Severance (Narrative)(Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended
	Nov. 30, 2011 2011 Severance Plan [Member] Employees	Jun. 30, 2013 2011 Severance Plan [Member]	Oct. 31, 2012 Duke Energy Ohio Union 2012 Severance Plan [Member] Employees	Jun. 30, 2013 Crystal River Unit 3 2013 Severance Plan [Member]	Dec. 31, 2012 Crystal River Unit 3 2013 Severance Plan [Member] Employees	Jun. 30, 2013 Progress Energy [Member] Crystal River Unit 3 2013 Severance Plan [Member]	Dec. 31, 2012 Progress Energy [Member] Crystal River Unit 3 2013 Severance Plan [Member] Employees	Jun. 30, 2013 Duke Energy Florida [Member] Crystal River Unit 3 2013 Severance Plan [Member]	Dec. 31, 2012 Duke Energy Florida [Member] Crystal River Unit 3 2013 Severance Plan [Member] Employees	Oct. 31, 2012 Duke Energy Ohio [Member] Duke Energy Ohio Union 2012 Severance Plan [Member] Employees
Restructuring Cost and Reserve [Line Items]
Number of employees that accepted the termination benefits	1,100		75							75
Number of eligible employees					600		600		600
Estimated severance expense		$ 10		$ 5		$ 5		$ 5
Deferred severance costs				$ 28		$ 28		$ 28