POLICY LIABILITIES - Summary of Interest Expense Related to Insurance Contracts Recognized (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 2,254	$ 2,310	$ 2,436
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	935	978	1,061
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	272	268	274
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	459	472	501
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	75	76	80
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	45	41	37
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	28	27	25
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	30	32	34
Aflac U.S. | Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	338	342	345
Aflac U.S. | Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	37	38	39
Aflac U.S. | Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	11	11	13
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 24	$ 25	$ 27