Schedule I - Statements of Cash Flows (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
Operating activities
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
Reconciliation to cash provided by operating activities
Equity in earnings of subsidiaries									(146.5)	(96.1)	(66.0)
Deferred income taxes									498.7	420.4	329.2
Change in -
Other current assets									103.1	(27.2)	(13.9)
Other current liabilities									(20.8)	14.1	(45.3)
Other, net									(53.8)	(209.1)	(87.3)
Investing activities
Purchase of subsidiary's common stock									(42.3)	(8.7)	(13.1)
Proceeds from the sale of assets and businesses									166.3	28.9	13.9
Other, net									3.0	57.0	3.6
Financing activities
Exercise of stock options									41.6	30.1	50.3
Purchase of common stock									(108.0)	(74.7)	(123.2)
Dividends paid on common stock									(624.9)	(455.4)	(352.0)
Issuance of long-term debt									400.0	2,150.0	250.0
Other, net									(13.6)	(18.9)	12.8
Net change in cash and cash equivalents									(12.3)	(12.1)	35.9
Cash and cash equivalents at beginning of year				49.8				61.9	49.8	61.9	26.0
Cash and cash equivalents at end of year	37.5				49.8				37.5	49.8	61.9
WEC Energy Group
Operating activities
Net income attributed to common shareholders									939.0	638.5	588.3
Reconciliation to cash provided by operating activities
Equity in earnings of subsidiaries									(996.5)	(695.7)	(635.0)
Dividends from subsidiaries									734.4	538.8	720.0
Deferred income taxes									23.2	30.9	60.1
Change in -
Prepaid taxes									(47.6)	0.0	0.0
Other current assets									13.0	(9.3)	(0.3)
Accrued taxes									(75.6)	175.7	4.1
Other current liabilities									(5.6)	(3.2)	5.1
Other, net									6.3	(18.4)	(8.1)
Net cash provided by operating activities									590.6	657.3	734.2
Investing activities
Business acquisition									0.0	(1,486.2)	0.0
Capital contributions to subsidiaries									(55.8)	(135.3)	(225.5)
Short-term notes receivable from related parties, net									46.8	(91.0)	0.0
Purchase of subsidiary's common stock									(66.4)	0.0	0.0
Proceeds from the sale of assets and businesses									0.0	20.8	0.0
Other, net									(0.4)	(0.1)	5.0
Net cash used in investing activities									(75.8)	(1,691.8)	(220.5)
Financing activities
Exercise of stock options									41.6	30.1	50.3
Purchase of common stock									(108.0)	(74.7)	(123.2)
Dividends paid on common stock									(624.9)	(455.4)	(352.0)
Issuance of long-term debt									0.0	1,200.0	0.0
Change in short-term debt									13.9	307.9	(72.0)
Short-term notes payable to related parties, net									162.3	1.8	3.5
Other, net									0.2	(11.2)	16.7
Net cash (used in) provided by financing activities									(514.9)	998.5	(476.7)
Net change in cash and cash equivalents									(0.1)	(36.0)	37.0
Cash and cash equivalents at beginning of year				$ 1.3				$ 37.3	1.3	37.3	0.3
Cash and cash equivalents at end of year	$ 1.2				$ 1.3				$ 1.2	$ 1.3	$ 37.3