POLICY LIABILITIES - Summary of Undiscounted Expected Future Gross Premiums and Future Benefits and Expenses (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 149,085	$ 156,494
Benefits and Expenses	182,776	193,058
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	55,096	59,169
Benefits and Expenses	61,876	66,427
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	35,735	38,583
Benefits and Expenses	37,277	39,884
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	11,637	12,677
Benefits and Expenses	39,439	42,541
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,824	2,719
Benefits and Expenses	3,367	3,260
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	9,097	9,095
Benefits and Expenses	4,551	4,548
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	5,819	5,776
Benefits and Expenses	3,210	3,177
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	20,008	19,886
Benefits and Expenses	20,712	20,626
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,985	4,922
Benefits and Expenses	3,058	3,025
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,161	1,162
Benefits and Expenses	729	726
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,646	1,781
Benefits and Expenses	6,923	7,448
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,077	724
Benefits and Expenses	$ 1,634	$ 1,396