POLICY LIABILITIES - Summary of Net Earned Premiums Recognized (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 3,381	$ 3,456
Reinsurance ceded	(88)	(69)
Corporate and other
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	198	165
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	839	878
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	529	605
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	316	339
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	169	138
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	311	325
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	352	333
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	441	444
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	184	185
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	49	59
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	32	34
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 49	$ 20