Investments in Debt and Equity Securities (Equity Securities, FV-NI - ASU 2016-01) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	$ 35	$ 19
Equity securities, FV-NI, realized loss	30	13
Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	2,923		$ 2,402
Equity Securities, FV-NI, Accumulated Unrealized Loss	65		95
Equity securities, FV-NI	5,061		4,475
Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	47		36
Equity Securities, FV-NI, Accumulated Unrealized Loss			1
Equity securities, FV-NI	112		99
Duke Energy Carolinas [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	23	10
Equity securities, FV-NI, realized loss	21	5
Duke Energy Carolinas [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,593		1,309
Equity Securities, FV-NI, Accumulated Unrealized Loss	37		54
Equity securities, FV-NI	2,791		2,484
Progress Energy [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	12	9
Equity securities, FV-NI, realized loss	9	8
Progress Energy [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,330		1,093
Equity Securities, FV-NI, Accumulated Unrealized Loss	28		41
Equity securities, FV-NI	2,270		1,991
Duke Energy Progress [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	10	8
Equity securities, FV-NI, realized loss	8	8
Duke Energy Progress [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,022		833
Equity Securities, FV-NI, Accumulated Unrealized Loss	20		30
Equity securities, FV-NI	1,812		1,588
Duke Energy Florida [Member]
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Equity securities, FV-NI, realized gain	2	1
Equity securities, FV-NI, realized loss	1	$ 0
Duke Energy Florida [Member] | Ndtf [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	308		260
Equity Securities, FV-NI, Accumulated Unrealized Loss	8		11
Equity securities, FV-NI	458		403
Duke Energy Indiana [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity Securities, FV-NI, Accumulated Unrealized Gain	37		29
Equity securities, FV-NI	76		67
Duke Energy Indiana [Member] | Other Classification [Member]
Equity Securities, FV-NI, Accumulated Unrealized Gain (Loss) [Abstract]
Equity securities, FV-NI	$ 76		$ 67