Organization and Basis of Presentation (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 303	$ 358
Other	139	138
Other Noncurrent Assets
Other	7	9
Total cash, cash equivalents and restricted cash	449	505	$ 427	$ 541
Progress Energy [Member]
Current Assets
Cash and cash equivalents	43	40
Other	14	40
Other Noncurrent Assets
Other	6	7
Total cash, cash equivalents and restricted cash	63	87	56	110
Duke Energy Florida [Member]
Current Assets
Cash and cash equivalents	20	13
Other	14	40
Other Noncurrent Assets
Total cash, cash equivalents and restricted cash	$ 34	$ 53	$ 28	$ 69