POLICY LIABILITIES - Summary of Discounted Expected Future Gross Premiums and Future Benefits and Expenses (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 117,475	$ 121,753
Benefits and Expenses	125,399	132,131
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	45,651	48,363
Benefits and Expenses	46,577	50,161	$ 54,766
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	28,885	30,757
Benefits and Expenses	23,665	25,257	27,419
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	10,582	11,240
Benefits and Expenses	27,675	29,731	31,954
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,098	1,914
Benefits and Expenses	1,919	1,764	1,526
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	6,381	6,369
Benefits and Expenses	3,250	3,109	3,098
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,551	4,488
Benefits and Expenses	2,417	2,422	2,445
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	12,585	12,417
Benefits and Expenses	11,387	11,290	11,489
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,484	3,419
Benefits and Expenses	1,985	1,943	2,074
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	796	807
Benefits and Expenses	461	478	488
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,384	1,512
Benefits and Expenses	4,850	5,178	5,582
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,078	467
Benefits and Expenses	$ 1,213	$ 798	$ 622