Investments in Debt Securities and Equity Securities (Available-for-sale, OCI - 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
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	$ 2,633		$ 2,633
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	53	$ 4	110	$ 14
Debt securities, available-for-sale, realized loss	36	7	83	32
Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	2,476		2,476		$ 2,231
Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	324		324		270
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	40		40		4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1		1		13
Debt securities, available-for-sale	633		633		566
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 gain, before tax	2		2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					2
Debt securities, available-for-sale	72		72		60
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	14		14		1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					4
Debt securities, available-for-sale	370		370		353
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	5		5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					1
Debt securities, available-for-sale	94		94		85
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	39		39		14
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					12
Debt securities, available-for-sale	1,217		1,217		1,076
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 gain, before tax	3		3		1
Debt securities, available-for-sale	40		40		45
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 gain, before tax	4		4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					2
Debt securities, available-for-sale	142		142		148
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 gain, before tax	1		1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					1
Debt securities, available-for-sale	65		65		58
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,159		1,159
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	21	4	46	13
Debt securities, available-for-sale, realized loss	13	6	34	24
Duke Energy Carolinas [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,195		1,195		1,069
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	24		24		2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1		1		9
Debt securities, available-for-sale	409		409		341
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	4		4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					1
Debt securities, available-for-sale	96		96		81
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	19		19		5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					8
Debt securities, available-for-sale	517		517		475
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 gain, before tax	4		4
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					2
Debt securities, available-for-sale	137		137		143
Progress Energy [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,255		1,255
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	31		62	1
Debt securities, available-for-sale, realized loss	23	1	49	8
Progress Energy [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	1,281		1,281		1,162
Progress Energy [Member] | Other Classification [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	101		101		64
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	16		16		2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					4
Debt securities, available-for-sale	224		224		225
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	10		10		1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					3
Debt securities, available-for-sale	274		274		272
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	4		4
Debt securities, available-for-sale	52		52		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	20		20		9
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					4
Debt securities, available-for-sale	700		700		601
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	5		5		5
Duke Energy Progress [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	923		923
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	2		4	1
Debt securities, available-for-sale, realized loss		$ 1	2	6
Duke Energy Progress [Member] | Ndtf [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	975		975		906
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	2		2		6
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	16		16		2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					3
Debt securities, available-for-sale	224		224		171
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	10		10		1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					3
Debt securities, available-for-sale	274		274		271
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	19		19		6
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					3
Debt securities, available-for-sale	420		420		415
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	5		5		3
Duke Energy Florida [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	332		332
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Debt securities, available-for-sale, realized gain	29		58
Debt securities, available-for-sale, realized loss	23		47	$ 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	306		306		256
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	56		56		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 loss, before tax					1
Debt securities, available-for-sale					54
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
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	4		4
Debt securities, available-for-sale	52		52		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		3
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					1
Debt securities, available-for-sale	280		280		186
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
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	43		43
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	6		6		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 gain, before tax	1		1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax					1
Debt securities, available-for-sale	36		36		$ 33
Duke Energy Indiana [Member] | US treasury and government [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax [Abstract]
Debt securities, available-for-sale	$ 1		$ 1