POLICY LIABILITIES - Summary of Net Earned Premiums 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]
Reinsurance ceded		$ (368)	$ (284)	$ (404)
Net earned premiums	[1]	13,548	13,440	14,123
Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Reinsurance ceded		(52)	(51)	(52)
Net earned premiums		1,875	1,754	1,973
Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums		6,744	6,930	8,047
Aflac Japan | Cancer
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		3,405	3,545	4,063
Aflac Japan | Medical and other health
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		2,131	2,181	2,631
Aflac Japan | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		1,227	1,225	1,532
Aflac Japan | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		129	134	149
Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums		5,999	5,829	5,675
Aflac U.S. | Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		683	565	475
Aflac U.S. | Accident
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		1,229	1,265	1,288
Aflac U.S. | Disability
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		1,408	1,327	1,256
Aflac U.S. | Critical care
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		1,763	1,763	1,749
Aflac U.S. | Hospital indemnity
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		728	727	725
Aflac U.S. | Dental/vision
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		207	202	214
Aflac U.S. | Other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		200	110	45
Corporate and other
Liability for Future Policy Benefit, Activity [Line Items]
Gross premiums		806	680	400
Net earned premiums		$ 805	$ 681	$ 400

[1] Includes a gain (loss) of $(52), $(81) and $20 in 2025, 2024 and 2023, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.