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Related Party Transactions (Narrative) (Details) (Duke Energy Ohio [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Related Party Transaction [Line Items]      
Intercompany loan payable $ 298us-gaap_NotesPayableRelatedPartiesClassifiedCurrent   $ 491us-gaap_NotesPayableRelatedPartiesClassifiedCurrent
DECAM [Member]
      
Related Party Transaction [Line Items]      
Intercompany loan payable 294us-gaap_NotesPayableRelatedPartiesClassifiedCurrent
/ us-gaap_ConsolidationItemsAxis
= duk_DecamMember
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember		   459us-gaap_NotesPayableRelatedPartiesClassifiedCurrent
/ us-gaap_ConsolidationItemsAxis
= duk_DecamMember
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
MarkTo Market Of Commodity Contracts And Sales Of Power [Member] | DECAM [Member]      
Related Party Transaction [Line Items]      
Related party transaction, expenses from transactions with related party $ 3us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
/ us-gaap_ConsolidationItemsAxis
= duk_DecamMember
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= duk_MarktoMarketOfCommodityContractsAndSalesOfPowerMember		 $ 54us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
/ us-gaap_ConsolidationItemsAxis
= duk_DecamMember
/ dei_LegalEntityAxis
= duk_DukeEnergyOhioMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= duk_MarktoMarketOfCommodityContractsAndSalesOfPowerMember