Investment In Leveraged Leases (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2013 MW
Leases [Abstract]
After tax charge to income	$ 16
Capacity generation facility	440
Commitment to invest capital	$ 60
Commitment term for nonrecourse debt	19 years

Capacity Of Circulating Fluidized Bed Lignite Coal-fired Generation Facility

No definition available.

Name:	so_CapacityOfCirculatingFluidizedBedLigniteCoalFiredGenerationFacility
Namespace Prefix:	so_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration