POLICY LIABILITIES - Summary of Interest Expense Related to Insurance Contracts 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]
Interest expense	$ 2,436	$ 2,546	$ 3,007
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	1,061	1,140	1,428
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	274	278	330
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	501	524	631
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	37	35	33
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	25	23	21
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	34	37	39
Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	345	346	343
Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	39	40	40
Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	13	12	13
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	80	84	102
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Interest expense	$ 27	$ 27	$ 27