Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 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 Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 9. See Note 10 for additional information related to investments by major security type for the Duke Energy Registrants.

	June 30, 2018
(in millions)	Total Fair Value			Level 1			Level 2			Level 3			Not Categorized
NDTF equity securities	$	4,988		$	4,918		$	—		$	—		$	70
NDTF debt securities	2,136			578			1,558			—			—
Other equity securities	109			109			—			—			—
Other debt securities	267			68			199			—			—
Derivative assets	87			3			31			53			—
Total assets	7,587			5,676			1,788			53			70
Derivative liabilities	(213		)	(1		)	(62		)	(150		)	—
Net assets (liabilities)	$	7,374		$	5,675		$	1,726		$	(97	)	$	70

	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' Condensed Consolidated Statements of Operations and Comprehensive Income. Amounts included in changes of net assets on the Duke Energy Registrants' Condensed Consolidated Balance Sheets are included in regulatory assets or liabilities. All derivative assets and liabilities are presented on a net basis.

	Three Months Ended June 30, 2018								Three Months Ended June 30, 2017
(in millions)	Investments		Derivatives (net)			Total			Investments			Derivatives (net)			Total
Balance at beginning of period	$	—	$	(124	)	$	(124	)	$	5		$	(135	)	$	(130	)
Total pretax realized or unrealized gains included in comprehensive income	—		—			—			1			—			1
Purchases, sales, issuances and settlements:						—
Purchases	—		56			56			—			55			55
Sales	—		—			—			(6		)	—			(6		)
Settlements	—		(15		)	(15		)	—			(9		)	(9		)
Total losses included on the Condensed Consolidated Balance Sheet	—		(14		)	(14		)	—			(2		)	(2		)
Balance at end of period	$	—	$	(97	)	$	(97	)	$	—		$	(91	)	$	(91	)

	Six Months Ended June 30, 2018								Six Months Ended June 30, 2017
(in millions)	Investments		Derivatives (net)			Total			Investments			Derivatives (net)			Total
Balance at beginning of period	$	—	$	(114	)	$	(114	)	$	5		$	(166	)	$	(161	)
Total pretax realized or unrealized gains included in comprehensive income	—		—			—			1			—			1
Purchases, sales, issuances and settlements:
Purchases	—		56			56			—			55			55
Sales	—		—			—			(6		)	—			(6		)
Settlements	—		(29		)	(29		)	—			(18		)	(18		)
Total (losses) gains included on the Condensed Consolidated Balance Sheet	—		(10		)	(10		)	—			38			38
Balance at end of period	$	—	$	(97	)	$	(97	)	$	—		$	(91	)	$	(91	)

Quantitative Information Table - Level 3

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

	June 30, 2018
	Fair Value
Investment Type	(in millions)			Valuation Technique	Unobservable Input	Range
Duke Energy Ohio
Financial Transmission Rights (FTRs)	$	9		RTO auction pricing	FTR price – per megawatt-hour (MWh)	$	0.67		-	$	3.32
Duke Energy Indiana
FTRs	44			RTO auction pricing	FTR price – per MWh	(2.31		)	-	11.01
Piedmont
Natural gas contracts	(150		)	Discounted cash flow	Forward natural gas curves – price per million British thermal unit (MMBtu)	1.88			-	3.42
Duke Energy
Total Level 3 derivatives	$	(97	)

	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.

	June 30, 2018				December 31, 2017
(in millions)	Book Value		Fair Value		Book Value		Fair Value
Duke Energy(a)	$	52,715	$	52,676	$	52,279	$	55,331
Duke Energy Carolinas	10,394		11,028		10,103		11,372
Progress Energy	18,194		19,357		17,837		20,000
Duke Energy Progress	7,358		7,527		7,357		7,992
Duke Energy Florida	7,452		7,945		7,095		7,953
Duke Energy Ohio	2,066		2,162		2,067		2,249
Duke Energy Indiana	3,782		4,223		3,783		4,464
Piedmont	2,037		2,087		2,037		2,209

(a) Book value of long-term debt includes $1.7 billion as of June 30, 2018, and 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 Condensed Consolidated Balance Sheets.

	June 30, 2018
(in millions)	Total Fair Value			Level 1		Level 2			Not Categorized
NDTF equity securities	$	2,732		$	2,662	$	—		$	70
NDTF debt securities	1,049			164		885			—
Derivative assets	3			—		3			—
Total assets	3,784			2,826		888			70
Derivative liabilities	(19		)	—		(19		)	—
Net assets	$	3,765		$	2,826	$	869		$	70

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

	Investments
	Three Months Ended June 30,					Six Months Ended June 30,
(in millions)	2018		2017			2018		2017
Balance at beginning of period	$	—	$	3		$	—	$	3
Total pretax realized or unrealized gains included in comprehensive income	—		1			—		1
Purchases, sales, issuances and settlements:
Sales	—		(4		)	—		(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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets.

	June 30, 2018
(in millions)	Total Fair Value			Level 1		Level 2
NDTF equity securities	$	2,256		$	2,256	$	—
NDTF debt securities	1,087			414		673
Other debt securities	58			11		47
Derivative assets	5			—		5
Total assets	3,406			2,681		725
Derivative liabilities	(35		)	—		(35		)
Net assets	$	3,371		$	2,681	$	690

	December 31, 2017
(in millions)	Total Fair Value			Level 1			Level 2
NDTF equity securities	$	2,222		$	2,222		$	—
NDTF debt securities	1,108			431			677
Other debt securities	59			12			47
Derivative assets	3			1			2
Total assets	3,392			2,666			726
Derivative liabilities	(36		)	(1		)	(35		)
Net assets	$	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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets.

	June 30, 2018
(in millions)	Total Fair Value			Level 1		Level 2
NDTF equity securities	$	1,819		$	1,819	$	—
NDTF debt securities	808			255		553
Other debt securities	1			1		—
Derivative assets	4			1		3
Total assets	2,632			2,076		556
Derivative liabilities	(21		)	—		(21		)
Net assets	$	2,611		$	2,076	$	535

	December 31, 2017
(in millions)	Total Fair Value			Level 1			Level 2
NDTF equity securities	$	1,795		$	1,795		$	—
NDTF debt securities	796			243			553
Other debt securities	1			1			—
Derivative assets	2			1			1
Total assets	2,594			2,040			554
Derivative liabilities	(18		)	(1		)	(17		)
Net assets	$	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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets.

	June 30, 2018
(in millions)	Total Fair Value			Level 1		Level 2
NDTF equity securities	$	437		$	437	$	—
NDTF debt securities	279			159		120
Other debt securities	48			1		47
Derivative assets	1			—		1
Total assets	765			597		168
Derivative liabilities	(5		)	—		(5		)
Net assets	$	760		$	597	$	163

	December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 2
NDTF equity securities	$	427		$	427	$	—
NDTF debt securities	312			188		124
Other debt securities	48			1		47
Derivative assets	1			—		1
Total assets	788			616		172
Derivative liabilities	(12		)	—		(12		)
Net assets	$	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 Condensed Consolidated Balance Sheets.

	June 30, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 2			Level 3		Total Fair Value			Level 2			Level 3
Derivative assets	$	9		$	—		$	9	$	1		$	—		$	1
Derivative liabilities	(4		)	(4		)	—		(5		)	(5		)	—
Net assets (liabilities)	$	5		$	(4	)	$	9	$	(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)
	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2018			2017			2018			2017
Balance at beginning of period	$	1		$	1		$	1		$	5
Purchases, sales, issuances and settlements:
Purchases	7			3			7			3
Settlements	(1		)	(1		)	(1		)	(2		)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	2			—			2			(3		)
Balance at end of period	$	9		$	3		$	9		$	3

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

	June 30, 2018
(in millions)	Total Fair Value		Level 1		Level 2		Level 3
Other equity securities	$	74	$	74	$	—	$	—
Other debt securities	41		—		41		—
Derivative assets	45		1		—		44
Total assets	$	160	$	75	$	41	$	44

	December 31, 2017
(in millions)	Total Fair Value		Level 1		Level 2		Level 3
Other equity securities	$	97	$	97	$	—	$	—
Other debt securities	31		—		31		—
Derivative assets	27		—		—		27
Total assets	$	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)
	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2018			2017			2018			2017
Balance at beginning of period	$	7		$	9		$	27		$	16
Purchases, sales, issuances and settlements:
Purchases	49			52			49			52
Settlements	(14		)	(9		)	(28		)	(16		)
Total gains (losses) included on the Condensed Consolidated Balance Sheet	2			(1		)	(4		)	(1		)
Balance at end of period	$	44		$	51		$	44		$	51

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

	June 30, 2018
(in millions)	Total Fair Value			Level 1		Level 3
Derivative assets	$	2		$	2	$	—
Derivative liabilities	(150		)	—		(150		)
Net (liabilities) assets	$	(148	)	$	2	$	(150	)

	December 31, 2017
(in millions)	Total Fair Value			Level 1		Level 3
Other debt securities	$	1		$	1	$	—
Derivative assets	2			2		—
Total assets	3			3		—
Derivative liabilities	(142		)	—		(142		)
Net (liabilities) assets	$	(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)
	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2018			2017			2018			2017
Balance at beginning of period	$	(132	)	$	(145	)	$	(142	)	$	(187	)
Total (losses) gains and settlements	(18		)	—			(8		)	42
Balance at end of period	$	(150	)	$	(145	)	$	(150	)	$	(145	)