Derivatives and Hedging (Gains and Losses Recognized on Cash Flow Hedges) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Pretax Gains (Losses) Recorded in AOCI, interest rate contracts	$ (11)	$ 2
Total Pretax Gains (Losses) Recorded in AOCI	(11)	2
Total Pretax Gains (Losses) Reclassified from AOCI into Earnings	(1)	(1)
Pretax Gains (Losses) expected to be recognized in earnings during the next 12 months, interest rate contracts	5
Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax Gains (Losses) Reclassified from AOCI into Earnings, interest rate contracts	(1)	(1)
Duke Energy Carolinas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Pretax Gains (Losses) Reclassified from AOCI into Earnings	(1)
Duke Energy Carolinas [Member] \| Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax Gains (Losses) Reclassified from AOCI into Earnings, interest rate contracts	(1)
Duke Energy Indiana [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Pretax Gains (Losses) Reclassified from AOCI into Earnings	1
Duke Energy Indiana [Member] \| Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax Gains (Losses) Reclassified from AOCI into Earnings, interest rate contracts	$ 1

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The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

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- Definition

Amount before tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

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- Definition

Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

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- Definition

Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

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-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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