POLICY LIABILITIES - Summary of Discounted Expected Future Gross Premiums and Future Benefits and Expenses (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 108,031	$ 105,686
Benefits and Expenses	113,348	111,508
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	40,989	40,170
Benefits and Expenses	41,438	40,781	$ 50,161
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	25,461	25,171
Benefits and Expenses	20,848	20,606	25,257
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	9,630	9,367
Benefits and Expenses	24,478	24,265	29,731
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,160	2,050
Benefits and Expenses	1,928	1,847	1,764
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	6,116	6,057
Benefits and Expenses	3,155	3,127	3,109
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	4,456	4,404
Benefits and Expenses	2,362	2,330	2,422
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	12,152	11,900
Benefits and Expenses	10,922	10,701	11,290
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	3,412	3,312
Benefits and Expenses	1,945	1,897	1,943
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	768	761
Benefits and Expenses	448	441	478
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,219	1,204
Benefits and Expenses	4,267	4,225	5,178
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,668	1,290
Benefits and Expenses	$ 1,557	$ 1,288	$ 798