REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Effects of Reinsurance [Line Items]
Direct earned premiums		$ 3,524	$ 3,565	$ 10,885	$ 11,472
Ceded premiums		(99)	(99)	(309)	(321)
Net earned premiums	[1]	3,476	3,535	10,737	11,379
Direct benefits and claims, excluding reserve remeasurement		2,106	2,178	6,545	7,029
Reserve remeasurement (gains) losses, direct benefits and claims		(219)	(73)	(327)	(132)
Direct benefits and claims		1,887	2,105	6,218	6,897
Reserve remeasurement (gains) losses, ceded benefits and claims		14	(20)	15	(20)
Benefits and claims, net		1,860	2,076	6,108	6,833
Intercompany eliminations
Effects of Reinsurance [Line Items]
Ceded benefits and claims		42	2	125	11
Assumed benefits and claims from other companies		(44)	(3)	(120)	(20)
All other
Effects of Reinsurance [Line Items]
Ceded premiums		(24)	(19)	(69)	(55)
Assumed premiums earned		18	34	65	116
Ceded benefits and claims		(49)	(2)	(154)	(21)
Assumed benefits and claims from other companies		52	25	156	104
Aflac Japan
Effects of Reinsurance [Line Items]
Net earned premiums	[1]	1,973	2,125	6,207	7,084
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums		(75)	(80)	(240)	(266)
Assumed premiums earned		33	35	96	112
Ceded benefits and claims		(71)	(72)	(222)	(237)
Assumed benefits and claims from other companies		$ 29	$ 41	$ 90	$ 119

[1] Includes a gain (loss) of $22 and $(41) for the three-month periods and $22 and $(42) for the nine-month periods ended September 30, 2023 and 2022, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.