Credit Losses - Gross Receivables and Related Allowances (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 2,017.7	$ 1,704.0
Allowance for credit losses	199.3	198.3	$ 220.1	$ 140.0
Accounts receivable and unbilled revenues, net	1,818.4	1,505.7
Total accounts receivable, net - past due greater than 90 days	$ 106.7	$ 86.5
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	96.80%	94.80%
Amount of net accounts receivable with regulatory protections	$ 1,079.1
Percent of net accounts receivable with regulatory protections	59.30%
Public utilities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 1,988.0	$ 1,681.9
Allowance for credit losses	199.3	198.3	220.1	139.9
Accounts receivable and unbilled revenues, net	1,788.7	1,483.6
Total accounts receivable, net - past due greater than 90 days	$ 106.7	$ 86.5
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	96.80%	94.80%
Wisconsin | Public utilities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 1,199.4	$ 1,053.1
Allowance for credit losses	82.0	84.0	102.1	59.9
Accounts receivable and unbilled revenues, net	1,117.4	969.1
Total accounts receivable, net - past due greater than 90 days	$ 51.9	$ 46.5
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	97.00%	97.60%
Illinois | Public utilities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 624.2	$ 523.1
Allowance for credit losses	111.0	105.5	111.6	75.9
Accounts receivable and unbilled revenues, net	513.2	417.6
Total accounts receivable, net - past due greater than 90 days	$ 52.9	$ 36.6
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	100.00%	100.00%
Other States | Public utilities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 164.4	$ 105.7
Allowance for credit losses	6.3	8.8	6.4	4.1
Accounts receivable and unbilled revenues, net	158.1	96.9
Total accounts receivable, net - past due greater than 90 days	$ 1.9	$ 3.4
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	0.00%	0.00%
Non-Utility Energy Infrastructure
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 25.4	$ 17.0
Allowance for credit losses	0.0	0.0
Accounts receivable and unbilled revenues, net	25.4	17.0
Total accounts receivable, net - past due greater than 90 days	$ 0.0	$ 0.0
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	0.00%	0.00%
Corporate and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 4.3	$ 5.1
Allowance for credit losses	0.0	0.0	$ 0.0	$ 0.1
Accounts receivable and unbilled revenues, net	4.3	5.1
Total accounts receivable, net - past due greater than 90 days	$ 0.0	$ 0.0
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	0.00%	0.00%