Regulatory Matters (Schedule of MISO Exit fees)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Restructuring Liability, beginning balance	$ 135
Cash Reductions	(67)
Restructuring Reserve, Period Expense	(31)	[1]
Restructuring Liability, ending balance	99
Duke Energy Ohio [Member] | RTO Realignment [Member]
Restructuring Liability, beginning balance	97
Cash Reductions	(1)
Restructuring Reserve Period Deferral	1
Restructuring Liability, ending balance	$ 97	[2]

[1] Provision / Adjustments includes $16 million of severance costs deferred related to Crystal River Unit 3.

[2] As of March 31, 2013, $71 million is recorded as a Regulatory asset on Duke Energy Ohio's Condensed Consolidated Balance Sheets.