Regulatory Matters (Refunds) (Details) (Duke Energy Florida [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Florida Public Service Commission Settlement Agreement 2012 [Member]
Regulatory Assets Liabilities [Line Items]
Total	$ 288
Refunded to date	233
2014	35
2015	10
2016	10
Retirement Decision Credits [Member]
Regulatory Assets Liabilities [Line Items]
Total	100
Refunded to date
2014
2015	40
2016	60
Neil Settlement [Member]
Regulatory Assets Liabilities [Line Items]
Total	490
Refunded to date	449
2014	41
2015
2016
Total Customer Refunds [Member]
Regulatory Assets Liabilities [Line Items]
Total	878
Refunded to date	682
2014	76
2015	50
2016	70
Accelerated Regulatory Asset Recovery [Member]
Regulatory Assets Liabilities [Line Items]
Total	(130)
Refunded to date	(28)
2014	(9)
2015	(37)
2016	(56)
Net Customer Refunds [Member]
Regulatory Assets Liabilities [Line Items]
Total	748
Refunded to date	654
2014	67
2015	13
2016	$ 14