Schedule I - Income Statements (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income statements
Equity in earnings of subsidiaries									$ 146.5	$ 96.1	$ 66.0
Other income, net									80.8	58.9	13.4
Interest expense									402.7	331.4	240.3
Income before income taxes									1,506.7	1,074.1	951.2
Income tax benefit									(566.5)	(433.8)	(361.7)
Net income attributed to common shareholders	$ 194.4	$ 217.0	$ 181.4	$ 346.2	$ 179.3	$ 182.5	$ 80.9	$ 195.8	939.0	638.5	588.3
WEC Energy Group
Income statements
Operating expenses									7.0	42.2	26.8
Equity in earnings of subsidiaries									996.5	695.7	635.0
Other income, net									2.7	23.2	2.8
Interest expense									90.0	71.2	53.1
Income before income taxes									902.2	605.5	557.9
Income tax benefit									36.8	33.0	30.4
Net income attributed to common shareholders									$ 939.0	$ 638.5	$ 588.3