Regulatory Matters (Refunds) (Details) (Duke Energy Florida [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Florida Public Service Commission Settlement Agreement 2012 [Member]
Regulatory Assets Liabilities [Line Items]
Customer refunds to date	$ 65
2013	64
2014	139
2015	10
2016	10
Total customer refunds	288
Retirement Decision Credits [Member]
Regulatory Assets Liabilities [Line Items]
2015	40
2016	60
Total customer refunds	100
Neil Settlement [Member]
Regulatory Assets Liabilities [Line Items]
Customer refunds to date	163
2013	163
2014	164
Total customer refunds	490
Total Customer Refunds [Member]
Regulatory Assets Liabilities [Line Items]
Customer refunds to date	228
2013	227
2014	303
2015	50
2016	70
Total customer refunds	878
Accelerated Regulatory Asset Recovery [Member]
Regulatory Assets Liabilities [Line Items]
2014	(38)
2015	(38)
2016	(59)
Total customer refunds	(135)
Net Customer Refunds [Member]
Regulatory Assets Liabilities [Line Items]
Customer refunds to date	228
2013	227
2014	265
2015	12
2016	11
Total customer refunds	$ 743