Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	$ 2,272	$ 2,272
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Gain	5	10
Debt Securities, Available-for-sale, Realized Loss	12	25
Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	2,136	2,136
Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	267	267
Corporate Debt Securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5	5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	12	12
Debt Securities, Available-for-sale	560	560
Corporate Debt Securities [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	68	68
Municipal Bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4	4
Debt Securities, Available-for-sale	341	341
Municipal Bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	87	87
US Treasury and Government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	20	20
Debt Securities, Available-for-sale	991	991
US Treasury and Government [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	52	52
Other Debt Obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3
Debt Securities, Available-for-sale	128	128
Other Debt Obligations [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	45	45
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1,017	1,017
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Gain	4	9
Debt Securities, Available-for-sale, Realized Loss	8	18
Duke Energy Carolinas [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1,049	1,049
Duke Energy Carolinas [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8	8
Debt Securities, Available-for-sale	347	347
Duke Energy Carolinas [Member] | Municipal Bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	72	72
Duke Energy Carolinas [Member] | US Treasury and Government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	12	12
Debt Securities, Available-for-sale	474	474
Duke Energy Carolinas [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3
Debt Securities, Available-for-sale	124	124
Progress Energy [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1,050	1,050
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Gain	1	1
Debt Securities, Available-for-sale, Realized Loss	4	7
Progress Energy [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1,087	1,087
Progress Energy [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	58	58
Progress Energy [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4	4
Debt Securities, Available-for-sale	213	213
Progress Energy [Member] | Municipal Bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3
Debt Securities, Available-for-sale	269	269
Progress Energy [Member] | Municipal Bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale	47	47
Progress Energy [Member] | US Treasury and Government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5	5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8	8
Debt Securities, Available-for-sale	517	517
Progress Energy [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	4	4
Duke Energy Progress [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	762	762
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Gain	1	1
Debt Securities, Available-for-sale, Realized Loss	3	5
Duke Energy Progress [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	808	808
Duke Energy Progress [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1	1
Duke Energy Progress [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3
Debt Securities, Available-for-sale	153	153
Duke Energy Progress [Member] | Municipal Bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3	3
Debt Securities, Available-for-sale	268	268
Duke Energy Progress [Member] | US Treasury and Government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	6	6
Debt Securities, Available-for-sale	339	339
Duke Energy Progress [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	2	2
Duke Energy Florida [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	288	288
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	1	2
Duke Energy Florida [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	279	279
Duke Energy Florida [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	48	48
Duke Energy Florida [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	60	60
Duke Energy Florida [Member] | Municipal Bonds [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	1	1
Duke Energy Florida [Member] | Municipal Bonds [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale	47	47
Duke Energy Florida [Member] | US Treasury and Government [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	2
Debt Securities, Available-for-sale	178	178
Duke Energy Florida [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	2	2
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	41	41
Duke Energy Indiana [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	41	41
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale	8	8
Duke Energy Indiana [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	1
Debt Securities, Available-for-sale	$ 33	$ 33