Retirement Benefits - Fair Values of Pension Plan and Other Postretirement Benefit Plan Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 9,647,000		$ 8,650,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(2,000)		(3,000)
Fair Value, Plan Assets and Liabilities	9,645,000		8,647,000
Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,408,000	[1]	2,272,000	[2]
Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	2,056,000	[1]	2,119,000	[2]
Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	699,000		599,000
Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	188,000		156,000
Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,135,000		978,000
Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	514,000		471,000
Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	663,000		224,000
Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	1,414,000		1,260,000
Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	570,000		571,000
Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	905,000		898,000
Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	203,000	[3]	202,000	[2]
Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	103,000	[3]	121,000	[2]
Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	29,000		34,000
Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000		6,000
Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	39,000		35,000
Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	41,000		46,000
Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	36,000		19,000
Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	381,000		369,000
Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	48,000		46,000
Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	19,000		20,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	3,070,000		2,795,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(2,000)		0
Fair Value, Plan Assets and Liabilities	3,068,000		2,795,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,704,000	[1]	1,433,000	[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	1,070,000	[1]	1,101,000	[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	3,000		1,000
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	293,000		260,000
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	203,000		206,000
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	147,000	[3]	157,000	[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	36,000	[3]	39,000	[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	9,000		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	11,000		10,000
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	4,886,000		4,284,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(3,000)
Fair Value, Plan Assets and Liabilities	4,886,000		4,281,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	704,000	[1]	839,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	986,000	[1]	1,018,000	[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	699,000		599,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	188,000		156,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,135,000		978,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	514,000		471,000
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	660,000		223,000
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	646,000		636,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	56,000	[3]	45,000	[2]
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	67,000	[3]	82,000	[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	29,000		34,000
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		6,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	39,000		35,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	41,000		46,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	27,000		19,000
Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	381,000		369,000
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	1,691,000		1,571,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	1,691,000		1,571,000
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		0
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	1,121,000		1,000,000		841,000
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	570,000		571,000		593,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	56,000		56,000
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	37,000		36,000		30,000
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	19,000		20,000		21,000
Alabama Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	2,385,000		2,256,000
Liabilities Fair Value
Fair Value, Plan Liabilities			(1,000)
Fair Value, Plan Assets and Liabilities			2,255,000
Alabama Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	595,000	[2]	593,000	[2]
Alabama Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	508,000	[2]	552,000	[2]
Alabama Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	173,000		156,000
Alabama Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	47,000		41,000
Alabama Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	280,000		255,000
Alabama Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	127,000		123,000
Alabama Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	164,000		58,000
Alabama Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	350,000		329,000
Alabama Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	141,000		149,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	391,000		387,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	84,000	[2]	78,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,000	[2]	27,000	[2]
Alabama Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	10,000		17,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2,000		2,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	14,000		12,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000		6,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	8,000		10,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	217,000		211,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	18,000		17,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	7,000		7,000
Alabama Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	759,000		729,000
Liabilities Fair Value
Fair Value, Plan Liabilities			0
Fair Value, Plan Assets and Liabilities			729,000
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	421,000	[2]	374,000	[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	264,000	[2]	287,000	[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	1,000		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
Fair Value, Plan Assets	73,000		68,000
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	94,000		85,000
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	76,000	[2]	67,000	[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	13,000	[2]	14,000	[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	5,000		4,000
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	1,208,000		1,117,000
Liabilities Fair Value
Fair Value, Plan Liabilities			(1,000)
Fair Value, Plan Assets and Liabilities			1,116,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	174,000	[2]	219,000	[2]
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	244,000	[2]	265,000	[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	173,000		156,000
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	47,000		41,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	280,000		255,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	127,000		123,000
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	163,000		58,000
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	277,000		282,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	8,000	[2]	11,000	[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	12,000	[2]	13,000	[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	10,000		17,000
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		2,000
Alabama Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	14,000		12,000
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		6,000
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	8,000		10,000
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	217,000		211,000
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	418,000		410,000
Liabilities Fair Value
Fair Value, Plan Liabilities			0
Fair Value, Plan Assets and Liabilities			410,000
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		0
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	277,000		261,000		220,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	141,000		149,000		155,000
Alabama Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	20,000		20,000
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		13,000		11,000
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		7,000		8,000
Georgia Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	3,368,000		3,055,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000)		(1,000)
Fair Value, Plan Assets and Liabilities	3,367,000		3,054,000
Georgia Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	841,000	[2]	802,000	[2]
Georgia Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	717,000	[2]	748,000	[2]
Georgia Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	244,000		212,000
Georgia Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	66,000		55,000
Georgia Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	398,000		346,000
Georgia Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	179,000		166,000
Georgia Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	231,000		79,000
Georgia Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	493,000		445,000
Georgia Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	199,000		202,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	401,000		406,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	93,000	[2]	99,000	[2]
Georgia Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	56,000	[2]	69,000	[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		7,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	2,000		2,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	12,000		11,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	29,000		34,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	19,000		6,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Trust-owned life insurance [Member]
Assets Fair Value
Fair Value, Plan Assets	162,000		158,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	15,000		14,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	6,000		6,000
Georgia Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	1,071,000		987,000
Liabilities Fair Value
Fair Value, Plan Liabilities	(1,000)		0
Fair Value, Plan Assets and Liabilities	1,070,000		987,000
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	595,000	[2]	506,000	[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	373,000	[2]	389,000	[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	1,000		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
Fair Value, Plan Assets	102,000		92,000
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	75,000		89,000
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	53,000	[2]	74,000	[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	11,000	[2]	12,000	[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	8,000		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		3,000
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	1,707,000		1,513,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(1,000)
Fair Value, Plan Assets and Liabilities	1,707,000		1,512,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	246,000	[2]	296,000	[2]
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	344,000	[2]	359,000	[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	244,000		212,000
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	66,000		55,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	398,000		346,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	179,000		166,000
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	230,000		79,000
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	308,000		300,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	40,000	[2]	25,000	[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	45,000	[2]	57,000	[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		7,000
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		2,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	12,000		11,000
Georgia Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	29,000		34,000
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	11,000		6,000
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	162,000		158,000
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	590,000		555,000
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	590,000		555,000
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		0
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	391,000		353,000		299,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	199,000		202,000		211,000
Georgia Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	18,000		17,000
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	12,000		11,000		10,000
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		6,000		7,000
Gulf Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	432,798		381,941
Liabilities Fair Value
Fair Value, Plan Liabilities	(87)		(115)
Fair Value, Plan Assets and Liabilities	432,711		381,826
Gulf Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	108,048	[2]	100,306	[2]
Gulf Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	92,211	[2]	93,547	[2]
Gulf Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	31,372		26,461
Gulf Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	8,438		6,873
Gulf Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	50,931		43,222
Gulf Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23,063		20,810
Gulf Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	29,727		9,889
Gulf Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	63,435		55,632
Gulf Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,573		25,201
Gulf Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	18,087		17,278
Liabilities Fair Value
Fair Value, Plan Liabilities	(4)		(5)
Fair Value, Plan Assets and Liabilities	18,083		17,273
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,388	[2]	4,406	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	3,747	[2]	4,109	[2]
Gulf Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,274		1,161
Gulf Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	342		303
Gulf Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,071		1,897
Gulf Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	937		1,417
Gulf Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1,713		434
Gulf Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2,576		2,443
Gulf Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,039		1,108
Gulf Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	137,732		123,406
Liabilities Fair Value
Fair Value, Plan Liabilities	(87)		0
Fair Value, Plan Assets and Liabilities	137,645		123,406
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	76,460	[2]	63,269	[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	47,988	[2]	48,606	[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	130		38
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	13,154		11,493
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	6,098		5,419
Liabilities Fair Value
Fair Value, Plan Liabilities	(4)		0
Fair Value, Plan Assets and Liabilities	6,094		5,419
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	3,105	[2]	2,778	[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	1,949	[2]	2,136	[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	510		1
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	534		504
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	219,212		189,195
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(115)
Fair Value, Plan Assets and Liabilities	219,212		189,080
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	31,588	[2]	37,037	[2]
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	44,223	[2]	44,941	[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	31,372		26,461
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	8,438		6,873
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	50,931		43,222
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23,063		20,810
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	29,597		9,851
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	8,908		8,812
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(5)
Fair Value, Plan Assets and Liabilities	8,908		8,807
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,283	[2]	1,628	[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	1,798	[2]	1,973	[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	1,274		1,161
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	342		303
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,071		1,897
Gulf Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	937		1,417
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	1,203		433
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		0
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	75,854		69,340
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	75,854		69,340
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		0
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	50,281		44,139		37,039
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	25,573		25,201		26,129
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	3,081		3,047
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	3,081		3,047
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		0
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	2,042		1,939		1,667
Gulf Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,039		1,108		1,155
Mississippi Power [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	443,463		383,687
Liabilities Fair Value
Fair Value, Plan Liabilities	(89)		(115)
Fair Value, Plan Assets and Liabilities	443,374		383,572
Mississippi Power [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	110,710	[2]	100,764	[2]
Mississippi Power [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	94,483	[2]	93,975	[2]
Mississippi Power [Member] | Pension Plans [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	32,145		26,582
Mississippi Power [Member] | Pension Plans [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	8,646		6,904
Mississippi Power [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	52,185		43,420
Mississippi Power [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23,632		20,905
Mississippi Power [Member] | Pension Plans [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	30,460		9,934
Mississippi Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	64,999		55,887
Mississippi Power [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	26,203		25,316
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	23,980		23,057
Liabilities Fair Value
Fair Value, Plan Liabilities	(5)		(5)
Fair Value, Plan Assets and Liabilities	23,975		23,052
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,875	[2]	4,898	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	4,162	[2]	4,568	[2]
Mississippi Power [Member] | Other Postretirement Benefits [Member] | U.S. Treasury, government, and agency bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	5,279		5,213
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Mortgage and asset backed securities [Member]
Assets Fair Value
Fair Value, Plan Assets	380		337
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,301		2,109
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,041		1,016
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Cash equivalents and other [Member]
Assets Fair Value
Fair Value, Plan Assets	1,926		969
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Assets Fair Value
Fair Value, Plan Assets	2,862		2,716
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,154		1,231
Mississippi Power [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	141,126		123,971
Liabilities Fair Value
Fair Value, Plan Liabilities	(89)		0
Fair Value, Plan Assets and Liabilities	141,037		123,971
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	78,344	[2]	63,558	[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	49,170	[2]	48,829	[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	133		38
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	13,479		11,546
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	6,797		6,025
Liabilities Fair Value
Fair Value, Plan Liabilities	(5)		0
Fair Value, Plan Assets and Liabilities	6,792		6,025
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	3,450	[2]	3,089	[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	2,165	[2]	2,375	[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	589		1
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	593		560
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	224,614		190,059
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(115)
Fair Value, Plan Assets and Liabilities	224,614		189,944
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	32,366	[2]	37,206	[2]
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | International Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	45,313	[2]	45,146	[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	32,145		26,582
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	8,646		6,904
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	52,185		43,420
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	23,632		20,905
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	30,327		9,896
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	13,760		13,645
Liabilities Fair Value
Fair Value, Plan Liabilities	0		(5)
Fair Value, Plan Assets and Liabilities	13,760		13,640
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Domestic Equity [Member]
Assets Fair Value
Fair Value, Plan Assets	1,425	[2]	1,809	[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	1,997	[2]	2,193	[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	5,279		5,213
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	380		337
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Corporate bonds [Member]
Assets Fair Value
Fair Value, Plan Assets	2,301		2,109
Mississippi Power [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Pooled funds [Member]
Assets Fair Value
Fair Value, Plan Assets	1,041		1,016
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	1,337		968
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		0
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
Assets Fair Value
Fair Value, Plan Assets	77,723		69,657
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	77,723		69,657
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		0
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	51,520		44,341		37,196
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	26,203		25,316		26,240
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member]
Assets Fair Value
Fair Value, Plan Assets	3,423		3,387
Liabilities Fair Value
Fair Value, Plan Liabilities	0		0
Fair Value, Plan Assets and Liabilities	3,423		3,387
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		0
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	2,269		2,156		1,865
Mississippi Power [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Assets Fair Value
Fair Value, Plan Assets	$ 1,154		$ 1,231		$ 1,293

[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, 2013:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$1,433 $839 $— $2,272International equity*1,101 1,018 — 2,119Fixed income: U.S. Treasury, government, and agency bonds— 599 — 599Mortgage- and asset-backed securities— 156 — 156Corporate bonds— 978 — 978Pooled funds— 471 — 471Cash equivalents and other1 223 — 224Real estate investments260 — 1,000 1,260Private equity— — 571 571Total$2,795 $4,284 $1,571 $8,650Liabilities: Derivatives$— $(3) $— $(3)Total$2,795 $4,281 $1,571 $8,647

[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, 2013:(Level 1) (Level 2) (Level 3) Total (in millions)Assets: Domestic equity*$157 $45 $— $202International equity*39 82 — 121Fixed income: U.S. Treasury, government, and agency bonds— 34 — 34Mortgage- and asset-backed securities— 6 — 6Corporate bonds— 35 — 35Pooled funds— 46 — 46Cash equivalents and other— 19 — 19Trust-owned life insurance— 369 — 369Real estate investments10 — 36 46Private equity— — 20 20Total$206 $636 $56 $898