Commitments and Contingencies (Schedule of Legal Reserves) (Details) - USD ($) $ in Millions |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | $ 91 | $ 98 |
| Duke Energy Carolinas [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 23 | 23 |
| Progress Energy [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 57 | 59 |
| Duke Energy Progress [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 13 | 14 |
| Duke Energy Florida [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 27 | 28 |
| Duke Energy Ohio [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | 4 | 4 |
| Piedmont Natural Gas [Member] | ||
| Loss Contingencies [Line Items] | ||
| Reserves for legal matters | $ 2 | $ 2 |