POLICY LIABILITIES - Summary of Discounted Expected Future Gross Premiums and Expected Future Policy Benefits and Expenses (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 92,615	$ 99,697
Benefits and Expenses	92,288	100,522
Aflac Japan \| Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	33,155	36,796
Benefits and Expenses	31,311	34,987	$ 40,781
Aflac Japan \| Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	19,461	22,239
Benefits and Expenses	15,685	17,692	20,606
Aflac Japan \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	7,885	8,625
Benefits and Expenses	18,440	20,894	24,265
Aflac Japan \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	897	1,018
Benefits and Expenses	3,261	3,671	4,225
Aflac U.S. \| Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,541	2,358
Benefits and Expenses	2,179	2,076	1,847
Aflac U.S. \| Accident
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	5,853	6,002
Benefits and Expenses	3,090	3,184	3,127
Aflac U.S. \| Disability
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,393	4,478
Benefits and Expenses	2,310	2,336	2,330
Aflac U.S. \| Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	11,773	11,988
Benefits and Expenses	10,687	10,845	10,701
Aflac U.S. \| Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,298	3,333
Benefits and Expenses	1,936	1,955	1,897
Aflac U.S. \| Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	729	755
Benefits and Expenses	431	438	441
Aflac U.S. \| Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,630	2,105
Benefits and Expenses	$ 2,958	$ 2,444	$ 1,288