Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 11	$ 10	$ 12
Interest cost	43	50	47
Expected return on plan assets	(70)	(60)	(69)
Amortization of prior service cost (credit)	0	(1)	(1)
Amortization of actuarial loss	34	36	35
Settlement losses	12	0	0
Total	30	35	24
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	4
Interest cost	7	9	8
Expected return on plan assets	(5)	(5)	(6)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	3	3	3
Settlement losses	0	0	0
Total	8	10	9
IPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	6	7
Interest cost	20	23	21
Expected return on plan assets	(33)	(28)	(32)
Amortization of actuarial loss	15	15	15
Settlement losses	7	0	0
Total	16	16	11
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2
Interest cost	3	3	3
Expected return on plan assets	(4)	(4)	(4)
Amortization of actuarial loss	1	2	1
Settlement losses	0	0	0
Total	1	2	2
WPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	3	4
Interest cost	19	21	20
Expected return on plan assets	(31)	(26)	(30)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	16	18	17
Total	8	16	11
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	2
Interest cost	3	3	3
Expected return on plan assets	(1)	(1)	(1)
Amortization of prior service cost (credit)	(1)	0	0
Amortization of actuarial loss	2	2	2
Total	$ 5	$ 5	$ 6