Leases (Finance Lease) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 172	$ 133
Finance lease liabilities, Other current liabilities	0	5
Finance lease liabilities, Other liabilities	172	131
Finance lease liabilities, Total	$ 172	$ 136
Finance lease, Remaining lease term	33 years	34 years
Finance lease, Discount rate, percent	5.00%	5.00%
Finance lease, Depreciation expense	$ 1	$ 0	$ 0
Finance lease, Interest expense	6	3	0
Finance lease, Total expense	$ 7	$ 3	0
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 172	$ 133
Finance lease liabilities, Other current liabilities	0	5
Finance lease liabilities, Other liabilities	$ 172	$ 131
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
IPL [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 33	$ 0
Finance lease liabilities, Other current liabilities	0
Finance lease liabilities, Other liabilities	33	0
Finance lease liabilities, Total	$ 33	0
Finance lease, Remaining lease term	29 years
Finance lease, Discount rate, percent	5.00%
Finance lease, Depreciation expense	$ 0	0	0
Finance lease, Interest expense	1	0	0
Finance lease, Total expense	1	0	0
IPL [Member] | Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	33	0
Finance lease liabilities, Other current liabilities	0	0
Finance lease liabilities, Other liabilities	33	0
WPL [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	218	148
Finance lease liabilities, Other current liabilities	11	17
Finance lease liabilities, Other liabilities	217	150
Finance lease liabilities, Total	$ 228	$ 167
Finance lease, Remaining lease term	27 years	28 years
Finance lease, Discount rate, percent	5.00%	5.00%
Finance lease, Depreciation expense	$ 6	$ 6	6
Finance lease, Interest expense	8	7	5
Finance lease, Total expense	14	13	$ 11
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	79	15
Finance lease liabilities, Other current liabilities	11	12
Finance lease liabilities, Other liabilities	78	19
WPL [Member] | Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	139	133
Finance lease liabilities, Other current liabilities	0	5
Finance lease liabilities, Other liabilities	$ 139	$ 131