POLICY LIABILITIES - Summary of Undiscounted Expected Future Gross Premiums and Expected Future Benefits and Expenses (Detail) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 143,474	$ 142,653
Benefits and Expenses	173,047	173,393
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	52,505	51,712
Benefits and Expenses	54,844	56,881
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	32,757	33,250
Benefits and Expenses	35,043	34,864
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	10,781	10,915
Benefits and Expenses	37,340	37,520
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,351	1,477
Benefits and Expenses	6,419	6,479
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,326	2,966
Benefits and Expenses	3,948	3,559
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	8,560	8,862
Benefits and Expenses	4,660	4,687
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	5,697	5,727
Benefits and Expenses	3,033	3,094
Aflac U.S. | Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	19,182	19,624
Benefits and Expenses	19,971	20,340
Aflac U.S. | Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,757	4,859
Benefits and Expenses	3,027	3,017
Aflac U.S. | Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,081	1,118
Benefits and Expenses	657	679
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,477	2,143
Benefits and Expenses	$ 4,105	$ 2,273