Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Consolidated net income	$ 4,744,000,000	$ 2,300,000,000	$ 926,000,000
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	3,331,000,000	3,549,000,000	3,457,000,000
Deferred income taxes	611,000,000	89,000,000	166,000,000
Utilization of federal investment tax credits	757,000,000	5,000,000	0
Amortization of investment tax credits	(181,000,000)	(87,000,000)	(79,000,000)
Allowance for equity funds used during construction	(128,000,000)	(138,000,000)	(160,000,000)
Pension, postretirement, and other employee benefits	(204,000,000)	(103,000,000)	(84,000,000)
Pension and postretirement funding	(1,136,000,000)	(4,000,000)	(2,000,000)
Settlement of asset retirement obligations	(328,000,000)	(244,000,000)	(177,000,000)
Storm damage reserve accruals	168,000,000	74,000,000	38,000,000
Stock based compensation expense	107,000,000	125,000,000	109,000,000
Estimated loss on plants under construction	15,000,000	1,093,000,000	3,179,000,000
Impairment charges	168,000,000	210,000,000	0
(Gain) loss on dispositions, net	(2,588,000,000)	(301,000,000)	(42,000,000)
Other, net	102,000,000	14,000,000	(63,000,000)
Changes in certain current assets and liabilities —
-Receivables	630,000,000	(426,000,000)	(202,000,000)
-Fossil fuel for generation	(120,000,000)	123,000,000	36,000,000
-Natural gas for sale	44,000,000	49,000,000	36,000,000
-Other current assets	70,000,000	(127,000,000)	(143,000,000)
-Accounts payable	(693,000,000)	291,000,000	(280,000,000)
-Accrued taxes	117,000,000	267,000,000	(142,000,000)
-Retail fuel cost over recovery	62,000,000	36,000,000	(212,000,000)
-Other current liabilities	61,000,000	30,000,000	(38,000,000)
-Accrued compensation	(9,000,000)	33,000,000	(8,000,000)
Net cash provided from operating activities	5,781,000,000	6,945,000,000	6,394,000,000
Investing Activities:
Business acquisitions, net of cash acquired	(50,000,000)	(65,000,000)	(1,054,000,000)
Property additions	(7,555,000,000)	(8,001,000,000)	(7,423,000,000)
Proceeds pursuant to the Toshiba Guarantee, net of joint owner portion	0	0	1,682,000,000
Nuclear decommissioning trust fund purchases	(888,000,000)	(1,117,000,000)	(811,000,000)
Nuclear decommissioning trust fund sales	882,000,000	1,111,000,000	805,000,000
Proceeds from dispositions and asset sales	5,122,000,000	2,956,000,000	97,000,000
Cost of removal, net of salvage	(393,000,000)	(388,000,000)	(313,000,000)
Change in construction payables, net	(169,000,000)	50,000,000	259,000,000
Investments in unconsolidated subsidiaries	(148,000,000)	(114,000,000)	(152,000,000)
Payments pursuant to LTSAs	(234,000,000)	(186,000,000)	(227,000,000)
Other investing activities	41,000,000	(6,000,000)	(53,000,000)
Net cash used for investing activities	(3,392,000,000)	(5,760,000,000)	(7,190,000,000)
Financing Activities:
Increase (decrease) in notes payable, net	640,000,000
Increase (decrease) in notes payable, net		(774,000,000)	(401,000,000)
Proceeds —
Long-term debt	5,220,000,000	2,478,000,000	5,858,000,000
Common stock	844,000,000	1,090,000,000	793,000,000
Preferred stock	0	0	250,000,000
Short-term borrowings	350,000,000	3,150,000,000	1,259,000,000
Redemptions and repurchases —
Long-term debt	(4,347,000,000)	(5,533,000,000)	(2,930,000,000)
Preferred and preference stock	0	(33,000,000)	(658,000,000)
Short-term borrowings	(1,850,000,000)	(1,900,000,000)	(659,000,000)
Distributions to noncontrolling interests	(256,000,000)	(153,000,000)	(119,000,000)
Capital contributions from noncontrolling interests	196,000,000	2,551,000,000	80,000,000
Payment of common stock dividends	(2,570,000,000)	(2,425,000,000)	(2,300,000,000)
Other financing activities	(157,000,000)	(264,000,000)	(222,000,000)
Net cash provided from (used for) financing activities	(1,930,000,000)	(1,813,000,000)	951,000,000
Net Change in Cash, Cash Equivalents, and Restricted Cash	459,000,000	(628,000,000)	155,000,000
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	1,519,000,000	2,147,000,000	1,992,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	1,978,000,000	1,519,000,000	2,147,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	1,651,000,000	1,794,000,000	1,676,000,000
Income taxes (net of refunds)	276,000,000	172,000,000	(410,000,000)
Noncash transactions —
Accrued property additions at year-end	932,000,000	1,103,000,000	985,000,000
Alabama Power
Operating Activities:
Consolidated net income	1,085,000,000	945,000,000	866,000,000
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	951,000,000	917,000,000	888,000,000
Deferred income taxes	197,000,000	174,000,000	409,000,000
Allowance for equity funds used during construction	(52,000,000)	(62,000,000)	(39,000,000)
Pension and postretirement funding	(362,000,000)	(4,000,000)	(2,000,000)
Settlement of asset retirement obligations	(127,000,000)	(55,000,000)	(26,000,000)
Natural disaster reserve accruals	138,000,000	16,000,000	4,000,000
Other deferred charges – affiliated	(42,000,000)	0	0
Other, net	(90,000,000)	(17,000,000)	9,000,000
Changes in certain current assets and liabilities —
-Receivables	9,000,000	(149,000,000)	(168,000,000)
-Prepayments	(4,000,000)	(2,000,000)	(2,000,000)
-Other current assets	(85,000,000)	30,000,000	20,000,000
-Accounts payable	(41,000,000)	24,000,000	71,000,000
-Accrued taxes	49,000,000	10,000,000	(84,000,000)
-Retail fuel cost over recovery	47,000,000	0	(76,000,000)
-Other current liabilities	97,000,000	128,000,000	3,000,000
-Materials and supplies	23,000,000	(82,000,000)	(34,000,000)
-Accrued compensation	(14,000,000)	8,000,000	(2,000,000)
Net cash provided from operating activities	1,779,000,000	1,881,000,000	1,837,000,000
Investing Activities:
Property additions	(1,757,000,000)	(2,158,000,000)	(1,882,000,000)
Nuclear decommissioning trust fund purchases	(261,000,000)	(279,000,000)	(237,000,000)
Nuclear decommissioning trust fund sales	260,000,000	278,000,000	237,000,000
Cost of removal, net of salvage	(103,000,000)	(130,000,000)	(112,000,000)
Change in construction payables, net	(71,000,000)	26,000,000	161,000,000
Other investing activities	(31,000,000)	(26,000,000)	(43,000,000)
Net cash used for investing activities	(1,963,000,000)	(2,289,000,000)	(1,876,000,000)
Proceeds —
Preferred stock	0	0	250,000,000
Senior notes	600,000,000	500,000,000	1,100,000,000
Pollution control revenue bonds	0	120,000,000	0
Capital contributions from parent company	1,240,000,000	511,000,000	361,000,000
Redemptions and repurchases —
Preferred and preference stock	0	0	(238,000,000)
Senior notes	(200,000,000)	0	(525,000,000)
Pollution control revenue bonds	0	(120,000,000)	(36,000,000)
Payment of common stock dividends	(844,000,000)	(801,000,000)	(714,000,000)
Other financing activities	(31,000,000)	(33,000,000)	(35,000,000)
Net cash provided from (used for) financing activities	765,000,000	177,000,000	163,000,000
Net Change in Cash, Cash Equivalents, and Restricted Cash	581,000,000	(231,000,000)	124,000,000
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	313,000,000	544,000,000	420,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	894,000,000	313,000,000	544,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	311,000,000	284,000,000	285,000,000
Income taxes (net of refunds)	26,000,000	106,000,000	236,000,000
Noncash transactions —
Accrued property additions at year-end	200,000,000	272,000,000	245,000,000
Georgia Power
Operating Activities:
Consolidated net income	1,720,000,000	793,000,000	1,428,000,000
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	1,193,000,000	1,142,000,000	1,100,000,000
Deferred income taxes	179,000,000	(260,000,000)	458,000,000
Pension, postretirement, and other employee benefits	(146,000,000)	(75,000,000)	(68,000,000)
Pension and postretirement funding	(200,000,000)	0	0
Settlement of asset retirement obligations	(151,000,000)	(116,000,000)	(120,000,000)
Retail fuel cost over recovery – long-term	73,000,000	0	0
Other deferred charges – affiliated	(108,000,000)	0	0
Estimated loss on plants under construction	0	1,060,000,000	0
Other, net	12,000,000	(21,000,000)	(83,000,000)
Changes in certain current assets and liabilities —
-Receivables	177,000,000	8,000,000	(256,000,000)
-Fossil fuel for generation	(41,000,000)	83,000,000	(16,000,000)
-Other current assets	(19,000,000)	(43,000,000)	(28,000,000)
-Accounts payable	(92,000,000)	95,000,000	(219,000,000)
-Accrued taxes	58,000,000	58,000,000	1,000,000
-Retail fuel cost over recovery	0	0	(84,000,000)
-Other current liabilities	150,000,000	(107,000,000)	(33,000,000)
-Prepaid income taxes	102,000,000	152,000,000	(168,000,000)
Net cash provided from operating activities	2,907,000,000	2,769,000,000	1,912,000,000
Investing Activities:
Property additions	(3,510,000,000)	(3,116,000,000)	(2,704,000,000)
Proceeds pursuant to the Toshiba Guarantee, net of joint owner portion	0	0	1,682,000,000
Nuclear decommissioning trust fund purchases	(628,000,000)	(839,000,000)	(574,000,000)
Nuclear decommissioning trust fund sales	622,000,000	833,000,000	568,000,000
Cost of removal, net of salvage	(186,000,000)	(107,000,000)	(100,000,000)
Payments pursuant to LTSAs	(81,000,000)	(54,000,000)	(64,000,000)
Change in construction payables, net of joint owner portion	(122,000,000)	68,000,000	223,000,000
Proceeds from dispositions and asset sales	14,000,000	138,000,000	96,000,000
Other investing activities	6,000,000	(32,000,000)	(39,000,000)
Net cash used for investing activities	(3,885,000,000)	(3,109,000,000)	(912,000,000)
Financing Activities:
Increase (decrease) in notes payable, net		294,000,000
Increase (decrease) in notes payable, net	(179,000,000)		(391,000,000)
Proceeds —
Short-term borrowings	250,000,000	0	700,000,000
Senior notes	750,000,000	0	1,350,000,000
Pollution control revenue bonds	584,000,000	108,000,000	65,000,000
Other long-term debt	0	0	370,000,000
Capital contributions from parent company	634,000,000	2,985,000,000	431,000,000
FFB loan	1,218,000,000	0	0
Redemptions and repurchases —
Preferred and preference stock	0	0	(270,000,000)
Short-term borrowings	0	(150,000,000)	(550,000,000)
Senior notes	(500,000,000)	(1,500,000,000)	(450,000,000)
Pollution control revenue bonds	(223,000,000)	(469,000,000)	(65,000,000)
Other long-term debt	0	(100,000,000)	0
Payment of common stock dividends	(1,576,000,000)	(1,396,000,000)	(1,281,000,000)
Premiums on redemption and repurchases of senior notes	0	(152,000,000)	0
Other financing activities	(40,000,000)	(20,000,000)	(60,000,000)
Net cash provided from (used for) financing activities	918,000,000	(400,000,000)	(151,000,000)
Net Change in Cash, Cash Equivalents, and Restricted Cash	(60,000,000)	(740,000,000)	849,000,000
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	112,000,000	852,000,000	3,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	52,000,000	112,000,000	852,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	373,000,000	408,000,000	386,000,000
Income taxes (net of refunds)	110,000,000	300,000,000	496,000,000
Noncash transactions —
Accrued property additions at year-end	560,000,000	683,000,000	550,000,000
Mississippi Power
Operating Activities:
Consolidated net income	139,000,000	236,000,000	(2,588,000,000)
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	197,000,000	177,000,000	198,000,000
Deferred income taxes	37,000,000	475,000,000	(727,000,000)
Allowance for equity funds used during construction	(1,000,000)	0	(72,000,000)
Pension and postretirement funding	(54,000,000)	0	0
Settlement of asset retirement obligations	(35,000,000)	(35,000,000)	(23,000,000)
Estimated loss on plants under construction	15,000,000	33,000,000	3,179,000,000
Other, net	21,000,000	18,000,000	(8,000,000)
Changes in certain current assets and liabilities —
-Receivables	6,000,000	(19,000,000)	540,000,000
-Fossil fuel for generation	(6,000,000)	(3,000,000)	24,000,000
-Other current assets	(2,000,000)	(7,000,000)	(13,000,000)
-Accounts payable	3,000,000	15,000,000	(3,000,000)
-Accrued taxes	11,000,000	(46,000,000)	80,000,000
-Other current liabilities	(20,000,000)	(41,000,000)	(4,000,000)
-Prepaid income taxes	12,000,000	(12,000,000)	0
-Accrued interest	0	(1,000,000)	(29,000,000)
-Over recovered regulatory clause revenues	16,000,000	14,000,000	(51,000,000)
Net cash provided from operating activities	339,000,000	804,000,000	503,000,000
Investing Activities:
Property additions	(202,000,000)	(188,000,000)	(429,000,000)
Change in construction payables, net	(1,000,000)	4,000,000	(47,000,000)
Payments pursuant to LTSAs	(23,000,000)	(29,000,000)	(10,000,000)
Other investing activities	(37,000,000)	(19,000,000)	(18,000,000)
Net cash used for investing activities	(263,000,000)	(232,000,000)	(504,000,000)
Financing Activities:
Increase (decrease) in notes payable, net	0	(4,000,000)	(18,000,000)
Proceeds —
Short-term borrowings	0	300,000,000	109,000,000
Senior notes	0	600,000,000	0
Pollution control revenue bonds	43,000,000	0	0
Capital contributions from parent company	51,000,000	15,000,000	1,002,000,000
Long-term debt issuance to parent company	0	0	40,000,000
Redemptions and repurchases —
Preferred and preference stock	0	(33,000,000)	0
Short-term borrowings	0	(300,000,000)	(109,000,000)
Senior notes	(25,000,000)	(155,000,000)	(35,000,000)
Pollution control revenue bonds	0	(43,000,000)	0
Long-term debt to parent company	0	0	(591,000,000)
Capital leases	0	0	(71,000,000)
Other long-term debt	0	(900,000,000)	(300,000,000)
Return of capital to parent company	(150,000,000)	0	0
Other financing activities	(2,000,000)	(7,000,000)	(2,000,000)
Net cash provided from (used for) financing activities	(83,000,000)	(527,000,000)	25,000,000
Net Change in Cash, Cash Equivalents, and Restricted Cash	(7,000,000)	45,000,000	24,000,000
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	293,000,000	248,000,000	224,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	286,000,000	293,000,000	248,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	71,000,000	80,000,000	65,000,000
Income taxes (net of refunds)	(27,000,000)	(525,000,000)	(424,000,000)
Noncash transactions —
Accrued property additions at year-end	35,000,000	35,000,000	32,000,000
Southern Power
Operating Activities:
Consolidated net income	329,000,000	246,000,000	1,117,000,000
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	505,000,000	524,000,000	536,000,000
Deferred income taxes	(74,000,000)	(244,000,000)	(263,000,000)
Utilization of federal investment tax credits	734,000,000	5,000,000	0
Amortization of investment tax credits	(151,000,000)	(58,000,000)	(57,000,000)
Pension and postretirement funding	(24,000,000)	0	0
Income taxes receivable, non-current	25,000,000	42,000,000	(61,000,000)
Impairment charges	3,000,000	156,000,000	0
(Gain) loss on dispositions, net	23,000,000	2,000,000	0
Accrued income taxes, non-current	0	(14,000,000)	14,000,000
Other, net	(33,000,000)	7,000,000	(13,000,000)
Changes in certain current assets and liabilities —
-Receivables	72,000,000	(20,000,000)	(60,000,000)
-Other current assets	(8,000,000)	(26,000,000)	(28,000,000)
-Accrued taxes	6,000,000	7,000,000	(55,000,000)
-Other current liabilities	(38,000,000)	(19,000,000)	1,000,000
-Prepaid income taxes	39,000,000	25,000,000	24,000,000
Net cash provided from operating activities	1,385,000,000	631,000,000	1,155,000,000
Investing Activities:
Business acquisitions, net of cash acquired	(50,000,000)	(65,000,000)	(1,016,000,000)
Property additions	(489,000,000)	(315,000,000)	(268,000,000)
Proceeds from dispositions and asset sales	572,000,000	203,000,000	0
Investments in unconsolidated subsidiaries	(116,000,000)	0	0
Change in construction payables, net of joint owner portion	7,000,000	(6,000,000)	(153,000,000)
Payments pursuant to LTSAs and for equipment not yet received	(104,000,000)	(75,000,000)	(203,000,000)
Other investing activities	13,000,000	31,000,000	15,000,000
Net cash used for investing activities	(167,000,000)	(227,000,000)	(1,625,000,000)
Financing Activities:
Increase (decrease) in notes payable, net	449,000,000
Increase (decrease) in notes payable, net		(105,000,000)	(104,000,000)
Proceeds —
Short-term borrowings	100,000,000	200,000,000	0
Senior notes	0	0	525,000,000
Other long-term debt	0	0	43,000,000
Capital contributions from parent company	64,000,000	2,000,000	0
Redemptions and repurchases —
Short-term borrowings	(100,000,000)	(100,000,000)	0
Senior notes	(600,000,000)	(350,000,000)	(500,000,000)
Other long-term debt	0	(420,000,000)	(18,000,000)
Return of capital to parent company	(755,000,000)	(1,650,000,000)	0
Distributions to noncontrolling interests	(256,000,000)	(153,000,000)	(119,000,000)
Capital contributions from noncontrolling interests	196,000,000	2,551,000,000	80,000,000
Purchase of membership interests from noncontrolling interests	0	0	(59,000,000)
Payment of common stock dividends	(206,000,000)	(312,000,000)	(317,000,000)
Other financing activities	(12,000,000)	(26,000,000)	(33,000,000)
Net cash provided from (used for) financing activities	(1,120,000,000)	(363,000,000)	(502,000,000)
Net Change in Cash, Cash Equivalents, and Restricted Cash	98,000,000	41,000,000	(972,000,000)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	181,000,000	140,000,000	1,112,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	279,000,000	181,000,000	140,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	167,000,000	173,000,000	189,000,000
Income taxes (net of refunds)	(664,000,000)	79,000,000	(487,000,000)
Noncash transactions —
Accrued property additions at year-end	57,000,000	31,000,000	32,000,000
Southern Company Gas
Operating Activities:
Consolidated net income	585,000,000	372,000,000	243,000,000
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	487,000,000	500,000,000	501,000,000
Deferred income taxes	213,000,000	(1,000,000)	236,000,000
Pension and postretirement funding	(145,000,000)	0	0
Impairment charges	115,000,000	42,000,000	0
(Gain) loss on dispositions, net	0	(291,000,000)	0
Mark-to-market adjustments	(56,000,000)	(19,000,000)	(24,000,000)
Other, net	(55,000,000)	(24,000,000)	(51,000,000)
Changes in certain current assets and liabilities —
-Receivables	467,000,000	(218,000,000)	(94,000,000)
-Natural gas for sale	44,000,000	49,000,000	36,000,000
-Other current assets	31,000,000	4,000,000	(24,000,000)
-Accounts payable	(520,000,000)	372,000,000	(20,000,000)
-Accrued taxes	(69,000,000)	10,000,000	110,000,000
-Other current liabilities	(71,000,000)	(22,000,000)	(8,000,000)
-Prepaid income taxes	40,000,000	(42,000,000)	(39,000,000)
-Accrued compensation	1,000,000	32,000,000	15,000,000
Net cash provided from operating activities	1,067,000,000	764,000,000	881,000,000
Investing Activities:
Property additions	(1,408,000,000)	(1,388,000,000)	(1,514,000,000)
Proceeds from dispositions and asset sales	32,000,000	2,609,000,000	0
Cost of removal, net of salvage	(82,000,000)	(96,000,000)	(66,000,000)
Change in construction payables, net	24,000,000	(37,000,000)	72,000,000
Investments in unconsolidated subsidiaries	(31,000,000)	(110,000,000)	(145,000,000)
Returned investment in unconsolidated subsidiaries	67,000,000	20,000,000	80,000,000
Other investing activities	12,000,000	0	5,000,000
Net cash used for investing activities	(1,386,000,000)	998,000,000	(1,568,000,000)
Financing Activities:
Increase (decrease) in notes payable, net	0		262,000,000
Increase (decrease) in notes payable, net		(868,000,000)
Proceeds —
First mortgage bonds	300,000,000	300,000,000	400,000,000
Senior notes	0	0	450,000,000
Capital contributions from parent company	821,000,000	24,000,000	103,000,000
Redemptions and repurchases —
Gas facility revenue bonds	0	(200,000,000)	0
Medium-term notes	0	0	(22,000,000)
Senior notes	(300,000,000)	(155,000,000)	0
First mortgage bonds	(50,000,000)	0	0
Return of capital to parent company	0	(400,000,000)	0
Payment of common stock dividends	(471,000,000)	(468,000,000)	(443,000,000)
Other financing activities	(2,000,000)	(3,000,000)	(9,000,000)
Net cash provided from (used for) financing activities	298,000,000	(1,770,000,000)	741,000,000
Net Change in Cash, Cash Equivalents, and Restricted Cash	(21,000,000)	(8,000,000)	54,000,000
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	70,000,000	78,000,000	24,000,000
Cash, Cash Equivalents, and Restricted Cash at End of Year	49,000,000	70,000,000	78,000,000
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	251,000,000	249,000,000	223,000,000
Income taxes (net of refunds)	(41,000,000)	524,000,000	72,000,000
Noncash transactions —
Accrued property additions at year-end	$ 122,000,000	$ 97,000,000	$ 135,000,000