Income Taxes (Deferred Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Jun. 30, 2017	Sep. 30, 2016	Jul. 31, 2016	Sep. 30, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						$ 143	$ 382
Capital lease obligations						49	60
Pension, postretirement and other employee benefits						295	561
Progress Energy merger purchase accounting adjustments						536	918
Tax credits and NOL carryforwards						4,527	4,682
Other						73	205
Valuation allowance						(519)	(96)
Total deferred income tax assets						5,104	6,712
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(1,419)	(1,892)
Accelerated depreciation rates						(9,216)	(14,872)
Regulatory assets and deferred debits, net						(1,090)	(4,103)
Total deferred income tax liabilities						(11,725)	(20,867)
Net deferred income tax liabilities						(6,621)	(14,155)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						8,982
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						4,527	4,682
Valuation allowance						(519)	(96)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						$ (6,621)	$ (14,155)
State [Member] | January 2015 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate								5.00%
State [Member] | January 2016 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate							4.00%
Net reduction in deferred tax liability				$ 95
State [Member] | January 2017 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate						3.00%
Net reduction in deferred tax liability		$ 80
State [Member] | Tax Year 2019 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Statutory Tax Rate						2.50%
Net reduction in deferred tax liability	$ 55
Investment Tax Credits [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,406
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						$ 1,406
Investment Tax Credits [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2024
Investment Tax Credits [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2037
Alternative Minimum Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,147
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						1,147
NOL Carryforwards [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						393
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						$ 393
NOL Carryforwards [Member] | Federal [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2022
NOL Carryforwards [Member] | Federal [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2036
NOL Carryforwards [Member] | State [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 296
Valuation allowance						(90)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						296
Valuation allowance						$ (90)
NOL Carryforwards [Member] | State [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2018
NOL Carryforwards [Member] | State [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2037
NOL Carryforwards [Member] | Foreign Jurisdictions [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 13
Valuation allowance						(13)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						13
Valuation allowance						$ (13)
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2027
NOL Carryforwards [Member] | Foreign Jurisdictions [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2036
Foreign Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards						$ 1,272
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						1,272
Foreign Tax Credit [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Valuation allowance						(416)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Valuation allowance						$ (416)
Foreign Tax Credit [Member] | Foreign Jurisdictions [Member] | Minimum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2024
Foreign Tax Credit [Member] | Foreign Jurisdictions [Member] | Maximum [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Expiration year						Dec. 31, 2027
Duke Energy Carolinas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						$ 33	$ 66
Capital lease obligations						14	8
Pension, postretirement and other employee benefits						(17)	16
Tax credits and NOL carryforwards						234	192
Regulatory liabilities and deferred credits						222
Other						10	16
Total deferred income tax assets						496	298
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(849)	(1,149)
Accelerated depreciation rates						(3,060)	(4,664)
Regulatory assets and deferred debits, net							(1,029)
Total deferred income tax liabilities						(3,909)	(6,842)
Net deferred income tax liabilities						(3,413)	(6,544)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						3,454
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						234	192
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(3,413)	(6,544)
Progress Energy [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						78	126
Pension, postretirement and other employee benefits						111	199
Tax credits and NOL carryforwards						402	1,165
Other						1	35
Valuation allowance						(14)	(12)
Total deferred income tax assets						578	1,513
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(470)	(597)
Accelerated depreciation rates						(2,803)	(4,490)
Regulatory assets and deferred debits, net						(807)	(1,672)
Total deferred income tax liabilities						(4,080)	(6,759)
Net deferred income tax liabilities						(3,502)	(5,246)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						3,282
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						402	1,165
Valuation allowance						(14)	(12)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(3,502)	(5,246)
Duke Energy Progress [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						23	40
Pension, postretirement and other employee benefits						44	91
Tax credits and NOL carryforwards						156	222
Other						4	8
Total deferred income tax assets						227	361
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(289)	(313)
Accelerated depreciation rates						(1,583)	(2,479)
Regulatory assets and deferred debits, net						(238)	(892)
Total deferred income tax liabilities						(2,110)	(3,684)
Net deferred income tax liabilities						(1,883)	(3,323)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,882
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						156	222
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(1,883)	(3,323)
Duke Energy Florida [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						49	93
Pension, postretirement and other employee benefits						60	96
Tax credits and NOL carryforwards						143	232
Total deferred income tax assets						252	421
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(187)	(297)
Accelerated depreciation rates						(1,257)	(2,038)
Regulatory assets and deferred debits, net						(569)	(780)
Total deferred income tax liabilities						(2,013)	(3,115)
Net deferred income tax liabilities						(1,761)	(2,694)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,420
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						143	232
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(1,761)	(2,694)
Duke Energy Ohio [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						11	21
Pension, postretirement and other employee benefits						14	22
Tax credits and NOL carryforwards						25	49
Regulatory liabilities and deferred credits						65
Investments and other assets							3
Other							5
Total deferred income tax assets						115	100
Deferred Tax Liabilities, Gross [Abstract]
Accelerated depreciation rates						(896)	(1,404)
Regulatory assets and deferred debits, net							(139)
Total deferred income tax liabilities						(896)	(1,543)
Net deferred income tax liabilities						(781)	(1,443)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						771
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						25	49
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(781)	(1,443)
Duke Energy Indiana [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						6	4
Capital lease obligations						2	1
Pension, postretirement and other employee benefits						18	37
Tax credits and NOL carryforwards						216	278
Investments and other assets						1
Other							9
Total deferred income tax assets						243	329
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets						(14)	(21)
Accelerated depreciation rates						(966)	(1,938)
Regulatory assets and deferred debits, net						(188)	(270)
Total deferred income tax liabilities						(1,168)	(2,229)
Net deferred income tax liabilities						(925)	(1,900)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						1,053
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						216	278
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						(925)	(1,900)
Piedmont Natural Gas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities						(5)	71
Pension, postretirement and other employee benefits						(4)	10
Tax credits and NOL carryforwards						70	192
Regulatory liabilities and deferred credits						61
Investments and other assets						18
Other							45
Valuation allowance							(1)
Total deferred income tax assets						140	317
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets							(21)
Accelerated depreciation rates						(697)	(1,080)
Regulatory assets and deferred debits, net							(147)
Other						(7)
Total deferred income tax liabilities						(704)	(1,248)
Net deferred income tax liabilities						(564)	(931)
Decrease In Deferred Taxes As A Result Of Tax Legislation Change						521
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards						70	192
Valuation allowance							(1)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities						$ (564)	$ (931)
Piedmont Natural Gas [Member] | State [Member] | January 2016 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Net reduction in deferred tax liability					$ 18
Piedmont Natural Gas [Member] | State [Member] | January 2017 [Member] | North Carolina Department of Revenue [Member]
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Net reduction in deferred tax liability			$ 16