Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 14. See Note 15 for additional information related to investments by major security type for the Duke Energy Registrants.

	December 31, 2018
(in millions)	Total Fair Value			Level 1			Level 2			Level 3			Not Categorized
NDTF equity securities	$	4,475		$	4,410		$	—		$	—		$	65
NDTF debt securities	2,231			576			1,655			—			—
Other equity securities	99			99			—			—			—
Other debt securities	270			67			203			—			—
Derivative assets	57			4			25			28			—
Total assets	7,132			5,156			1,883			28			65
Derivative liabilities	(242		)	(11		)	(90		)	(141		)	—
Net assets (liabilities)	$	6,890		$	5,145		$	1,793		$	(113	)	$	65

	December 31, 2017
(in millions)	Total Fair Value			Level 1			Level 2			Level 3			Not Categorized
NDTF equity securities	$	4,914		$	4,840		$	—		$	—		$	74
NDTF debt securities	2,174			635			1,539			—			—
Other equity securities	123			123			—			—			—
Other debt securities	241			57			184			—			—
Derivative assets	51			3			20			28			—
Total assets	7,503			5,658			1,743			28			74
Derivative liabilities	(230		)	(2		)	(86		)	(142		)	—
Net assets (liabilities)	$	7,273		$	5,656		$	1,657		$	(114	)	$	74

Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs

The following tables provide reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements. Amounts included in earnings for derivatives are primarily included in Cost of natural gas on the Duke Energy Registrants' Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis.

	December 31, 2018			December 31, 2017
(in millions)	Derivatives (net)			Investments			Derivatives (net)			Total
Balance at beginning of period	$	(114	)	$	5		$	(166	)	$	(161	)
Total pretax realized or unrealized gains included in comprehensive income	—			1			—			1
Purchases, sales, issuances and settlements:
Purchases	57			—			55			55
Sales	—			(6		)	—			(6		)
Settlements	(57		)	—			(47		)	(47		)
Total gains included on the Consolidated Balance Sheet	1			—			44			44
Balance at end of period	$	(113	)	$	—		$	(114	)	$	(114	)

Quantitative Information Table - Level 3

The following tables include quantitative information about the Duke Energy Registrants' derivatives classified as Level 3.

	December 31, 2018
	Fair Value
Investment Type	(in millions)			Valuation Technique	Unobservable Input	Range
Duke Energy Ohio
FTRs	$	6		RTO auction pricing	FTR price – per MWh	$	1.19		–	$	4.59
Duke Energy Indiana
FTRs	22			RTO auction pricing	FTR price – per MWh	(2.07		)	–	8.27
Piedmont
Natural gas contracts	(141		)	Discounted cash flow	Forward natural gas curves — price per MMBtu	1.87			–	2.95
Duke Energy
Total Level 3 derivatives	$	(113	)

	December 31, 2017
	Fair Value
Investment Type	(in millions)			Valuation Technique	Unobservable Input	Range
Duke Energy Ohio
FTRs	$	1		RTO auction pricing	FTR price – per MWh	$	0.07		–	$	1.41
Duke Energy Indiana
FTRs	27			RTO auction pricing	FTR price – per MWh	(0.77		)	–	7.44
Piedmont
Natural gas contracts	(142		)	Discounted cash flow	Forward natural gas curves — price per MMBtu	2.10			–	2.88
Duke Energy
Total Level 3 derivatives	$	(114	)

Schedule of Long-term debt Fair Value

The fair value and book value of long-term debt, including current maturities, is summarized in the following table. Estimates determined are not necessarily indicative of amounts that could have been settled in current markets. Fair value of long-term debt uses Level 2 measurements.

	December 31, 2018				December 31, 2017
(in millions)	Book Value		Fair Value		Book Value		Fair Value
Duke Energy(a)	$	54,529	$	54,534	$	52,279	$	55,331
Duke Energy Carolinas	10,939		11,471		10,103		11,372
Progress Energy	18,911		19,885		17,837		20,000
Duke Energy Progress	8,204		8,300		7,357		7,992
Duke Energy Florida	7,321		7,742		7,095		7,953
Duke Energy Ohio	2,165		2,239		2,067		2,249
Duke Energy Indiana	3,782		4,158		3,783		4,464
Piedmont	2,138		2,180		2,037		2,209

(a) Book value of long-term debt includes $1.6 billion as of December 31, 2018, and $1.7 billion as of December 31, 2017, of unamortized debt discount and premium, net in purchase accounting adjustments related to the mergers with Progress Energy and Piedmont that are excluded from fair value of long-term debt.

Duke Energy Carolinas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018
(in millions)	Total Fair Value			Level 1		Level 2			Not Categorized
NDTF equity securities	$	2,484		$	2,419	$	—		$	65
NDTF debt securities	1,069			149		920			—
Derivative assets	3			—		3			—
Total assets	3,556			2,568		923			65
Derivative liabilities	(33		)	—		(33		)	—
Net assets	$	3,523		$	2,568	$	890		$	65

	December 31, 2017
(in millions)	Total Fair Value			Level 1			Level 2			Not Categorized
NDTF equity securities	$	2,692		$	2,618		$	—		$	74
NDTF debt securities	1,066			204			862			—
Derivative assets	2			—			2			—
Total assets	3,760			2,822			864			74
Derivative liabilities	(35		)	(1		)	(34		)	—
Net assets	$	3,725		$	2,821		$	830		$	74

Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs

The following table provides reconciliations of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements.

	Investments
	Year Ended December 31,
(in millions)	2017
Balance at beginning of period	$	3
Total pretax realized or unrealized gains included in comprehensive income	1
Purchases, sales, issuances and settlements:
Sales	(4		)
Balance at end of period	$	—

Progress Energy [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 2			Total Fair Value			Level 1			Level 2
NDTF equity securities	$	1,991		$	1,991	$	—		$	2,222		$	2,222		$	—
NDTF debt securities	1,162			427		735			1,108			431			677
Other debt securities	64			17		47			59			12			47
Derivative assets	4			—		4			3			1			2
Total assets	3,221			2,435		786			3,392			2,666			726
Derivative liabilities	(44		)	—		(44		)	(36		)	(1		)	(35		)
Net assets	$	3,177		$	2,435	$	742		$	3,356		$	2,665		$	691

Duke Energy Progress [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 2			Total Fair Value			Level 1			Level 2
NDTF equity securities	$	1,588		$	1,588	$	—		$	1,795		$	1,795		$	—
NDTF debt securities	906			294		612			796			243			553
Other debt securities	6			6		—			1			1			—
Derivative assets	4			—		4			2			1			1
Total assets	2,504			1,888		616			2,594			2,040			554
Derivative liabilities	(27		)	—		(27		)	(18		)	(1		)	(17		)
Net assets	$	2,477		$	1,888	$	589		$	2,576		$	2,039		$	537

Duke Energy Florida [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 2			Total Fair Value			Level 1		Level 2
NDTF equity securities	$	403		$	403	$	—		$	427		$	427	$	—
NDTF debt securities	256			133		123			312			188		124
Other debt securities	48			1		47			48			1		47
Derivative assets	—			—		—			1			—		1
Total assets	707			537		170			788			616		172
Derivative liabilities	(9		)	—		(9		)	(12		)	—		(12		)
Net assets	$	698		$	537	$	161		$	776		$	616	$	160

Duke Energy Ohio [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 2			Level 3		Total Fair Value			Level 2			Level 3
Derivative assets	$	6		$	—		$	6	$	1		$	—		$	1
Derivative liabilities	(5		)	(5		)	—		(5		)	(5		)	—
Net assets (liabilities)	$	1		$	(5	)	$	6	$	(4	)	$	(5	)	$	1

Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs

The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements.

	Derivatives (net)
	Years Ended December 31,
(in millions)	2018			2017
Balance at beginning of period	$	1		$	5
Purchases, sales, issuances and settlements:
Purchases	7			3
Settlements	(4		)	(4		)
Total gains included on the Consolidated Balance Sheet	2			(3		)
Balance at end of period	$	6		$	1

Duke Energy Indiana [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value		Level 1		Level 2		Level 3		Total Fair Value		Level 1		Level 2		Level 3
Other equity securities	$	67	$	67	$	—	$	—	$	97	$	97	$	—	$	—
Other debt securities	41		—		41		—		31		—		31		—
Derivative assets	23		1		—		22		27		—		—		27
Total assets	$	131	$	68	$	41	$	22	$	155	$	97	$	31	$	27

Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs

The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements.

	Derivatives (net)
	Years Ended December 31,
(in millions)	2018			2017
Balance at beginning of period	$	27		$	16
Purchases, sales, issuances and settlements:
Purchases	50			52
Settlements	(53		)	(43		)
Total (losses) gains included on the Consolidated Balance Sheet	(2		)	2
Balance at end of period	$	22		$	27

Piedmont Natural Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Measurement Amounts For Assets And Liabilities

The following table provides recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.

	December 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 3			Total Fair Value			Level 1		Level 3
Other debt securities	$	—		$	—	$	—		$	1		$	1	$	—
Derivative assets	3			3		—			2			2		—
Total assets	3			3		—			3			3		—
Derivative liabilities	(141		)	—		(141		)	(142		)	—		(142		)
Net (liabilities) assets	$	(138	)	$	3	$	(141	)	$	(139	)	$	3	$	(142	)

Reconciliation Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Unobservable Inputs

The following table provides a reconciliation of beginning and ending balances of assets and liabilities measured at fair value using Level 3 measurements.

	Derivatives (net)
	Years Ended December 31,
(in millions)	2018			2017
Balance at beginning of period	$	(142	)	$	(187	)
Total gains and settlements	1			45
Balance at end of period	$	(141	)	$	(142	)