Commitments and Contingencies (Schedule of Reserves) (Details) - USD ($) $ in Millions |
Sep. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | $ 178 | $ 323 |
| Duke Energy Carolinas [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 12 | 72 |
| Progress Energy [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 74 | 93 |
| Duke Energy Progress [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 17 | 37 |
| Duke Energy Florida [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 36 | $ 36 |
| Duke Energy Ohio [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | $ 81 |