Commitments and Contingencies (Table)

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts Disclosure [Line Items]

Schedule of Additional Possible Losses in Excess of Recorded Environmental Reserves

Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below.

(in millions)
Duke Energy	$	56
Duke Energy Carolinas	19
Duke Energy Ohio	30
Piedmont	2

Schedule of Legal Reserves

The table below presents recorded reserves based on management’s best estimate of probable loss for legal matters, excluding asbestos-related reserves and the exit obligation discussed above related to the termination of an EPC contract. Reserves are classified on the Consolidated Balance Sheets in Other within Other Noncurrent Liabilities and Accounts payable and Other within Current Liabilities. The reasonably possible range of loss in excess of recorded reserves is not material, other than as described above.

	December 31,
(in millions)	2017		2016
Reserves for Legal Matters
Duke Energy	$	88	$	98
Duke Energy Carolinas	30		23
Progress Energy	55		59
Duke Energy Progress	13		14
Duke Energy Florida	24		28
Duke Energy Ohio	—		4
Piedmont	2		2

Schedule of Purchase Power Obligations

The following table presents executory purchased power contracts with terms exceeding one year, excluding contracts classified as leases. Amounts at Duke Energy Ohio were immaterial.

		Minimum Purchase Amount at December 31, 2017
	Contract
(in millions)	Expiration	2018		2019		2020		2021		2022		Thereafter		Total
Duke Energy Progress(a)	2019-2031	$	68	$	68	$	51	$	52	$	30	$	239	$	508
Duke Energy Florida(b)	2021-2043	357		374		394		378		376		770		2,649

(a)    Contracts represent between 15 percent and 100 percent of net plant output.

(b)     Contracts represent between 81 percent and 100 percent of net plant output.

Schedule of Natural Gas Supply Contract Commitments [Table Text Block]

The following table presents future unconditional purchase obligations under natural gas supply and capacity contracts as of December 31, 2017.

(in millions)	Duke Energy		Duke Energy Ohio		Piedmont
2018	$	314	$	37	$	277
2019	280		28		252
2020	252		25		227
2021	249		26		223
2022	226		11		215
Thereafter	1,121		3		1,118
Total	$	2,442	$	130	$	2,312

Schedule of Operating Lease Rent Expense

The following tables present rental expense for operating leases. These amounts are included in Operation, maintenance and other on the Consolidated Statements of Operations.

	Years Ended December 31,
(in millions)	2017		2016		2015
Duke Energy	$	241	$	242	$	313
Duke Energy Carolinas	44		45		41
Progress Energy	130		140		230
Duke Energy Progress	75		68		149
Duke Energy Florida	55		72		81
Duke Energy Ohio	15		16		13
Duke Energy Indiana	23		23		20

	Year Ended		Two Months Ended		Years Ended October 31,
(in millions)	December 31, 2017		December 31, 2016		2016		2015
Piedmont	$	7	$	1	$	5	$	5

Schedule of Future Minimum Rental Payments for Operating Leases

The following table presents future minimum lease payments under operating leases, which at inception had a non-cancelable term of more than one year.

	December 31, 2017
			Duke				Duke		Duke		Duke		Duke
	Duke		Energy		Progress		Energy		Energy		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida		Ohio		Indiana		Piedmont
2018	$	233	$	36	$	133	$	77	$	56	$	20	$	22	$	6
2019	203		29		126		72		54		12		14		5
2020	183		25		117		62		55		10		10		5
2021	150		19		97		48		49		7		8		6
2022	135		16		90		42		48		4		5		6
Thereafter	882		52		525		344		181		5		7		16
Total	$	1,786	$	177	$	1,088	$	645	$	443	$	58	$	66	$	44

Schedule of Future Minimum Lease Payments for Capital Leases

The following table presents future minimum lease payments under capital leases.

	December 31, 2017
				Duke						Duke			Duke			Duke		Duke
	Duke			Energy			Progress			Energy			Energy			Energy		Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio		Indiana
2018	$	168		$	13		$	46		$	21		$	25		$	3	$	2
2019	169			13			45			20			25			1		1
2020	174			13			47			21			26			—		1
2021	176			8			45			22			25			—		1
2022	169			8			45			21			24			—		1
Thereafter	745			109			323			227			95			—		38
Minimum annual payments	1,601			164			551			332			220			4		44
Less: amount representing interest	(601		)	(103		)	(283		)	(192		)	(91		)	—		(33		)
Total	$	1,000		$	61		$	268		$	140		$	129		$	4	$	11

Reserve for Environmental Costs [Member]

Valuation and Qualifying Accounts Disclosure [Line Items]

Schedule of Legal Reserves

The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Consolidated Balance Sheets.

				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana
Balance at December 31, 2014	$	92		$	10		$	17		$	5		$	12		$	54		$	10
Provisions/adjustments	11			1			4			—			4			1			5
Cash reductions	(9		)	(1		)	(4		)	(2		)	(2		)	(1		)	(3		)
Balance at December 31, 2015	94			10			17			3			14			54			12
Provisions/adjustments	19			4			7			2			4			7			1
Cash reductions	(15		)	(4		)	(6		)	(2		)	(4		)	(2		)	(3		)
Balance at December 31, 2016	98			10			18			3			14			59			10
Provisions/adjustments	8			3			3			2			2			3			(4		)
Cash reductions	(25		)	(3		)	(6		)	(2		)	(4		)	(15		)	(1		)
Balance at December 31, 2017	$	81		$	10		$	15		$	3		$	12		$	47		$	5

As of December 31, 2016, October 31, 2016, 2015 and 2014, Piedmont's environmental reserve was $1 million. In 2017, a $1 million provision was recorded, resulting in a reserve balance of $2 million at December 31, 2017.