Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 2,633
Derivative assets	31	$ 57
Total assets	8,165	7,132
Derivative liabilities	(353)	(242)
Net assets (liabilities)	7,812	6,890
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	4
Total assets	6,178	5,156
Derivative liabilities	(25)	(11)
Net assets (liabilities)	6,153	5,145
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	8	25
Total assets	1,912	1,883
Derivative liabilities	(217)	(90)
Net assets (liabilities)	1,695	1,793
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	21	28
Total assets	21	28
Derivative liabilities	(111)	(141)
Net assets (liabilities)	(90)	(113)
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	54	65
Net assets (liabilities)	54	65
Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,222	4,475
Debt securities, available-for-sale	2,476	2,231
Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	5,168	4,410
Debt securities, available-for-sale	804	576
Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,672	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	54	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	324	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	92	67
Other Classification [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	232	203
Duke Energy Carolinas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,159
Derivative assets		3
Total assets	4,096	3,556
Derivative liabilities	(67)	(33)
Net assets (liabilities)	4,029	3,523
Duke Energy Carolinas [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	3,036	2,568
Net assets (liabilities)	3,036	2,568
Duke Energy Carolinas [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		3
Total assets	1,006	923
Derivative liabilities	(67)	(33)
Net assets (liabilities)	939	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	54	65
Net assets (liabilities)	54	65
Duke Energy Carolinas [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,901	2,484
Debt securities, available-for-sale	1,195	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	2,847	2,419
Debt securities, available-for-sale	189	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	1,006	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	54	65
Progress Energy [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,255
Derivative assets	5	4
Total assets	3,708	3,221
Derivative liabilities	(113)	(44)
Net assets (liabilities)	3,595	3,177
Progress Energy [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	2,985	2,435
Derivative liabilities	0
Net assets (liabilities)	2,985	2,435
Progress Energy [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5	4
Total assets	723	786
Derivative liabilities	(113)	(44)
Net assets (liabilities)	610	742
Progress Energy [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,321	1,991
Debt securities, available-for-sale	1,281	1,162
Progress Energy [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,321	1,991
Debt securities, available-for-sale	615	427
Progress Energy [Member] | Ndtf [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	666	735
Progress Energy [Member] | Other Classification [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	101	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	49	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	52	47
Duke Energy Progress [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	923
Derivative assets		4
Total assets	2,884	2,504
Derivative liabilities	(43)	(27)
Net assets (liabilities)	2,841	2,477
Duke Energy Progress [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	2,218	1,888
Derivative liabilities	0
Net assets (liabilities)	2,218	1,888
Duke Energy Progress [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		4
Total assets	666	616
Derivative liabilities	(43)	(27)
Net assets (liabilities)	623	589
Duke Energy Progress [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,907	1,588
Debt securities, available-for-sale	975	906
Duke Energy Progress [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	1,907	1,588
Debt securities, available-for-sale	309	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	666	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	332
Derivative assets	5
Total assets	781	707
Derivative liabilities	(54)	(9)
Net assets (liabilities)	727	698
Duke Energy Florida [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	724	537
Net assets (liabilities)	724	537
Duke Energy Florida [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5
Total assets	57	170
Derivative liabilities	(54)	(9)
Net assets (liabilities)	3	161
Duke Energy Florida [Member] | Ndtf [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	414	403
Debt securities, available-for-sale	306	256
Duke Energy Florida [Member] | Ndtf [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	414	403
Debt securities, available-for-sale	306	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	56	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	4	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	52	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	43
Derivative assets	16	23
Total assets	133	131
Duke Energy Indiana [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets		1
Total assets	74	68
Duke Energy Indiana [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	43	41
Duke Energy Indiana [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	16	22
Total assets	16	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	(111)	(141)
Net assets (liabilities)	(109)	(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	(111)	(141)
Net assets (liabilities)	(111)	(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	43	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	$ 43	$ 41