Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 2,577
Derivative assets	38	$ 57
Total assets	8,068	7,132
Derivative liabilities	(342)	(242)
Net assets (liabilities)	7,726	6,890
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	4
Total assets	6,203	5,156
Derivative liabilities	(12)	(11)
Net assets (liabilities)	6,191	5,145
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		25
Total assets	1,771	1,883
Derivative liabilities	(216)	(90)
Net assets (liabilities)	1,555	1,793
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	35	28
Total assets	35	28
Derivative liabilities	(114)	(141)
Net assets (liabilities)	(79)	(113)
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	59	65
Net assets (liabilities)	59	65
Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,178	4,475
Debt securities, available-for-sale	2,425	2,231
Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,119	4,410
Debt securities, available-for-sale	870	576
Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,555	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	59	65
Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	112	99
Debt securities, available-for-sale	315	270
Other Classification [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	112	99
Debt securities, available-for-sale	99	67
Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	216	203
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,120
Derivative assets		3
Total assets	4,044	3,556
Derivative liabilities	(93)	(33)
Net assets (liabilities)	3,951	3,523
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	3,074	2,568
Net assets (liabilities)	3,074	2,568
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		3
Total assets	911	923
Derivative liabilities	(93)	(33)
Net assets (liabilities)	818	890
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	59	65
Net assets (liabilities)	59	65
Duke Energy Carolinas [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,883	2,484
Debt securities, available-for-sale	1,161	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	2,824	2,419
Debt securities, available-for-sale	250	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	911	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	59	65
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,241
Derivative assets		4
Total assets	3,656	3,221
Derivative liabilities	(90)	(44)
Net assets (liabilities)	3,566	3,177
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	2,962	2,435
Net assets (liabilities)	2,962	2,435
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	4
Total assets	694	786
Derivative liabilities	(90)	(44)
Net assets (liabilities)	604	742
Progress Energy [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,295	1,991
Debt securities, available-for-sale	1,264	1,162
Progress Energy [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,295	1,991
Debt securities, available-for-sale	620	427
Progress Energy [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	644	735
Progress Energy [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	97	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	47	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	50	47
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	906
Derivative assets		4
Total assets	2,836	2,504
Derivative liabilities	(35)	(27)
Net assets (liabilities)	2,801	2,477
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	2,192	1,888
Net assets (liabilities)	2,192	1,888
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		4
Total assets	644	616
Derivative liabilities	(35)	(27)
Net assets (liabilities)	609	589
Duke Energy Progress [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,886	1,588
Debt securities, available-for-sale	948	906
Duke Energy Progress [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,886	1,588
Debt securities, available-for-sale	304	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	644	612
Duke Energy Progress [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	2	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	2	6
Duke Energy Florida [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	335
Total assets	777	707
Derivative liabilities	(39)	(9)
Net assets (liabilities)	738	698
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	727	537
Net assets (liabilities)	727	537
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	50	170
Derivative liabilities	(39)	(9)
Net assets (liabilities)	11	161
Duke Energy Florida [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	409	403
Debt securities, available-for-sale	316	256
Duke Energy Florida [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	409	403
Debt securities, available-for-sale	316	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	52	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	2	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	50	47
Duke Energy Indiana [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	74	67
Debt securities, available-for-sale	42
Derivative assets	29	23
Total assets	145	131
Derivative liabilities	(2)
Net assets (liabilities)	143	131
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	1
Total assets	75	68
Derivative liabilities	(2)
Net assets (liabilities)	73	68
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	42	41
Net assets (liabilities)	42	41
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	22
Total assets	28	22
Net assets (liabilities)	28	22
Duke Energy Indiana [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	74	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	74	67
Piedmont Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Derivative liabilities	(114)	(141)
Net assets (liabilities)	(112)	(138)
Piedmont Natural Gas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	3
Net assets (liabilities)	2	3
Piedmont Natural Gas [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(114)	(141)
Net assets (liabilities)	(114)	(141)
Debt Securities [Member] | Duke Energy Indiana [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	42	41
Debt Securities [Member] | Duke Energy Indiana [Member] | Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 42	$ 41