Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,210	$ 1,081	$ 3,298	$ 3,005
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,124	999	2,828	2,579
Electric [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	408	378	1,027	966
Electric [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	282	239	705	616
Electric [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	306	270	782	730
Electric [Member] \| Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	51	58	148	147
Electric [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	77	54	166	120
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	51	49	366	322
Gas [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24	24	211	189
Gas [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	13	106	92
Gas [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	10	8
Gas [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	11	39	33
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	12	37	36
Other Utility [Member] \| Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	9	28	29
Other Utility [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	3	9	7
Non-Utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	21	67	68
Non-Utility and Other [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	21	67	68
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	647	561	1,676	1,527
IPL [Member] \| Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	608	523	1,455	1,318
IPL [Member] \| Electric [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	215	202	512	502
IPL [Member] \| Electric [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	192	153	462	385
IPL [Member] \| Electric [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	167	142	403	372
IPL [Member] \| Electric [Member] \| Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	19	39	45
IPL [Member] \| Electric [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	7	39	14
IPL [Member] \| Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27	27	185	175
IPL [Member] \| Gas [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	13	107	103
IPL [Member] \| Gas [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7	7	49	48
IPL [Member] \| Gas [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	6	5
IPL [Member] \| Gas [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7	6	23	19
IPL [Member] \| Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	11	36	34
IPL [Member] \| Other Utility [Member] \| Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	9	28	29
IPL [Member] \| Other Utility [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	2	8	5
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	540	499	1,555	1,410
WPL [Member] \| Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	516	476	1,373	1,261
WPL [Member] \| Electric [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	193	176	515	464
WPL [Member] \| Electric [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	90	86	243	231
WPL [Member] \| Electric [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	139	128	379	358
WPL [Member] \| Electric [Member] \| Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	40	39	109	102
WPL [Member] \| Electric [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	54	47	127	106
WPL [Member] \| Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24	22	181	147
WPL [Member] \| Gas [Member] \| Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	11	104	86
WPL [Member] \| Gas [Member] \| Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	6	57	44
WPL [Member] \| Gas [Member] \| Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	4	3
WPL [Member] \| Gas [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	5	16	14
WPL [Member] \| Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	1	2
WPL [Member] \| Other Utility [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 1	$ 1	$ 2