Summary of Significant Accounting Policies (Allowance for Doubtful Accounts)(Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	$ 14	$ 14		$ 12
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	2		3
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	4	6		6
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	1	4		4
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	3	2		2
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	3	2		2
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	1		1
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables	2	3	$ 2	2
Variable Interest Entity [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	54	54		53
Variable Interest Entity [Member] | Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	7	7		7
Variable Interest Entity [Member] | Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	7	7		8
Variable Interest Entity [Member] | Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	5	5		5
Variable Interest Entity [Member] | Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Allowance for doubtful accounts - receivables of VIEs	$ 2	$ 2		$ 3