Disclosures about Derivative Instruments and Hedging Activities (Details 2) (USD $)	6 Months Ended	3 Months Ended
	Jun. 30, 2012	Dec. 31, 2011 LIBOR swaptions	Jun. 30, 2012 LIBOR swaptions	Jun. 30, 2012 LIBOR swaptions 2013	Jun. 30, 2012 LIBOR swaptions 2014	Jun. 30, 2012 LIBOR swaptions 2015	Jun. 30, 2012 LIBOR swaptions 2016	Jun. 30, 2012 LIBOR swaptions 2017	Jun. 30, 2012 LIBOR swaptions Minimum	Jun. 30, 2012 LIBOR swaptions Maximum
Derivative instruments and hedging activities
Maximum borrowing capacity, to construct Plant Vogtle Units No.3 and No. 4, with the Department of Energy	$ 3,057,000,000
Purchased amount of derivative instrument	43,070,000	100,000,000
Hedged amount of the expected Department of Energy-guaranteed loan		2,200,000,000
Fixed interest rates above current LIBOR swap rates (as a percent)									1.50%	2.50%
Weighted average fixed rate (as a percent)			4.17%
Fair value of assets		69,446,000	39,215,000
Collateral thresholds range									0	10,000,000
Funds posted as collateral by the counterparties		43,070,000	20,690,000
Carrying amount of derivative assets		26,376,000	18,525,000
Notional Dollar Amount			$ 2,179,204,000	$ 754,452,000	$ 563,425,000	$ 470,625,000	$ 310,533,000	$ 80,169,000