Introduction - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 1,662	$ 1,798
Restricted cash:
Total cash, cash equivalents, and restricted cash	1,673	1,829	$ 1,801	$ 1,068
Other current assets
Restricted cash:
Restricted cash	2	2
Other deferred charges and assets
Restricted cash:
Restricted cash	9	29
SOUTHERN POWER CO
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	130	107
Restricted cash:
Total cash, cash equivalents, and restricted cash	139	135	343	182
SOUTHERN POWER CO | Other current assets
Restricted cash:
Restricted cash	0	0
SOUTHERN POWER CO | Other deferred charges and assets
Restricted cash:
Restricted cash	9	29
SOUTHERN POWER CO | Tax Equity Contributions | Garland
Restricted cash:
Restricted cash		19
SOUTHERN POWER CO | Estimated Construction Completion Costs | Deuel Harvest
Restricted cash:
Restricted cash	9	10
SOUTHERN Co GAS
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	31	45
Restricted cash:
Total cash, cash equivalents, and restricted cash	33	48	$ 311	$ 19
SOUTHERN Co GAS | Other current assets
Restricted cash:
Restricted cash	2	2
SOUTHERN Co GAS | Other deferred charges and assets
Restricted cash:
Restricted cash	$ 0	$ 0