Effective Tax Rate and Unrecognized Tax Benefits (Details 1) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Impact on effective tax rate
Tax positions impacting the effective tax rate	$ 38	$ 69
Tax positions not impacting the effective tax rate	60	51
Balance of unrecognized tax benefits	98	120
Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued as of December 31, 2011	10
Interest reclassified due to settlements	(9)
Interest accrued during the period	0
Balance as of September 30, 2012	1
Georgia Power [Member]
Impact on effective tax rate
Balance of unrecognized tax benefits	$ 25	$ 47