Retirement Benefits - Fair Values of Pension Plan and Other Postretirement Benefit Plan Assets (Details) (USD $)	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Pension Plans [Member]
Assets Fair Value
Total	$ 7,890,000,000		$ 6,722,000,000
Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	1,833,000,000	[1]	1,688,000,000	[2]
Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	1,891,000,000	[1]	1,527,000,000	[2]
Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	516,000,000		433,000,000
Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	127,000,000		135,000,000
Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	879,000,000		835,000,000
Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	399,000,000		380,000,000
Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	553,000,000		140,000,000
Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	1,099,000,000		1,002,000,000
Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	593,000,000		582,000,000
Other Postretirement Benefits [Member]
Assets Fair Value
Total	817,000,000		786,000,000
Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	183,000,000	[3]	194,000,000	[2]
Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	108,000,000	[3]	84,000,000	[2]
Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	24,000,000		24,000,000
Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	4,000,000		5,000,000
Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	31,000,000		32,000,000
Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	42,000,000		48,000,000
Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	44,000,000		46,000,000
Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	320,000,000		291,000,000
Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	40,000,000		39,000,000
Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	21,000,000		23,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Total	2,338,000,000		2,563,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	1,163,000,000	[1]	1,155,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	912,000,000	[1]	1,187,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	5,000,000		1,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	258,000,000		220,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	183,000,000		210,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	140,000,000	[3]	156,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	33,000,000	[3]	45,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	10,000,000		9,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Total	4,115,000,000		2,792,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	670,000,000	[1]	533,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	979,000,000	[1]	340,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	516,000,000		433,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	127,000,000		135,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	876,000,000		832,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	399,000,000		380,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	548,000,000		139,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	583,000,000		523,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	43,000,000	[3]	38,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	75,000,000	[3]	39,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	24,000,000		24,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	4,000,000		5,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	31,000,000		32,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	42,000,000		48,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	44,000,000		46,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	320,000,000		291,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Total	1,437,000,000		1,367,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[1]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	0	[1]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	3,000,000		3,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	841,000,000		782,000,000		674,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	593,000,000		582,000,000		638,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	51,000,000		53,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[3]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	0	[3]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	30,000,000		30,000,000		26,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	21,000,000		23,000,000		23,000,000
Gulf Power [Member] | Pension Plans [Member]
Assets Fair Value
Total	347,458,000		300,848,000
Gulf Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	80,714,000	[2]	75,543,000	[2]
Gulf Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	83,286,000	[2]	68,353,000	[2]
Gulf Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	22,724,000		19,375,000
Gulf Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	5,594,000		6,047,000
Gulf Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	38,673,000		37,394,000
Gulf Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	17,581,000		16,998,000
Gulf Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	24,356,000		6,258,000
Gulf Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	48,401,000		44,827,000
Gulf Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	26,129,000		26,053,000
Gulf Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	16,056,000		14,747,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	3,609,000	[2]	3,573,000	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	3,723,000	[2]	3,230,000	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	1,016,000		918,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	250,000		286,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,728,000		1,761,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	1,298,000		1,328,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	1,087,000		296,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	2,175,000		2,123,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	1,170,000		1,232,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Total	102,951,000		114,684,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	51,215,000	[2]	51,686,000	[2]
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	40,166,000	[2]	53,130,000	[2]
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	208,000		30,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	11,362,000		9,838,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	4,602,000		5,423,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	2,290,000	[2]	2,445,000	[2]
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	1,795,000	[2]	2,511,000	[2]
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	9,000		1,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	508,000		466,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Total	181,200,000		125,002,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	29,499,000	[2]	23,857,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	43,120,000	[2]	15,223,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	22,724,000		19,375,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	5,594,000		6,047,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	38,534,000		37,274,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	17,581,000		16,998,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	24,148,000		6,228,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	8,626,000		6,435,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	1,319,000	[2]	1,128,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	1,928,000	[2]	719,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	1,016,000		918,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	250,000		286,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,722,000		1,761,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	1,298,000		1,328,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	1,078,000		295,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	15,000		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Total	63,307,000		61,162,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	139,000		120,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	37,039,000		34,989,000		30,355,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	26,129,000		26,053,000		28,727,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	2,828,000		2,889,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	6,000		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	1,667,000		1,657,000		1,452,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	1,155,000		1,232,000		1,375,000
Mississippi Power [Member] | Pension Plans [Member]
Assets Fair Value
Total	348,933,000		278,878,000
Mississippi Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	81,057,000	[2]	70,026,000	[2]
Mississippi Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	83,640,000	[2]	63,361,000	[2]
Mississippi Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	22,820,000		17,960,000
Mississippi Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	5,618,000		5,605,000
Mississippi Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	38,836,000		34,664,000
Mississippi Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	17,656,000		15,757,000
Mississippi Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	24,460,000		5,801,000
Mississippi Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	48,606,000		41,553,000
Mississippi Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	26,240,000		24,151,000
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	21,842,000		20,322,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	4,036,000	[2]	3,993,000	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	4,164,000	[2]	3,611,000	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	5,187,000		4,796,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	280,000		320,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,932,000		1,968,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	879,000		898,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	1,623,000		988,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	2,434,000		2,371,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	1,307,000		1,377,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Total	103,389,000		106,308,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	51,433,000	[2]	47,911,000	[2]
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	40,337,000	[2]	49,250,000	[2]
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	209,000		28,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	11,410,000		9,119,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	5,149,000		6,061,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	2,561,000	[2]	2,733,000	[2]
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	2,008,000	[2]	2,807,000	[2]
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	11,000		1,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	569,000		520,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Total	181,968,000		115,873,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	29,624,000	[2]	22,115,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	43,303,000	[2]	14,111,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	22,820,000		17,960,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	5,618,000		5,605,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	38,696,000		34,552,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	17,656,000		15,757,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	24,251,000		5,773,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	13,528,000		11,033,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	1,475,000	[2]	1,260,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	2,156,000	[2]	804,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	5,187,000		4,796,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	280,000		320,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,925,000		1,968,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	879,000		898,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	1,612,000		987,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	14,000		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Total	63,576,000		56,697,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	140,000		112,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	37,196,000		32,434,000		27,976,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	26,240,000		24,151,000		26,475,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	3,165,000		3,228,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	7,000		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	1,865,000		1,851,000		1,625,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	1,293,000		1,377,000		1,538,000
Georgia Power [Member] | Pension Plans [Member]
Assets Fair Value
Total	2,805,000,000		2,545,000,000
Georgia Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	651,000,000	[2]	639,000,000	[2]
Georgia Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	672,000,000	[2]	578,000,000	[2]
Georgia Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	183,000,000		164,000,000
Georgia Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	45,000,000		51,000,000
Georgia Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	313,000,000		317,000,000
Georgia Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	142,000,000		144,000,000
Georgia Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	197,000,000		53,000,000
Georgia Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	391,000,000		379,000,000
Georgia Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	211,000,000		220,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	382,000,000		385,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	92,000,000	[2]	109,000,000	[2]
Georgia Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	61,000,000	[2]	46,000,000	[2]
Georgia Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	6,000,000		5,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	1,000,000		1,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	10,000,000		10,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	32,000,000		38,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	18,000,000		26,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	142,000,000		131,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	13,000,000		12,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	7,000,000		7,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Total	831,000,000		969,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	413,000,000	[2]	437,000,000	[2]
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	324,000,000	[2]	449,000,000	[2]
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	2,000,000		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	92,000,000		83,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	78,000,000		103,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	65,000,000	[2]	85,000,000	[2]
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	10,000,000	[2]	15,000,000	[2]
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	3,000,000		3,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Total	1,463,000,000		1,059,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	238,000,000	[2]	202,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	348,000,000	[2]	129,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	183,000,000		164,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	45,000,000		51,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	312,000,000		316,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	142,000,000		144,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	195,000,000		53,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	287,000,000		266,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	27,000,000	[2]	24,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	51,000,000	[2]	31,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	6,000,000		5,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	1,000,000		1,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	10,000,000		10,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	32,000,000		38,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	18,000,000		26,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	142,000,000		131,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Total	511,000,000		517,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,000,000		1,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	299,000,000		296,000,000		258,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	211,000,000		220,000,000		245,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	17,000,000		16,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	10,000,000		9,000,000		8,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	7,000,000		7,000,000		8,000,000
Alabama Power [Member] | Pension Plans [Member]
Assets Fair Value
Total	2,062,000,000		1,864,000,000
Alabama Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	479,000,000	[2]	468,000,000	[2]
Alabama Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	494,000,000	[2]	423,000,000	[2]
Alabama Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	135,000,000		120,000,000
Alabama Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	33,000,000		37,000,000
Alabama Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	231,000,000		233,000,000
Alabama Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	104,000,000		105,000,000
Alabama Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	144,000,000		39,000,000
Alabama Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	287,000,000		278,000,000
Alabama Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	155,000,000		161,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	341,000,000		317,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	71,000,000	[2]	65,000,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	25,000,000	[2]	22,000,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	7,000,000		9,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	2,000,000		2,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	11,000,000		12,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	5,000,000		5,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	19,000,000		19,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	178,000,000		160,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	15,000,000		15,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	8,000,000		8,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Total	610,000,000		710,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	304,000,000	[2]	320,000,000	[2]
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	238,000,000	[2]	329,000,000	[2]
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	1,000,000		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	67,000,000		61,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	78,000,000		78,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	62,000,000	[2]	57,000,000	[2]
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	12,000,000	[2]	17,000,000	[2]
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	4,000,000		4,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Total	1,076,000,000		775,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	175,000,000	[2]	148,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	256,000,000	[2]	94,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	135,000,000		120,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	33,000,000		37,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	230,000,000		232,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	104,000,000		105,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	143,000,000		39,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	244,000,000		220,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	9,000,000	[2]	8,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	13,000,000	[2]	5,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	7,000,000		9,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	2,000,000		2,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	11,000,000		12,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	5,000,000		5,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	19,000,000		19,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	178,000,000		160,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Total	376,000,000		379,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Total	1,000,000		1,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Total	220,000,000		217,000,000		191,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Total	155,000,000		161,000,000		180,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Total	19,000,000		19,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Total	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Total	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Total	11,000,000		11,000,000		10,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Total	$ 8,000,000		$ 8,000,000		$ 9,000,000

[1] *Level 1 securities consist of actively traded stocks while Level 2 securities consist of pooled funds. Management believes that the portfolio is well-diversified with no significant concentrations of risk. Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets SignificantOtherObservableInputs Significant Unobservable Inputs As of December 31, 2011:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$1,155 $533 $— $1,688International equity*1,187 340 — 1,527Fixed income: U.S. Treasury, government, and agency bonds— 433 — 433Mortgage- and asset-backed securities— 135 — 135Corporate bonds— 832 3 835Pooled funds— 380 — 380Cash equivalents and other1 139 — 140Real estate investments220 — 782 1,002Private equity— — 582 582Total$2,563 $2,792 $1,367 $6,722

[2] *Level 1 securities consist of actively traded stocks while Level 2 securities consist of pooled funds. Management believes that the portfolio is well-diversified with no significant concentrations of risk.

[3] *Level 1 securities consist of actively traded stocks while Level 2 securities consist of pooled funds. Management believes that the portfolio is well-diversified with no significant concentrations of risk. Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets SignificantOtherObservableInputs Significant Unobservable Inputs As of December 31, 2011:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$156 $38 $— $194International equity*45 39 — 84Fixed income: U.S. Treasury, government, and agency bonds— 24 — 24Mortgage- and asset-backed securities— 5 — 5Corporate bonds— 32 — 32Pooled funds— 48 — 48Cash equivalents and other— 46 — 46Trust-owned life insurance— 291 — 291Real estate investments9 — 30 39Private equity— — 23 23Total$210 $523 $53 $786