Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale
Estimated Fair Value	$ 2,626
Total Investments
Unrealized Holding Gains	3,675	$ 2,458
Unrealized Holding Losses	57	131
Estimated Fair Value	8,562	7,075
NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	3,523	2,402
Gross Unrealized Holding Losses	55	95
Estimated Fair Value	5,661	4,475
Debt Securities, Available-for-sale
Estimated Fair Value	2,469	2,231
Total Investments
Unrealized Holding Gains	3,609	2,421
Unrealized Holding Losses	57	126
Estimated Fair Value	8,130	6,706
NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments	101	88
NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	37	4
Gross Unrealized Holding Losses	1	13
Estimated Fair Value	603	566
NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	13	1
Gross Unrealized Holding Losses	0	4
Estimated Fair Value	368	353
NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	33	14
Gross Unrealized Holding Losses	1	12
Estimated Fair Value	1,256	1,076
NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	2
Estimated Fair Value	141	148
Other Investments
Equity Securities, FV-NI
Gross Unrealized Holding Gains	57	36
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	122	99
Debt Securities, Available-for-sale
Estimated Fair Value	310	270
Total Investments
Unrealized Holding Gains	66	37
Unrealized Holding Losses	0	5
Estimated Fair Value	432	369
Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments	52	22
Other Investments | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	2
Estimated Fair Value	67	60
Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	4	0
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	94	85
Other Investments | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2	1
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	41	45
Other Investments | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	56	58
Duke Energy Carolinas
Equity Securities, FV-NI
Estimated Fair Value		2,484
Debt Securities, Available-for-sale
Estimated Fair Value	1,172
Duke Energy Carolinas | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,914	1,309
Gross Unrealized Holding Losses	8	54
Estimated Fair Value	3,154	2,484
Debt Securities, Available-for-sale
Estimated Fair Value	1,193	1,069
Total Investments
Unrealized Holding Gains	1,957	1,316
Unrealized Holding Losses	10	74
Estimated Fair Value	4,347	3,553
Duke Energy Carolinas | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments	21	29
Duke Energy Carolinas | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	21	2
Gross Unrealized Holding Losses	1	9
Estimated Fair Value	361	341
Duke Energy Carolinas | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	96	81
Duke Energy Carolinas | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	5
Gross Unrealized Holding Losses	1	8
Estimated Fair Value	578	475
Duke Energy Carolinas | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	2
Estimated Fair Value	137	143
Progress Energy
Debt Securities, Available-for-sale
Estimated Fair Value	1,247
Total Investments
Unrealized Holding Gains	1,655	1,105
Unrealized Holding Losses	47	52
Estimated Fair Value	3,883	3,217
Progress Energy | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,609	1,093
Gross Unrealized Holding Losses	47	41
Estimated Fair Value	2,507	1,991
Debt Securities, Available-for-sale
Estimated Fair Value	1,276	1,162
Total Investments
Unrealized Holding Gains	1,652	1,105
Unrealized Holding Losses	47	52
Estimated Fair Value	3,783	3,153
Progress Energy | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments	80	59
Progress Energy | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	2
Gross Unrealized Holding Losses	0	4
Estimated Fair Value	242	225
Progress Energy | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	10	1
Gross Unrealized Holding Losses	0	3
Estimated Fair Value	272	272
Progress Energy | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	17	9
Gross Unrealized Holding Losses	0	4
Estimated Fair Value	678	601
Progress Energy | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	4	5
Progress Energy | Other Investments
Debt Securities, Available-for-sale
Estimated Fair Value	100	64
Total Investments
Unrealized Holding Gains	3	0
Unrealized Holding Losses	0	0
Estimated Fair Value	100	64
Progress Energy | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments	49	17
Progress Energy | Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	51	47
Duke Energy Progress
Debt Securities, Available-for-sale
Estimated Fair Value	921
Total Investments
Unrealized Holding Gains	1,300	842
Unrealized Holding Losses	21	39
Estimated Fair Value	3,053	2,500
Duke Energy Progress | NDTF
Available-for-sale Securities
Cash And Cash Equivalent Investments	53
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,258	833
Gross Unrealized Holding Losses	21	30
Estimated Fair Value	2,077	1,588
Debt Securities, Available-for-sale
Estimated Fair Value	974	906
Total Investments
Unrealized Holding Gains	1,300	842
Unrealized Holding Losses	21	39
Estimated Fair Value	3,051	2,494
Duke Energy Progress | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments		46
Duke Energy Progress | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	2
Gross Unrealized Holding Losses	0	3
Estimated Fair Value	242	171
Duke Energy Progress | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	10	1
Gross Unrealized Holding Losses	0	3
Estimated Fair Value	272	271
Duke Energy Progress | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	6
Gross Unrealized Holding Losses	0	3
Estimated Fair Value	403	415
Duke Energy Progress | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	4	3
Duke Energy Progress | Other Investments
Available-for-sale Securities
Cash And Cash Equivalent Investments	2
Debt Securities, Available-for-sale
Estimated Fair Value	2	6
Total Investments
Unrealized Holding Gains	0	0
Unrealized Holding Losses	0	0
Estimated Fair Value	2	6
Duke Energy Progress | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments		6
Duke Energy Florida
Debt Securities, Available-for-sale
Estimated Fair Value	326
Total Investments
Unrealized Holding Gains	355	263
Unrealized Holding Losses	26	13
Estimated Fair Value	787	707
Duke Energy Florida | NDTF
Available-for-sale Securities
Cash And Cash Equivalent Investments	27
Equity Securities, FV-NI
Gross Unrealized Holding Gains	351	260
Gross Unrealized Holding Losses	26	11
Estimated Fair Value	430	403
Debt Securities, Available-for-sale
Estimated Fair Value	302	256
Total Investments
Unrealized Holding Gains	352	263
Unrealized Holding Losses	26	13
Estimated Fair Value	732	659
Duke Energy Florida | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments		13
Duke Energy Florida | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	0	54
Duke Energy Florida | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	0	1
Duke Energy Florida | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	3
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	275	186
Duke Energy Florida | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	0	2
Duke Energy Florida | Other Investments
Available-for-sale Securities
Cash And Cash Equivalent Investments	4
Debt Securities, Available-for-sale
Estimated Fair Value	55	48
Total Investments
Unrealized Holding Gains	3	0
Unrealized Holding Losses	0	0
Estimated Fair Value	55	48
Duke Energy Florida | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash And Cash Equivalent Investments		1
Duke Energy Florida | Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	51	47
Duke Energy Indiana
Equity Securities, FV-NI
Gross Unrealized Holding Gains	43	29
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	81	67
Debt Securities, Available-for-sale
Estimated Fair Value	44
Total Investments
Unrealized Holding Gains	44	29
Unrealized Holding Losses		1
Estimated Fair Value	125	108
Duke Energy Indiana | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	6	8
Duke Energy Indiana | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	0
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	36	33
Duke Energy Indiana | Other Investments
Equity Securities, FV-NI
Estimated Fair Value	81	67
Debt Securities, Available-for-sale
Estimated Fair Value	44	41
Duke Energy Indiana | Other Investments | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Estimated Fair Value	$ 2	$ 0