Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Estimated Fair Value	$ 2,532
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	3,257	$ 3,675
Unrealized Holding Losses	98	57
Estimated Fair Value	8,531	8,562
NDTF
Available-for-sale Securities
Cash and cash equivalents	731	101
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	3,034	3,523
Equity Securities, FV-NI, Accumulated Unrealized Loss	92	55
Equity securities, FV-NI	5,039	5,661
Debt Securities, Available-for-sale
Estimated Fair Value	2,230	2,368
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	3,189	3,609
Unrealized Holding Losses	96	57
Estimated Fair Value	8,000	8,130
Other Investments
Available-for-sale Securities
Cash and cash equivalents	113	52
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	51	57
Equity securities, FV-NI	116	122
Debt Securities, Available-for-sale
Estimated Fair Value	302	258
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	68	66
Unrealized Holding Losses	2
Estimated Fair Value	531	432
Duke Energy Carolinas
Debt Securities, Available-for-sale
Estimated Fair Value	1,239
Duke Energy Carolinas | NDTF
Available-for-sale Securities
Cash and cash equivalents	30	21
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,796	1,914
Equity Securities, FV-NI, Accumulated Unrealized Loss	47	8
Equity securities, FV-NI	2,989	3,154
Debt Securities, Available-for-sale
Estimated Fair Value	1,239	1,172
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,880	1,957
Unrealized Holding Losses	50	10
Estimated Fair Value	4,258	4,347
Progress Energy
Debt Securities, Available-for-sale
Estimated Fair Value	1,043
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,313	1,655
Unrealized Holding Losses	46	47
Estimated Fair Value	3,902	3,883
Progress Energy | NDTF
Available-for-sale Securities
Cash and cash equivalents	701	80
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,238	1,609
Equity Securities, FV-NI, Accumulated Unrealized Loss	45	47
Equity securities, FV-NI	2,050	2,507
Debt Securities, Available-for-sale
Estimated Fair Value	991	1,196
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,309	1,652
Unrealized Holding Losses	46	47
Estimated Fair Value	3,742	3,783
Progress Energy | Other Investments
Available-for-sale Securities
Cash and cash equivalents	108	49
Debt Securities, Available-for-sale
Estimated Fair Value	52	51
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	4	3
Estimated Fair Value	160	100
Duke Energy Progress
Debt Securities, Available-for-sale
Estimated Fair Value	991
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,247	1,300
Unrealized Holding Losses	46	21
Estimated Fair Value	3,032	3,053
Duke Energy Progress | NDTF
Available-for-sale Securities
Cash and cash equivalents	63	53
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,176	1,258
Equity Securities, FV-NI, Accumulated Unrealized Loss	45	21
Equity securities, FV-NI	1,977	2,077
Debt Securities, Available-for-sale
Estimated Fair Value	991	921
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,247	1,300
Unrealized Holding Losses	46	21
Estimated Fair Value	3,031	3,051
Duke Energy Progress | Other Investments
Available-for-sale Securities
Cash and cash equivalents	1	2
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Estimated Fair Value	1	2
Duke Energy Florida
Debt Securities, Available-for-sale
Estimated Fair Value	52
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	66	355
Unrealized Holding Losses		26
Estimated Fair Value	765	787
Duke Energy Florida | NDTF
Available-for-sale Securities
Cash and cash equivalents	638	27
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	62	351
Equity Securities, FV-NI, Accumulated Unrealized Loss		26
Equity securities, FV-NI	73	430
Debt Securities, Available-for-sale
Estimated Fair Value		275
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	62	352
Unrealized Holding Losses		26
Estimated Fair Value	711	732
Duke Energy Florida | Other Investments
Available-for-sale Securities
Cash and cash equivalents	2	4
Debt Securities, Available-for-sale
Estimated Fair Value	52	51
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	4	3
Estimated Fair Value	54	55
Duke Energy Indiana
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	39	43
Equity securities, FV-NI	77	81
Debt Securities, Available-for-sale
Estimated Fair Value	45
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	40	44
Unrealized Holding Losses	1
Estimated Fair Value	122	125
Duke Energy Indiana | Other Investments
Equity Securities, FV-NI
Equity securities, FV-NI	77	81
Debt Securities, Available-for-sale
Estimated Fair Value	45	44
Corporate debt securities | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	66	37
Gross Unrealized Holding Losses	2	1
Estimated Fair Value	806	603
Corporate debt securities | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	8	3
Estimated Fair Value	125	67
Corporate debt securities | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	41	21
Gross Unrealized Holding Losses	2	1
Estimated Fair Value	519	361
Corporate debt securities | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	25	16
Estimated Fair Value	287	242
Corporate debt securities | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	25	16
Estimated Fair Value	287	242
Corporate debt securities | Duke Energy Indiana
Debt Securities, Available-for-sale
Estimated Fair Value	3	6
Municipal bonds | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	18	13
Gross Unrealized Holding Losses	1
Estimated Fair Value	417	368
Municipal bonds | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5	4
Gross Unrealized Holding Losses	1
Estimated Fair Value	103	94
Municipal bonds | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	6	3
Estimated Fair Value	133	96
Municipal bonds | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	12	10
Gross Unrealized Holding Losses	1
Estimated Fair Value	284	272
Municipal bonds | Progress Energy | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	4	3
Estimated Fair Value	52	51
Municipal bonds | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	12	10
Gross Unrealized Holding Losses	1
Estimated Fair Value	284	272
Municipal bonds | Duke Energy Florida | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	4	3
Estimated Fair Value	52	51
Municipal bonds | Duke Energy Indiana
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses	1
Estimated Fair Value	39	36
U.S. government bonds | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	62	33
Gross Unrealized Holding Losses		1
Estimated Fair Value	813	1,256
U.S. government bonds | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	2
Estimated Fair Value	40	41
U.S. government bonds | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	30	16
Gross Unrealized Holding Losses		1
Estimated Fair Value	399	578
U.S. government bonds | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	32	17
Estimated Fair Value	414	678
U.S. government bonds | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	32	16
Estimated Fair Value	414	403
U.S. government bonds | Duke Energy Florida | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains		1
Estimated Fair Value		275
U.S. government bonds | Duke Energy Indiana
Debt Securities, Available-for-sale
Estimated Fair Value	3	2
Other debt securities | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	9	3
Gross Unrealized Holding Losses	1
Estimated Fair Value	194	141
Other debt securities | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Gross Unrealized Holding Losses	1
Estimated Fair Value	34	56
Other debt securities | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	7	3
Gross Unrealized Holding Losses	1
Estimated Fair Value	188	137
Other debt securities | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2
Estimated Fair Value	6	4
Other debt securities | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	2
Estimated Fair Value	$ 6	$ 4