Benefit Plans (Funded Status of Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	$ 1,251	$ 1,351
Change in benefit obligation:
Net benefit obligation at January 1	1,351	1,280
Service cost	11	11	$ 10
Interest cost	34	43	50
Plan participants' contributions	0	0
Actuarial (gain) loss	(46)	132
Gross benefits paid	(99)	(115)
Net benefit obligation at December 31	1,251	1,351	1,280
Change in plan assets:
Fair value of plan assets at January 1	984	931
Actual return on plan assets	87	108
Employer contributions	39	60
Plan participants' contributions	0	0
Gross benefits paid	(99)	(115)
Fair value of plan assets at December 31	1,011	984	931
Under funded status at December 31	(240)	(367)
Fair value of plan assets	1,011	984	931
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	567	615
Change in benefit obligation:
Net benefit obligation at January 1	615	581
Service cost	7	7	6
Interest cost	16	20	23
Plan participants' contributions	0	0
Actuarial (gain) loss	(23)	60
Gross benefits paid	(48)	(53)
Net benefit obligation at December 31	567	615	581
Change in plan assets:
Fair value of plan assets at January 1	453	436
Actual return on plan assets	40	51
Employer contributions	17	19
Plan participants' contributions	0	0
Gross benefits paid	(48)	(53)
Fair value of plan assets at December 31	462	453	436
Under funded status at December 31	(105)	(162)
Fair value of plan assets	462	453	436
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	546	588
Change in benefit obligation:
Net benefit obligation at January 1	588	550
Service cost	4	4	3
Interest cost	15	19	21
Plan participants' contributions	0	0
Actuarial (gain) loss	(18)	55
Gross benefits paid	(43)	(40)
Net benefit obligation at December 31	546	588	550
Change in plan assets:
Fair value of plan assets at January 1	436	406
Actual return on plan assets	39	48
Employer contributions	18	22
Plan participants' contributions	0	0
Gross benefits paid	(43)	(40)
Fair value of plan assets at December 31	450	436	406
Under funded status at December 31	(96)	(152)
Fair value of plan assets	450	436	406
Other Postretirement Benefits Plans [Member]
Change in benefit obligation:
Net benefit obligation at January 1	227	214
Service cost	4	3	3
Interest cost	5	7	9
Plan participants' contributions	5	4
Actuarial (gain) loss	(12)	18
Gross benefits paid	(19)	(19)
Net benefit obligation at December 31	210	227	214
Change in plan assets:
Fair value of plan assets at January 1	108	105
Actual return on plan assets	4	11
Employer contributions	8	7
Plan participants' contributions	5	4
Gross benefits paid	(19)	(19)
Fair value of plan assets at December 31	106	108	105
Under funded status at December 31	(104)	(119)
Fair value of plan assets	106	108	105
Other Postretirement Benefits Plans [Member] | IPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	91	86
Service cost	1	1	1
Interest cost	2	3	3
Plan participants' contributions	2	1
Actuarial (gain) loss	(4)	8
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	84	91	86
Change in plan assets:
Fair value of plan assets at January 1	74	72
Actual return on plan assets	4	7
Employer contributions	2	2
Plan participants' contributions	2	1
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	74	74	72
Under funded status at December 31	(10)	(17)
Fair value of plan assets	74	74	72
Other Postretirement Benefits Plans [Member] | WPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	89	85
Service cost	1	2	1
Interest cost	2	3	3
Plan participants' contributions	2	2
Actuarial (gain) loss	(5)	5
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	81	89	85
Change in plan assets:
Fair value of plan assets at January 1	18	17
Actual return on plan assets	0	2
Employer contributions	5	5
Plan participants' contributions	2	2
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	17	18	17
Under funded status at December 31	(64)	(71)
Fair value of plan assets	$ 17	$ 18	$ 17