Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

Components of Income Tax Expense

	Year Ended 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
Current income taxes
Federal	$	(247	)	$	221		$	(436	)	$	(95	)	$	(188	)	$	(37	)	$	128	$	(90	)
State	4			20			(5		)	2			(11		)	2			21		(3		)
Foreign	3			—			—			—			—			—			—		—
Total current income taxes	(240		)	241			(441		)	(93		)	(199		)	(35		)	149		(93		)
Deferred income taxes
Federal	1,344			381			664			378			194			99			138		147
State	102			35			44			10			51			(4		)	14		8
Total deferred income taxes(a) (b)	1,446			416			708			388			245			95			152		155
Investment tax credit amortization	(10		)	(5		)	(3		)	(3		)	—			(1		)	—		—
Income tax expense from continuing operations	1,196			652			264			292			46			59			301		62
Tax benefit from discontinued operations	(6		)	—			—			—			—			—			—		—
Total income tax expense included in Consolidated Statements of Operations	$	1,190		$	652		$	264		$	292		$	46		$	59		$	301	$	62

(a) Includes utilization of NOL (Net operating loss) carryforwards and tax credit carryforwards of $428 million at Duke Energy, $74 million at Progress Energy, $36 million at Duke Energy Florida, $17 million at Duke Energy Ohio, $42 million at Duke Energy Indiana and $79 million at Piedmont. In addition the total deferred income taxes Includes benefits of NOL carryforwards and tax credit carryforwards of $10 million at Duke Energy Carolinas and $1 million at Duke Energy Progress.

(b) As a result of the Tax Act, Duke Energy's deferred tax assets and liabilities were revalued as of December 31, 2017. See the Statutory Rate Reconciliation section below for additional information on the Tax Act's impact on income tax expense.

	Year Ended December 31, 2016
				Duke						Duke			Duke		Duke			Duke
	Duke			Energy			Progress			Energy			Energy		Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida		Ohio			Indiana
Current income taxes
Federal	$	—		$	139		$	15		$	(59	)	$	76	$	(7	)	$	7
State	(15		)	25			(19		)	(25		)	22		(13		)	6
Foreign	2			—			—			—			—		—			—
Total current income taxes	(13		)	164			(4		)	(84		)	98		(20		)	13
Deferred income taxes
Federal	1,064			430			486			350			199		88			202
State	117			45			50			40			25		11			11
Total deferred income taxes(a)	1,181			475			536			390			224		99			213
Investment tax credit amortization	(12		)	(5		)	(5		)	(5		)	—		(1		)	(1		)
Income tax expense from continuing operations	1,156			634			527			301			322		78			225
Tax (benefit) expense from discontinued operations	(30		)	—			1			—			—		(36		)	—
Total income tax expense included in Consolidated Statements of Operations	$	1,126		$	634		$	528		$	301		$	322	$	42		$	225

(a) Includes benefits of NOL carryforwards and utilization of NOL and tax credit carryforwards of $648 million at Duke Energy, $4 million at Duke Energy Carolinas, $190 million at Progress Energy, $60 million at Duke Energy Progress, $49 million at Duke Energy Florida, $26 million at Duke Energy Ohio and $58 million at Duke Energy Indiana.

	Year Ended December 31, 2015
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana
Current income taxes
Federal	$	—		$	216		$	(193	)	$	(56	)	$	1		$	(18	)	$	(86	)
State	(12		)	14			1			(4		)	(7		)	(1		)	(12		)
Foreign	4			—			—			—			—			—			—
Total current income taxes	(8		)	230			(192		)	(60		)	(6		)	(19		)	(98		)
Deferred income taxes
Federal	1,097			345			694			334			290			96			245
State	181			57			27			27			58			5			17
Total deferred income taxes(a)	1,278			402			721			361			348			101			262
Investment tax credit amortization	(14		)	(5		)	(7		)	(7		)	—			(1		)	(1		)
Income tax expense from continuing operations	1,256			627			522			294			342			81			163
Tax expense (benefit) from discontinued operations	89			—			(1		)	—			—			22			—
Total income tax expense included in Consolidated Statements of Operations	$	1,345		$	627		$	521		$	294		$	342		$	103		$	163

(a) Includes utilization of NOL carryforwards and tax credit carryforwards of $264 million at Duke Energy, $15 million at Duke Energy Carolinas, $119 million at Progress Energy, $21 million at Duke Energy Progress, $84 million at Duke Energy Florida, $3 million at Duke Energy Ohio and $45 million at Duke Energy Indiana.

Schedule of Income before Income Tax, Domestic and Foreign

Duke Energy Income from Continuing Operations before Income Taxes

	Years Ended December 31,
(in millions)	2017		2016		2015
Domestic(a)	$	4,207	$	3,689	$	3,831
Foreign	59		45		79
Income from continuing operations before income taxes	$	4,266	$	3,734	$	3,910

(a) Includes a $16 million expense in 2017 related to the Tax Act impact on equity earnings included within Equity in earnings (losses) of unconsolidated affiliates on the Consolidated Statement of Operations.

Summary of Effective Tax Rates

The following tables present a reconciliation of income tax expense at the U.S. federal statutory tax rate to the actual tax expense from continuing operations.

	Year Ended 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
Income tax expense, computed at the statutory rate of 35 percent	$	1,493		$	653		$	536		$	353		$	265		$	88		$	229		$	70
State income tax, net of federal income tax effect	69			36			25			8			26			(1		)	23			3
AFUDC equity income	(81		)	(37		)	(32		)	(17		)	(16		)	(4		)	(8		)	—
Renewable energy production tax credits	(132		)	—			—			—			—			—			—			—
Tax Act(a)	(112		)	15			(246		)	(40		)	(226		)	(23		)	55			(12		)
Tax true-up	(52		)	(24		)	(19		)	(13		)	(7		)	(5		)	(6		)	—
Other items, net	11			9			—			1			4			4			8			1
Income tax expense from continuing operations	$	1,196		$	652		$	264		$	292		$	46		$	59		$	301		$	62
Effective tax rate	28.0		%	34.9		%	17.2		%	29.0		%	6.1		%	23.4		%	46.0		%	30.8		%

(a) Amounts primarily include but are not limited to items that are excluded for ratemaking purposes related to abandoned or impaired assets, certain wholesale fixed rate contracts, remeasurement of nonregulated net deferred tax liabilities, Federal net operating losses, and valuation allowance on foreign tax credits.

	Year Ended December 31, 2016
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana
Income tax expense, computed at the statutory rate of 35 percent	$	1,307		$	630		$	548		$	315		$	306		$	95		$	212
State income tax, net of federal income tax effect	64			46			20			10			30			(2		)	11
AFUDC equity income	(70		)	(36		)	(26		)	(17		)	(9		)	(2		)	(6		)
Renewable energy production tax credits	(97		)	—			—			—			—			—			—
Audit adjustment	5			3			—			—			—			—			—
Tax true-up	(14		)	(14		)	(11		)	(3		)	(9		)	(16		)	2
Other items, net	(39		)	5			(4		)	(4		)	4			3			6
Income tax expense from continuing operations	$	1,156		$	634		$	527		$	301		$	322		$	78		$	225
Effective tax rate	31.0		%	35.2		%	33.7		%	33.4		%	36.9		%	28.9		%	37.1		%

	Year Ended December 31, 2015
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana
Income tax expense, computed at the statutory rate of 35 percent	$	1,369		$	598		$	555		$	302		$	330		$	81		$	168
State income tax, net of federal income tax effect	109			46			18			15			33			2			2
AFUDC equity income	(58		)	(34		)	(19		)	(17		)	(3		)	(1		)	(4		)
Renewable energy production tax credits	(72		)	—			(1		)	—			—			—			—
Audit adjustment	(22		)	—			(23		)	1			(24		)	—			—
Tax true-up	2			2			(3		)	(4		)	2			(5		)	(9		)
Other items, net	(72		)	15			(5		)	(3		)	4			4			6
Income tax expense from continuing operations	$	1,256		$	627		$	522		$	294		$	342		$	81		$	163
Effective tax rate	32.1		%	36.7		%	32.9		%	34.2		%	36.3		%	35.2		%	34.0		%

Schedule of Deferred Tax Assets and Liabilities

	December 31, 2016
				Duke						Duke			Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Ohio			Indiana			Piedmont
Deferred credits and other liabilities	$	382		$	66		$	126		$	40		$	93		$	21		$	4		$	71
Capital lease obligations	60			8			—			—			—			—			1			—
Pension, post-retirement and other employee benefits	561			16			199			91			96			22			37			10
Progress Energy merger purchase accounting adjustments(a)	918			—			—			—			—			—			—			—
Tax credits and NOL carryforwards	4,682			192			1,165			222			232			49			278			192
Investments and other assets	—			—			—			—			—			3			—			—
Other	205			16			35			8			—			5			9			45
Valuation allowance	(96		)	—			(12		)	—			—			—			—			(1		)
Total deferred income tax assets	6,712			298			1,513			361			421			100			329			317
Investments and other assets	(1,892		)	(1,149		)	(597		)	(313		)	(297		)	—			(21		)	(21		)
Accelerated depreciation rates	(14,872		)	(4,664		)	(4,490		)	(2,479		)	(2,038		)	(1,404		)	(1,938		)	(1,080		)
Regulatory assets and deferred debits, net	(4,103		)	(1,029		)	(1,672		)	(892		)	(780		)	(139		)	(270		)	(147		)
Total deferred income tax liabilities	(20,867		)	(6,842		)	(6,759		)	(3,684		)	(3,115		)	(1,543		)	(2,229		)	(1,248		)
Net deferred income tax liabilities	$	(14,155	)	$	(6,544	)	$	(5,246	)	$	(3,323	)	$	(2,694	)	$	(1,443	)	$	(1,900	)	$	(931	)

(a) Primarily related to capital lease obligations and debt fair value adjustments.

Net Deferred Income Tax Liability Components

	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
Deferred credits and other liabilities	$	143		$	33		$	78		$	23		$	49		$	11		$	6		$	(5	)
Capital lease obligations	49			14			—			—			—			—			2			—
Pension, post-retirement and other employee benefits	295			(17		)	111			44			60			14			18			(4		)
Progress Energy merger purchase accounting adjustments(a)	536			—			—			—			—			—			—			—
Tax credits and NOL carryforwards	4,527			234			402			156			143			25			216			70
Regulatory liabilities and deferred credits	—			222			—			—			—			65			—			61
Investments and other assets	—			—			—			—			—			—			1			18
Other	73			10			1			4			—			—			—			—
Valuation allowance	(519		)	—			(14		)	—			—			—			—			—
Total deferred income tax assets	5,104			496			578			227			252			115			243			140
Investments and other assets	(1,419		)	(849		)	(470		)	(289		)	(187		)	—			(14		)	—
Accelerated depreciation rates	(9,216		)	(3,060		)	(2,803		)	(1,583		)	(1,257		)	(896		)	(966		)	(697		)
Regulatory assets and deferred debits, net	(1,090		)	—			(807		)	(238		)	(569		)	—			(188		)	—
Other	—			—			—			—			—			—			—			(7		)
Total deferred income tax liabilities	(11,725		)	(3,909		)	(4,080		)	(2,110		)	(2,013		)	(896		)	(1,168		)	(704		)
Net deferred income tax liabilities	$	(6,621	)	$	(3,413	)	$	(3,502	)	$	(1,883	)	$	(1,761	)	$	(781	)	$	(925	)	$	(564	)

(a) Primarily related to capital lease obligations and debt fair value adjustments.

As noted above, as a result of the Tax Act, Duke Energy revalued its existing deferred tax assets and liabilities as of December 31, 2017, to account for the estimated future impact of lower corporate tax rates on these deferred amounts. The following table shows the decrease reflected in the net deferred income tax liabilities balance above:

(in millions)	December 31, 2017
Duke Energy	$	8,982
Duke Energy Carolinas	3,454
Progress Energy	3,282
Duke Energy Progress	1,882
Duke Energy Florida	1,420
Duke Energy Ohio	771
Duke Energy Indiana	1,053
Piedmont	521

Summary of Tax Credit Carryforwards

The following table presents the expiration of tax credits and NOL carryforwards.

	December 31, 2017
(in millions)	Amount		Expiration Year
Investment tax credits	$	1,406	2024	—	2037
Alternative minimum tax credits	1,147		Refundable by 2021
Federal NOL carryforwards	393		2022	—	2036
State NOL carryforwards and credits(a)	296		2018	—	2037
Foreign NOL carryforwards(b)	13		2027	—	2036
Foreign Tax Credits(c)	1,272		2024	—	2027
Total tax credits and NOL carryforwards	4,527

(a) A valuation allowance of $90 million has been recorded on the state NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table.

(b) A valuation allowance of $13 million has been recorded on the foreign NOL carryforwards, as presented in the Net Deferred Income Tax Liability Components table.

(c) A valuation allowance of $416 million has been recorded on the foreign tax credits, as presented in the Net Deferred Income Tax Liability Components table.

Schedule of Unrecognized Tax Benefits Roll Forward

The following tables present changes to unrecognized tax benefits.

	Year Ended 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
Unrecognized tax benefits – January 1	$	17		$	1	$	2	$	2	$	4	$	4		$	—	$	—
Unrecognized tax benefits increases (decreases)
Gross increases – tax positions in prior periods	12			4		3		3		1		1			1		3
Gross decreases – tax positions in prior periods	(4		)	—		—		—		—		(4		)	—		—
Total changes	8			4		3		3		1		(3		)	1		3
Unrecognized tax benefits – December 31	$	25		$	5	$	5	$	5	$	5	$	1		$	1	$	3

	Year Ended December 31, 2016
				Duke						Duke			Duke		Duke		Duke
	Duke			Energy			Progress			Energy			Energy		Energy		Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida		Ohio		Indiana
Unrecognized tax benefits – January 1	$	88		$	72		$	1		$	3		$	—	$	—	$	1
Unrecognized tax benefits increases (decreases)
Gross increases – tax positions in prior periods	—			—			—			—			4		4		—
Gross decreases – tax positions in prior periods	(4		)	(4		)	(1		)	(1		)	—		—		—
Decreases due to settlements	(68		)	(67		)	—			—			—		—		(1		)
Reduction due to lapse of statute of limitations	1			—			2			—			—		—		—
Total changes	(71		)	(71		)	1			(1		)	4		4		(1		)
Unrecognized tax benefits – December 31	$	17		$	1		$	2		$	2		$	4	$	4	$	—

	Year Ended December 31, 2015
				Duke						Duke			Duke			Duke
	Duke			Energy			Progress			Energy			Energy			Energy
(in millions)	Energy			Carolinas			Energy			Progress			Florida			Indiana
Unrecognized tax benefits – January 1	$	213		$	160		$	32		$	23		$	8		$	1
Unrecognized tax benefits increases (decreases)
Gross increases – tax positions in prior periods	—			—			1			1			—			—
Gross decreases – tax positions in prior periods	(48		)	(45		)	—			—			—			—
Decreases due to settlements	(45		)	(43		)	—			—			—			—
Reduction due to lapse of statute of limitations	(32		)	—			(32		)	(21		)	(8		)	—
Total changes	(125		)	(88		)	(31		)	(20		)	(8		)	—
Unrecognized tax benefits – December 31	$	88		$	72		$	1		$	3		$	—		$	1

Summary of Income Tax Contingencies

The following table includes additional information regarding the Duke Energy Registrants' unrecognized tax benefits at December 31, 2017. During the first quarter of 2018, Duke Energy recognized an approximate $8 million reduction and Duke Energy Carolinas recognized an approximate $1 million reduction in unrecognized tax benefits. No additional material reductions are expected in the next 12 months.

	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
Amount that if recognized, would affect the effective tax rate or regulatory liability(a)	$	15	$	4	$	7	$	5	$	1	$	1	$	1	$	3
Amount that if recognized, would be recorded as a component of discontinued operations	7		—		—		—		—		2		—		—

(a) Duke Energy, Duke Energy Carolinas, Progress Energy, Duke Energy Progress, Duke Energy Florida, Duke Energy Indiana and Piedmont are unable to estimate the specific amounts that would affect the effective tax rate versus the regulatory liability.

The following tables include interest recognized in the Consolidated Statements of Operations and the Consolidated Balance Sheets.

	Year Ended December 31, 2017
			Duke				Duke		Duke
	Duke		Energy		Progress		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida
Net interest income recognized related to income taxes	$	—	$	—	$	1	$	—	$	1
Net interest expense recognized related to income taxes	—		2		—		—		—
Interest payable related to income taxes	5		25		1		1		—

	Year Ended December 31, 2016
			Duke				Duke		Duke
	Duke		Energy		Progress		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida
Net interest income recognized related to income taxes	$	—	$	—	$	1	$	—	$	2
Net interest expense recognized related to income taxes	—		7		—		—		—
Interest payable related to income taxes	4		23		1		1		—

	Year Ended December 31, 2015
			Duke				Duke		Duke		Duke
	Duke		Energy		Progress		Energy		Energy		Energy
(in millions)	Energy		Carolinas		Energy		Progress		Florida		Indiana
Net interest income recognized related to income taxes	$	12	$	—	$	2	$	2	$	1	$	1
Net interest expense recognized related to income taxes	—		1		—		—		—		—
Interest receivable related to income taxes	3		—		—		—		—		3
Interest payable related to income taxes	—		14		—		1		—		—

Piedmont Natural Gas [Member]

Income Tax Disclosure [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

	Piedmont
	Two Months Ended			Years Ended October 31,
(in millions)	December 31, 2016			2016		2015
Current income taxes
Federal	$	4		$	27	$	(1	)
State	(2		)	12		1
Total current income taxes	2			39		—
Deferred income taxes
Federal	24			79		78
State	6			6		12
Total deferred income taxes(a)(b)	30			85		90
Total income tax expense from continuing operations included in Consolidated Statements of Operations	$	32		$	124	$	90

(a) Includes benefits of NOL and tax carryforwards of $17 million and $91 million for the two months ended December 31, 2016, and the year ended October 31, 2016, respectively.

(b) Includes benefits and utilization of NOL carryforwards of $46 million for the year ended October 31, 2015.

Summary of Effective Tax Rates

	Piedmont
	Two Months Ended			Years Ended October 31,
(in millions)	December 31, 2016			2016			2015
Income tax expense, computed at the statutory rate of 35 percent	$	30		$	111		$	79
State income tax, net of federal income tax effect	1			11			9
Other items, net	1			2			2
Income tax expense from continuing operations	$	32		$	124		$	90
Effective tax rate	37.2		%	39.1		%	39.7		%