weighted-Average Exercise Price, Ending		$ 33.41	$ 33.58
Options - Additional Disclosures
Outstanding, Weighted-Average Remaining Contractual Life (Years)		4 years 7 months
Outstanding, Aggregate Intrinsic Value		$ 32.4
Exercisable, shares		1,010,061
Exercisable, Weighted-Average Exercise Price		$ 29.64
Exercisable, Weighted-Average Remaining Contractual Life (Years)		3 years 8 months
Exercisable, Aggregate Intrinsic Value		$ 29.3
Intrinsic value of options exercised		14.1	$ 34.6	$ 47.5
Actual tax benefit realized for the tax deductions		$ 5.6	$ 14.0	$ 18.8
Estimated fair value per non-qualified stock option (in dollars per share)		$ 4.92	$ 5.29	$ 4.18
Subsequent event
Options Activity [Roll Forward]
Granted, shares	80,770
Options - Weighted Average Exercise Price
Granted, Weighted-Average Exercise Price	$ 58.31
Options - Additional Disclosures
Estimated fair value per non-qualified stock option (in dollars per share)	$ 7.12
WEC Energy Group
Options - Additional Disclosures
Cash received by WEC Energy Group from options exercised by WE employees		$ 12.1	$ 29.2	$ 47.9