Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	$ 159
Due after one through five years	957
Due after five through 10 years	550
Due after 10 years	1,525
Total	3,191
Duke Energy Carolinas
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	3
Due after one through five years	337
Due after five through 10 years	226
Due after 10 years	875
Total	1,441
Progress Energy
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	138
Due after one through five years	546
Due after five through 10 years	248
Due after 10 years	544
Total	1,476
Duke Energy Progress
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	31
Due after one through five years	256
Due after five through 10 years	231
Due after 10 years	507
Total	1,025
Duke Energy Florida
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	107
Due after one through five years	290
Due after five through 10 years	17
Due after 10 years	37
Total	451
Duke Energy Indiana
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	7
Due after one through five years	25
Due after five through 10 years	10
Due after 10 years	22
Total	$ 64