Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 25	$ 81
Accounts receivable, less allowance for expected credit losses	361	427
Production fuel, at weighted average cost	53	54
Gas stored underground, at weighted average cost	16	55
Materials and supplies, at weighted average cost	196	186
Regulatory assets	172	210
Other	146	171
Total current assets	969	1,184
Property, plant and equipment, net	19,022	18,701
Investments:
ATC Holdings	426	415
Other	224	224
Total investments	650	639
Other assets:
Regulatory assets	2,102	2,064
Deferred charges and other	108	126
Total other assets	2,210	2,190
Total assets	22,851	22,714
Current liabilities:
Current maturities of long-term debt	1,371	1,171
Commercial paper	678	558
Accounts payable	405	532
Regulatory liabilities	109	69
Other	325	385
Total current liabilities	2,888	2,715
Long-term debt, net (excluding current portion)	8,580	8,677
Other liabilities:
Deferred tax liabilities	2,147	2,188
Regulatory liabilities	974	959
Pension and other benefit obligations	210	224
Other	959	947
Total other liabilities	4,290	4,318
Commitments and contingencies (Note 12)
Common equity:
Common stock	3	3
Additional paid-in capital	3,066	3,060
Retained earnings	4,037	3,954
Accumulated other comprehensive income (loss)	0	1
Shares in deferred compensation trust - 347,775 and 372,116 shares at a weighted average cost of $37.17 and $36.56 per share	(13)	(14)
Total common equity	7,093	7,004
Total liabilities and equity	22,851	22,714
IPL [Member]
Current assets:
Cash and cash equivalents	12	29
Accounts receivable, less allowance for expected credit losses	112	192
Production fuel, at weighted average cost	27	30
Gas stored underground, at weighted average cost	5	25
Materials and supplies, at weighted average cost	121	113
Regulatory assets	71	77
Other	44	43
Total current assets	392	509
Property, plant and equipment, net	9,584	9,336
Other assets:
Regulatory assets	1,522	1,509
Deferred charges and other	42	53
Total other assets	1,564	1,562
Total assets	11,540	11,407
Current liabilities:
Current maturities of long-term debt	300	300
Commercial paper	109	50
Accounts payable	193	263
Accounts payable to associated companies	39	47
Accrued taxes	78	77
Accrued interest	38	48
Regulatory liabilities	76	54
Other	72	89
Total current liabilities	905	928
Long-term debt, net (excluding current portion)	3,891	3,790
Other liabilities:
Deferred tax liabilities	1,171	1,179
Regulatory liabilities	485	492
Pension and other benefit obligations	45	46
Other	516	511
Total other liabilities	2,217	2,228
Commitments and contingencies (Note 12)
Common equity:
Common stock	33	33
Additional paid-in capital	3,257	3,212
Retained earnings	1,237	1,216
Total common equity	4,527	4,461
Total liabilities and equity	11,540	11,407
WPL [Member]
Current assets:
Cash and cash equivalents	11	51
Accounts receivable, less allowance for expected credit losses	235	220
Production fuel, at weighted average cost	26	24
Gas stored underground, at weighted average cost	11	30
Materials and supplies, at weighted average cost	70	69
Regulatory assets	101	133
Prepaid gross receipts tax	39	51
Other	40	57
Total current assets	533	635
Property, plant and equipment, net	8,937	8,861
Other assets:
Regulatory assets	580	555
Deferred charges and other	51	55
Total other assets	631	610
Total assets	10,101	10,106
Current liabilities:
Commercial paper	212	183
Accounts payable	155	209
Accrued interest	41	44
Regulatory liabilities	33	15
Other	85	94
Total current liabilities	526	545
Long-term debt, net (excluding current portion)	3,371	3,370
Other liabilities:
Deferred tax liabilities	828	865
Regulatory liabilities	489	467
Pension and other benefit obligations	92	102
Other	659	656
Total other liabilities	2,068	2,090
Commitments and contingencies (Note 12)
Common equity:
Common stock	66	66
Additional paid-in capital	2,533	2,533
Retained earnings	1,537	1,502
Total common equity	4,136	4,101
Total liabilities and equity	$ 10,101	$ 10,106