Organization and Basis of Presentation (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 304	$ 358
Restricted Cash and Cash Equivalents, Current	115	138
Restricted Cash and Cash Equivalents, Noncurrent	8	9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	427	505	$ 471	$ 541
Progress Energy [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	37	40
Restricted Cash and Cash Equivalents, Current	31	40
Restricted Cash and Cash Equivalents, Noncurrent	6	7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	74	87	79	110
Duke Energy Florida [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	14	13
Restricted Cash and Cash Equivalents, Current	31	40
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 45	$ 53	$ 41	$ 69