Retirement Benefits - Fair Values of Pension Plan and Other Postretirement Benefit Plan Assets (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 8,650,000,000		$ 7,890,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(3,000,000)
Fair Value, Plan Assets and Liabilities	8,647,000,000
Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,272,000,000	[1]	1,833,000,000	[2]
Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,119,000,000	[1]	1,891,000,000	[2]
Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	599,000,000		516,000,000
Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	156,000,000		127,000,000
Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	978,000,000		879,000,000
Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	471,000,000		399,000,000
Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	224,000,000		553,000,000
Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,260,000,000		1,099,000,000
Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	571,000,000		593,000,000
Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	898,000,000		817,000,000
Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	202,000,000	[3]	183,000,000	[2]
Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	121,000,000	[3]	108,000,000	[2]
Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	34,000,000		24,000,000
Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		4,000,000
Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	35,000,000		31,000,000
Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	46,000,000		42,000,000
Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	19,000,000		44,000,000
Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	369,000,000		320,000,000
Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	46,000,000		40,000,000
Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	20,000,000		21,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	2,795,000,000		2,338,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	2,795,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,433,000,000	[1]	1,163,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,101,000,000	[1]	912,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1,000,000		5,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	260,000,000		258,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	206,000,000		183,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	157,000,000	[3]	140,000,000	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	39,000,000	[3]	33,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	10,000,000		10,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	4,284,000,000		4,115,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(3,000,000)
Fair Value, Plan Assets and Liabilities	4,281,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	839,000,000	[1]	670,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,018,000,000	[1]	979,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	599,000,000		516,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	156,000,000		127,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	978,000,000		876,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	471,000,000		399,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	223,000,000		548,000,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	636,000,000		583,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	45,000,000	[3]	43,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	82,000,000	[3]	75,000,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	34,000,000		24,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		4,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	35,000,000		31,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	46,000,000		42,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	19,000,000		44,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	369,000,000		320,000,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,571,000,000		1,437,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	1,571,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[1]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[1]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		3,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,000,000,000		841,000,000		782,000,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	571,000,000		593,000,000		582,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	56,000,000		51,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[3]	0	[2]
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	36,000,000		30,000,000		30,000,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	20,000,000		21,000,000		23,000,000
Alabama Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	2,256,000,000		2,062,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000,000)
Fair Value, Plan Assets and Liabilities	2,255,000,000
Alabama Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	593,000,000	[2]	479,000,000	[2]
Alabama Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	552,000,000	[2]	494,000,000	[2]
Alabama Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	156,000,000		135,000,000
Alabama Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	41,000,000		33,000,000
Alabama Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	255,000,000		231,000,000
Alabama Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	123,000,000		104,000,000
Alabama Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	58,000,000		144,000,000
Alabama Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	329,000,000		287,000,000
Alabama Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	149,000,000		155,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	387,000,000		341,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	78,000,000	[2]	71,000,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	27,000,000	[2]	25,000,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	17,000,000		7,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2,000,000		2,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	12,000,000		11,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		5,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	10,000,000		19,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	211,000,000		178,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	17,000,000		15,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7,000,000		8,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	729,000,000		610,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	729,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	374,000,000	[2]	304,000,000	[2]
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	287,000,000	[2]	238,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		1,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	68,000,000		67,000,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	85,000,000		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
Fair Value, Plan Assets	67,000,000	[2]	62,000,000	[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
Fair Value, Plan Assets	14,000,000	[2]	12,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,117,000,000		1,076,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000,000)
Fair Value, Plan Assets and Liabilities	1,116,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	219,000,000	[2]	175,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	265,000,000	[2]	256,000,000	[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
Fair Value, Plan Assets	156,000,000		135,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	41,000,000		33,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	255,000,000		230,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	123,000,000		104,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	58,000,000		143,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	282,000,000		244,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	11,000,000	[2]	9,000,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	13,000,000	[2]	13,000,000	[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
Fair Value, Plan Assets	17,000,000		7,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	12,000,000		11,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		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
Fair Value, Plan Assets	10,000,000		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
Fair Value, Plan Assets	211,000,000		178,000,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	410,000,000		376,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	410,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		1,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	261,000,000		220,000,000		217,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	149,000,000		155,000,000		161,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	20,000,000		19,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	13,000,000		11,000,000		11,000,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7,000,000		8,000,000		8,000,000
Georgia Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	3,055,000,000		2,805,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000,000)
Fair Value, Plan Assets and Liabilities	3,054,000,000
Georgia Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	802,000,000	[2]	651,000,000	[2]
Georgia Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	748,000,000	[2]	672,000,000	[2]
Georgia Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	212,000,000		183,000,000
Georgia Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	55,000,000		45,000,000
Georgia Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	346,000,000		313,000,000
Georgia Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	166,000,000		142,000,000
Georgia Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	79,000,000		197,000,000
Georgia Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	445,000,000		391,000,000
Georgia Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	202,000,000		211,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	406,000,000		382,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	99,000,000	[2]	92,000,000	[2]
Georgia Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	69,000,000	[2]	61,000,000	[2]
Georgia Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	7,000,000		6,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2,000,000		1,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	11,000,000		10,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	34,000,000		32,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		18,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	158,000,000		142,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	14,000,000		13,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		7,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	987,000,000		831,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	987,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	506,000,000	[2]	413,000,000	[2]
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	389,000,000	[2]	324,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		2,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	92,000,000		92,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	89,000,000		78,000,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	74,000,000	[2]	65,000,000	[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
Fair Value, Plan Assets	12,000,000	[2]	10,000,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,513,000,000		1,463,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000,000)
Fair Value, Plan Assets and Liabilities	1,512,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	296,000,000	[2]	238,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	359,000,000	[2]	348,000,000	[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
Fair Value, Plan Assets	212,000,000		183,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	55,000,000		45,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	346,000,000		312,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	166,000,000		142,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	79,000,000		195,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	300,000,000		287,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,000,000	[2]	27,000,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	57,000,000	[2]	51,000,000	[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
Fair Value, Plan Assets	7,000,000		6,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2,000,000		1,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	11,000,000		10,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	34,000,000		32,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		18,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	158,000,000		142,000,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	555,000,000		511,000,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	555,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		1,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	353,000,000		299,000,000		296,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	202,000,000		211,000,000		220,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	17,000,000		17,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	11,000,000		10,000,000		9,000,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000,000		7,000,000		7,000,000
Gulf Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	381,941,000		347,458,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(115,000)
Fair Value, Plan Assets and Liabilities	381,826,000
Gulf Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	100,306,000	[2]	80,714,000	[2]
Gulf Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	93,547,000	[2]	83,286,000	[2]
Gulf Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	26,461,000		22,724,000
Gulf Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,873,000		5,594,000
Gulf Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	43,222,000		38,673,000
Gulf Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	20,810,000		17,581,000
Gulf Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	9,889,000		24,356,000
Gulf Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	55,632,000		48,401,000
Gulf Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,201,000		26,129,000
Gulf Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	17,278,000		16,056,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(5,000)
Fair Value, Plan Assets and Liabilities	17,273,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,406,000	[2]	3,609,000	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,109,000	[2]	3,723,000	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,161,000		1,016,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	303,000		250,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,897,000		1,728,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,417,000		1,298,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	434,000		1,087,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2,443,000		2,175,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,108,000		1,170,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	123,406,000		102,951,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	123,406,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	63,269,000	[2]	51,215,000	[2]
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	48,606,000	[2]	40,166,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	38,000		208,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	11,493,000		11,362,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	5,419,000		4,602,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	5,419,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,778,000	[2]	2,290,000	[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
Fair Value, Plan Assets	2,136,000	[2]	1,795,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	1,000		9,000
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
Fair Value, Plan Assets	504,000		508,000
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	189,195,000		181,200,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(115,000)
Fair Value, Plan Assets and Liabilities	189,080,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	37,037,000	[2]	29,499,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	44,941,000	[2]	43,120,000	[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
Fair Value, Plan Assets	26,461,000		22,724,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,873,000		5,594,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	43,222,000		38,534,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	20,810,000		17,581,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	9,851,000		24,148,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	8,812,000		8,626,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(5,000)
Fair Value, Plan Assets and Liabilities	8,807,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,628,000	[2]	1,319,000	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,973,000	[2]	1,928,000	[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
Fair Value, Plan Assets	1,161,000		1,016,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	303,000		250,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,897,000		1,722,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,417,000		1,298,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	433,000		1,078,000
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		15,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	69,340,000		63,307,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	69,340,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		139,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	44,139,000		37,039,000		34,989,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,201,000		26,129,000		26,053,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	3,047,000		2,828,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	3,047,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		6,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,939,000		1,667,000		1,657,000
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,108,000		1,155,000		1,232,000
Mississippi Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	383,687,000		348,933,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(115,000)
Fair Value, Plan Assets and Liabilities	383,572,000
Mississippi Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	100,764,000	[2]	81,057,000	[2]
Mississippi Power [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	93,975,000	[2]	83,640,000	[2]
Mississippi Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	26,582,000		22,820,000
Mississippi Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,904,000		5,618,000
Mississippi Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	43,420,000		38,836,000
Mississippi Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	20,905,000		17,656,000
Mississippi Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	9,934,000		24,460,000
Mississippi Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	55,887,000		48,606,000
Mississippi Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,316,000		26,240,000
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	23,057,000		21,842,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(5,000)
Fair Value, Plan Assets and Liabilities	23,052,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,898,000	[2]	4,036,000	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,568,000	[2]	4,164,000	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	5,213,000		5,187,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	337,000		280,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,109,000		1,932,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,016,000		879,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	969,000		1,623,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2,716,000		2,434,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,231,000		1,307,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	123,971,000		103,389,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	123,971,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	63,558,000	[2]	51,433,000	[2]
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	48,829,000	[2]	40,337,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	38,000		209,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	11,546,000		11,410,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	6,025,000		5,149,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	6,025,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	3,089,000	[2]	2,561,000	[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
Fair Value, Plan Assets	2,375,000	[2]	2,008,000	[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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	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
Fair Value, Plan Assets	1,000		11,000
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
Fair Value, Plan Assets	560,000		569,000
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	190,059,000		181,968,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(115,000)
Fair Value, Plan Assets and Liabilities	189,944,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	37,206,000	[2]	29,624,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	45,146,000	[2]	43,303,000	[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
Fair Value, Plan Assets	26,582,000		22,820,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,904,000		5,618,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	43,420,000		38,696,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	20,905,000		17,656,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	9,896,000		24,251,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	13,645,000		13,528,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(5,000)
Fair Value, Plan Assets and Liabilities	13,640,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,809,000	[2]	1,475,000	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,193,000	[2]	2,156,000	[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
Fair Value, Plan Assets	5,213,000		5,187,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	337,000		280,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,109,000		1,925,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,016,000		879,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	968,000		1,612,000
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0		14,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	69,657,000		63,576,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	69,657,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		140,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	44,341,000		37,196,000		32,434,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,316,000		26,240,000		24,151,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	3,387,000		3,165,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0
Fair Value, Plan Assets and Liabilities	3,387,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Assets Fair Value
Fair Value, Plan Assets	0	[2]	0	[2]
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Assets Fair Value
Fair Value, Plan Assets	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
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		7,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	0		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2,156,000		1,865,000		1,851,000
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 1,231,000		$ 1,293,000		$ 1,377,000

[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 SignificantUnobservableInputs As of December 31, 2012:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$1,163 $670 $— $1,833International equity*912 979 — 1,891Fixed income: U.S. Treasury, government, and agency bonds— 516 — 516Mortgage- and asset-backed securities— 127 — 127Corporate bonds— 876 3 879Pooled funds— 399 — 399Cash equivalents and other5 548 — 553Real estate investments258 — 841 1,099Private equity— — 593 593Total$2,338 $4,115 $1,437 $7,890

[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 SignificantUnobservableInputs As of December 31, 2012:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$140 $43 $— $183International equity*33 75 — 108Fixed income: U.S. Treasury, government, and agency bonds— 24 — 24Mortgage- and asset-backed securities— 4 — 4Corporate bonds— 31 — 31Pooled funds— 42 — 42Cash equivalents and other— 44 — 44Trust-owned life insurance— 320 — 320Real estate investments10 — 30 40Private equity— — 21 21Total$183 $583 $51 $817