Consolidated Statements of Cash Flows - GAS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Consolidated net income	$ 2,309	$ 3,103	$ 4,744
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	3,973	3,905	3,331
Deferred income taxes	(49)	(241)	611
Pension and postretirement funding	0	(2)	(1,136)
Gain on dispositions, net	(176)	(66)	(2,588)
Natural gas cost under recovery – long-term	(207)	0	0
Other, net	86	(74)	115
Changes in certain current assets and liabilities —
-Receivables	(81)	(222)	630
-Natural gas cost under recovery	(266)	0	0
-Other current assets	(170)	(161)	12
-Accounts payable	(8)	(27)	(693)
-Accrued taxes	(54)	242	117
-Other current liabilities	(49)	76	(73)
Net cash provided from operating activities	6,169	6,696	5,781
Investing Activities:
Property additions	(7,240)	(7,441)	(7,555)
Cost of removal, net of salvage	(442)	(361)	(393)
Change in construction payables, net	(124)	37	(169)
Proceeds from dispositions	917	1,049	5,122
Other investing activities	74	(16)	(107)
Net cash used for investing activities	(7,353)	(7,030)	(3,392)
Financing Activities:
Increase (decrease) in notes payable, net	530		640
Increase (decrease) in notes payable, net		(1,096)
Proceeds —
Short-term borrowings	325	615	350
Redemptions and repurchases —
Payment of common stock dividends	(2,777)	(2,685)	(2,570)
Other financing activities	(266)	(325)	(157)
Net cash provided from (used for) financing activities	1,945	(576)	(1,930)
Net Change in Cash, Cash Equivalents, and Restricted Cash	761	(910)	459
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	1,068	1,978	1,519
Cash, Cash Equivalents, and Restricted Cash at End of Year	1,829	1,068	1,978
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	1,718	1,683	1,651
Income taxes, net	93	64	276
Noncash transactions —
Accrued property additions at year-end	866	989	932
Southern Company Gas
Operating Activities:
Consolidated net income	539	590	585
Adjustments to reconcile consolidated net income to net cash provided from operating activities —
Depreciation and amortization, total	536	500	487
Deferred income taxes	259	56	213
Pension and postretirement funding	0	0	(145)
Impairment charges	84	0	115
Gain on dispositions, net	(127)	(22)	0
Mark-to-market adjustments	194	61	(56)
Natural gas cost under recovery – long-term	(207)	0	0
Other, net	(30)	(29)	(55)
Changes in certain current assets and liabilities —
-Receivables	(143)	(93)	467
-Natural gas for sale	8	18	44
-Prepaid income taxes	(82)	19	40
-Natural gas cost under recovery	(266)	0	0
-Other current assets	(116)	(10)	31
-Accounts payable	40	103	(520)
-Accrued taxes	45	13	(69)
-Accrued compensation	23	7	1
-Other current liabilities	(94)	(6)	(71)
Net cash provided from operating activities	663	1,207	1,067
Investing Activities:
Property additions	(1,421)	(1,471)	(1,408)
Cost of removal, net of salvage	(106)	(100)	(82)
Change in construction payables, net	(29)	20	24
Investments in unconsolidated subsidiaries	(5)	(79)	(31)
Returned investment in unconsolidated subsidiaries	22	13	67
Proceeds from dispositions	150	211	32
Other investing activities	10	(11)	12
Net cash used for investing activities	(1,379)	(1,417)	(1,386)
Financing Activities:
Increase (decrease) in notes payable, net	585
Increase (decrease) in notes payable, net		(326)	0
Proceeds —
Senior notes	450	500	0
Short-term borrowings	300	0	0
First mortgage bonds	200	325	300
Redemptions and repurchases —
Senior notes	(300)	0	(300)
Medium-term notes	(30)	0	0
First mortgage bonds	0	0	(50)
Capital contributions from parent company	72	216	821
Payment of common stock dividends	(530)	(533)	(471)
Other financing activities	(2)	(2)	(2)
Net cash provided from (used for) financing activities	745	180	298
Net Change in Cash, Cash Equivalents, and Restricted Cash	29	(30)	(21)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	19	49	70
Cash, Cash Equivalents, and Restricted Cash at End of Year	48	19	49
Supplemental Cash Flow Information:
Interest, net of amounts capitalized	244	232	251
Income taxes, net	57	25	(41)
Noncash transactions —
Accrued property additions at year-end	$ 113	$ 142	$ 122