Fair Value Measurements (Tables)

3 Months Ended

Mar. 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 Condensed Consolidated Balance Sheets. Derivative amounts in the tables below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 8. See Note 9 for additional information related to investments by major security type for the Duke Energy Registrants.

	March 31, 2018
(in millions)	Total Fair Value			Level 1			Level 2			Level 3			Not Categorized
NDTF equity securities	$	4,857		$	4,785		$	—		$	—		$	72
NDTF debt securities	2,169			633			1,536			—			—
Other equity securities	130			130			—			—			—
Other debt securities	258			66			192			—			—
Derivative assets	37			2			27			8			—
Total assets	7,451			5,616			1,755			8			72
Derivative liabilities	(190		)	(1		)	(57		)	(132		)	—
Net assets (liabilities)	$	7,261		$	5,615		$	1,698		$	(124	)	$	72

	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 table provides 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 March 31, 2018								Three Months Ended March 31, 2017
(in millions)	Investments		Derivatives (net)			Total			Investments		Derivatives (net)			Total
Balance at beginning of period	$	—	$	(114	)	$	(114	)	$	5	$	(166	)	$	(161	)
Purchases, sales, issuances and settlements:
Settlements	—		(14		)	(14		)	—		(9		)	(9		)
Total gains included on the Condensed Consolidated Balance Sheet	—		4			4			—		40			40
Balance at end of period	$	—	$	(124	)	$	(124	)	$	5	$	(135	)	$	(130	)

Quantitative Information Table - Level 3

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

	March 31, 2018
	Fair Value
Investment Type	(in millions)			Valuation Technique	Unobservable Input	Range
Duke Energy Ohio
Financial Transmission Rights (FTRs)	$	1		RTO auction pricing	FTR price – per megawatt-hour (MWh)	$	—		-	$	2.88
Duke Energy Indiana
FTRs	7			RTO auction pricing	FTR price – per MWh	(5.09		)	-	7.58
Piedmont
Natural gas contracts	(132		)	Discounted cash flow	Forward natural gas curves – price per million British thermal unit (MMBtu)	2.15			-	3.65
Duke Energy
Total Level 3 derivatives	$	(124	)

	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.

	March 31, 2018				December 31, 2017
(in millions)	Book Value		Fair Value		Book Value		Fair Value
Duke Energy	$	52,981	$	54,383	$	52,279	$	55,331
Duke Energy Carolinas	10,694		11,556		10,103		11,372
Progress Energy	17,757		19,270		17,837		20,000
Duke Energy Progress	7,357		7,687		7,357		7,992
Duke Energy Florida	7,015		7,632		7,095		7,953
Duke Energy Ohio	2,067		2,217		2,067		2,249
Duke Energy Indiana	3,782		4,322		3,783		4,464
Piedmont	2,037		2,209		2,037		2,209

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.

	March 31, 2018
(in millions)	Total Fair Value			Level 1			Level 2			Not Categorized
NDTF equity securities	$	2,669		$	2,597		$	—		$	72
NDTF debt securities	1,068			209			859			—
Derivative assets	2			—			2			—
Total assets	3,739			2,806			861			72
Derivative liabilities	(11		)	(1		)	(10		)	—
Net assets	$	3,728		$	2,805		$	851		$	72

	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

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.

	March 31, 2018
(in millions)	Total Fair Value			Level 1			Level 2
NDTF equity securities	$	2,188		$	2,188		$	—
NDTF debt securities	1,101			424			677
Other debt securities	57			10			47
Derivative assets	3			—			3
Total assets	3,349			2,622			727
Derivative liabilities	(37		)	(1		)	(36		)
Net assets	$	3,312		$	2,621		$	691

	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.

	March 31, 2018
(in millions)	Total Fair Value			Level 1			Level 2
NDTF equity securities	$	1,765		$	1,765		$	—
NDTF debt securities	806			254			552
Other debt securities	1			1			—
Derivative assets	2			—			2
Total assets	2,574			2,020			554
Derivative liabilities	(21		)	(1		)	(20		)
Net assets	$	2,553		$	2,019		$	534

	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.

	March 31, 2018
(in millions)	Total Fair Value			Level 1		Level 2
NDTF equity securities	$	423		$	423	$	—
NDTF debt securities	295			170		125
Other debt securities	47			—		47
Derivative assets	1			—		1
Total assets	766			593		173
Derivative liabilities	(7		)	—		(7		)
Net assets	$	759		$	593	$	166

	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.

	March 31, 2018								December 31, 2017
(in millions)	Total Fair Value			Level 2			Level 3		Total Fair Value			Level 2			Level 3
Derivative assets	$	1		$	—		$	1	$	1		$	—		$	1
Derivative liabilities	(4		)	(4		)	—		(5		)	(5		)	—
Net (liabilities) assets	$	(3	)	$	(4	)	$	1	$	(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 March 31,
(in millions)	2018		2017
Balance at beginning of period	$	1	$	5
Purchases, sales, issuances and settlements:
Settlements	—		(1		)
Total losses included on the Condensed Consolidated Balance Sheet	—		(3		)
Balance at end of period	$	1	$	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 tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Condensed Consolidated Balance Sheets.

	March 31, 2018
(in millions)	Total Fair Value		Level 1		Level 2		Level 3
Other equity securities	$	96	$	96	$	—	$	—
Other debt securities	31		—		31		—
Derivative assets	7		—		—		7
Total assets	134		96		31		7
Derivative liabilities	—		—		—		—
Net assets	$	134	$	96	$	31	$	7

	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
Derivative liabilities	—		—		—		—
Net 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 March 31,
(in millions)	2018			2017
Balance at beginning of period	$	27		$	16
Purchases, sales, issuances and settlements:
Settlements	(14		)	(7		)
Total (losses) gains included on the Condensed Consolidated Balance Sheet	(6		)	—
Balance at end of period	$	7		$	9

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.

	March 31, 2018
(in millions)	Total Fair Value			Level 1		Level 3
Derivative assets	$	1		$	1	$	—
Derivative liabilities	(132		)	—		(132		)
Net (liabilities) assets	$	(131	)	$	1	$	(132	)

	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 March 31,
(in millions)	2018			2017
Balance at beginning of period	$	(142	)	$	(187	)
Total gains and settlements	10			42
Balance at end of period	$	(132	)	$	(145	)