Commitments and Contingencies (Schedule of Environmental Loss Contingencies)(Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Accrual for Environmental Loss Contingencies	$ 61	[1]	$ 88	[1]
Amounts accrued for environmental loss contingencies	43	[1],[2]	5	[1]
Expenditures for environmental loss contingencies	(19)	[1]	(21)	[1]
Accrual for Environmental Loss Contingencies	85	[1],[2]	72	[1]
Environmental reserves assumed as a result of merger			32
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies	12		13
Amounts accrued for environmental loss contingencies	1		0
Expenditures for environmental loss contingencies	0		0
Accrual for Environmental Loss Contingencies	13		13
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies	28	[1]	50	[1]
Amounts accrued for environmental loss contingencies	10	[1]	3	[1]
Expenditures for environmental loss contingencies	(15)	[1]	(17)	[1]
Accrual for Environmental Loss Contingencies	23	[1]	36	[1]
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies	9		11
Amounts accrued for environmental loss contingencies	2		1
Expenditures for environmental loss contingencies	(2)		(2)
Accrual for Environmental Loss Contingencies	$ 9		$ 10

[1] Environmental reserves relate primarily to former Manufactured Gas Plants (MGP) and Other Sites.

[2] Amounts at Duke Energy include $32 million in environmental reserves assumed during the Progress Energy merger.