Acquisitions and Sales of Other Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					0 Months Ended	3 Months Ended				3 Months Ended					3 Months Ended			0 Months Ended	3 Months Ended			0 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Jul. 02, 2012	Jan. 12, 2012	Jan. 12, 2012 Wabash Valley Power Association [Member]	Mar. 31, 2013 Ibener [Member]	Apr. 30, 2013 Ibener [Member]	Mar. 31, 2013 Duke Energy Carolinas [Member]	Dec. 31, 2012 Duke Energy Carolinas [Member]	Mar. 31, 2013 Progress Energy [Member]	Mar. 31, 2012 Progress Energy [Member]	Dec. 31, 2012 Progress Energy [Member]	Mar. 31, 2013 Duke Energy Progress [Member]	Dec. 31, 2012 Duke Energy Progress [Member]	Mar. 31, 2013 Duke Energy Florida [Member]	Mar. 31, 2012 Duke Energy Florida [Member]	Dec. 31, 2012 Duke Energy Florida [Member]	Jan. 12, 2012 Duke Energy Ohio [Member]	Mar. 31, 2013 Duke Energy Ohio [Member]	Mar. 31, 2012 Duke Energy Ohio [Member]	Dec. 31, 2012 Duke Energy Ohio [Member]	Jan. 12, 2012 Duke Energy Indiana [Member]	Mar. 31, 2013 Duke Energy Indiana [Member]	Mar. 31, 2012 Duke Energy Indiana [Member]	Dec. 31, 2012 Duke Energy Indiana [Member]
Significant Acquisitions and Disposals [Line Items]
Adjusted conversion ratio, after reverse stock split adjustment				87.083%
Fair value of outstanding earned stock compensation awards				$ 62
Total estimated purchase price				18,071
Costs to achieve the merger	10
Impairment of other long-lived assets	0	407									0	0				0	0			0	2			0	400
Transfer of Vermillion Generating Station																					(28)			0	26
Proceeds from sale of interest in jointly owned utility plant						14													82				68
Sale of ownership interest in Vermillion Generating Station					75.00%
Available capacity														(722)		(587)
Cash collateral returned								192
Cash paid							415
Property, plant and equipment	23,122						383
Intangibles							30
Deferred tax							57
Working capital							6
Bridge loan							190
Goodwill	12,477						53
Revolving loan under credit agreement							200
Current maturities of long-term debt	$ 3,323		$ 3,110						$ 406	$ 406	$ 718		$ 843	$ 407	$ 407	$ 10		$ 435		$ 259		$ 261		$ 405		$ 405
Percentage of loan collateralized by cash deposits							101.00%
Debt instrument year due							Dec. 20, 2013
Debt instrument maturity date option to extend							13 years 0 months 0 days