Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - ASU 2016-01) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	$ 2,269
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-Sale, Realized Gain	5
Debt Securities, Available-for-sale, Realized Loss	13
Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	2,169
Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	258
Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8
Available-for-sale Securities, Debt Securities	549
Corporate Debt Securities [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	64
Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	333
Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	80
US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	18
Available-for-sale Securities, Debt Securities	1,014
US Treasury and Government [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	51
Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	130
Other Debt Obligations [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	48
Duke Energy Carolinas [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,018
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-Sale, Realized Gain	5
Debt Securities, Available-for-sale, Realized Loss	10
Duke Energy Carolinas [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,068
Duke Energy Carolinas [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	333
Duke Energy Carolinas [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	69
Duke Energy Carolinas [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	11
Available-for-sale Securities, Debt Securities	494
Duke Energy Carolinas [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	122
Progress Energy [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,055
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	3
Progress Energy [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1,101
Progress Energy [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	57
Progress Energy [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	3
Available-for-sale Securities, Debt Securities	216
Progress Energy [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4
Available-for-sale Securities, Debt Securities	264
Progress Energy [Member] | Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Securities, Debt Securities	47
Progress Energy [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7
Available-for-sale Securities, Debt Securities	520
Progress Energy [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	8
Duke Energy Progress [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	747
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	2
Duke Energy Progress [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	806
Duke Energy Progress [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1
Duke Energy Progress [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	153
Duke Energy Progress [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4
Available-for-sale Securities, Debt Securities	263
Duke Energy Progress [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5
Available-for-sale Securities, Debt Securities	326
Duke Energy Progress [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	5
Duke Energy Florida [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	308
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt Securities, Available-for-sale, Realized Loss	1
Duke Energy Florida [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	295
Duke Energy Florida [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | Corporate Debt Securities [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	63
Duke Energy Florida [Member] | Municipal Bonds [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	1
Duke Energy Florida [Member] | Municipal Bonds [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Securities, Debt Securities	47
Duke Energy Florida [Member] | US Treasury and Government [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2
Available-for-sale Securities, Debt Securities	194
Duke Energy Florida [Member] | Other Debt Obligations [Member] | Ndtf [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	3
Duke Energy Indiana [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Other Classification [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	31
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Available-for-sale Securities, Debt Securities	5
Duke Energy Indiana [Member] | Municipal Bonds [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Available-for-sale Securities, Debt Securities	$ 26