Regulatory Matters (Schedule of MISO Exit fees)(Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Restructuring Reserve [Roll Forward]
Balance at December 31, 2012	$ 135
Cash reductions	114
Restructuring reserve, period expense	(41)	[1]
Balance at September 30, 2013	62
Duke Energy Ohio [Member] | RTO Realignment [Member]
Restructuring Reserve [Roll Forward]
Balance at December 31, 2012	97
Cash reductions	(3)
Restructuring reserve, accrual adjustment	3
Balance at September 30, 2013	$ 97	[2]

[1] Provision / Adjustments for Duke Energy, Progress Energy and Duke Energy Florida includes $26 million of severance costs deferred related to Crystal River Unit 3.

[2] As of September 30, 2013, $70 million is recorded as a Regulatory asset on Duke Energy Ohio's Condensed Consolidated Balance Sheets.