v3.7.0.1
Investments in Debt and Equity Securities (Maturities) (Details)
$ in Millions
Mar. 31, 2017
USD ($)
Debt Instrument [Line Items]  
Due in one year or less $ 82
Due after one through five years 640
Due after five through 10 years 514
Due after 10 years 986
Total 2,222
Duke Energy Carolinas [Member]  
Debt Instrument [Line Items]  
Due in one year or less 2
Due after one through five years 221
Due after five through 10 years 269
Due after 10 years 517
Total 1,009
Progress Energy [Member]  
Debt Instrument [Line Items]  
Due in one year or less 72
Due after one through five years 355
Due after five through 10 years 189
Due after 10 years 417
Total 1,033
Duke Energy Progress [Member]  
Debt Instrument [Line Items]  
Due in one year or less 17
Due after one through five years 215
Due after five through 10 years 142
Due after 10 years 316
Total 690
Duke Energy Florida [Member]  
Debt Instrument [Line Items]  
Due in one year or less 55
Due after one through five years 140
Due after five through 10 years 47
Due after 10 years 101
Total 343
Duke Energy Indiana [Member]  
Debt Instrument [Line Items]  
Due in one year or less 2
Due after one through five years 15
Due after five through 10 years 9
Due after 10 years 5
Total $ 31