Overview and Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024 USD ($) generating_station MW	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($) generating_station MW	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	May 31, 2021
Debt Instrument [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,310,361			$ 1,097,595	$ 1,053,303		$ 1,310,361	$ 1,097,595	$ 1,129,722
Asset Retirement Obligation, Revision of Estimate							81,714	0
Asset Retirement Obligation, Accretion Expense							9,244	7,352
Accumulated Other Comprehensive Income (Loss), Net of Tax	35,812						35,812		29,294	$ 22,269
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0			7,482			6,626	7,325
Inventories	55,977						55,977		77,198
Cash and cash equivalents	$ 48,308			28,579			$ 48,308	28,579	28,579
Number of customers	530,000						530,000
Number of generating stations | generating_station	4						4
Restricted Cash and Cash Equivalents	$ 5			5			$ 5	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	48,313			21,542			48,313	21,542	28,584	201,553
Regulatory assets, current	69,113						69,113		66,392
Inventory, Net	125,090						125,090		143,590
Other Comprehensive Income (Loss), Net of Tax	(434)	$ (434)	$ 7,386	8,840	$ 9,732	$ (7,174)	6,518	11,398
Accounts Receivable, Allowance for Credit Loss, Current	17,087			1,064			17,087	1,064	2,283	1,117
Accounts Receivable, Credit Loss Expense (Reversal)							14,018	5,536
Accounts Receivable, Allowance for Credit Loss, Writeoff							(577)	(6,940)
Accounts Receivable, Allowance for Credit Loss, Recovery							1,363	1,351
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	35,812						35,812		29,294	22,269
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				7,482				7,325
Income Tax Expense (Benefit)	8,314			3,802			24,833	8,663
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	54,940	41,794	17,162			19,115
Capitalized Computer Software, Amortization	6,729			3,654			20,458	9,665
Income Tax Expense (Benefit)	8,314			3,802			24,833	8,663
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	54,940	$ 41,794	$ 17,162			$ 19,115
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	$ (434)			1,358			$ (108)	4,073
Petersburg Unit 1 retired MW											230
Petersburg Unit 2 Planned Retirement MW in 2023							415
Preferred Resource Portfolio Coal-Fired Generation Retirement MW by 2023	630						630
Asset Retirement Obligation	$ 346,550			216,791			$ 346,550	216,791	249,930	$ 218,729
Asset Retirement Obligation, Liabilities Incurred							8,864	656
Asset Retirement Obligation, Liabilities Settled							(3,202)	(9,946)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net	115			0			(1,422)	0
Allowance for Funds Used During Construction, Capitalized Interest	7,436			3,841			19,123	9,505
Allowance for Funds Used During Construction, Equity Portion	1,485			3,134			3,585	7,089
Capitalized Computer Software, Amortization	6,729			3,654			20,458	9,665
Capitalized Computer Software, Gross	279,878						279,878		261,872
Project development intangible assets	83,430						83,430		84,097
Emissions Allowance	797						797		797
Capitalized Computer Software, Accumulated Amortization	129,969						129,969		111,110
Intangible Assets, Net (Including Goodwill)	$ 234,136						$ 234,136		$ 235,656
Petersburg Energy Center Project MW							250
Petersburg Energy Storage Project MW							45
Petersburg Energy Storage Project MwH							180
Hardy Hills Solar Project MW							195
Hoosier Wind Project MW							106
Pike Co BESS Project MW							200
Pike Co BESS Project MwH							800
Indianapolis Power And Light Company [Member]
Debt Instrument [Line Items]
Electric generation capability for winter, megawatts | MW	3,070						3,070
Electric generation capability for summer, megawatts | MW	2,925						2,925
Aes U.S. Investments [Member]
Debt Instrument [Line Items]
Ownership percentage by parent (percent)	82.35%						82.35%
CDPQ [Member]
Debt Instrument [Line Items]
Ownership percentage by parent (percent)	17.65%						17.65%
Ownership interest in parent company (percent)	15.00%						15.00%
AES U.S. Holdings, LLC [Member]
Debt Instrument [Line Items]
Ownership interest in parent company (percent)	85.00%						85.00%
Harding Street [Member]
Debt Instrument [Line Items]
Amount of New Operation for Battery Storage Unit, megawatts | MW	20						20
Interest Rate Contract [Member]
Debt Instrument [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ 35,812			33,667			$ 35,812	33,667
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Debt Instrument [Line Items]
Interest and Debt Expense	578			(1,807)			144	(5,421)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and Debt Expense	578			(1,807)			144	(5,421)
Income Tax Expense (Benefit)	(144)			449			(36)	1,348
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(434)			1,358			(108)	4,073
Income Tax Expense (Benefit)	(144)			449			(36)	1,348
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (434)			$ 1,358			$ (108)	$ 4,073