REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Effects of Reinsurance [Line Items]
Direct earned premiums	$ 3,482	$ 3,738
Ceded premiums	(69)	(104)
Net earned premiums	3,456	3,688
Direct benefits and claims, excluding reserve remeasurement	2,082	2,256
Benefits and claims, excluding reserve remeasurement	2,066	2,203
Reserve remeasurement (gains) losses, direct	(57)	(53)
Reserve remeasurement gains (losses), ceded	1	0
Reserve remeasurement (gains) losses, assumed	0	0
Reserve remeasurement (gains) losses	(56)	(53)
Benefits and claims, net	2,010	2,150
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(35)	(25)
Assumed premiums earned	14	23
Ceded benefits and claims	(15)	(27)
Assumed benefits and claims from other companies	4	10
Aflac Japan \| Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(34)	(82)
Assumed premiums earned	29	34
Ceded benefits and claims	(18)	(77)
Assumed benefits and claims from other companies	$ 13	$ 41

Liability for Future Policy Benefit, Remeasurement Gain (Loss), Assumed

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Liability for Future Policy Benefit, Remeasurement Gain (Loss), Ceded

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Liability for Future Policy Benefit, Remeasurement Gain (Loss), Direct

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Policyholder Benefits and Claims Incurred, Direct, Excluding Reserve Remeasurement

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Policyholder Benefits and Claims Incurred, Excluding Reserve Remeasurement (Gain) Loss

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Amount of earned premiums assumed from other entities.

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Amount of earned premiums ceded to other entities.

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of remeasurement gain (loss) on liability for future policy benefit from application of revised benefit ratio as of contract issue. Includes, but is not limited to, remeasurement gain (loss) for annuitization insurance benefit, death and other insurance benefits, and traditional and limited-payment contracts.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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Amount of policy benefits and costs incurred for policies assumed.

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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