Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 125	$ 145
Assets, fair value disclosure	5,754	5,712
Derivative liabilities	(334)	(321)
Net assets, fair value	5,420	5,391
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	35	33
Assets, fair value disclosure	4,115	4,057
Derivative liabilities	(41)	11
Net assets, fair value	4,074	4,068
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	72	70
Assets, fair value disclosure	1,522	1,515
Derivative liabilities	(261)	(303)
Net assets, fair value	1,261	1,212
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	18	42
Assets, fair value disclosure	117	140
Derivative liabilities	(32)	(29)
Net assets, fair value	85	111
NDTF [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,623	3,579
NDTF [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,535	3,495
NDTF [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	61	57
NDTF [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	27	27
NDTF [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,609	1,553
NDTF [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	426	402
NDTF [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,131	1,100
NDTF [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	52	51
Other Classification [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	92	102
Other Classification [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	92	91
Other Classification [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		11
Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	305	333
Other Classification [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	27	36
Other Classification [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	258	277
Other Classification [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	20	20
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,903	2,837
Derivative liabilities	(4)	2
Net assets, fair value	2,899	2,835
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,084	2,047
Net assets, fair value	2,084	2,047
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	737	709
Net assets, fair value	737	709
Duke Energy Carolinas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	82	81
Derivative liabilities	(4)	2
Net assets, fair value	78	79
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,982	1,964
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,894	1,879
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	61	58
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	27	27
Duke Energy Carolinas [Member] | NDTF [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	918	870
Duke Energy Carolinas [Member] | NDTF [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	190	168
Duke Energy Carolinas [Member] | NDTF [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	676	651
Duke Energy Carolinas [Member] | NDTF [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	52	51
Duke Energy Carolinas [Member] | Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	3
Duke Energy Carolinas [Member] | Other Classification [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	3
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	3
Assets, fair value disclosure	2,392	2,353
Derivative liabilities	(158)	(187)
Net assets, fair value	2,234	2,166
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	1,893	1,867
Net assets, fair value	1,893	1,867
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	3
Assets, fair value disclosure	499	486
Derivative liabilities	(155)	(187)
Net assets, fair value	344	299
Progress Energy [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(3)
Net assets, fair value	(3)
Progress Energy [Member] | NDTF [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,641	1,615
Progress Energy [Member] | NDTF [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,641	1,615
Progress Energy [Member] | NDTF [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	691	677
Progress Energy [Member] | NDTF [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	236	233
Progress Energy [Member] | NDTF [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	455	444
Progress Energy [Member] | Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	56	58
Progress Energy [Member] | Other Classification [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	16	19
Progress Energy [Member] | Other Classification [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	40	39
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Assets, fair value disclosure	1,570	1,543
Derivative liabilities	(58)	(66)
Net assets, fair value	1,512	1,477
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	1,240	1,209
Net assets, fair value	1,240	1,209
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Assets, fair value disclosure	330	334
Derivative liabilities	(55)	(66)
Net assets, fair value	275	268
Duke Energy Progress [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(3)
Net assets, fair value	(3)
Duke Energy Progress [Member] | NDTF [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,088	1,069
Duke Energy Progress [Member] | NDTF [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,088	1,069
Duke Energy Progress [Member] | NDTF [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	481	470
Duke Energy Progress [Member] | NDTF [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	152	137
Duke Energy Progress [Member] | NDTF [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	329	333
Duke Energy Progress [Member] | Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Duke Energy Progress [Member] | Other Classification [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	1
Assets, fair value disclosure	808	801
Derivative liabilities	(99)	(116)
Net assets, fair value	709	685
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	639	644
Net assets, fair value	639	644
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	1
Assets, fair value disclosure	169	157
Derivative liabilities	(99)	(116)
Net assets, fair value	70	41
Duke Energy Florida [Member] | NDTF [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	553	546
Duke Energy Florida [Member] | NDTF [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	553	546
Duke Energy Florida [Member] | NDTF [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	210	214
Duke Energy Florida [Member] | NDTF [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	84	96
Duke Energy Florida [Member] | NDTF [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	126	118
Duke Energy Florida [Member] | Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	42	40
Duke Energy Florida [Member] | Other Classification [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2	2
Duke Energy Florida [Member] | Other Classification [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	40	38
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	63	96
Derivative liabilities	(113)	(95)
Net assets, fair value	(50)	1
Duke Energy Ohio [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	31	50
Derivative liabilities	(33)	(1)
Net assets, fair value	(2)	49
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	25	21
Derivative liabilities	(54)	(65)
Net assets, fair value	(29)	(44)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	25
Derivative liabilities	(26)	(29)
Net assets, fair value	(19)	(4)
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	12
Assets, fair value disclosure	103	106
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Assets, fair value disclosure	67	65
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	29	29
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	12
Assets, fair value disclosure	7	12
Duke Energy Indiana [Member] | Other Classification [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	66	65
Duke Energy Indiana [Member] | Other Classification [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	66	65
Duke Energy Indiana [Member] | Other Classification [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	29	29
Duke Energy Indiana [Member] | Other Classification [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 29	$ 29