Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Mar. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	$ 162
Due after one through five years	969
Due after five through 10 years	536
Due after 10 years	1,466
Total	3,133
Duke Energy Carolinas
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	7
Due after one through five years	367
Due after five through 10 years	235
Due after 10 years	810
Total	1,419
Progress Energy
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	139
Due after one through five years	528
Due after five through 10 years	228
Due after 10 years	557
Total	1,452
Duke Energy Progress
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	32
Due after one through five years	270
Due after five through 10 years	212
Due after 10 years	517
Total	1,031
Duke Energy Florida
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	107
Due after one through five years	258
Due after five through 10 years	16
Due after 10 years	40
Total	421
Duke Energy Indiana
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	8
Due after one through five years	24
Due after five through 10 years	6
Due after 10 years	25
Total	$ 63