Investments in Debt and Equity Securities (Maturities) (Details) $ in Millions	Jun. 30, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	$ 365
Due after one through five years	527
Due after five through 10 years	499
Due after 10 years	1,186
Total	2,577
Duke Energy Carolinas [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	43
Due after one through five years	213
Due after five through 10 years	242
Due after 10 years	622
Total	1,120
Progress Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	315
Due after one through five years	265
Due after five through 10 years	203
Due after 10 years	458
Total	1,241
Duke Energy Progress [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	29
Due after one through five years	257
Due after five through 10 years	192
Due after 10 years	428
Total	906
Duke Energy Florida [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	286
Due after one through five years	8
Due after five through 10 years	11
Due after 10 years	30
Total	335
Duke Energy Indiana [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less	4
Due after one through five years	15
Due after five through 10 years	4
Due after 10 years	19
Total	$ 42