Schedule I - Statements of Comprehensive Income (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
Statements of comprehensive income
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
Derivatives accounted for as cash flow hedges
Gains on settlement, net of tax of $7.6									0.0	11.4	0.0
Reclassification of gains to net income, net of tax									(1.3)	(0.8)	0.0
Cash flow hedges, net									(1.3)	10.6	0.0
Defined benefit plans
Pension and OPEB costs arising during the period, net of tax									(0.8)	(6.3)	0.0
Amortization of pension and OPEB costs included in net periodic benefit cost, net of tax									0.4	0.0	0.0
Defined benefit plans, net									(0.4)	(6.3)	0.0
Other comprehensive (loss) income, net of tax									(1.7)	4.3	0.0
Comprehensive income attributed to common shareholders									937.3	642.8	588.3
Other comprehensive (loss) income, tax
Gains on settlement, tax										7.6
WEC Energy Group
Statements of comprehensive income
Net income attributed to common shareholders									939.0	638.5	588.3
Derivatives accounted for as cash flow hedges
Gains on settlement, net of tax of $7.6									0.0	11.4	0.0
Reclassification of gains to net income, net of tax									(1.3)	(0.8)	0.0
Cash flow hedges, net									(1.3)	10.6	0.0
Defined benefit plans
Pension and OPEB costs arising during the period, net of tax									(1.0)	(1.5)	0.0
Amortization of pension and OPEB costs included in net periodic benefit cost, net of tax									0.3	0.0	0.0
Defined benefit plans, net									(0.7)	(1.5)	0.0
Other comprehensive income (loss) from subsidiaries, net of tax									0.3	(4.8)	0.0
Other comprehensive (loss) income, net of tax									(1.7)	4.3	0.0
Comprehensive income attributed to common shareholders									$ 937.3	642.8	$ 588.3
Other comprehensive (loss) income, tax
Gains on settlement, tax										$ 7.6