Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Estimated Fair Value	$ 3,002
Total Investments
Unrealized Holding Gains	4,387	$ 3,675
Unrealized Holding Losses	55	57
Estimated Fair Value	9,687	8,562
NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	4,138	3,523
Gross Unrealized Holding Losses	54	55
Estimated Fair Value	6,235	5,661
Debt Securities, Available-for-sale
Estimated Fair Value	2,717	2,368
Total Investments
Unrealized Holding Gains	4,295	3,609
Unrealized Holding Losses	55	57
Estimated Fair Value	9,129	8,130
NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	177	101
NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	76	37
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	806	603
NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	22	13
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	370	368
NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	51	33
Gross Unrealized Holding Losses		1
Estimated Fair Value	1,361	1,256
NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	8	3
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	180	141
Other Investments
Equity Securities, FV-NI
Gross Unrealized Holding Gains	79	57
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	146	122
Debt Securities, Available-for-sale
Estimated Fair Value	285	258
Total Investments
Unrealized Holding Gains	92	66
Unrealized Holding Losses	0	0
Estimated Fair Value	558	432
Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	127	52
Other Investments | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	8	3
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	110	67
Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5	4
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	86	94
Other Investments | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	2
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	42	41
Other Investments | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	47	56
Duke Energy Carolinas
Equity Securities, FV-NI
Estimated Fair Value		3,154
Debt Securities, Available-for-sale
Estimated Fair Value	1,250
Duke Energy Carolinas | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	2,442	1,914
Gross Unrealized Holding Losses	23	8
Estimated Fair Value	3,685	3,154
Debt Securities, Available-for-sale
Estimated Fair Value	1,250	1,172
Total Investments
Unrealized Holding Gains	2,529	1,957
Unrealized Holding Losses	24	10
Estimated Fair Value	4,965	4,347
Duke Energy Carolinas | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	30	21
Duke Energy Carolinas | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	49	21
Gross Unrealized Holding Losses	1	1
Estimated Fair Value	510	361
Duke Energy Carolinas | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	6	3
Estimated Fair Value	91	96
Duke Energy Carolinas | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	25	16
Gross Unrealized Holding Losses		1
Estimated Fair Value	475	578
Duke Energy Carolinas | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	7	3
Estimated Fair Value	174	137
Progress Energy
Debt Securities, Available-for-sale
Estimated Fair Value	1,493
Total Investments
Unrealized Holding Gains	1,769	1,655
Unrealized Holding Losses	31	47
Estimated Fair Value	4,296	3,883
Progress Energy | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,696	1,609
Gross Unrealized Holding Losses	31	47
Estimated Fair Value	2,550	2,507
Debt Securities, Available-for-sale
Estimated Fair Value	1,467	1,196
Total Investments
Unrealized Holding Gains	1,766	1,652
Unrealized Holding Losses	31	47
Estimated Fair Value	4,164	3,783
Progress Energy | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	147	80
Progress Energy | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	27	16
Gross Unrealized Holding Losses	0
Estimated Fair Value	296	242
Progress Energy | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	10
Gross Unrealized Holding Losses	0
Estimated Fair Value	279	272
Progress Energy | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	26	17
Gross Unrealized Holding Losses	0
Estimated Fair Value	886	678
Progress Energy | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	6	4
Progress Energy | Other Investments
Debt Securities, Available-for-sale
Estimated Fair Value	26	51
Total Investments
Unrealized Holding Gains	3	3
Unrealized Holding Losses	0	0
Estimated Fair Value	132	100
Progress Energy | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	106	49
Progress Energy | Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	3
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	26	51
Duke Energy Progress
Debt Securities, Available-for-sale
Estimated Fair Value	993
Total Investments
Unrealized Holding Gains	1,687	1,300
Unrealized Holding Losses	31	21
Estimated Fair Value	3,529	3,053
Duke Energy Progress | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	1,617	1,258
Gross Unrealized Holding Losses	31	21
Estimated Fair Value	2,459	2,077
Debt Securities, Available-for-sale
Estimated Fair Value	993	921
Total Investments
Unrealized Holding Gains	1,687	1,300
Unrealized Holding Losses	31	21
Estimated Fair Value	3,528	3,051
Duke Energy Progress | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	76	53
Duke Energy Progress | NDTF | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	27	16
Estimated Fair Value	296	242
Duke Energy Progress | NDTF | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	16	10
Estimated Fair Value	279	272
Duke Energy Progress | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	26	16
Estimated Fair Value	412	403
Duke Energy Progress | NDTF | Other debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	6	4
Duke Energy Progress | Other Investments
Total Investments
Unrealized Holding Gains	0	0
Unrealized Holding Losses	0	0
Estimated Fair Value	1	2
Duke Energy Progress | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	1	2
Duke Energy Florida
Debt Securities, Available-for-sale
Estimated Fair Value	500
Total Investments
Unrealized Holding Gains	82	355
Unrealized Holding Losses	0	26
Estimated Fair Value	663	787
Duke Energy Florida | NDTF
Equity Securities, FV-NI
Gross Unrealized Holding Gains	79	351
Gross Unrealized Holding Losses		26
Estimated Fair Value	91	430
Debt Securities, Available-for-sale
Estimated Fair Value	474	275
Total Investments
Unrealized Holding Gains	79	352
Unrealized Holding Losses	0	26
Estimated Fair Value	636	732
Duke Energy Florida | NDTF | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	71	27
Duke Energy Florida | NDTF | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains		1
Estimated Fair Value	474	275
Duke Energy Florida | Other Investments
Debt Securities, Available-for-sale
Estimated Fair Value	26	51
Total Investments
Unrealized Holding Gains	3	3
Unrealized Holding Losses	0	0
Estimated Fair Value	27	55
Duke Energy Florida | Other Investments | Cash and cash equivalents
Available-for-sale Securities
Cash and cash equivalents	1	4
Duke Energy Florida | Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	3
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	26	51
Duke Energy Indiana
Debt Securities, Available-for-sale
Estimated Fair Value	45
Total Investments
Unrealized Holding Gains	59	44
Unrealized Holding Losses		0
Estimated Fair Value	143	125
Duke Energy Indiana | Other Investments
Available-for-sale Securities
Cash and cash equivalents	1
Equity Securities, FV-NI
Gross Unrealized Holding Gains	58	43
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	97	81
Debt Securities, Available-for-sale
Estimated Fair Value	45	44
Duke Energy Indiana | Other Investments | Corporate debt securities
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	3	6
Duke Energy Indiana | Other Investments | Municipal bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	38	36
Duke Energy Indiana | Other Investments | U.S. government bonds
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	0	0
Estimated Fair Value	$ 4	$ 2