Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale Securities
Gross Unrealized Holding Gains		$ 2,899
Gross Unrealized Holding Losses		42
Estimated Fair Value		7,451
Debt Securities, Available-for-sale
Estimated Fair Value	$ 2,391
Total Investments
Unrealized Holding Gains	2,458
Unrealized Holding Losses	131
Estimated Fair Value	7,075
NDTF [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	88
Available-for-sale Securities
Gross Unrealized Holding Gains		2,837
Gross Unrealized Holding Losses		40
Estimated Fair Value		7,088
Equity Securities, FV-NI
Gross Unrealized Holding Gains	2,402
Gross Unrealized Holding Losses	95
Estimated Fair Value	4,475
Debt Securities, Available-for-sale
Estimated Fair Value	2,231
Total Investments
Unrealized Holding Gains	2,421
Unrealized Holding Losses	126
Estimated Fair Value	6,706
NDTF [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		115
NDTF [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		2,805
Gross Unrealized Holding Losses		27
Estimated Fair Value		4,914
NDTF [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		17
Gross Unrealized Holding Losses		2
Estimated Fair Value		570
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	4
Gross Unrealized Holding Losses	13
Estimated Fair Value	566
NDTF [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		4
Gross Unrealized Holding Losses		3
Estimated Fair Value		344
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Gross Unrealized Holding Losses	4
Estimated Fair Value	353
NDTF [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		11
Gross Unrealized Holding Losses		7
Estimated Fair Value		1,027
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	14
Gross Unrealized Holding Losses	12
Estimated Fair Value	1,076
NDTF [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Gross Unrealized Holding Losses		1
Estimated Fair Value		118
Debt Securities, Available-for-sale
Gross Unrealized Holding Losses	2
Estimated Fair Value	148
Other Classification [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	22
Available-for-sale Securities
Gross Unrealized Holding Gains		62
Gross Unrealized Holding Losses		2
Estimated Fair Value		363
Equity Securities, FV-NI
Gross Unrealized Holding Gains	36
Gross Unrealized Holding Losses	1
Estimated Fair Value	99
Debt Securities, Available-for-sale
Estimated Fair Value	270
Total Investments
Unrealized Holding Gains	37
Unrealized Holding Losses	5
Estimated Fair Value	369
Other Classification [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		15
Other Classification [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		59
Estimated Fair Value		123
Other Classification [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		1
Estimated Fair Value		57
Debt Securities, Available-for-sale
Gross Unrealized Holding Losses	2
Estimated Fair Value	60
Other Classification [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Gross Unrealized Holding Losses		1
Estimated Fair Value		83
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	1
Estimated Fair Value	85
Other Classification [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Estimated Fair Value		41
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Estimated Fair Value	45
Other Classification [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Gross Unrealized Holding Losses		1
Estimated Fair Value		44
Debt Securities, Available-for-sale
Gross Unrealized Holding Losses	1
Estimated Fair Value	58
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale
Estimated Fair Value	1,040
Duke Energy Carolinas [Member] | NDTF [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	29
Available-for-sale Securities
Gross Unrealized Holding Gains		1,543
Gross Unrealized Holding Losses		20
Estimated Fair Value		3,758
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,309
Gross Unrealized Holding Losses	54
Estimated Fair Value	2,484
Debt Securities, Available-for-sale
Estimated Fair Value	1,069
Total Investments
Unrealized Holding Gains	1,316
Unrealized Holding Losses	74
Estimated Fair Value	3,553
Duke Energy Carolinas [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		32
Duke Energy Carolinas [Member] | NDTF [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		1,531
Gross Unrealized Holding Losses		12
Estimated Fair Value		2,692
Duke Energy Carolinas [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		9
Gross Unrealized Holding Losses		2
Estimated Fair Value		359
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2
Gross Unrealized Holding Losses	9
Estimated Fair Value	341
Duke Energy Carolinas [Member] | NDTF [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Losses		1
Estimated Fair Value		60
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	1
Estimated Fair Value	81
Duke Energy Carolinas [Member] | NDTF [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		3
Gross Unrealized Holding Losses		4
Estimated Fair Value		503
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5
Gross Unrealized Holding Losses	8
Estimated Fair Value	475
Duke Energy Carolinas [Member] | NDTF [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Gross Unrealized Holding Losses		1
Estimated Fair Value		112
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	2
Estimated Fair Value	143
Progress Energy [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		1,296
Gross Unrealized Holding Losses		20
Estimated Fair Value		3,389
Debt Securities, Available-for-sale
Estimated Fair Value	1,150
Total Investments
Unrealized Holding Gains	1,105
Unrealized Holding Losses	52
Estimated Fair Value	3,217
Progress Energy [Member] | NDTF [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	59
Available-for-sale Securities
Gross Unrealized Holding Gains		1,294
Gross Unrealized Holding Losses		20
Estimated Fair Value		3,330
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,093
Gross Unrealized Holding Losses	41
Estimated Fair Value	1,991
Debt Securities, Available-for-sale
Estimated Fair Value	1,162
Total Investments
Unrealized Holding Gains	1,105
Unrealized Holding Losses	52
Estimated Fair Value	3,153
Progress Energy [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		83
Progress Energy [Member] | NDTF [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		1,274
Gross Unrealized Holding Losses		15
Estimated Fair Value		2,222
Progress Energy [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		8
Estimated Fair Value		211
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2
Gross Unrealized Holding Losses	4
Estimated Fair Value	225
Progress Energy [Member] | NDTF [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		4
Gross Unrealized Holding Losses		2
Estimated Fair Value		284
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Gross Unrealized Holding Losses	3
Estimated Fair Value	272
Progress Energy [Member] | NDTF [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		8
Gross Unrealized Holding Losses		3
Estimated Fair Value		524
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	9
Gross Unrealized Holding Losses	4
Estimated Fair Value	601
Progress Energy [Member] | NDTF [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Estimated Fair Value		6
Debt Securities, Available-for-sale
Estimated Fair Value	5
Progress Energy [Member] | Other Classification [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	17
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Estimated Fair Value		59
Debt Securities, Available-for-sale
Estimated Fair Value	64
Total Investments
Unrealized Holding Gains	0
Estimated Fair Value	64
Progress Energy [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		12
Progress Energy [Member] | Other Classification [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Estimated Fair Value		47
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Estimated Fair Value	47
Duke Energy Progress [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		995
Gross Unrealized Holding Losses		16
Estimated Fair Value		2,592
Debt Securities, Available-for-sale
Estimated Fair Value	860
Total Investments
Unrealized Holding Gains	842
Unrealized Holding Losses	39
Estimated Fair Value	2,500
Duke Energy Progress [Member] | NDTF [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	46
Available-for-sale Securities
Gross Unrealized Holding Gains		995
Gross Unrealized Holding Losses		16
Estimated Fair Value		2,591
Equity Securities, FV-NI
Gross Unrealized Holding Gains	833
Gross Unrealized Holding Losses	30
Estimated Fair Value	1,588
Debt Securities, Available-for-sale
Estimated Fair Value	906
Total Investments
Unrealized Holding Gains	842
Unrealized Holding Losses	39
Estimated Fair Value	2,494
Duke Energy Progress [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		50
Duke Energy Progress [Member] | NDTF [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		980
Gross Unrealized Holding Losses		12
Estimated Fair Value		1,795
Duke Energy Progress [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		6
Estimated Fair Value		149
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2
Gross Unrealized Holding Losses	3
Estimated Fair Value	171
Duke Energy Progress [Member] | NDTF [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		4
Gross Unrealized Holding Losses		2
Estimated Fair Value		283
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Gross Unrealized Holding Losses	3
Estimated Fair Value	271
Duke Energy Progress [Member] | NDTF [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		5
Gross Unrealized Holding Losses		2
Estimated Fair Value		310
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	6
Gross Unrealized Holding Losses	3
Estimated Fair Value	415
Duke Energy Progress [Member] | NDTF [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Estimated Fair Value		4
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	3
Duke Energy Progress [Member] | Other Classification [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	6
Available-for-sale Securities
Estimated Fair Value		1
Debt Securities, Available-for-sale
Estimated Fair Value	6
Total Investments
Estimated Fair Value	6
Duke Energy Progress [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		1
Duke Energy Florida [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		301
Gross Unrealized Holding Losses		4
Estimated Fair Value		787
Debt Securities, Available-for-sale
Estimated Fair Value	290
Total Investments
Unrealized Holding Gains	263
Unrealized Holding Losses	13
Estimated Fair Value	707
Duke Energy Florida [Member] | NDTF [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	13
Available-for-sale Securities
Gross Unrealized Holding Gains		299
Gross Unrealized Holding Losses		4
Estimated Fair Value		739
Equity Securities, FV-NI
Gross Unrealized Holding Gains	260
Gross Unrealized Holding Losses	11
Estimated Fair Value	403
Debt Securities, Available-for-sale
Estimated Fair Value	256
Total Investments
Unrealized Holding Gains	263
Unrealized Holding Losses	13
Estimated Fair Value	659
Duke Energy Florida [Member] | NDTF [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		33
Duke Energy Florida [Member] | NDTF [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		294
Gross Unrealized Holding Losses		3
Estimated Fair Value		427
Duke Energy Florida [Member] | NDTF [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Estimated Fair Value		62
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	1
Estimated Fair Value	54
Duke Energy Florida [Member] | NDTF [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Estimated Fair Value		1
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	1
Duke Energy Florida [Member] | NDTF [Member] | US Treasury and Government [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		3
Gross Unrealized Holding Losses		1
Estimated Fair Value		214
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3
Gross Unrealized Holding Losses	1
Estimated Fair Value	186
Duke Energy Florida [Member] | NDTF [Member] | Other Debt Obligations [Member]
Available-for-sale Securities
Estimated Fair Value		2
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	2
Duke Energy Florida [Member] | Other Classification [Member]
Investment [Line Items]
Cash And Cash Equivalent Investments	1
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Estimated Fair Value		48
Debt Securities, Available-for-sale
Estimated Fair Value	48
Total Investments
Estimated Fair Value	48
Duke Energy Florida [Member] | Other Classification [Member] | Cash and Cash Equivalents [Member]
Available-for-sale Securities
Estimated Fair Value		1
Duke Energy Florida [Member] | Other Classification [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		2
Estimated Fair Value		47
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0
Estimated Fair Value	47
Duke Energy Indiana [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		49
Gross Unrealized Holding Losses		1
Estimated Fair Value		128
Equity Securities, FV-NI
Gross Unrealized Holding Gains	29
Estimated Fair Value	67
Debt Securities, Available-for-sale
Estimated Fair Value	41
Total Investments
Unrealized Holding Gains	29
Unrealized Holding Losses	1
Estimated Fair Value	108
Duke Energy Indiana [Member] | Equity Securities [Member]
Available-for-sale Securities
Gross Unrealized Holding Gains		49
Estimated Fair Value		97
Duke Energy Indiana [Member] | Corporate Debt Securities [Member]
Available-for-sale Securities
Estimated Fair Value		3
Debt Securities, Available-for-sale
Estimated Fair Value	8
Duke Energy Indiana [Member] | Municipal Bonds [Member]
Available-for-sale Securities
Gross Unrealized Holding Losses		1
Estimated Fair Value		$ 28
Debt Securities, Available-for-sale
Gross Unrealized Holding Losses	1
Estimated Fair Value	33
Duke Energy Indiana [Member] | Other Classification [Member]
Equity Securities, FV-NI
Estimated Fair Value	$ 67