Income Taxes (Other Disclosures) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Feb. 21, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	$ 25	$ 17	$ 88		$ 213
Gross increases-tax positions in prior periods		12
Gross decreases-tax positions in prior periods		(4)	(4)		(48)
Decreases due to settlements			(68)		(45)
Reduction due to lapse of statute of limitations			1		(32)
Total changes		8	(71)		(125)
Unrecognized Tax Benefits - December 31		25	17		88
Amount that if recognized, would affect the effective tax rate or regulatory liability		15
Amount that if recognized, would be recorded as a component of discontinued operations		7
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					12
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes					3
Interest payable related to income taxes		5	4
Duke Energy Carolinas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	1	72		160
Gross increases-tax positions in prior periods		4
Gross decreases-tax positions in prior periods			(4)		(45)
Decreases due to settlements			(67)		(43)
Total changes		4	(71)		(88)
Unrecognized Tax Benefits - December 31		5	1		72
Amount that if recognized, would affect the effective tax rate or regulatory liability		4
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest expense recognized related to income taxes		2	7		1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		25	23		14
Progress Energy [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	2	1		32
Gross increases-tax positions in prior periods		3			1
Gross decreases-tax positions in prior periods			(1)
Reduction due to lapse of statute of limitations			2		(32)
Total changes		3	1		(31)
Unrecognized Tax Benefits - December 31		5	2		1
Amount that if recognized, would affect the effective tax rate or regulatory liability		7
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		1	1		2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		1	1
Duke Energy Progress [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	2	3		23
Gross increases-tax positions in prior periods		3			1
Gross decreases-tax positions in prior periods			(1)
Reduction due to lapse of statute of limitations					(21)
Total changes		3	(1)		(20)
Unrecognized Tax Benefits - December 31		5	2		3
Amount that if recognized, would affect the effective tax rate or regulatory liability		5
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					2
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest payable related to income taxes		1	1		1
Duke Energy Florida [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	5	4			8
Gross increases-tax positions in prior periods		1	4
Reduction due to lapse of statute of limitations					(8)
Total changes		1	4		(8)
Unrecognized Tax Benefits - December 31		5	4
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes		1	2		1
Duke Energy Ohio [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	1	4
Gross increases-tax positions in prior periods		1	4
Gross decreases-tax positions in prior periods		(4)
Total changes		(3)	4
Unrecognized Tax Benefits - December 31		1	4
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Amount that if recognized, would be recorded as a component of discontinued operations		2
Duke Energy Indiana [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	1		1		1
Gross increases-tax positions in prior periods		1
Decreases due to settlements			(1)
Total changes		1	$ (1)
Unrecognized Tax Benefits - December 31		1			1
Amount that if recognized, would affect the effective tax rate or regulatory liability		1
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes					1
Income Tax Examination, Penalties and Interest Accrued [Abstract]
Interest receivable related to income taxes					$ 3
Piedmont Natural Gas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits - January 1	3
Gross increases-tax positions in prior periods		3
Total changes		3
Unrecognized Tax Benefits - December 31		3
Amount that if recognized, would affect the effective tax rate or regulatory liability		$ 3
Income Tax Examination, Penalties and Interest Expense [Abstract]
Net interest income recognized related to income taxes				$ 1
Subsequent Event [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Total changes	(8)
Subsequent Event [Member] | Duke Energy Carolinas [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Total changes	$ (1)