Schedule I - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net income attributed to common shareholders	$ 1,300.3	$ 1,199.9	$ 1,134.0
Reconciliation to cash provided by operating activities
Equity income in subsidiaries, net of distributions	(25.1)	(29.1)	(2.9)
Deferred income taxes, net	111.0	182.2	167.7
Loss on debt extinguishment	36.3	38.4	0.0
Change in -
Other current liabilities	(17.2)	(41.2)	78.7
Other, net	(93.0)	3.4	20.6
Net cash provided by operating activities	2,032.7	2,196.0	2,345.5
Investing activities
Capital contributions to subsidiaries	0.0	(21.2)	(52.6)
Other, net	20.3	(5.3)	16.5
Net cash used in investing activities	(2,311.8)	(2,806.8)	(2,494.9)
Financing activities
Exercise of stock options	15.7	43.8	67.0
Purchase of common stock	(33.1)	(99.2)	(140.1)
Dividends paid on common stock	(854.8)	(798.0)	(744.5)
Issuance of long-term debt	2,383.8	2,373.6	1,895.0
Retirement of long-term debt	(1,260.4)	(1,767.0)	(360.1)
Issuance of short-term loan	0.9	340.0	0.0
Repayment of short-term loan	(340.0)	0.0	0.0
Change in other short-term debt	459.2	606.1	(609.3)
Payments for debt extinguishment and issuance costs	(67.2)	(55.8)	(12.5)
Other, net	(10.1)	(11.4)	(9.9)
Net cash used in financing activities	(294.0)	(601.1)	(85.6)
Cash and cash equivalents at beginning of year	24.8	37.5
Cash and cash equivalents at end of year	16.3	24.8	37.5
WEC Energy Group
Operating activities
Net income attributed to common shareholders	1,300.3	1,199.9	1,134.0
Reconciliation to cash provided by operating activities
Equity income in subsidiaries, net of distributions	(571.3)	(385.7)	(475.2)
Deferred income taxes, net	(1.9)	12.7	9.1
Loss on debt extinguishment	23.1	38.4	0.0
Change in -
Accounts receivable from related parties	0.1	0.0	3.3
Prepaid taxes	(2.1)	(7.9)	(46.5)
Accounts payable to related parties	(26.2)	29.2	(5.2)
Other current liabilities	8.6	(2.4)	1.5
Other, net	(2.5)	9.6	7.0
Net cash provided by operating activities	728.1	893.8	628.0
Investing activities
Capital contributions to subsidiaries	(734.0)	(1,026.1)	(602.3)
Return of capital from subsidiaries	196.1	602.8	337.3
Short-term notes receivable from related parties, net	81.8	(88.3)	48.5
Redemption of long-term notes receivable from UMERC	0.0	0.0	150.0
Other, net	(1.1)	3.7	(0.6)
Net cash used in investing activities	(457.2)	(507.9)	(67.1)
Financing activities
Exercise of stock options	15.7	43.8	67.0
Purchase of common stock	(33.1)	(99.2)	(140.1)
Dividends paid on common stock	(854.8)	(798.0)	(744.5)
Issuance of long-term debt	1,100.0	1,650.0	350.0
Retirement of long-term debt	(300.0)	(1,430.0)	0.0
Issuance of short-term loan	0.0	340.0	0.0
Repayment of short-term loan	(340.0)	0.0	0.0
Change in other short-term debt	255.7	145.7	(213.7)
Short-term notes payable to related parties, net	(82.6)	(186.3)	90.4
Payments for debt extinguishment and issuance costs	(33.9)	(47.3)	(0.8)
Other, net	(1.4)	(1.1)	(1.5)
Net cash used in financing activities	274.4	382.4	593.2
Net change in cash and cash equivalents	(3.5)	3.5	(32.3)
Cash and cash equivalents at beginning of year	4.0	0.5	32.8
Cash and cash equivalents at end of year	$ 0.5	$ 4.0	$ 0.5