Income Taxes (Deferred Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		$ 164	$ 143
Capital lease obligations		60	49
Pension, postretirement and other employee benefits		347	295
Progress Energy merger purchase accounting adjustments		483	536
Tax credits and NOL carryforwards		4,580	4,527
Other		25	73
Valuation allowance		(484)	(519)
Total deferred income tax assets		5,175	5,104
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(1,317)	(1,419)
Accelerated depreciation rates		(10,124)	(9,216)
Regulatory assets and deferred debits, net		(1,540)	(1,090)
Total deferred income tax liabilities		(12,981)	(11,725)
Net deferred income tax liabilities		(7,806)	(6,621)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		4,580	4,527
Valuation allowance		(484)	(519)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		$ (7,806)	(6,621)
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		$ 1,614
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		1,614
Alternative Minimum Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		574
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		574
NOL Carryforwards [Member] | Federal [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		788
Valuation allowance		(4)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		788
Valuation allowance		(4)
NOL Carryforwards [Member] | State [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		301
Valuation allowance		(85)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		301
Valuation allowance		(85)
NOL Carryforwards [Member] | Foreign Jurisdictions [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		12
Valuation allowance		(12)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		12
Valuation allowance		(12)
Foreign Tax Credit [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		1,271
Valuation allowance		(383)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		1,271
Valuation allowance		(383)
Charitable contribution carryforwards [Member]
Deferred Tax Assets, Gross [Abstract]
Tax credits and NOL carryforwards		20
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		20
Duke Energy Carolinas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		64	33
Capital lease obligations		26	14
Pension, postretirement and other employee benefits		24	(17)
Tax credits and NOL carryforwards		257	234
Regulatory liabilities and deferred credits			222
Other		6	10
Total deferred income tax assets		377	496
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(795)	(849)
Accelerated depreciation rates		(3,207)	(3,060)
Regulatory assets and deferred debits, net		(64)
Total deferred income tax liabilities		(4,066)	(3,909)
Net deferred income tax liabilities		(3,689)	(3,413)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		257	234
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(3,689)	(3,413)
Progress Energy [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		35	78
Pension, postretirement and other employee benefits		110	111
Tax credits and NOL carryforwards		693	402
Other		5	1
Valuation allowance			(14)
Total deferred income tax assets		843	578
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(430)	(470)
Accelerated depreciation rates		(3,369)	(2,803)
Regulatory assets and deferred debits, net		(985)	(807)
Total deferred income tax liabilities		(4,784)	(4,080)
Net deferred income tax liabilities		(3,941)	(3,502)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		693	402
Valuation allowance			(14)
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(3,941)	(3,502)
Duke Energy Progress [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		53	23
Pension, postretirement and other employee benefits		47	44
Tax credits and NOL carryforwards		215	156
Other		5	4
Total deferred income tax assets		320	227
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(272)	(289)
Accelerated depreciation rates		(1,735)	(1,583)
Regulatory assets and deferred debits, net		(432)	(238)
Total deferred income tax liabilities		(2,439)	(2,110)
Net deferred income tax liabilities		(2,119)	(1,883)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		215	156
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(2,119)	(1,883)
Duke Energy Florida [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities			49
Pension, postretirement and other employee benefits		58	60
Tax credits and NOL carryforwards		363	143
Total deferred income tax assets		421	252
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(163)	(187)
Accelerated depreciation rates		(1,670)	(1,257)
Regulatory assets and deferred debits, net		(574)	(569)
Total deferred income tax liabilities		(2,407)	(2,013)
Net deferred income tax liabilities		(1,986)	(1,761)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		363	143
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(1,986)	(1,761)
Duke Energy Ohio [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		17	11
Pension, postretirement and other employee benefits		16	14
Tax credits and NOL carryforwards		42	25
Regulatory liabilities and deferred credits		56	65
Investments and other assets		18
Other		1
Total deferred income tax assets		150	115
Deferred Tax Liabilities, Gross [Abstract]
Accelerated depreciation rates		(967)	(896)
Total deferred income tax liabilities		(967)	(896)
Net deferred income tax liabilities		(817)	(781)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		42	25
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(817)	(781)
Duke Energy Indiana [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		6	6
Capital lease obligations		2	2
Pension, postretirement and other employee benefits		24	18
Tax credits and NOL carryforwards		237	216
Investments and other assets			1
Other		(1)
Total deferred income tax assets		268	243
Deferred Tax Liabilities, Gross [Abstract]
Investments and other assets		(5)	(14)
Accelerated depreciation rates		(1,081)	(966)
Regulatory assets and deferred debits, net		(191)	(188)
Total deferred income tax liabilities		(1,277)	(1,168)
Net deferred income tax liabilities		(1,009)	(925)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		237	216
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		(1,009)	(925)
Piedmont Natural Gas [Member]
Deferred Tax Assets, Gross [Abstract]
Deferred credits and other liabilities		17	(5)
Pension, postretirement and other employee benefits		(1)	(4)
Tax credits and NOL carryforwards		110	70
Regulatory liabilities and deferred credits		48	61
Investments and other assets		16	18
Total deferred income tax assets		190	140
Deferred Tax Liabilities, Gross [Abstract]
Accelerated depreciation rates		(733)	(697)
Other		(8)	(7)
Total deferred income tax liabilities		(741)	(704)
Net deferred income tax liabilities		(551)	(564)
Components and Expiration Dates of Tax Credits and NOL Carryforwards [Abstract]
Tax credits and NOL carryforwards		110	70
Classification of Deferred Tax Assets (Liabiliities) in the Consolidated Balance Sheets [Abstract]
Net deferred income tax liabilities		$ (551)	$ (564)