POLICY LIABILITIES - Schedule of Changes in Other Policyholders' Funds (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2025	Dec. 31, 2024
Policyholder Account Balance [Line Items]
Other deposit type reserves		$ 330	$ 239
Other policyholders’ funds		5,785	5,460
Aflac Japan | Fixed Annuity
Policyholder Account Balance [Line Items]
Beginning balance	[1]	5,221	5,939
Premiums received	[1]	78	104
Transfers from WAYS conversions	[1]	243	249
Surrenders and withdrawals	[1]	(50)	(58)
Benefit payments	[1]	(404)	(446)
Interest credited	[1]	39	49
Foreign currency translation and other	[1]	328	(616)
Ending balance	[1]	$ 5,455	$ 5,221

[1] Aflac Japan fixed annuities