Benefit Plans (Funded Status of Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	$ 876	$ 875
Change in benefit obligation:
Net benefit obligation at January 1	875	1,251
Service cost	5	9	$ 11
Interest cost	47	36	34
Plan participants' contributions	0	0
Actuarial (gain) loss	23	(269)
Gross benefits paid	(74)	(152)
Net benefit obligation at December 31	876	875	1,251
Change in plan assets:
Fair value of plan assets at January 1	706	1,011
Actual return on plan assets	86	(204)
Employer contributions	14	51
Plan participants' contributions	0	0
Gross benefits paid	(74)	(152)
Fair value of plan assets at December 31	732	706	1,011
Under funded status at December 31	(144)	(169)
Fair value of plan assets	732	706
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	387	389
Change in benefit obligation:
Net benefit obligation at January 1	389	567
Service cost	3	6	7
Interest cost	21	16	16
Plan participants' contributions	0	0
Actuarial (gain) loss	9	(123)
Gross benefits paid	(35)	(77)
Net benefit obligation at December 31	387	389	567
Change in plan assets:
Fair value of plan assets at January 1	344	462
Actual return on plan assets	42	(92)
Employer contributions	1	51
Plan participants' contributions	0	0
Gross benefits paid	(35)	(77)
Fair value of plan assets at December 31	352	344	462
Under funded status at December 31	(35)	(45)
Fair value of plan assets	352	344
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	381	381
Change in benefit obligation:
Net benefit obligation at January 1	381	546
Service cost	2	3	4
Interest cost	20	16	15
Plan participants' contributions	0	0
Actuarial (gain) loss	10	(117)
Gross benefits paid	(32)	(67)
Net benefit obligation at December 31	381	381	546
Change in plan assets:
Fair value of plan assets at January 1	291	450
Actual return on plan assets	35	(92)
Employer contributions	12	0
Plan participants' contributions	0	0
Gross benefits paid	(32)	(67)
Fair value of plan assets at December 31	306	291	450
Under funded status at December 31	(75)	(90)
Fair value of plan assets	306	291
Other Postretirement Benefits Plans [Member]
Change in benefit obligation:
Net benefit obligation at January 1	168	210
Service cost	2	3	4
Interest cost	9	6	5
Plan participants' contributions	4	4
Actuarial (gain) loss	(3)	(37)
Gross benefits paid	(20)	(18)
Net benefit obligation at December 31	160	168	210
Change in plan assets:
Fair value of plan assets at January 1	83	106
Actual return on plan assets	8	(17)
Employer contributions	8	8
Plan participants' contributions	4	4
Gross benefits paid	(20)	(18)
Fair value of plan assets at December 31	83	83	106
Under funded status at December 31	(77)	(85)
Other Postretirement Benefits Plans [Member] | IPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	68	84
Service cost	1	1	1
Interest cost	3	2	2
Plan participants' contributions	2	2
Actuarial (gain) loss	(1)	(14)
Gross benefits paid	(8)	(7)
Net benefit obligation at December 31	65	68	84
Change in plan assets:
Fair value of plan assets at January 1	58	74
Actual return on plan assets	7	(12)
Employer contributions	2	1
Plan participants' contributions	2	2
Gross benefits paid	(8)	(7)
Fair value of plan assets at December 31	61	58	74
Under funded status at December 31	(4)	(10)
Other Postretirement Benefits Plans [Member] | WPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	65	81
Service cost	1	1	1
Interest cost	3	2	2
Plan participants' contributions	2	2
Actuarial (gain) loss	(2)	(13)
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	61	65	81
Change in plan assets:
Fair value of plan assets at January 1	14	17
Actual return on plan assets	1	(2)
Employer contributions	5	5
Plan participants' contributions	2	2
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	14	14	$ 17
Under funded status at December 31	$ (47)	$ (51)