Leases (Expected Maturities of Operating and Finance Lease Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	$ 0
Operating Leases Liability, 2020	2
Operating Leases Liability, 2021	2
Operating Leases Liability, 2022	2
Operating Leases Liability, 2023	2
Operating Leases Liability, Thereafter	13
Operating Leases Liability, Total	21
Operating Leases Liability, Less: amount representing interest	4
Operating Leases Liability, Present value of minimum lease payments	17
IPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	0
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	9
Operating Leases Liability, Total	13
Operating Leases Liability, Less: amount representing interest	3
Operating Leases Liability, Present value of minimum lease payments	10
WPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	0
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	4
Operating Leases Liability, Total	8
Operating Leases Liability, Less: amount representing interest	1
Operating Leases Liability, Present value of minimum lease payments	7
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance Lease Liability, Remainder of 2019	4
Finance Lease Liability, 2020	15
Finance Lease Liability, 2021	15
Finance Lease Liability, 2022	15
Finance Lease Liability, 2023	15
Finance Lease Liability, Thereafter	20
Finance Lease Liability, Total	84
Finance Lease Liability, Less: amount representing interest	22
Finance Lease Liability, Present value of minimum lease payments	$ 62