Income Taxes (Other Disclosures) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	$ 230us-gaap_UnrecognizedTaxBenefits	$ 540us-gaap_UnrecognizedTaxBenefits	$ 385us-gaap_UnrecognizedTaxBenefits
Acquisitions			128
Gross increases-tax positions in prior periods			29
Gross decreases-tax positions in prior periods	(2)	(231)	(4)
Gross increases-current period tax positions			28
Gross decreases - current period tax positions			(9)
Decreases due to settlements	(15)	(66)	(13)
Reduction due to lapse of statute of limitations		(13)	(4)
Total changes	(17)	(310)	155
Unrecognized Tax Benefits - December 31	213us-gaap_UnrecognizedTaxBenefits	230us-gaap_UnrecognizedTaxBenefits	540us-gaap_UnrecognizedTaxBenefits
Amount that if recognized, would affect the effective tax rate or regulatory liability	121
Amount that if recognized, would be recorded as a component of discontinued operations	8
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	28
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	6duk_IncomeTaxExaminationInterestIncome	2duk_IncomeTaxExaminationInterestIncome	10duk_IncomeTaxExaminationInterestIncome
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes	13	27	7
Duke Energy Carolinas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	171	271	260
Gross increases-tax positions in prior periods			12
Gross decreases-tax positions in prior periods		(100)
Gross increases-current period tax positions			15
Gross decreases - current period tax positions			(5)
Decreases due to settlements	(11)		(11)
Total changes	(11)	(100)	11
Unrecognized Tax Benefits - December 31	160	171	271
Amount that if recognized, would affect the effective tax rate or regulatory liability	112
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		2	9
Net interest expense recognized related to income taxes	1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes			7
Interest payable related to income taxes	13	8
Progress Energy [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	32	131	173
Gross increases-tax positions in prior periods	1		23
Gross decreases-tax positions in prior periods		(86)	(72)
Gross increases-current period tax positions			8
Gross decreases - current period tax positions			(1)
Decreases due to settlements	(1)
Reduction due to lapse of statute of limitations		(13)
Total changes		(99)	(42)
Unrecognized Tax Benefits - December 31	32	32	131
Amount that if recognized, would affect the effective tax rate or regulatory liability	3
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	28
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	3	6
Net interest expense recognized related to income taxes			2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes	5	10	17
Duke Energy Progress [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	22	67	73
Gross increases-tax positions in prior periods	1		10
Gross decreases-tax positions in prior periods		(45)	(19)
Gross increases-current period tax positions			4
Gross decreases - current period tax positions			(1)
Total changes	1	(45)	(6)
Unrecognized Tax Benefits - December 31	23	22	67
Amount that if recognized, would affect the effective tax rate or regulatory liability	2
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	17
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		7
Net interest expense recognized related to income taxes	1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes	3	2	8
Duke Energy Florida [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	8	44	80
Gross increases-tax positions in prior periods			12
Gross decreases-tax positions in prior periods		(37)	(52)
Gross increases-current period tax positions			4
Reduction due to lapse of statute of limitations		1
Total changes		(36)	(36)
Unrecognized Tax Benefits - December 31	8	8	44
Amount that if recognized, would affect the effective tax rate or regulatory liability	2
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	7
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	1
Net interest expense recognized related to income taxes			2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes	5	7	9
Duke Energy Ohio [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1		36	32
Gross increases-tax positions in prior periods			2
Gross decreases-tax positions in prior periods		(36)
Gross increases-current period tax positions			4
Gross decreases - current period tax positions			(2)
Total changes		(36)	4
Unrecognized Tax Benefits - December 31			36
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	4	4
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes			3
Duke Energy Indiana [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	1	32	24
Gross increases-tax positions in prior periods			6
Gross decreases-tax positions in prior periods		(31)
Gross increases-current period tax positions			4
Gross decreases - current period tax positions			(2)
Total changes		(31)	8
Unrecognized Tax Benefits - December 31	1	1	32
Amount that if recognized, would affect the effective tax rate or regulatory liability	2
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes	4	1	2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes	2
Interest payable related to income taxes			$ 1

The amount of estimated interest income recognized in the period arising from income tax examinations.

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The amount of interest receivable recorded on the balance sheet related to income taxes.

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Unrecognized Tax Benefits That Would Impact Discontinued Operations

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The amount of estimated interest accrued as of the balance sheet date arising from income tax examinations.

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The amount of estimated interest recognized in the period arising from income tax examinations.

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The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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