Leases (Operating Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 14	$ 15
Operating leases liabilities, Other current liabilities	2	2
Operating leases liabilities, Other liabilities	12	13
Operating leases liabilities, Total	$ 14	$ 15
Operating leases, Weighted average remaining lease term	9 years	10 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other	Other
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other	Other
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
IPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 9	$ 9
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	8	8
Operating leases liabilities, Total	$ 9	$ 9
Operating leases, Weighted average remaining lease term	11 years	11 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 5	$ 6
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	4	5
Operating leases liabilities, Total	$ 5	$ 6
Operating leases, Weighted average remaining lease term	8 years	9 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%