Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
|
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | $ 34 | $ 30 | $ 120 | $ 110 |
| Duke Energy Carolinas [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | 11 | 10 | 40 | 36 |
| Progress Energy [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | 10 | 10 | 36 | 33 |
| Duke Energy Progress [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | 7 | 7 | 26 | 23 |
| Duke Energy Florida [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | 3 | 3 | 10 | 10 |
| Duke Energy Ohio [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | 2 | 2 | ||
| Duke Energy Indiana [Member] | ||||
| Employee Savings Plans [Abstract] | ||||
| Employer matching contributions | $ 1 | $ 1 | $ 5 | $ 5 |