Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 52us-gaap_DerivativeAssets	$ 110us-gaap_DerivativeAssets
Assets, fair value disclosure	5,943us-gaap_AssetsFairValueDisclosure	6,018us-gaap_AssetsFairValueDisclosure
Derivative liabilities	(625)us-gaap_DerivativeLiabilities	(668)us-gaap_DerivativeLiabilities
Net assets, fair value	5,318us-gaap_FairValueNetAssetLiability	5,350us-gaap_FairValueNetAssetLiability
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	49
Assets, fair value disclosure	4,196	4,327
Derivative liabilities	(119)	(162)
Net assets, fair value	4,077	4,165
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	22	24
Assets, fair value disclosure	1,555	1,498
Derivative liabilities	(497)	(468)
Net assets, fair value	1,058	1,030
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	23	37
Assets, fair value disclosure	192	193
Derivative liabilities	(9)	(38)
Net assets, fair value	183	155
Equity Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,643	3,650
Equity Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,476	3,493
Equity Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	6
Equity Securities [Member] \| Ndtf [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	164	151
Equity Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	98	96
Equity Securities [Member] \| Other Classification [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	98	96
Debt Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,827	1,899
Debt Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	542	648
Debt Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,285	1,251
Debt Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	323	263
Debt Securities [Member] \| Other Classification [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	73	41
Debt Securities [Member] \| Other Classification [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	245	217
Debt Securities [Member] \| Other Classification [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	5	5
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	3,015	3,035
Derivative liabilities	(27)	(19)
Net assets, fair value	2,988	3,016
Duke Energy Carolinas [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,091	2,143
Net assets, fair value	2,091	2,143
Duke Energy Carolinas [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	757	738
Derivative liabilities	(27)	(19)
Net assets, fair value	730	719
Duke Energy Carolinas [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	167	154
Net assets, fair value	167	154
Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,127	2,162
Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,960	2,005
Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	6
Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	164	151
Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	885	870
Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	131	138
Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	754	732
Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Other Classification [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	6	4
Assets, fair value disclosure	2,524	2,579
Derivative liabilities	(395)	(373)
Net assets, fair value	2,129	2,206
Progress Energy [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	1,943	2,013
Net assets, fair value	1,943	2,013
Progress Energy [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	4
Assets, fair value disclosure	581	566
Derivative liabilities	(395)	(373)
Net assets, fair value	186	193
Progress Energy [Member] \| Equity Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,516	1,488
Progress Energy [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,516	1,488
Progress Energy [Member] \| Debt Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	942	1,029
Progress Energy [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	411	510
Progress Energy [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	531	519
Progress Energy [Member] \| Debt Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	60	58
Progress Energy [Member] \| Debt Securities [Member] \| Other Classification [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	16	15
Progress Energy [Member] \| Debt Securities [Member] \| Other Classification [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	44	43
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2
Assets, fair value disclosure	1,742	1,711
Derivative liabilities	(131)	(132)
Net assets, fair value	1,611	1,579
Duke Energy Progress [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	1,335	1,322
Net assets, fair value	1,335	1,322
Duke Energy Progress [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2
Assets, fair value disclosure	407	389
Derivative liabilities	(131)	(132)
Net assets, fair value	276	257
Duke Energy Progress [Member] \| Equity Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,194	1,171
Duke Energy Progress [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,194	1,171
Duke Energy Progress [Member] \| Debt Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	545	540
Duke Energy Progress [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	140	151
Duke Energy Progress [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	405	389
Duke Energy Progress [Member] \| Debt Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1
Duke Energy Progress [Member] \| Debt Securities [Member] \| Other Classification [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	4
Assets, fair value disclosure	767	854
Derivative liabilities	(264)	(241)
Net assets, fair value	503	613
Duke Energy Florida [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	593	676
Net assets, fair value	593	676
Duke Energy Florida [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	4
Assets, fair value disclosure	174	178
Derivative liabilities	(264)	(241)
Net assets, fair value	(90)	(63)
Duke Energy Florida [Member] \| Equity Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	322	317
Duke Energy Florida [Member] \| Equity Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	322	317
Duke Energy Florida [Member] \| Debt Securities [Member] \| Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	397	489
Duke Energy Florida [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	271	359
Duke Energy Florida [Member] \| Debt Securities [Member] \| Ndtf [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	126	130
Duke Energy Florida [Member] \| Debt Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	44	44
Duke Energy Florida [Member] \| Debt Securities [Member] \| Other Classification [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	44	44
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	44	49
Derivative liabilities	(134)	(181)
Net assets, fair value	(90)	(132)
Duke Energy Ohio [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	20	20
Derivative liabilities	(108)	(117)
Net assets, fair value	(88)	(97)
Duke Energy Ohio [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	9
Derivative liabilities	(17)	(26)
Net assets, fair value	(9)	(17)
Duke Energy Ohio [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	16	20
Derivative liabilities	(9)	(38)
Net assets, fair value	7	(18)
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	14
Net assets, fair value	106	115
Duke Energy Indiana [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net assets, fair value	73	71
Duke Energy Indiana [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net assets, fair value	30	30
Duke Energy Indiana [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	14
Net assets, fair value	3	14
Duke Energy Indiana [Member] \| Equity Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale equity securities	73	71
Duke Energy Indiana [Member] \| Equity Securities [Member] \| Other Classification [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale equity securities	73	71
Duke Energy Indiana [Member] \| Debt Securities [Member] \| Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale debt securities	30	30
Duke Energy Indiana [Member] \| Debt Securities [Member] \| Other Classification [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale debt securities	$ 30	$ 30

Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) (USD $)
In Millions, unless otherwise specified

Mar. 31, 2015

Dec. 31, 2014

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Derivative assets

$ 52

$ 110

Assets, fair value disclosure

5,943

6,018

Derivative liabilities

(625)