Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2018

Defined Benefit Plan Disclosure [Line Items]

Defined Contribution Plan Disclosures

The following table includes employer contributions made by Duke Energy and expensed by the Subsidiary Registrants.

			Duke				Duke		Duke		Duke		Duke
	Duke		Energy		Progress		Energy		Energy		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida		Ohio		Indiana		Piedmont
Three Months Ended September 30,
2018	$	49	$	15	$	13	$	9	$	4	$	—	$	3	$	4
2017	43		14		12		9		4		1		2		2
Nine Months Ended September 30,
2018	$	167	$	53	$	45	$	31	$	14	$	2	$	8	$	10
2017	147		49		42		30		13		3		7		5

Qualified Pension Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Defined Benefit Plans Disclosures

The following table presents contributions made by the Duke Energy Registrants to their qualified defined benefit pension plans during the nine months ended September 30, 2018.

			Duke				Duke		Duke		Duke
	Duke		Energy		Progress		Energy		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida		Indiana
Contributions	$	141	$	46	$	45	$	25	$	20	$	8

Components of Net Periodic Pension Costs

The following tables include the components of net periodic pension costs for qualified pension plans.

	Three Months Ended September 30, 2018
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana			Piedmont
Service cost	$	47		$	15		$	13		$	7		$	5		$	2		$	2		$	2
Interest cost on projected benefit obligation	74			18			24			10			13			4			6			3
Expected return on plan assets	(140		)	(37		)	(45		)	(21		)	(23		)	(7		)	(10		)	(6		)
Amortization of actuarial loss	33			7			11			6			6			1			2			3
Amortization of prior service credit	(8		)	(2		)	(1		)	—			—			—			—			(3		)
Net periodic pension costs	$	6		$	1		$	2		$	2		$	1		$	—		$	—		$	(1	)

	Three Months Ended September 30, 2017
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana			Piedmont
Service cost	$	40		$	12		$	12		$	6		$	5		$	1		$	2		$	3
Interest cost on projected benefit obligation	82			20			25			12			13			4			7			3
Expected return on plan assets	(136		)	(35		)	(43		)	(21		)	(21		)	(7		)	(11		)	(6		)
Amortization of actuarial loss	36			8			14			6			7			1			3			3
Amortization of prior service credit	(6		)	(2		)	(1		)	—			—			—			—			(1		)
Other	2			—			1			—			—			—			—			—
Net periodic pension costs	$	18		$	3		$	8		$	3		$	4		$	(1	)	$	1		$	2

	Nine Months Ended September 30, 2018
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana			Piedmont
Service cost	$	137		$	45		$	39		$	22		$	16		$	4		$	7		$	6
Interest cost on projected benefit obligation	224			54			70			31			38			13			18			9
Expected return on plan assets	(420		)	(111		)	(133		)	(63		)	(69		)	(21		)	(31		)	(18		)
Amortization of actuarial loss	99			21			33			16			18			3			6			9
Amortization of prior service credit	(24		)	(6		)	(3		)	(1		)	(1		)	—			—			(9		)
Net periodic pension costs	$	16		$	3		$	6		$	5		$	2		$	(1	)	$	—		$	(3	)

	Nine Months Ended September 30, 2017
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana			Piedmont
Service cost	$	120		$	36		$	36		$	18		$	15		$	3		$	6		$	9
Interest cost on projected benefit obligation	246			60			75			36			39			14			21			9
Expected return on plan assets	(408		)	(106		)	(129		)	(63		)	(63		)	(21		)	(33		)	(18		)
Amortization of actuarial loss	108			24			42			18			21			3			9			9
Amortization of prior service credit	(18		)	(6		)	(3		)	—			—			—			—			(3		)
Other	6			—			3			1			—			—			—			1
Net periodic pension costs	$	54		$	8		$	24		$	10		$	12		$	(1	)	$	3		$	7

Non-Qualified Pension Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Components of Net Periodic Pension Costs

The following tables include the components of net periodic pension costs for non-qualified pension plans for registrants with non-qualified pension costs.

	Three Months Ended September 30, 2018
			Duke				Duke		Duke
	Duke		Energy		Progress		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida
Interest cost on projected benefit obligation	$	3	$	—	$	1	$	—	$	—
Amortization of actuarial loss	2		—		—		—		—
Net periodic pension costs	$	5	$	—	$	1	$	—	$	—

	Three Months Ended September 30, 2017
			Duke				Duke		Duke
	Duke		Energy		Progress		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida
Interest cost on projected benefit obligation	$	4	$	—	$	1	$	1	$	1
Amortization of actuarial loss	2		—		1		—		—
Net periodic pension costs	$	6	$	—	$	2	$	1	$	1

	Nine Months Ended September 30, 2018
				Duke				Duke		Duke
	Duke			Energy		Progress		Energy		Energy
(in millions)	Energy			Carolinas		Energy		Progress		Florida
Service cost	$	1		$	1	$	—	$	—	$	—
Interest cost on projected benefit obligation	9			—		3		1		1
Amortization of actuarial loss	6			—		—		—		—
Amortization of prior service (credit) cost	(1		)	—		1		—		—
Net periodic pension costs	$	15		$	1	$	4	$	1	$	1

	Nine Months Ended September 30, 2017
			Duke				Duke		Duke
	Duke		Energy		Progress		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida
Interest cost on projected benefit obligation	$	10	$	1	$	3	$	2	$	2
Amortization of actuarial loss	6		—		3		—		—
Net periodic pension costs	$	16	$	1	$	6	$	2	$	2

Other Post-Retirement Benefit Plans [Member]

Defined Benefit Plan Disclosure [Line Items]

Components of Net Periodic Pension Costs

The following tables include the components of net periodic other post-retirement benefit costs.

	Three Months Ended September 30, 2018
				Duke						Duke		Duke			Duke		Duke
	Duke			Energy			Progress			Energy		Energy			Energy		Energy
(in millions)	Energy			Carolinas			Energy			Progress		Florida			Ohio		Indiana		Piedmont
Service cost	$	2		$	—		$	—		$	—	$	—		$	—	$	—	$	—
Interest cost on accumulated post-retirement benefit obligation	7			2			3			2		1			—		1		—
Expected return on plan assets	(4		)	(2		)	—			—		—			—		—		—
Amortization of actuarial loss	2			1			—			—		—			—		1		—
Amortization of prior service credit	(5		)	(1		)	(2		)	—		(1		)	—		—		—
Net periodic other post-retirement benefit costs	$	2		$	—		$	1		$	2	$	—		$	—	$	2	$	—

	Three Months Ended September 30, 2017
				Duke						Duke			Duke			Duke		Duke
	Duke			Energy			Progress			Energy			Energy			Energy		Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio		Indiana		Piedmont
Service cost	$	1		$	—		$	—		$	—		$	—		$	—	$	—	$	—
Interest cost on accumulated post-retirement benefit obligation	9			2			4			2			2			—		1		—
Expected return on plan assets	(3		)	(2		)	—			—			—			—		—		—
Amortization of actuarial loss	2			—			5			3			2			—		—		—
Amortization of prior service credit	(29		)	(2		)	(21		)	(14		)	(8		)	—		—		—
Net periodic other post-retirement benefit costs	$	(20	)	$	(2	)	$	(12	)	$	(9	)	$	(4	)	$	—	$	1	$	—

	Nine Months Ended September 30, 2018
				Duke						Duke		Duke			Duke		Duke
	Duke			Energy			Progress			Energy		Energy			Energy		Energy
(in millions)	Energy			Carolinas			Energy			Progress		Florida			Ohio		Indiana		Piedmont
Service cost	$	5		$	1		$	—		$	—	$	—		$	—	$	—	$	—
Interest cost on accumulated post-retirement benefit obligation	21			5			9			5		4			1		3		—
Expected return on plan assets	(10		)	(6		)	—			—		—			—		—		—
Amortization of actuarial loss	5			2			1			—		—			—		3		—
Amortization of prior service credit	(15		)	(3		)	(6		)	—		(4		)	—		—		(1		)
Net periodic other post-retirement benefit costs	$	6		$	(1	)	$	4		$	5	$	—		$	1	$	6	$	(1	)

	Nine Months Ended September 30, 2017
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana		Piedmont
Service cost	$	3		$	—		$	—		$	—		$	—		$	—		$	—	$	—
Interest cost on accumulated post-retirement benefit obligation	27			6			11			6			6			—			1		—
Expected return on plan assets	(10		)	(6		)	—			—			—			—			—		—
Amortization of actuarial loss (gain)	6			(2		)	15			9			6			(1		)	—		—
Amortization of prior service credit	(87		)	(6		)	(63		)	(41		)	(23		)	—			—		—
Net periodic other post-retirement benefit costs	$	(61	)	$	(8	)	$	(37	)	$	(26	)	$	(11	)	$	(1	)	$	1	$	—