POLICY LIABILITIES - Summary of Discounted Expected Future Gross Premiums and Expected Future Benefits and Expenses (Detail) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 99,697	$ 105,686
Benefits and Expenses	100,522	111,508
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	36,796	40,170
Benefits and Expenses	34,987	40,781	$ 50,161
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	22,239	25,171
Benefits and Expenses	17,692	20,606	25,257
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	8,625	9,367
Benefits and Expenses	20,894	24,265	29,731
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,018	1,204
Benefits and Expenses	3,671	4,225	5,178
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,358	2,050
Benefits and Expenses	2,076	1,847	1,764
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	6,002	6,057
Benefits and Expenses	3,184	3,127	3,109
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,478	4,404
Benefits and Expenses	2,336	2,330	2,422
Aflac U.S. | Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	11,988	11,900
Benefits and Expenses	10,845	10,701	11,290
Aflac U.S. | Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,333	3,312
Benefits and Expenses	1,955	1,897	1,943
Aflac U.S. | Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	755	761
Benefits and Expenses	438	441	478
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,105	1,290
Benefits and Expenses	$ 2,444	$ 1,288	$ 798