Leases - Future Minimum Lease Payments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Total operating leases
2022	$ 4.7
2023	4.5
2024	4.3
2025	3.8
2026	3.9
Thereafter	20.8
Total minimum lease payments	42.0
Less: interest	(9.2)
Less: short-term lease liabilities	(3.7)
Long-term lease liabilities	$ 29.1
Operating lease liability, current	Other
Operating lease liability, noncurrent	Other
Finance leases
2022	$ 80.0
2023	1.4
2024	1.4
2025	1.4
2026	1.5
Thereafter	115.9
Total minimum lease payments	201.6
Less: interest	(71.9)
Less: short-term lease liabilities	(78.4)
Long-term lease liabilities	$ 51.3
Finance lease liability, current	Current portion of long-term debt (December 31, 2021 includes $8.8 related to WEPCo Environmental Trust)
Finance lease liability, noncurrent	Long-term debt (December 31, 2021 includes $102.7 related to WEPCo Environmental Trust)
Total Liabilities
Total operating leases
Present value of minimum lease payments	$ 32.8
Finance leases
Present value of minimum lease payments	129.7	$ 63.4
Power purchase commitment
Finance leases
2022	79.0
2023	0.0
2024	0.0
2025	0.0
2026	0.0
Thereafter	0.0
Total minimum lease payments	79.0
Less: interest	(0.6)
Present value of minimum lease payments	78.4	12.1
Less: short-term lease liabilities	(78.4)
Long-term lease liabilities	0.0
Two Creeks
Finance leases
2022	0.2
2023	0.2
2024	0.2
2025	0.2
2026	0.3
Thereafter	21.7
Total minimum lease payments	22.8
Less: interest	(13.0)
Present value of minimum lease payments	9.8	7.9
Less: short-term lease liabilities	0.0
Long-term lease liabilities	9.8
Badger Hollow I
Finance leases
2022	0.5
2023	0.5
2024	0.5
2025	0.5
2026	0.5
Thereafter	39.3
Total minimum lease payments	41.8
Less: interest	(24.2)
Present value of minimum lease payments	17.6	20.3
Less: short-term lease liabilities	0.0
Long-term lease liabilities	17.6
Badger Hollow II
Finance leases
2022	0.3
2023	0.7
2024	0.7
2025	0.7
2026	0.7
Thereafter	54.3
Total minimum lease payments	57.4
Less: interest	(33.8)
Present value of minimum lease payments	23.6	$ 23.1
Less: short-term lease liabilities	0.0
Long-term lease liabilities	23.6
Other, finance lease
Finance leases
2022	0.0
2023	0.0
2024	0.0
2025	0.0
2026	0.0
Thereafter	0.6
Total minimum lease payments	0.6
Less: interest	(0.3)
Present value of minimum lease payments	0.3
Less: short-term lease liabilities	0.0
Long-term lease liabilities	$ 0.3