Segment Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment information
Number of reportable segments | segment	6
Operating revenues	$ 8,316.0	$ 7,241.7	$ 7,523.1
Other operation and maintenance	2,005.5	2,032.2	2,184.8
Depreciation and amortization	1,074.3	975.9	926.3
Equity in earnings of transmission affiliates	158.1	175.8	127.6
Interest expense	471.1	493.7	501.5
Loss on debt extinguishment	36.3	38.4	0.0
Income tax expense (benefit)	200.3	227.9	125.0
Net income (loss)	1,298.5	1,201.4	1,134.7
Net income attributed to common shareholders	1,300.3	1,199.9	1,134.0
Capital expenditures and asset acquisitions	2,372.7	2,874.3	2,529.0
Total assets	38,988.5	37,028.1	34,951.8
Reconciling eliminations
Segment information
Other operation and maintenance	(9.2)	(9.2)	0.2
Depreciation and amortization	(60.0)	(52.8)	(15.8)
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	(340.5)	(345.5)	(354.1)
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	0.0	0.0	0.0
Net income (loss)	0.0	0.0	0.0
Net income attributed to common shareholders	0.0	0.0	0.0
Capital expenditures and asset acquisitions	0.0	0.0	0.0
Total assets	(3,264.6)	(3,361.2)	(3,344.5)
WE | Reconciling eliminations
Segment information
Total assets	1,729.9	1,824.5	1,896.7
Wisconsin
Segment information
Operating revenues	6,037.0	5,473.5	5,647.1
Illinois
Segment information
Operating revenues	1,672.8	1,321.9	1,357.1
Other States
Segment information
Operating revenues	519.0	384.1	426.0
Electric transmission
Segment information
Other operation and maintenance	0.0	0.0	0.0
Depreciation and amortization	0.0	0.0	0.0
Equity in earnings of transmission affiliates	158.1	175.8	127.6
Interest expense	19.4	19.4	13.1
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	32.3	43.7	27.1
Net income (loss)	106.3	112.6	87.4
Net income attributed to common shareholders	106.3	112.6	87.4
Capital expenditures and asset acquisitions	0.0	0.0	0.0
Total assets	$ 1,792.7	1,764.7	1,723.1
Non-Utility Energy Infrastructure
Segment information
Natural gas storage needs provided to Wisconsin utilities	33.00%
Operating revenues	$ 539.5	508.5	495.9
Other operation and maintenance	43.1	24.9	19.7
Depreciation and amortization	125.3	98.9	92.0
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	71.0	60.8	62.1
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	3.1	44.7	59.9
Net income (loss)	276.2	261.1	245.5
Net income attributed to common shareholders	279.2	260.8	246.0
Capital expenditures and asset acquisitions	335.3	661.8	389.9
Total assets	4,627.7	4,455.2	3,654.1
Corporate and other
Segment information
Operating revenues	0.5	2.2	4.4
Other operation and maintenance	(7.5)	17.4	14.0
Depreciation and amortization	25.9	25.1	24.3
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	92.8	124.0	140.9
Loss on debt extinguishment	36.3	38.4
Income tax expense (benefit)	(45.8)	(72.4)	(71.0)
Net income (loss)	(50.5)	(106.4)	(62.8)
Net income attributed to common shareholders	(50.5)	(106.4)	(62.8)
Capital expenditures and asset acquisitions	18.1	33.1	26.5
Total assets	$ 785.3	762.2	814.0
Bishop Hill III | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	90.00%
Coyote Ridge | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	80.00%
Upstream | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	90.00%
Blooming Grove | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	90.00%
Tatanka Ridge | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	85.00%
Jayhawk | Non-Utility Energy Infrastructure
Segment information
WEC's ownership interest	90.00%
ATC
Segment information
Equity method investment, ownership interest (as a percent)	60.00%
Operating revenues	$ 754.8	758.1	744.4
Equity in earnings of transmission affiliates	166.4	174.3	132.8
Total assets	$ 5,717.9	5,493.3
ATC | Electric transmission
Segment information
Equity method investment, ownership interest (as a percent)	60.00%
ATC Holdco
Segment information
Equity method investment, ownership interest (as a percent)	75.00%
Equity in earnings of transmission affiliates	$ (8.3)	1.5	(5.2)
ATC Holdco | Electric transmission
Segment information
Equity method investment, ownership interest (as a percent)	75.00%
Public Utilities
Segment information
Other operation and maintenance	$ 1,979.1	1,999.1	2,150.9
Depreciation and amortization	983.1	904.7	825.8
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	628.4	635.0	639.5
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	210.7	211.9	109.0
Net income (loss)	966.5	934.1	864.6
Net income attributed to common shareholders	965.3	932.9	863.4
Capital expenditures and asset acquisitions	2,019.3	2,179.4	2,112.6
Total assets	35,047.4	33,407.2	32,105.1
Public Utilities | Wisconsin
Segment information
Other operation and maintenance	1,455.2	1,476.7	1,591.3
Depreciation and amortization	726.9	674.5	617.0
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	555.6	561.3	572.0
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	119.9	132.7	35.2
Net income (loss)	707.7	691.6	651.1
Net income attributed to common shareholders	706.5	690.4	649.9
Capital expenditures and asset acquisitions	1,389.7	1,382.4	1,378.6
Total assets	25,687.9	24,599.2	23,934.8
Public Utilities | Illinois
Segment information
Other operation and maintenance	433.5	435.4	461.1
Depreciation and amortization	218.1	196.7	181.3
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	66.6	63.5	59.0
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	79.3	66.1	60.2
Net income (loss)	223.0	203.5	170.3
Net income attributed to common shareholders	223.0	203.5	170.3
Capital expenditures and asset acquisitions	533.7	652.7	624.9
Total assets	7,853.4	7,471.8	6,932.5
Public Utilities | Other States
Segment information
Other operation and maintenance	90.4	87.0	98.5
Depreciation and amortization	38.1	33.5	27.5
Equity in earnings of transmission affiliates	0.0	0.0	0.0
Interest expense	6.2	10.2	8.5
Loss on debt extinguishment	0.0	0.0
Income tax expense (benefit)	11.5	13.1	13.6
Net income (loss)	35.8	39.0	43.2
Net income attributed to common shareholders	35.8	39.0	43.2
Capital expenditures and asset acquisitions	95.9	144.3	109.1
Total assets	1,506.1	1,336.2	1,237.8
External Revenues | Reconciling eliminations
Segment information
Operating revenues	0.0	0.0	0.0
External Revenues | Electric transmission
Segment information
Operating revenues	0.0	0.0	0.0
External Revenues | Non-Utility Energy Infrastructure
Segment information
Operating revenues	86.7	60.0	88.5
External Revenues | Corporate and other
Segment information
Operating revenues	0.5	2.2	4.4
External Revenues | Public Utilities
Segment information
Operating revenues	8,228.8	7,179.5	7,430.2
External Revenues | Public Utilities | Wisconsin
Segment information
Operating revenues	6,037.0	5,473.5	5,647.1
External Revenues | Public Utilities | Illinois
Segment information
Operating revenues	1,672.8	1,321.9	1,357.1
External Revenues | Public Utilities | Other States
Segment information
Operating revenues	519.0	384.1	426.0
Intersegment Transactions
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Reconciling eliminations
Segment information
Operating revenues	(452.8)	(448.5)	(407.4)
Intersegment Transactions | Electric transmission
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Non-Utility Energy Infrastructure
Segment information
Operating revenues	452.8	448.5	407.4
Intersegment Transactions | Corporate and other
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Public Utilities
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Public Utilities | Wisconsin
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Public Utilities | Illinois
Segment information
Operating revenues	0.0	0.0	0.0
Intersegment Transactions | Public Utilities | Other States
Segment information
Operating revenues	$ 0.0	$ 0.0	$ 0.0