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Related Party Transactions (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Service Company [Member]    
Related Party Transaction [Line Items]    
Costs incurred by related party $ 6.0us-gaap_CostsAndExpensesRelatedParty
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cik0000728391_ServiceCompanyMember		 $ 8.4us-gaap_CostsAndExpensesRelatedParty
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cik0000728391_ServiceCompanyMember
Prepaid balance to related party 2.4cik0000728391_PrepaidExpenseToRelatedParty
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cik0000728391_ServiceCompanyMember		 0.4cik0000728391_PrepaidExpenseToRelatedParty
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cik0000728391_ServiceCompanyMember
Ipalco Enterprises, Inc. [Member]    
Related Party Transaction [Line Items]    
Costs incurred by related party $ 1.7us-gaap_CostsAndExpensesRelatedParty
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember		 $ 1.0us-gaap_CostsAndExpensesRelatedParty
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember