Related Party Transactions (Other Revenue and Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Duke Energy Carolinas | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 207	$ 198	$ 653	$ 528
Duke Energy Carolinas | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	5	18	15
Duke Energy Carolinas | JDA | Duke Energy Progress
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	68	28	133	72
Related party transaction, other revenues from transactions with related party	6	6	32	16
Duke Energy Carolinas | Intercompany natural gas purchases and sales | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	14	10	43	26
Progress Energy | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	201	185	615	520
Progress Energy | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	10	9	31	27
Progress Energy | JDA | Duke Energy Carolinas
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	6	32	16
Related party transaction, other revenues from transactions with related party	68	28	133	72
Progress Energy | Intercompany natural gas purchases and sales | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	19	18	56	56
Duke Energy Progress | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	121	113	367	301
Duke Energy Progress | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	4	4	14	13
Duke Energy Progress | JDA | Duke Energy Carolinas
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	6	32	16
Related party transaction, other revenues from transactions with related party	68	28	133	72
Duke Energy Progress | Intercompany natural gas purchases and sales | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	19	18	56	56
Duke Energy Florida | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	80	72	248	219
Duke Energy Florida | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	6	5	17	14
Duke Energy Ohio | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	79	80	237	241
Duke Energy Ohio | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	3	3
Duke Energy Indiana | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	96	102	302	300
Duke Energy Indiana | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	2	2	6	6
Piedmont | Corporate governance and shared service expenses | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	32	31	101	102
Piedmont | Indemnification coverages | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	1	1	3	2
Piedmont | Intercompany natural gas purchases and sales | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, other revenues from transactions with related party	33	28	99	82
Piedmont | Natural gas storage and transportation costs | Affiliated Entity
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party	$ 6	$ 6	$ 17	$ 17