Leases (Operating Leases) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 17	$ 17
Operating leases liabilities, Other current liabilities	2	2
Operating leases liabilities, Other liabilities	15	15
Operating leases liabilities, Total	$ 17	$ 17
Operating Lease, Weighted Average Remaining Lease Term	11 years	11 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 1
IPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	10	10
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	9	9
Operating leases liabilities, Total	$ 10	$ 10
Operating Lease, Weighted Average Remaining Lease Term	13 years	13 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 0
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	7	7
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	6	6
Operating leases liabilities, Total	$ 7	$ 7
Operating Lease, Weighted Average Remaining Lease Term	10 years	10 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 0