POLICY LIABILITIES - Summary of Net Earned Premiums Recognized (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 3,456	$ 3,688
Reinsurance ceded	(69)	(104)
Corporate and other
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	165	90
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	878	1,132
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	605	689
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	339	399
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	138	115
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	325	329
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	333	309
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	444	443
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	185	184
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	59	53
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	34	39
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 20	$ 10