Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 110us-gaap_DerivativeAssets	$ 145us-gaap_DerivativeAssets
Assets, fair value disclosure	6,018us-gaap_AssetsFairValueDisclosure	5,712us-gaap_AssetsFairValueDisclosure
Derivative liabilities	(668)us-gaap_DerivativeLiabilities	(321)us-gaap_DerivativeLiabilities
Net assets, fair value	5,350us-gaap_FairValueNetAssetLiability	5,391us-gaap_FairValueNetAssetLiability
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	49	33
Assets, fair value disclosure	4,327	4,057
Derivative liabilities	(162)	11
Net assets, fair value	4,165	4,068
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	24	70
Assets, fair value disclosure	1,498	1,515
Derivative liabilities	(468)	(303)
Net assets, fair value	1,030	1,212
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	37	42
Assets, fair value disclosure	193	140
Derivative liabilities	(38)	(29)
Net assets, fair value	155	111
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	3,035	2,837
Derivative liabilities	(19)	(2)
Net assets, fair value	3,016	2,835
Duke Energy Carolinas [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,143	2,047
Net assets, fair value	2,143	2,047
Duke Energy Carolinas [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	738	709
Derivative liabilities	(19)
Net assets, fair value	719	709
Duke Energy Carolinas [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	154	81
Derivative liabilities		(2)
Net assets, fair value	154	79
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	3
Assets, fair value disclosure	2,579	2,353
Derivative liabilities	(373)	(187)
Net assets, fair value	2,206	2,166
Progress Energy [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	2,013	1,867
Net assets, fair value	2,013	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	566	486
Derivative liabilities	(373)	(187)
Net assets, fair value	193	299
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		1
Assets, fair value disclosure	1,711	1,543
Derivative liabilities	(132)	(66)
Net assets, fair value	1,579	1,477
Duke Energy Progress [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	1,322	1,209
Net assets, fair value	1,322	1,209
Duke Energy Progress [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		1
Assets, fair value disclosure	389	334
Derivative liabilities	(132)	(66)
Net assets, fair value	257	268
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Assets, fair value disclosure	854	801
Derivative liabilities	(241)	(116)
Net assets, fair value	613	685
Duke Energy Florida [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	676	644
Net assets, fair value	676	644
Duke Energy Florida [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Assets, fair value disclosure	178	157
Derivative liabilities	(241)	(116)
Net assets, fair value	(63)	41
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	49	96
Derivative liabilities	(181)	(95)
Net assets, fair value	(132)	1
Duke Energy Ohio [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	20	50
Derivative liabilities	(117)	(1)
Net assets, fair value	(97)	49
Duke Energy Ohio [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	9	21
Derivative liabilities	(26)	(65)
Net assets, fair value	(17)	(44)
Duke Energy Ohio [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	20	25
Derivative liabilities	(38)	(29)
Net assets, fair value	(18)	(4)
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	14	12
Net assets, fair value	115	106
Duke Energy Indiana [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net assets, fair value	71	65
Duke Energy Indiana [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net assets, fair value	30	29
Duke Energy Indiana [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	14	12
Net assets, fair value	14	12
NDTF [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,650	3,579
NDTF [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,493	3,495
NDTF [Member] \| Equity Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	6	57
NDTF [Member] \| Equity Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	151	27
NDTF [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,899	1,553
NDTF [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	648	402
NDTF [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,251	1,100
NDTF [Member] \| Debt Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		51
NDTF [Member] \| Duke Energy Carolinas [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,162	1,964
NDTF [Member] \| Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2,005	1,879
NDTF [Member] \| Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	6	58
NDTF [Member] \| Duke Energy Carolinas [Member] \| Equity Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	151	27
NDTF [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	870	870
NDTF [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	138	168
NDTF [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	732	651
NDTF [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		51
NDTF [Member] \| Progress Energy [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,488	1,615
NDTF [Member] \| Progress Energy [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,488	1,615
NDTF [Member] \| Progress Energy [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,029	677
NDTF [Member] \| Progress Energy [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	510	233
NDTF [Member] \| Progress Energy [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	519	444
NDTF [Member] \| Duke Energy Progress [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,171	1,069
NDTF [Member] \| Duke Energy Progress [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,171	1,069
NDTF [Member] \| Duke Energy Progress [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	540	470
NDTF [Member] \| Duke Energy Progress [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	151	137
NDTF [Member] \| Duke Energy Progress [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	389	333
NDTF [Member] \| Duke Energy Florida [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	317	546
NDTF [Member] \| Duke Energy Florida [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	317	546
NDTF [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	489	214
NDTF [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	359	96
NDTF [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	130	118
Other Classification [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	96	102
Other Classification [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	96	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	263	333
Other Classification [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	41	36
Other Classification [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	217	277
Other Classification [Member] \| Debt Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	5	20
Other Classification [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	3
Other Classification [Member] \| Duke Energy Carolinas [Member] \| Debt Securities [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3	3
Other Classification [Member] \| Progress Energy [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	58	58
Other Classification [Member] \| Progress Energy [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	15	19
Other Classification [Member] \| Progress Energy [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	43	39
Other Classification [Member] \| Duke Energy Progress [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Other Classification [Member] \| Duke Energy Progress [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		3
Other Classification [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	44	40
Other Classification [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2
Other Classification [Member] \| Duke Energy Florida [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	44	38
Other Classification [Member] \| Duke Energy Indiana [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, equity securities	71	65
Other Classification [Member] \| Duke Energy Indiana [Member] \| Equity Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, equity securities	71	65
Other Classification [Member] \| Duke Energy Indiana [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, debt securities	30	29
Other Classification [Member] \| Duke Energy Indiana [Member] \| Debt Securities [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, debt securities	$ 30	$ 29

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

Dec. 31, 2014

Dec. 31, 2013

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

Derivative assets

$ 110

$ 145

Assets, fair value disclosure

6,018

5,712

Derivative liabilities

(668)