POLICY LIABILITIES - Summary of Net Earned Premiums Recognized (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Reinsurance ceded		$ (92)	$ (71)	$ (271)	$ (206)
Net earned premiums	[1]	3,372	3,328	10,223	10,109
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		850	885	2,574	2,595
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		535	577	1,621	1,752
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		281	251	925	906
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		34	35	99	104
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		171	141	510	420
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		305	314	925	955
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		349	333	1,055	998
Aflac U.S. | Critical Care
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		439	439	1,323	1,324
Aflac U.S. | Hospital Indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		181	181	548	548
Aflac U.S. | Dental/Vision
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		52	54	153	159
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		53	29	143	75
Corporate and other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		$ 214	$ 160	$ 618	$ 479

[1] Includes a gain (loss) of $(55) and $(75) for the three-month periods and $(55) and $(80) for the nine-month periods ended September 30, 2025 and 2024, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.