Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Allowance for Doubtful Accounts)(Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	$ 18	$ 17	$ 30
Restricted receivables, allowance for doubtful accounts	53	51	43
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	3	3	3
Restricted receivables, allowance for doubtful accounts	7	6	6
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	6	8	14
Restricted receivables, allowance for doubtful accounts	8	8
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	4	7	10
Restricted receivables, allowance for doubtful accounts	5	5
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	2	2	4
Restricted receivables, allowance for doubtful accounts	3	3
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	2	2	2
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Receivables, allowance for doubtful accounts	$ 1	$ 1	$ 1