Variable Interest Entities (Sales and Cash Flows)(Details) - Cinergy Receivables [Member] - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
|
| Duke Energy Ohio [Member] | ||||
| Variable Interest Entities [Line Items] | ||||
| Receivables sold | $ 449 | $ 477 | $ 1,518 | $ 1,705 |
| Loss recognized on sale | 2 | 3 | 7 | 9 |
| Cash proceeds from receivables sold | 461 | 494 | 1,568 | 1,761 |
| Collection fees received | 0 | 1 | 1 | |
| Return received on retained interests | 0 | 2 | 3 | |
| Duke Energy Indiana [Member] | ||||
| Variable Interest Entities [Line Items] | ||||
| Receivables sold | 679 | 739 | 2,032 | 2,173 |
| Loss recognized on sale | 3 | 3 | 8 | 8 |
| Cash proceeds from receivables sold | 692 | 759 | 2,074 | 2,233 |
| Collection fees received | 0 | 1 | 1 | |
| Return received on retained interests | $ 1 | $ 2 | $ 4 | $ 5 |