POLICY LIABILITIES - Summary of Interest Expense Related to Insurance Contracts Recognized (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 525	$ 568	$ 1,590	$ 1,703
Aflac Japan \| Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	208	236	639	710
Aflac Japan \| Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	66	69	197	204
Aflac Japan \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	105	117	317	347
Aflac Japan \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	18	19	54	57
Aflac U.S. \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	12	11	37	34
Aflac U.S. \| Accident
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	7	7	21	20
Aflac U.S. \| Disability
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	7	8	21	23
Aflac U.S. \| Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	83	84	250	254
Aflac U.S. \| Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	9	9	27	28
Aflac U.S. \| Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	3	2	8	8
Aflac U.S. \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 7	$ 6	$ 19	$ 18