Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 2,391
Derivative assets	57	$ 51
Total assets	7,132	7,503
Derivative liabilities	(242)	(230)
Net assets (liabilities)	6,890	7,273
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	3
Total assets	5,156	5,658
Derivative liabilities	(11)	(2)
Net assets (liabilities)	5,145	5,656
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	25	20
Total assets	1,883	1,743
Derivative liabilities	(90)	(86)
Net assets (liabilities)	1,793	1,657
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	28
Total assets	28	28
Derivative liabilities	(141)	(142)
Net assets (liabilities)	(113)	(114)
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	65	74
Net assets (liabilities)	65	74
NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	4,475
Debt securities, available-for-sale	2,231
NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	4,410
Debt securities, available-for-sale	576
NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,655
NDTF [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	65
Investments		74
Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	99
Debt securities, available-for-sale	270
Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	99
Debt securities, available-for-sale	67
Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	203
Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		4,914
Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		4,840
Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		123
Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		123
Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2,174
Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		635
Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1,539
Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		241
Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		57
Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		184
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,040
Derivative assets	3	2
Total assets	3,556	3,760
Derivative liabilities	(33)	(35)
Net assets (liabilities)	3,523	3,725
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	2,568	2,822
Derivative liabilities	0	(1)
Net assets (liabilities)	2,568	2,821
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	2
Total assets	923	864
Derivative liabilities	(33)	(34)
Net assets (liabilities)	890	830
Duke Energy Carolinas [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	65	74
Net assets (liabilities)	65	74
Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,484
Debt securities, available-for-sale	1,069
Duke Energy Carolinas [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,419
Debt securities, available-for-sale	149
Duke Energy Carolinas [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	920
Duke Energy Carolinas [Member] | NDTF [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	65
Investments		74
Duke Energy Carolinas [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2,692
Duke Energy Carolinas [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2,618
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1,066
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		204
Duke Energy Carolinas [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		862
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,150
Derivative assets	4	3
Total assets	3,221	3,392
Derivative liabilities	(44)	(36)
Net assets (liabilities)	3,177	3,356
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	2,435	2,666
Derivative liabilities	0	(1)
Net assets (liabilities)	2,435	2,665
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	2
Total assets	786	726
Derivative liabilities	(44)	(35)
Net assets (liabilities)	742	691
Progress Energy [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,991
Debt securities, available-for-sale	1,162
Progress Energy [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,991
Debt securities, available-for-sale	427
Progress Energy [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	735
Progress Energy [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	64
Progress Energy [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	17
Progress Energy [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	47
Progress Energy [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2,222
Progress Energy [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		2,222
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1,108
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		431
Progress Energy [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		677
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		59
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		12
Progress Energy [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		47
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	860
Derivative assets	4	2
Total assets	2,504	2,594
Derivative liabilities	(27)	(18)
Net assets (liabilities)	2,477	2,576
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	1,888	2,040
Derivative liabilities	0	(1)
Net assets (liabilities)	1,888	2,039
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Total assets	616	554
Derivative liabilities	(27)	(17)
Net assets (liabilities)	589	537
Duke Energy Progress [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,588
Debt securities, available-for-sale	906
Duke Energy Progress [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,588
Debt securities, available-for-sale	294
Duke Energy Progress [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	612
Duke Energy Progress [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	6
Duke Energy Progress [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	6
Duke Energy Progress [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1,795
Duke Energy Progress [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1,795
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		796
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		243
Duke Energy Progress [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		553
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1
Duke Energy Progress [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	290
Derivative assets		1
Total assets	707	788
Derivative liabilities	(9)	(12)
Net assets (liabilities)	698	776
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	537	616
Net assets (liabilities)	537	616
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	1
Total assets	170	172
Derivative liabilities	(9)	(12)
Net assets (liabilities)	161	160
Duke Energy Florida [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	403
Debt securities, available-for-sale	256
Duke Energy Florida [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	403
Debt securities, available-for-sale	133
Duke Energy Florida [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	123
Duke Energy Florida [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	48
Duke Energy Florida [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1
Duke Energy Florida [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	47
Duke Energy Florida [Member] | Equity Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		427
Duke Energy Florida [Member] | Equity Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		427
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		312
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		188
Duke Energy Florida [Member] | Debt Securities [Member] | NDTF [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		124
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		48
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1
Duke Energy Florida [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		47
Duke Energy Ohio [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	1
Derivative liabilities	(5)	(5)
Net assets (liabilities)	1	(4)
Duke Energy Ohio [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(5)	(5)
Net assets (liabilities)	(5)	(5)
Duke Energy Ohio [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	1
Net assets (liabilities)	6	1
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	67
Debt securities, available-for-sale	41
Derivative assets	23	27
Net assets (liabilities)	131	155
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1
Net assets (liabilities)	68	97
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net assets (liabilities)	41	31
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	22	27
Net assets (liabilities)	22	27
Duke Energy Indiana [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	67
Duke Energy Indiana [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	67
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		97
Duke Energy Indiana [Member] | Equity Securities [Member] | Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		97
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	41
Investments		31
Duke Energy Indiana [Member] | Debt Securities [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	41
Investments		31
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0
Derivative assets	3	2
Total assets	3	3
Derivative liabilities	(141)	(142)
Net assets (liabilities)	(138)	(139)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0
Derivative assets	3	2
Total assets	3	3
Net assets (liabilities)	3	3
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(141)	(142)
Net assets (liabilities)	$ (141)	(142)
Piedmont Natural Gas [Member] | Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		1
Piedmont Natural Gas [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		$ 1