Overview and Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) customer generating_station item segment mi MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Significant Accounting Policies [Line Items]
NonservicePensionCosts	$ (2.1)	$ 0.9
Capitalized Computer Software, Gross	99,400,000	91,700,000
Service cost	7,344,000	7,018,000	$ 8,314,000
Interest cost	$ 25,305,000	$ 25,815,000	29,638,000
Ownership interest in IPALCO by AES U.S. Investments (percent)	82.35%
Ownership interest in IPALCO by CDPQ (percent)		17.65%
Number of customers | customer	490,000
Distance of Furthest Customer from Indianapolis | mi	40
Number of generating stations | generating_station	4
Electric generation capability for winter, megawatts | MW	2,996
Electric generation capability for summer, megawatts | MW	2,881
Total other assets	$ 22,723,000	$ 18,404,000
Unbilled energy revenues	61,600,000	57,000,000
Operating revenues	1,349,588,000	1,347,430,000	1,250,399,000
Provision for doubtful accounts	5,900,000	4,100,000	$ 4,300,000
Loss contingencies accrued	$ 4,100,000	$ 11,600,000
Number of suppliers | item	4
Capitalized amount, rate	6.60%	7.20%	8.10%
Depreciation rate	4.10%	4.30%	4.20%
Depreciation expense	$ 209,800,000	$ 209,500,000	$ 194,400,000
Utility plant assets	$ 3,980,991,000	3,880,918,000	3,441,000,000
Number of segments | segment	2
Capitalized Computer Software, Accumulated Amortization	$ 83,400,000	79,700,000
Capitalized Computer Software, Amortization	4,300,000	5,900,000	5,200,000
Capitalized Software, estimated amortization expense over remaining useful life	16,000,000
Capitalized software, estimated amortization expense in year two	$ 3,200,000
Harding Street [Member]
Significant Accounting Policies [Line Items]
Amount of unit retired, megawatts | MW	90
Amount of New Operation for Battery Storage Unit, megawatts | MW	20
Eagle Valley [Member]
Significant Accounting Policies [Line Items]
Expected CCGT Output, megawatts | MW	671
Labor Force Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	67.00%
Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	50.00%
Indianapolis Power And Light Company [Member]
Significant Accounting Policies [Line Items]
NonservicePensionCosts	$ (2.1)	0.9
Capitalized Computer Software, Gross	99,400,000	91,700,000
Service cost	7,344,000	7,018,000	8,314,000
Interest cost	$ 25,305,000	25,815,000	29,638,000
Number of customers | customer	490,000
Distance of Furthest Customer from Indianapolis | mi	40
Electric generation capability for winter, megawatts | MW	2,996
Electric generation capability for summer, megawatts | MW	2,881
Total other assets	$ 17,666,000	13,239,000
Unbilled energy revenues	61,600,000	57,000,000
Operating revenues	1,349,588,000	1,347,430,000	1,250,399,000
Provision for doubtful accounts	5,900,000	4,100,000	$ 4,300,000
Loss contingencies accrued	$ 4,100,000	$ 11,600,000
Number of suppliers | item	4
Capitalized amount, rate	6.60%	7.20%	8.10%
Depreciation rate	4.10%	4.30%	4.20%
Depreciation expense	$ 209,800,000	$ 209,500,000	$ 194,400,000
Utility plant assets	3,980,991,000	3,880,918,000
Capitalized Computer Software, Accumulated Amortization	83,400,000	79,700,000
Capitalized Computer Software, Amortization	4,300,000	$ 5,900,000	$ 5,200,000
Capitalized Software, estimated amortization expense over remaining useful life	16,000,000
Capitalized software, estimated amortization expense in year two	$ 3,200,000
Indianapolis Power And Light Company [Member] | Harding Street [Member]
Significant Accounting Policies [Line Items]
Amount of unit retired, megawatts | MW	90
Amount of New Operation for Battery Storage Unit, megawatts | MW	20
Indianapolis Power And Light Company [Member] | Eagle Valley [Member]
Significant Accounting Policies [Line Items]
Expected CCGT Output, megawatts | MW	671
Indianapolis Power And Light Company [Member] | Eagle Valley CCGT And Harding Street Refueling Project [Member]
Significant Accounting Policies [Line Items]
Capitalized amount, rate	6.60%	7.10%	7.30%
Indianapolis Power And Light Company [Member] | Labor Force Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	67.00%
Indianapolis Power And Light Company [Member] | Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	50.00%
AES U.S. Holdings, LLC [Member]
Significant Accounting Policies [Line Items]
Ownership Interest in Parent Company, Percent	85.00%
CDPQ [Member]
Significant Accounting Policies [Line Items]
Ownership Interest in Parent Company, Percent	15.00%
Physical Unit [Member]
Significant Accounting Policies [Line Items]
Collective bargaining agreement expiration date	Dec. 10, 2018
Physical Unit [Member] | Indianapolis Power And Light Company [Member]
Significant Accounting Policies [Line Items]
Collective bargaining agreement expiration date	Dec. 10, 2018
Clerical-Technical Unit [Member]
Significant Accounting Policies [Line Items]
Collective bargaining agreement expiration date	Feb. 17, 2020
Clerical-Technical Unit [Member] | Indianapolis Power And Light Company [Member]
Significant Accounting Policies [Line Items]
Collective bargaining agreement expiration date	Feb. 17, 2020
Maximum [Member] | Indianapolis Power And Light Company [Member]
Significant Accounting Policies [Line Items]
Outstanding receivables purchased amount	$ 50,000,000