Risk Management, Derivative Instruments And Hedging Activities (Undesignated Contracts - Location And Amount Of Pre-Tax Gains And (Losses) Recognized In Income Or As Regulatory Assets Or Liabilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	$ (14)	$ (11)	$ 12	$ 0
Total Pre-tax Losses Recognized in Earnings	0	(12)	36	(26)
Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	(1)	(1)	(1)
Total Pre-tax Losses Recognized in Earnings	3	(17)	74	(24)
Interest Rate Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Losses Recognized in Earnings	(1)	(1)	(1)	(1)
Revenue, Non-Regulated Electric, Natural Gas And Other [Member] | Commodity Contracts [Member]
Total Pre-tax Losses Recognized in Earnings	0	(12)	36	(25)
Revenue, Non-Regulated Electric, Natural Gas And Other [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Losses Recognized in Earnings	4	(16)	75	(22)
Fuel Used In Electric Generation And Purchased Power-Non-Regulated [Member] | Commodity Contracts [Member]
Total Pre-tax Losses Recognized in Earnings				(1)
Fuel Used In Electric Generation And Purchased Power-Non-Regulated [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Losses Recognized in Earnings				(1)
Regulatory Asset [Member] | Interest Rate Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	(32)	(21)	(10)	(9)
Regulatory Asset [Member] | Interest Rate Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	(1)
Regulatory Asset [Member] | Commodity Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	1	(1)		(1)
Regulatory Asset [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	0	0	(2)	(1)
Regulatory Liability [Member] | Commodity Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	17	11	22	10
Regulatory Liability [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		$ (1)	$ 1