POLICY LIABILITIES - Summary of Interest Expense Related to Insurance Contracts 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]
Interest expense	$ 568	$ 603	$ 1,703	$ 1,744
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	236	257	710	740
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	69	71	204	202
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	117	123	347	355
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	19	20	57	57
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	11	11	34	31
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	7	7	20	20
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	8	9	23	25
Aflac U.S. | Critical Care
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	84	85	254	256
Aflac U.S. | Hospital Indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	9	10	28	29
Aflac U.S. | Dental/Vision
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	2	3	8	9
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 6	$ 7	$ 18	$ 20