Commitments and Contingencies (Table)

3 Months Ended

Mar. 31, 2018

Valuation and Qualifying Accounts Disclosure [Line Items]

Schedule of Additional Possible Losses in Excess of Recorded Environmental Reserves

Additional losses in excess of recorded reserves that could be incurred for the stages of investigation, remediation and monitoring for environmental sites that have been evaluated at this time are not material except as presented in the table below.

(in millions)
Duke Energy	$	57
Duke Energy Carolinas	19
Duke Energy Ohio	30
Piedmont	2

Reserve for Environmental Costs [Member]

Valuation and Qualifying Accounts Disclosure [Line Items]

Schedule of Legal Reserves

The following tables contain information regarding reserves for probable and estimable costs related to the various environmental sites. These reserves are recorded in Accounts Payable within Current Liabilities and Other within Other Noncurrent Liabilities on the Condensed Consolidated Balance Sheets.

	Three Months Ended March 31, 2018
				Duke					Duke			Duke			Duke			Duke
	Duke			Energy		Progress			Energy			Energy			Energy			Energy
(in millions)	Energy			Carolinas		Energy			Progress			Florida			Ohio			Indiana		Piedmont
Balance at beginning of period	$	81		$	10	$	15		$	3		$	12		$	47		$	5	$	2
Provisions/adjustments	4			1		3			1			1			—			1		—
Cash reductions	(5		)	—		(2		)	(1		)	(1		)	(3		)	—		—
Balance at end of period	$	80		$	11	$	16		$	3		$	12		$	44		$	6	$	2

	Three Months Ended March 31, 2017
				Duke					Duke		Duke			Duke			Duke
	Duke			Energy		Progress			Energy		Energy			Energy			Energy
(in millions)	Energy			Carolinas		Energy			Progress		Florida			Ohio			Indiana			Piedmont
Balance at beginning of period	$	98		$	10	$	18		$	3	$	14		$	59		$	10		$	1
Provisions/adjustments	6			1		—			—		1			4			(1		)	1
Cash reductions	(6		)	—		(1		)	—		(1		)	(4		)	—			—
Balance at end of period	$	98		$	11	$	17		$	3	$	14		$	59		$	9		$	2

Legal Reserve [Member]

Valuation and Qualifying Accounts Disclosure [Line Items]

Schedule of Legal Reserves

The table below presents recorded reserves based on management’s best estimate of probable loss for legal matters, excluding asbestos-related reserves and the exit obligation related to the termination of an EPC contract discussed above. Reserves are classified on the Condensed Consolidated Balance Sheets in Other within Other Noncurrent Liabilities and Accounts payable and Other within Current Liabilities. The reasonably possible range of loss in excess of recorded reserves is not material, other than as described above.

(in millions)	March 31, 2018		December 31, 2017
Reserves for Legal Matters
Duke Energy	$	74	$	88
Duke Energy Carolinas	20		30
Progress Energy	51		55
Duke Energy Progress	10		13
Duke Energy Florida	24		24
Piedmont	2		2