POLICY LIABILITIES - Summary of Interest Expense Related to Insurance Contracts Recognized (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 537	$ 559
Aflac Japan \| Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	217	233
Aflac Japan \| Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	66	66
Aflac Japan \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	108	114
Aflac Japan \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	18	18
Aflac U.S. \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	12	11
Aflac U.S. \| Accident
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	7	7
Aflac U.S. \| Disability
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	7	7
Aflac U.S. \| Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	83	85
Aflac U.S. \| Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	10	9
Aflac U.S. \| Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	3	3
Aflac U.S. \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 6	$ 6