Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	$ 60	$ 19	$ 161	$ 85
Equity securities, FV-NI, realized loss	43	16	136	60
Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	3,118		3,118		$ 2,402
Equity Securities, FV-NI, Accumulated Unrealized Loss	63		63		95
Equity securities, FV-NI	5,222		5,222		4,475
Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	48		48		36
Equity Securities, FV-NI, Accumulated Unrealized Loss					1
Equity securities, FV-NI	112		112		99
Duke Energy Carolinas [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	34	11	101	47
Equity securities, FV-NI, realized loss	26	8	95	30
Duke Energy Carolinas [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,680		1,680		1,309
Equity Securities, FV-NI, Accumulated Unrealized Loss	15		15		54
Equity securities, FV-NI	2,901		2,901		2,484
Progress Energy [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	26	8	60	38
Equity securities, FV-NI, realized loss	17	8	41	30
Progress Energy [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,438		1,438		1,093
Equity Securities, FV-NI, Accumulated Unrealized Loss	48		48		41
Equity securities, FV-NI	2,321		2,321		1,991
Duke Energy Progress [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	10	7	27	32
Equity securities, FV-NI, realized loss	9	7	24	27
Duke Energy Progress [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,107		1,107		833
Equity Securities, FV-NI, Accumulated Unrealized Loss	30		30		30
Equity securities, FV-NI	1,907		1,907		1,588
Duke Energy Florida [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	16	1	33	6
Equity securities, FV-NI, realized loss	8	$ 1	17	$ 3
Duke Energy Florida [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	331		331		260
Equity Securities, FV-NI, Accumulated Unrealized Loss	18		18		11
Equity securities, FV-NI	414		414		403
Duke Energy Indiana [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	37		37		29
Equity securities, FV-NI	74		74		67
Duke Energy Indiana [Member] | Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI	$ 74		$ 74		$ 67