Business Segments (Business Segment Data) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Unaffiliated Revenues	$ 3,630		$ 3,663
Total Revenues	3,630		3,663
Segment income/consolidated net inocome	299		513
U.S. Franchised Electric And Gas [Member]
Unaffiliated Revenues	2,660	[1]	2,674
Intersegment Revenues	8	[1]	9
Total Revenues	2,668	[1]	2,683
Segment income/consolidated net inocome	136	[1]	341
Commercial Power [Member]
Unaffiliated Revenues	564		642
Intersegment Revenues	16		2
Total Revenues	580		644
Segment income/consolidated net inocome	31		49
International Energy [Member]
Unaffiliated Revenues	402		348
Total Revenues	402		348
Segment income/consolidated net inocome	142		128
Total Reportable Segments [Member]
Unaffiliated Revenues	3,626		3,664
Intersegment Revenues	24		11
Total Revenues	3,650		3,675
Segment income/consolidated net inocome	309		518
Other [Member]
Unaffiliated Revenues	4		(1)
Intersegment Revenues	11		12
Total Revenues	15		11
Segment income/consolidated net inocome	(16)		(7)
Eliminations [Member]
Intersegment Revenues	(35)		(23)
Total Revenues	(35)		(23)
Add Back Of Noncontrolling Interest Component [Member]
Segment income/consolidated net inocome	4		2
Income From Discontinued Operations, Net Of Tax [Member]
Segment income/consolidated net inocome	$ 2

[1] As discussed further in Note 4, Duke Energy recorded pre-tax impairment and other charges of $420 million in the first quarter of 2012 related to Edwardsport integrated gasification combined cycle (IGCC) project.