POLICY LIABILITIES - Summary of Discounted Expected Future Gross Premiums and Future Benefits and Expenses (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 115,301	$ 132,451
Benefits and Expenses	123,918	141,463
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	45,569	53,278
Benefits and Expenses	47,209	54,766	$ 72,747
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	29,117	34,693
Benefits and Expenses	23,593	27,419	36,021
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	10,780	12,951
Benefits and Expenses	27,928	31,954	42,720
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,797	1,663
Benefits and Expenses	1,608	1,526	1,843
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	6,144	6,510
Benefits and Expenses	2,964	3,098	3,949
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,319	4,468
Benefits and Expenses	2,351	2,445	2,871
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	11,752	12,659
Benefits and Expenses	10,460	11,489	15,388
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,301	3,483
Benefits and Expenses	1,847	2,074	2,552
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	768	821
Benefits and Expenses	450	488	616
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,438	1,697
Benefits and Expenses	4,856	5,582	7,322
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	316	228
Benefits and Expenses	$ 652	$ 622	$ 837