Investments in Debt and Equity Securities (Realized Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
FV-NI:
Realized gains	$ 302	$ 66	$ 325	$ 101
Realized losses	67	63	132	93
AFS:
Realized gains	27	47	47	57
Realized losses	13	36	19	47
Duke Energy Carolinas
FV-NI:
Realized gains	27	44	36	67
Realized losses	25	48	70	69
AFS:
Realized gains	18	16	30	25
Realized losses	8	11	13	21
Progress Energy
FV-NI:
Realized gains	275	22	289	34
Realized losses	42	15	62	24
AFS:
Realized gains	6	30	11	31
Realized losses	4	25	5	26
Duke Energy Progress
FV-NI:
Realized gains	26	7	40	17
Realized losses	27	7	47	15
AFS:
Realized gains	6	1	11	2
Realized losses	4	1	5	2
Duke Energy Florida
FV-NI:
Realized gains	249	15	249	17
Realized losses	$ 15	8	$ 15	9
AFS:
Realized gains		29		29
Realized losses		$ 24		$ 24