Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	$ 372
Due after one through five years	550
Due after five through 10 years	452
Due after 10 years	1,252
Total	2,626
Duke Energy Carolinas
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	51
Due after one through five years	253
Due after five through 10 years	181
Due after 10 years	687
Total	1,172
Progress Energy
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	311
Due after one through five years	256
Due after five through 10 years	211
Due after 10 years	469
Total	1,247
Duke Energy Progress
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	34
Due after one through five years	247
Due after five through 10 years	204
Due after 10 years	436
Total	921
Duke Energy Florida
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	277
Due after one through five years	9
Due after five through 10 years	7
Due after 10 years	33
Total	326
Duke Energy Indiana
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	4
Due after one through five years	16
Due after five through 10 years	7
Due after 10 years	17
Total	$ 44