Contingencies and Regulatory Matters (Details) (Vogtle Units No.3 and No.4, USD $)	3 Months Ended
	Mar. 31, 2013 MW item
Nuclear Construction
Number of Westinghouse AP1000 nuclear generating units	2
Nominally rated generating capacity for each unit	1,100
Costs associated with design changes, delays in the project schedule and issuance of the combined construction permits and operating licenses
Nuclear Construction
Contractor's estimated adjustment attributable to the entity	280,000,000