Overview and Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024 USD ($) generating_station MW	Mar. 31, 2024 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2024 USD ($) generating_station MW	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	May 31, 2021
Debt Instrument [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,311,552		$ 1,053,303		$ 1,311,552	$ 1,053,303	$ 1,129,722
Asset Retirement Obligation, Revision of Estimate					80,221	0
Asset Retirement Obligation, Accretion Expense					5,684	5,021
Accumulated Other Comprehensive Income (Loss), Net of Tax	36,246				36,246		29,294	$ 22,269
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0		8,374		6,626	(158)
Inventories	66,004				66,004		77,198
Cash and cash equivalents	$ 33,408		28,579		$ 33,408	28,579	28,579
Number of customers	526,000				526,000
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	33,413		92,183		33,413	92,183	28,584	201,553
Regulatory assets, current	68,349				68,349		66,392
Inventory, Net	134,353				134,353		143,590
Other Comprehensive Income (Loss), Net of Tax	(434)	$ 7,386	9,732	$ (7,174)	6,952	2,558
Accounts Receivable, Allowance for Credit Loss, Current	7,021		955		7,021	955	2,283	1,117
Accounts Receivable, Credit Loss Expense (Reversal)					3,987	3,327
Accounts Receivable, Allowance for Credit Loss, Writeoff					(320)	(4,401)
Accounts Receivable, Allowance for Credit Loss, Recovery					1,071	912
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	36,246				36,246		29,294	22,269
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			8,374			(158)
Income Tax Expense (Benefit)	12,610		(353)		16,519	4,861
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	41,794	17,162		19,115
Capitalized Computer Software, Amortization	6,788		3,024		13,728	6,011
Income Tax Expense (Benefit)	12,610		(353)		16,519	4,861
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	41,794	$ 17,162		$ 19,115
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	$ (434)		1,358		$ 326	2,716
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	$ 342,540		217,449		$ 342,540	217,449	249,930	$ 218,729
Asset Retirement Obligation, Liabilities Incurred					8,507	236
Asset Retirement Obligation, Liabilities Settled					(1,802)	(6,537)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net	(14)		0		(1,537)	0
Allowance for Funds Used During Construction, Capitalized Interest	6,411		2,679		11,687	5,664
Allowance for Funds Used During Construction, Equity Portion	1,269		2,385		2,100	3,955
Capitalized Computer Software, Amortization	6,788		3,024		13,728	6,011
Capitalized Computer Software, Gross	271,812				271,812		261,872
Project development intangible assets	83,710				83,710		84,097
Emissions Allowance	797				797		797
Capitalized Computer Software, Accumulated Amortization	123,521				123,521		111,110
Intangible Assets, Net (Including Goodwill)	$ 232,798				$ 232,798		$ 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	$ 36,246		24,827		$ 36,246	24,827
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Debt Instrument [Line Items]
Interest and Debt Expense	578		(1,807)		(434)	(3,614)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and Debt Expense	578		(1,807)		(434)	(3,614)
Income Tax Expense (Benefit)	(144)		449		108	898
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(434)		1,358		326	2,716
Income Tax Expense (Benefit)	(144)		449		108	898
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (434)		$ 1,358		$ 326	$ 2,716