Investments In Debt And Equity Securities (Unrealized Losses Of Available-For-Sale Debt And Equity Securities In A Continuous Loss Position) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Fair Value	$ 322		$ 584
Unrealized Loss Position greater than 12 months	38		25
Unrealized Loss Position less than 12 months	32		17
Other Classification [Member]
Fair Value	76		284
Unrealized Loss Position greater than 12 months	24		19
Unrealized Loss Position less than 12 months	16		0
Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	114	[1]	289	[1]
Unrealized Loss Position greater than 12 months	0	[1]	6	[1]
Unrealized Loss Position less than 12 months	7	[1]	16	[1]
Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	15	[1]	11	[1]
Unrealized Loss Position greater than 12 months	0	[1]	0	[1]
Unrealized Loss Position less than 12 months	0	[1]	1	[1]
Progress Energy [Member] | NDTF [Member]
Fair Value	117	[1]
Unrealized Loss Position greater than 12 months	(14)	[1]
Unrealized Loss Position less than 12 months	(9)	[1]
Equity Securities [Member] | Other Classification [Member]
Fair Value	6		4
Unrealized Loss Position greater than 12 months	1		1
Unrealized Loss Position less than 12 months	0		0
Equity Securities [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	60		111
Unrealized Loss Position greater than 12 months	0		4
Unrealized Loss Position less than 12 months	5		12
Equity Securities [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	9		8
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		1
Equity Securities [Member] | Progress Energy [Member] | NDTF [Member]
Fair Value	89
Unrealized Loss Position greater than 12 months	(13)
Unrealized Loss Position less than 12 months	(8)
Corporate Debt Securities [Member] | Other Classification [Member]
Fair Value	1		201
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	0		0
Corporate Debt Securities [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	10		57
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	1		1
Corporate Debt Securities [Member] | Progress Energy [Member] | NDTF [Member]
Fair Value	3
Unrealized Loss Position greater than 12 months	0
Unrealized Loss Position less than 12 months	0
Municipal Bonds [Member] | Other Classification [Member]
Fair Value	4		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Municipal Bonds [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	1		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Municipal Bonds [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	6		3
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Municipal Bonds [Member] | Progress Energy [Member] | NDTF [Member]
Fair Value	14
Unrealized Loss Position greater than 12 months	(1)
Unrealized Loss Position less than 12 months	0
US Treasury and Government [Member] | Other Classification [Member]
Fair Value	6		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
US Treasury and Government [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	27		8
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
US Treasury and Government [Member] | Progress Energy [Member] | NDTF [Member]
Fair Value	10
Unrealized Loss Position greater than 12 months	0
Unrealized Loss Position less than 12 months	0
Auction Rate Securities [Member] | Other Classification [Member]
Fair Value	41		71
Unrealized Loss Position greater than 12 months	9		17
Unrealized Loss Position less than 12 months	0		0
Auction Rate Securities [Member] | Duke Energy Carolinas [Member] | Other Classification [Member]
Fair Value	6	[2]	12	[2]
Unrealized Loss Position greater than 12 months	1	[2]	3	[2]
Other Debt Obligations [Member] | Other Classification [Member]
Fair Value	18		8
Unrealized Loss Position greater than 12 months	14		0
Unrealized Loss Position less than 12 months	16		0
Other Debt Obligations [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	16		113
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	1		3
Other Debt Obligations [Member] | Progress Energy [Member] | NDTF [Member]
Fair Value	1
Unrealized Loss Position greater than 12 months	0
Unrealized Loss Position less than 12 months	$ (1)

[1] Unrealized losses on investments within the Duke Energy Carolinas NDTF, Progress Energy NDTF, and the Duke Energy Indiana and Progress Energy grantor trusts are deferred as regulatory assets pursuant to regulatory accounting treatment.

[2] At September 30, 2012 and December 31, 2011, $6 million and $12 million of these securities, respectively, were held by Duke Energy Carolinas. The gross unrealized losses on these securities held by Duke Energy Carolinas which were in an unrealized loss position greater than 12 months were $1million at September 30, 2012 and $3 million at December 31, 2011.