Regulatory Matters (Details)		1 Months Ended		3 Months Ended	12 Months Ended
	Apr. 26, 2017 USD ($)	Mar. 31, 2016 USD ($)	May 31, 2014 MW	Mar. 31, 2018 MW	Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 124,500,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					9.10%
Capacity Sales, Percent Shared with Customers		50.00%
Increase in basic rates and charges					$ 96,700,000
Increase in basic rates and charges, percentage					7.10%
Equipment recovery approved amount					$ 772,000,000
Revenue requirement to be included in rate					48,000,000
CCT expenditures					59,100,000	$ 158,900,000	$ 252,600,000
Public Utlities, Approved Shareholder Incentives					10,700,000
Regulatory assets					378,904,000	450,710,000
Regulatory Assets					414,245,000	484,622,000
Regulatory assets					35,341,000	33,912,000
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 30,800,000
Wholesale Sales Margins, Percent Shared with Customers		50.00%
Benchmark for Wholesale Sales Margin		$ 6,300,000
Eagle Valley [Member]
Regulatory Matters [Line Items]
Public Utilities, Approved Production Plan Capacity , Maximum | MW			685
Public Utilities, Approved Production Plant Capacity, Minimum | MW			644
Deferred Project Costs [Member]
Regulatory Matters [Line Items]
Regulatory assets						114,359,000
Regulatory Assets					117,700,000
Deferred MISO Non-fuel Costs [Member]
Regulatory Matters [Line Items]
Regulatory assets					101,562,000
Regulatory assets					11,800,000.0
Indianapolis Power And Light Company [Member]
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 124,500,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					9.10%
Capacity Sales, Percent Shared with Customers		50.00%
Increase in basic rates and charges					$ 96,700,000
Increase in basic rates and charges, percentage					7.10%
Equipment recovery approved amount					$ 772,000,000
Revenue requirement to be included in rate					48,000,000
CCT expenditures					59,100,000	158,900,000	$ 252,600,000
Public Utlities, Approved Shareholder Incentives					10,700,000
Regulatory assets					378,904,000	450,710,000
Regulatory Assets					414,245,000	484,622,000
Regulatory assets					35,341,000	33,912,000
Wholesale Sales Margins, Percent Shared with Customers		50.00%
Benchmark for Wholesale Sales Margin		$ 6,300,000
Indianapolis Power And Light Company [Member] | Deferred Project Costs [Member]
Regulatory Matters [Line Items]
Regulatory Assets					117,700,000
Indianapolis Power And Light Company [Member] | Deferred MISO Non-fuel Costs [Member]
Regulatory Matters [Line Items]
Regulatory assets					101,562,000	$ 114,359,000
Regulatory assets					$ 11,800,000.0
Indianapolis Power And Light Company [Member] | Indiana [Member]
Regulatory Matters [Line Items]
Amount of electricity required to be purchased under purchase power agreement | MW					100
Indianapolis Power And Light Company [Member] | Minnesota [Member]
Regulatory Matters [Line Items]
Amount of electricity required to be purchased under purchase power agreement | MW					200
Indianapolis Power And Light Company [Member] | Solar Generated Electricity [Member]
Regulatory Matters [Line Items]
Amount of electricity required to be purchased under purchase power agreement | MW					95
Subsequent Event [Member] | Indianapolis Power And Light Company [Member] | Solar Generated Electricity [Member]
Regulatory Matters [Line Items]
Amount of electricity required to be purchased under purchase power agreement | MW				97
Increase to Annual Depreciation Rate [Member]
Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		24,300,000
Increase to Annual Depreciation Rate [Member] | Indianapolis Power And Light Company [Member]
Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 24,300,000
NAAQs [Member]
Regulatory Matters [Line Items]
Percentage of approved qualifying costs to recover	80.00%
Public Utilities, approved capital cost for compliance projects	$ 29,000,000
NAAQs [Member] | Indianapolis Power And Light Company [Member]
Regulatory Matters [Line Items]
Percentage of approved qualifying costs to recover	80.00%
Public Utilities, approved capital cost for compliance projects	$ 29,000,000
CCR [Member]
Regulatory Matters [Line Items]
Percentage of approved qualifying costs to recover	80.00%
Public Utilities, approved capital cost for compliance projects	$ 47,000,000
CCR [Member] | Indianapolis Power And Light Company [Member]
Regulatory Matters [Line Items]
Percentage of approved qualifying costs to recover	80.00%
Public Utilities, approved capital cost for compliance projects	$ 47,000,000