Contingencies and Regulatory Matters - Cost Recovery Clause (Details) - Under Recovered Regulatory Clause Revenues [Member] - Gulf Power [Member] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Under Recovered Fuel Cost	$ 24	$ 40
Under Recovered Purchased Power Capacity Costs	2	0
Under Recovered Environmental Cost	7	10
Under Recovered Energy Conservation Costs	$ 0	$ 3