Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 32	$ 62
Accounts receivable, less allowance for expected credit losses	426	475
Production fuel, at weighted average cost	60	62
Gas stored underground, at weighted average cost	52	79
Materials and supplies, at weighted average cost	208	202
Regulatory assets	218	232
Other	112	160
Total current assets	1,108	1,272
Property, plant and equipment, net	17,354	17,157
Investments:
ATC Holdings	392	386
Other	219	216
Total investments	611	602
Other assets:
Regulatory assets	2,002	2,029
Deferred charges and other	173	177
Total other assets	2,175	2,206
Total assets	21,248	21,237
Current liabilities:
Current maturities of long-term debt	809	809
Commercial paper	334	475
Accounts payable	438	611
Regulatory liabilities	100	107
Other	303	302
Total current liabilities	1,984	2,304
Long-term debt, net (excluding current portion)	8,524	8,225
Other liabilities:
Deferred tax liabilities	2,038	2,042
Regulatory liabilities	1,036	1,023
Pension and other benefit obligations	245	249
Other	604	617
Total other liabilities	3,923	3,931
Commitments and contingencies (Note 13)
Common equity:
Common stock	3	3
Additional paid-in capital	3,033	3,030
Retained earnings	3,791	3,756
Accumulated other comprehensive income	2	1
Shares in deferred compensation trust - 341,937 and 379,006 shares at a weighted average cost of $34.96 and $34.48 per share	(12)	(13)
Total common equity	6,817	6,777
Total liabilities and equity	21,248	21,237
IPL [Member]
Current assets:
Cash and cash equivalents	12	53
Accounts receivable, less allowance for expected credit losses	204	242
Production fuel, at weighted average cost	29	27
Gas stored underground, at weighted average cost	17	35
Materials and supplies, at weighted average cost	126	122
Regulatory assets	85	93
Other	42	51
Total current assets	515	623
Property, plant and equipment, net	8,450	8,298
Other assets:
Regulatory assets	1,482	1,484
Deferred charges and other	85	84
Total other assets	1,567	1,568
Total assets	10,532	10,489
Current liabilities:
Current maturities of long-term debt	500	500
Accounts payable	213	262
Accrued taxes	61	50
Accrued interest	49	40
Regulatory liabilities	79	72
Other	97	101
Total current liabilities	999	1,025
Long-term debt, net (excluding current portion)	3,445	3,445
Other liabilities:
Deferred tax liabilities	1,098	1,091
Regulatory liabilities	569	572
Pension and other benefit obligations	49	51
Other	335	331
Total other liabilities	2,051	2,045
Commitments and contingencies (Note 13)
Common equity:
Common stock	33	33
Additional paid-in capital	2,937	2,887
Retained earnings	1,067	1,054
Total common equity	4,037	3,974
Total liabilities and equity	10,532	10,489
WPL [Member]
Current assets:
Cash and cash equivalents	11	7
Accounts receivable, less allowance for expected credit losses	209	219
Production fuel, at weighted average cost	31	35
Gas stored underground, at weighted average cost	35	44
Materials and supplies, at weighted average cost	78	77
Regulatory assets	133	139
Prepaid gross receipts tax	38	49
Other	19	43
Total current assets	554	613
Property, plant and equipment, net	8,450	8,415
Other assets:
Regulatory assets	520	545
Deferred charges and other	57	61
Total other assets	577	606
Total assets	9,581	9,634
Current liabilities:
Commercial paper	0	318
Accounts payable	174	293
Accrued interest	42	40
Regulatory liabilities	21	35
Other	105	89
Total current liabilities	342	775
Long-term debt, net (excluding current portion)	3,367	3,070
Other liabilities:
Deferred tax liabilities	811	827
Regulatory liabilities	467	451
Pension and other benefit obligations	119	121
Other	480	493
Total other liabilities	1,877	1,892
Commitments and contingencies (Note 13)
Common equity:
Common stock	66	66
Additional paid-in capital	2,533	2,478
Retained earnings	1,396	1,353
Total common equity	3,995	3,897
Total liabilities and equity	$ 9,581	$ 9,634