Electric plant, construction and related agreements: (Details 2) (USD $)			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2008 Vogtle Units No.3 and No.4 item MW	Dec. 31, 2013 Vogtle Units No.3 and No.4
Construction
Number of Westinghouse AP1000 nuclear generating units			2
Nominally rated generating capacity for each unit			1,100
Ownership interest (as a percent)				30.00%
Revised estimated proportionate share of construction cost				$ 4,500,000,000
Total construction work in progress	2,212,224,000	2,240,920,000
Total construction project cost				$ 2,051,000,000