Contingencies and Regulatory Matters - Recovery Balance of Each Regulatory Clause - Gulf Power (Details) - Gulf Power [Member] - USD ($) $ in Millions |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Other regulatory liabilities, current [Member] | ||
| Loss Contingencies [Line Items] | ||
| Fuel Cost Recovery | $ 5 | $ 15 |
| Environmental Cost Recovery | 40 | 13 |
| Under recovered regulatory clause revenues [Member] | ||
| Loss Contingencies [Line Items] | ||
| Purchased Power Capacity Recovery | 4 | 0 |
| Energy Conservation Cost Recovery | $ 3 | $ 4 |