POLICY LIABILITIES - Summary of Net Earned Premiums Recognized (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 14,123	$ 14,901	$ 17,095
Reinsurance ceded	(404)	(419)	(504)
Corporate and other
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	400	145	180
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	4,063	4,716	5,731
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	2,631	2,917	3,570
Life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Reinsurance ceded	(52)	(35)	(29)
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	1,532	1,769	2,282
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	475	396	350
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	1,288	1,317	1,366
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	1,256	1,179	1,170
Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	1,749	1,758	1,801
Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	725	725	733
Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	214	199	188
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	149	161	186
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Net earned premiums	$ 45	$ 38	$ 42