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Investments in Unconsolidated Affiliates (Investments in Equity Method Unconsolidated Affiliates) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Investments In Unconsolidated Affiliates [Line Items]      
Investments in unconsolidated affiliates $ 358us-gaap_EquityMethodInvestments $ 390us-gaap_EquityMethodInvestments  
Equity in earnings (losses) of unconsolidated affiliates 130us-gaap_IncomeLossFromEquityMethodInvestments 122us-gaap_IncomeLossFromEquityMethodInvestments 148us-gaap_IncomeLossFromEquityMethodInvestments
Regulated Utilities [Member]      
Investments In Unconsolidated Affiliates [Line Items]      
Investments in unconsolidated affiliates 3us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_RegulatedUtilitiesMember
4us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_RegulatedUtilitiesMember
 
Equity in earnings (losses) of unconsolidated affiliates (3)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_RegulatedUtilitiesMember
(1)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_RegulatedUtilitiesMember
(5)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_RegulatedUtilitiesMember
International Energy [Member]      
Investments In Unconsolidated Affiliates [Line Items]      
Investments in unconsolidated affiliates 69us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_InternationalEnergyMember
82us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_InternationalEnergyMember
 
Equity in earnings (losses) of unconsolidated affiliates 120us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_InternationalEnergyMember
110us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_InternationalEnergyMember
134us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_InternationalEnergyMember
Commercial Power [Member]      
Investments In Unconsolidated Affiliates [Line Items]      
Investments in unconsolidated affiliates 258us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_CommercialPowerMember
252us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_CommercialPowerMember
 
Equity in earnings (losses) of unconsolidated affiliates 10us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_CommercialPowerMember
7us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_CommercialPowerMember
14us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= duk_CommercialPowerMember
Other [Member]      
Investments In Unconsolidated Affiliates [Line Items]      
Investments in unconsolidated affiliates 28us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
52us-gaap_EquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
 
Equity in earnings (losses) of unconsolidated affiliates $ 3us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
$ 6us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
$ 5us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember