Consolidated Statements of Common Stockholders' Equity - GAS - USD ($) $ in Millions	Total	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Southern Company Gas	Southern Company Gas Paid-In Capital	Southern Company Gas Retained Earnings	Southern Company Gas Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2020				$ 9,767	$ 9,930	$ (141)	$ (22)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 2,309			539		539
Capital contributions from parent company				94	94
Other comprehensive income (loss)	158		$ 158	46			46
Cash dividends on common stock	(2,777)	$ (2,777)		(530)		(530)
Ending balance at Dec. 31, 2021				9,916	10,024	(132)	24
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	3,428			572		572
Capital contributions from parent company				421	421
Other comprehensive income (loss)	71		71	7			7
Cash dividends on common stock	(2,907)	(2,907)		(519)		(519)
Ending balance at Dec. 31, 2022	30,408			10,397	10,445	(79)	31
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	3,849			615		615
Capital contributions from parent company				391	391
Other comprehensive income (loss)	(10)		$ (10)	(15)			(15)
Cash dividends on common stock	(3,035)	$ (3,035)		(585)		(585)
Ending balance at Dec. 31, 2023	$ 31,444			$ 10,803	$ 10,836	$ (49)	$ 16