Regulatory Matters (Schedule of MISO Exit fees)(Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Restructuring Liability, beginning balance	$ 32
Cash Reductions	(68)
Restructuring Reserve, Period Expense	(171)
Restructuring Liability, ending balance	135
Duke Energy Ohio [Member] | Regional Transmission Organization Realignment [Member]
Restructuring Liability, beginning balance	110
Cash Reductions	(18)
Restructuring Reserve, Period Expense		(36)
Restructuring Reserve Period Deferral	5
Restructuring Liability, ending balance	$ 97	$ 110