REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Effects of Reinsurance [Line Items]
Direct earned premiums		$ 3,352	$ 3,623	$ 6,834	$ 7,361
Ceded premiums		(66)	(103)	(135)	(210)
Net earned premiums	[1]	3,325	3,573	6,781	7,262
Direct benefits and claims, excluding reserve remeasurement		1,995	2,182	4,077	4,438
Benefits and claims, excluding reserve remeasurement		1,972	2,152	4,039	4,354
Reserve remeasurement (gains) losses, direct		(51)	(54)	(108)	(107)
Reserve remeasurement gains (losses), ceded		0	0	1	0
Reserve remeasurement (gains) losses, assumed		0	0	0	0
Reserve remeasurement (gains) losses		(51)	(54)	(107)	(107)
Benefits and claims, net		1,921	2,098	3,932	4,247
All other
Effects of Reinsurance [Line Items]
Ceded premiums		(35)	(23)	(70)	(45)
Assumed premiums earned		12	23	26	47
Ceded benefits and claims		(19)	6	(33)	(21)
Assumed benefits and claims from other companies		1	18	5	27
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums		(31)	(80)	(65)	(165)
Assumed premiums earned		27	30	56	64
Ceded benefits and claims		(17)	(74)	(35)	(151)
Assumed benefits and claims from other companies		$ 12	$ 20	$ 25	$ 61

[1] Includes a gain (loss) of $(2) and $(1) for the three-month periods and $(5) and $(1) for the six-month periods ended June 30, 2024 and 2023, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.