Contingencies and Regulatory Matters - Table - GPC Nuclear Construction - Cost and Schedule (Details) - Plant Vogtle Units 3 And 4 - GEORGIA POWER CO $ in Billions	Dec. 31, 2017 USD ($)
Commitments [Line Items]
Cost settlement agreement revised forecast, net of payments	$ 7.3
Net investment as of December 31, 2017	3.4
Remaining estimate to complete	$ 3.9