Leases (Future Minimum Operating and Capital Lease Payments) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Leases [Line Items]
Operating Leases, 2019	$ 5
Operating Leases, 2020	5
Operating Leases, 2021	3
Operating Leases, 2022	3
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	30
IPL [Member]
Leases [Line Items]
Operating Leases, 2019	3
Operating Leases, 2020	2
Operating Leases, 2021	2
Operating Leases, 2022	2
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	23
WPL [Member]
Leases [Line Items]
Operating Leases, 2019	2
Operating Leases, 2020	3
Operating Leases, 2021	1
Operating Leases, 2022	0
Operating Leases, 2023	0
Operating Leases, Thereafter	0
Operating Leases, Total	6
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Capital Leases, 2019	15
Capital Leases, 2020	15
Capital Leases, 2021	15
Capital Leases, 2022	15
Capital Leases, 2023	15
Capital Leases, Thereafter	19
Capital Leases, Total	94
Capital Leases, Less: amount representing interest	26
Capital Leases, Present value of minimum capital lease payments	$ 68