Guarantees and Indemnifications(Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Liabilities Recorded for Third Party Guarantees [Abstract]
Face value of guarantees	$ 28	$ 24
Surety Bond [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	44
Guarantor obligations, term	At December 31, 2014, Duke Energy had guaranteed $44 million of outstanding surety bonds, most of which have no set expiration.
Standby Letters Of Credit [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	452
Guarantor obligations, term	At December 31, 2014, Duke Energy had issued a total of $452 million in letters of credit, which expire between 2015 and 2020.
Unused letters of credit	46
Performance Guarantee [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	267
Maximum potential of future amounts associated with guarantees with expiration dates	120
Guarantor obligations, term	The maximum potential amount of future payments required under these guarantees as of December 31, 2014, was $267 million. Of this amount, $15 million relates to guarantees issued on behalf of less than wholly owned consolidated entities, with the remainder related to guarantees issued on behalf of third parties and unconsolidated affiliates of Duke Energy. Of the guarantees noted above, $120 million of the guarantees expire between 2015 and 2033, with the remaining performance guarantees having no contractual expiration.
Performance Guarantee [Member] | Less Than Wholly Owned Entity [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	15
Spectra Capital [Member] | Performance Guarantee [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	205
Guarantor obligations, term	At December 31, 2014, the maximum potential amount of future payments associated with these guarantees was $205 million, the majority of which expires by 2028.
Progress Energy [Member]
Liabilities Recorded for Third Party Guarantees [Abstract]
Face value of guarantees	13	9
Progress Energy [Member] | Indemnification Agreement [Member]
Guarantor Obligations [Line Items]
Maximum potential amount of future payments associated with guarantees	107
Maximum potential amount of future payments associated with guarantees with no expiration date	7
Guarantee obligations, unlimited exposure	Certain indemnifications related to discontinued operations have no limitations as to time or maximum potential future payments.
Guarantor obligations, term	At December 31, 2014, the estimated maximum exposure for these indemnifications was $107 million, the majority of which expires in 2017. Of this amount, $7 million has no contractual expiration.
Duke Energy Florida [Member]
Liabilities Recorded for Third Party Guarantees [Abstract]
Face value of guarantees	$ 7	$ 3