Debt and Credit Facilities (Summary of Debt and Related Terms) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Unsecured Debt	$ 20,409,000,000	$ 17,812,000,000
Secured Debt	4,458,000,000	3,909,000,000
First mortgage bonds	23,529,000,000	21,879,000,000
Capital leases	1,000,000,000	1,100,000,000
Tax exempt bonds	941,000,000	1,053,000,000
Notes payable and commercial paper	2,788,000,000	3,112,000,000
Fair value hedge carrying value adjustment	6,000,000	6,000,000
Unamortized debt discount and premium, net	1,582,000,000	1,753,000,000
Unamortized debt issuance costs	(271,000,000)	(242,000,000)
Total debt	54,442,000,000	50,382,000,000
Short-term notes payable and commercial paper	(2,163,000,000)	(2,487,000,000)
Current maturities of long-term debt	(3,244,000,000)	(2,319,000,000)
Total long-term debt	$ 49,035,000,000	$ 45,576,000,000
Weighted-average rate	4.09%	4.07%
Short term obligations classified as long-term debt	$ 937,000,000	$ 972,000,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2073	Dec. 31, 2073
Weighted-average rate	4.17%	4.30%
Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2037	Dec. 31, 2037
Weighted-average rate	3.15%	2.60%
First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2047	Dec. 31, 2046
Weighted-average rate	4.51%	4.61%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2018	Dec. 31, 2018
Debt Instrument, Maturity Date Range, End	Dec. 31, 2051	Dec. 31, 2051
Weighted-average rate	4.55%	4.48%
Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2019	Dec. 31, 2017
Debt Instrument, Maturity Date Range, End	Dec. 31, 2041	Dec. 31, 2041
Weighted-average rate	3.23%	2.84%
Short term obligations classified as long-term debt	$ 312,000,000	$ 347,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	$ 625,000,000	$ 625,000,000
Notes Payable And Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted-average rate	1.57%	1.01%
Short term obligations classified as long-term debt	$ 625,000,000	$ 625,000,000
Weighted Average Days to Maturity	14 days	14 days
Parent Company [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 47,000,000	$ 53,000,000
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Unsecured Debt	1,150,000,000	1,150,000,000
Secured Debt	450,000,000	425,000,000
First mortgage bonds	7,959,000,000	7,410,000,000
Capital leases	61,000,000	22,000,000
Tax exempt bonds	243,000,000	355,000,000
Money pool borrowings	404,000,000	300,000,000
Fair value hedge carrying value adjustment	6,000,000	6,000,000
Unamortized debt discount and premium, net	(19,000,000)	(20,000,000)
Unamortized debt issuance costs	(47,000,000)	(45,000,000)
Total debt	10,207,000,000	9,603,000,000
Short-term money pool borrowings	(104,000,000)
Current maturities of long-term debt	(1,205,000,000)	(116,000,000)
Total long-term debt	8,898,000,000	9,487,000,000
Short term obligations classified as long-term debt	300,000,000	335,000,000
Duke Energy Carolinas [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt		35,000,000
Duke Energy Carolinas [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	300,000,000	300,000,000
Progress Energy [Member]
Debt Instrument [Line Items]
Unsecured Debt	3,950,000,000	3,551,000,000
Secured Debt	1,757,000,000	1,819,000,000
First mortgage bonds	11,801,000,000	10,800,000,000
Capital leases	269,000,000	285,000,000
Tax exempt bonds	48,000,000	48,000,000
Money pool borrowings	955,000,000	1,902,000,000
Unamortized debt discount and premium, net	(30,000,000)	(31,000,000)
Unamortized debt issuance costs	(108,000,000)	(104,000,000)
Total debt	18,642,000,000	18,270,000,000
Short-term money pool borrowings	(805,000,000)	(729,000,000)
Current maturities of long-term debt	(771,000,000)	(778,000,000)
Total long-term debt	17,066,000,000	16,763,000,000
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Secured Debt	300,000,000	300,000,000
First mortgage bonds	6,776,000,000	6,425,000,000
Capital leases	139,000,000	142,000,000
Tax exempt bonds	48,000,000	48,000,000
Money pool borrowings	390,000,000	150,000,000
Unamortized debt discount and premium, net	(16,000,000)	(16,000,000)
Unamortized debt issuance costs	(40,000,000)	(38,000,000)
Total debt	7,597,000,000	7,011,000,000
Short-term money pool borrowings	(240,000,000)
Current maturities of long-term debt	(3,000,000)	(452,000,000)
Total long-term debt	7,354,000,000	6,559,000,000
Short term obligations classified as long-term debt	150,000,000	150,000,000
Duke Energy Progress [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	150,000,000	150,000,000
Duke Energy Progress [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Capital leases	81,000,000	98,000,000
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Unsecured Debt	550,000,000	150,000,000
Secured Debt	1,457,000,000	1,519,000,000
First mortgage bonds	5,025,000,000	4,375,000,000
Capital leases	129,000,000	143,000,000
Money pool borrowings		297,000,000
Unamortized debt discount and premium, net	(10,000,000)	(10,000,000)
Unamortized debt issuance costs	(56,000,000)	(52,000,000)
Total debt	7,095,000,000	6,422,000,000
Short-term money pool borrowings		(297,000,000)
Current maturities of long-term debt	(768,000,000)	(326,000,000)
Total long-term debt	6,327,000,000	5,799,000,000
Duke Energy Florida [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Capital leases	603,000,000	670,000,000
Duke Energy Ohio [Member]
Debt Instrument [Line Items]
Unsecured Debt	900,000,000	810,000,000
First mortgage bonds	1,100,000,000	1,000,000,000
Capital leases	5,000,000	7,000,000
Tax exempt bonds	77,000,000	77,000,000
Money pool borrowings	54,000,000	41,000,000
Unamortized debt discount and premium, net	(33,000,000)	(28,000,000)
Unamortized debt issuance costs	(7,000,000)	(7,000,000)
Total debt	2,096,000,000	1,900,000,000
Short-term money pool borrowings	(29,000,000)	(16,000,000)
Current maturities of long-term debt	(3,000,000)	(1,000,000)
Total long-term debt	2,064,000,000	1,883,000,000
Short term obligations classified as long-term debt	52,000,000	52,000,000
Duke Energy Ohio [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	27,000,000	27,000,000
Duke Energy Ohio [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	25,000,000	25,000,000
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Unsecured Debt	411,000,000	415,000,000
First mortgage bonds	2,669,000,000	2,669,000,000
Capital leases	11,000,000	11,000,000
Tax exempt bonds	572,000,000	572,000,000
Money pool borrowings	311,000,000	150,000,000
Unamortized debt discount and premium, net	(9,000,000)	(9,000,000)
Unamortized debt issuance costs	(21,000,000)	(22,000,000)
Total debt	3,944,000,000	3,786,000,000
Short-term money pool borrowings	(161,000,000)	0
Current maturities of long-term debt	(3,000,000)	(3,000,000)
Total long-term debt	3,780,000,000	3,783,000,000
Short term obligations classified as long-term debt	435,000,000	435,000,000
Duke Energy Indiana [Member] | Tax Exempt Bonds [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	285,000,000	285,000,000
Duke Energy Indiana [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Short term obligations classified as long-term debt	150,000,000	150,000,000
Piedmont Natural Gas [Member]
Debt Instrument [Line Items]
Unsecured Debt	2,050,000,000	1,835,000,000
Money pool borrowings	364,000,000
Unamortized debt discount and premium, net	(1,000,000)	(1,000,000)
Unamortized debt issuance costs	(12,000,000)	(13,000,000)
Total debt	2,401,000,000	1,821,000,000
Short-term notes payable and commercial paper		(330,000,000)
Short-term money pool borrowings	(364,000,000)
Current maturities of long-term debt	(250,000,000)	(35,000,000)
Total long-term debt	1,787,000,000	$ 1,786,000,000
Piedmont Natural Gas [Member] | Notes Payable And Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted Average Days to Maturity		8 days
International Energy [Member] | Progress Energy [Member]
Debt Instrument [Line Items]
Money pool borrowings		$ 1,000,000,000
Piedmont Natural Gas [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt discount and premium, net	176,000,000	197,000,000
Progress Energy [Member] | Purchase Accounting Adjustments [Member]
Debt Instrument [Line Items]
Unamortized debt discount and premium, net	$ 1,509,000,000	$ 1,653,000,000