Investments in Debt and Equity Securities (Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Estimated Fair Value	$ 2,711
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	2,671	$ 3,675
Unrealized Holding Losses	193	57
Estimated Fair Value	7,511	8,562
NDTF
Available-for-sale Securities
Cash and cash equivalents	119	101
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	2,499	3,523
Equity Securities, FV-NI, Accumulated Unrealized Loss	170	55
Equity securities, FV-NI	4,488	5,661
Debt Securities, Available-for-sale
Estimated Fair Value	2,540	2,469
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	2,629	3,609
Unrealized Holding Losses	191	57
Estimated Fair Value	7,048	8,130
Other Investments
Available-for-sale Securities
Cash and cash equivalents	78	52
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	31	57
Equity Securities, FV-NI, Accumulated Unrealized Loss	1
Equity securities, FV-NI	95	122
Debt Securities, Available-for-sale
Estimated Fair Value	368	310
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	42	66
Unrealized Holding Losses	2
Estimated Fair Value	463	432
Duke Energy Carolinas
Debt Securities, Available-for-sale
Estimated Fair Value	1,181
Duke Energy Carolinas | NDTF
Available-for-sale Securities
Cash and cash equivalents	33	21
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,355	1,914
Equity Securities, FV-NI, Accumulated Unrealized Loss	81	8
Equity securities, FV-NI	2,498	3,154
Debt Securities, Available-for-sale
Estimated Fair Value	1,214	1,193
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,411	1,957
Unrealized Holding Losses	97	10
Estimated Fair Value	3,712	4,347
Progress Energy
Debt Securities, Available-for-sale
Estimated Fair Value	1,293
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,223	1,655
Unrealized Holding Losses	94	47
Estimated Fair Value	3,458	3,883
Progress Energy | NDTF
Available-for-sale Securities
Cash and cash equivalents	86	80
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	1,144	1,609
Equity Securities, FV-NI, Accumulated Unrealized Loss	89	47
Equity securities, FV-NI	1,990	2,507
Debt Securities, Available-for-sale
Estimated Fair Value	1,326	1,276
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	1,218	1,652
Unrealized Holding Losses	94	47
Estimated Fair Value	3,336	3,783
Progress Energy | Other Investments
Available-for-sale Securities
Cash and cash equivalents	69	49
Debt Securities, Available-for-sale
Estimated Fair Value	122	100
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	5	3
Estimated Fair Value	122	100
Duke Energy Progress
Debt Securities, Available-for-sale
Estimated Fair Value	966
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	934	1,300
Unrealized Holding Losses	84	21
Estimated Fair Value	2,650	3,053
Duke Energy Progress | NDTF
Available-for-sale Securities
Cash and cash equivalents	51	53
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	881	1,258
Equity Securities, FV-NI, Accumulated Unrealized Loss	79	21
Equity securities, FV-NI	1,631	2,077
Debt Securities, Available-for-sale
Estimated Fair Value	1,017	974
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	934	1,300
Unrealized Holding Losses	84	21
Estimated Fair Value	2,648	3,051
Duke Energy Progress | Other Investments
Available-for-sale Securities
Cash and cash equivalents	2	2
Debt Securities, Available-for-sale
Estimated Fair Value	2	2
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Estimated Fair Value	2	2
Duke Energy Florida
Debt Securities, Available-for-sale
Estimated Fair Value	327
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	289	355
Unrealized Holding Losses	10	26
Estimated Fair Value	744	787
Duke Energy Florida | NDTF
Available-for-sale Securities
Cash and cash equivalents	35	27
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	263	351
Equity Securities, FV-NI, Accumulated Unrealized Loss	10	26
Equity securities, FV-NI	359	430
Debt Securities, Available-for-sale
Estimated Fair Value	309	302
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	284	352
Unrealized Holding Losses	10	26
Estimated Fair Value	688	732
Duke Energy Florida | Other Investments
Available-for-sale Securities
Cash and cash equivalents	3	4
Debt Securities, Available-for-sale
Estimated Fair Value	56	55
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	5	3
Estimated Fair Value	56	55
Duke Energy Indiana
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	26	43
Equity Securities, FV-NI, Accumulated Unrealized Loss	1
Equity securities, FV-NI	63	81
Debt Securities, Available-for-sale
Estimated Fair Value	43
Investments, Accumulated Gross Unrealized Gains (Losses) [Abstract]
Unrealized Holding Gains	27	44
Unrealized Holding Losses	2
Estimated Fair Value	106	125
Duke Energy Indiana | Other Investments
Equity Securities, FV-NI
Equity securities, FV-NI	63	81
Corporate debt securities | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	26	37
Gross Unrealized Holding Losses	16	1
Estimated Fair Value	642	603
Corporate debt securities | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains		3
Estimated Fair Value	89	67
Corporate debt securities | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	15	21
Gross Unrealized Holding Losses	12	1
Estimated Fair Value	392	361
Corporate debt securities | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	11	16
Gross Unrealized Holding Losses	4
Estimated Fair Value	250	242
Corporate debt securities | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	11	16
Gross Unrealized Holding Losses	4
Estimated Fair Value	250	242
Corporate debt securities | Duke Energy Indiana
Debt Securities, Available-for-sale
Estimated Fair Value	4	6
Municipal bonds | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	10	13
Gross Unrealized Holding Losses	2
Estimated Fair Value	404	368
Municipal bonds | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	6	4
Gross Unrealized Holding Losses	1
Estimated Fair Value	98	94
Municipal bonds | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	3
Gross Unrealized Holding Losses	1
Estimated Fair Value	128	96
Municipal bonds | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	7	10
Gross Unrealized Holding Losses	1
Estimated Fair Value	276	272
Municipal bonds | Progress Energy | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5	3
Estimated Fair Value	53	51
Municipal bonds | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	7	10
Gross Unrealized Holding Losses	1
Estimated Fair Value	276	272
Municipal bonds | Duke Energy Florida | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5	3
Estimated Fair Value	53	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	36	36
U.S. government bonds | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	70	33
Gross Unrealized Holding Losses		1
Estimated Fair Value	1,212	1,256
U.S. government bonds | Other Investments
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	5	2
Estimated Fair Value	51	41
U.S. government bonds | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	35	16
Gross Unrealized Holding Losses		1
Estimated Fair Value	502	578
U.S. government bonds | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	35	17
Estimated Fair Value	710	678
U.S. government bonds | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	34	16
Estimated Fair Value	436	403
U.S. government bonds | Duke Energy Florida | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1	1
Estimated Fair Value	274	275
U.S. government bonds | Duke Energy Indiana
Debt Securities, Available-for-sale
Estimated Fair Value	3	2
NDTF equity security contracts | NDTF
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	20
Equity securities, FV-NI	20
NDTF equity security contracts | Progress Energy | NDTF
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	20
Equity securities, FV-NI	20
NDTF equity security contracts | Duke Energy Florida | NDTF
Equity Securities, FV-NI
Equity Securities, FV-NI, Accumulated Unrealized Gain	20
Equity securities, FV-NI	20
Other debt securities | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	4	3
Gross Unrealized Holding Losses	3
Estimated Fair Value	163	141
Other debt securities | Other Investments
Debt Securities, Available-for-sale
Estimated Fair Value	52	56
Other debt securities | Duke Energy Carolinas | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	3	3
Gross Unrealized Holding Losses	3
Estimated Fair Value	159	137
Other debt securities | Progress Energy | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Estimated Fair Value	4	4
Other debt securities | Duke Energy Progress | NDTF
Debt Securities, Available-for-sale
Gross Unrealized Holding Gains	1
Estimated Fair Value	$ 4	$ 4