SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Impact from Adoption to Liability For Future Policy Benefit, Expected Future Policy Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, Activity [Line Items]
Ending balance	$ 123,918	$ 141,463
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	41,546	47,677	$ 56,807
Effect of changes in discount rate assumptions	5,663	7,089
Ending balance	47,209	54,766	72,747
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	23,763	27,566	31,398
Effect of changes in discount rate assumptions	(170)	(147)
Ending balance	23,593	27,419	36,021
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	28,796	32,800	39,002
Effect of changes in discount rate assumptions	(868)	(846)
Ending balance	27,928	31,954	42,720
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	1,952	1,778	1,694
Effect of changes in discount rate assumptions	(344)	(252)
Ending balance	1,608	1,526	1,843
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	5,188	5,940	6,787
Effect of changes in discount rate assumptions	(332)	(358)
Ending balance	4,856	5,582	7,322
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	687	624	645
Effect of changes in discount rate assumptions	(35)	(2)
Ending balance	652	622	837
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	3,339	3,391	3,594
Effect of changes in discount rate assumptions	(375)	(293)
Ending balance	2,964	3,098	3,949
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	2,584	2,636	2,670
Effect of changes in discount rate assumptions	(233)	(191)
Ending balance	2,351	2,445	2,871
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	12,203	12,846	13,079
Effect of changes in discount rate assumptions	(1,743)	(1,357)
Ending balance	10,460	11,489	15,388
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	2,106	2,300	2,300
Effect of changes in discount rate assumptions	(259)	(226)
Ending balance	1,847	2,074	2,552
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	508	532	549
Effect of changes in discount rate assumptions	(58)	(44)
Ending balance	$ 450	$ 488	616
Accounting Standards Update 2018-12 | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			56,807		$ 64,056
Effect of changes in discount rate assumptions			15,940
Ending balance			72,747	$ 82,567
Accounting Standards Update 2018-12 | Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			31,398		34,638
Effect of changes in discount rate assumptions			4,623
Ending balance			36,021	39,618
Accounting Standards Update 2018-12 | Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			39,002		43,729
Effect of changes in discount rate assumptions			3,718
Ending balance			42,720	47,951
Accounting Standards Update 2018-12 | Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			1,694		1,562
Effect of changes in discount rate assumptions			149
Ending balance			1,843	1,789
Accounting Standards Update 2018-12 | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			6,787		7,620
Effect of changes in discount rate assumptions			535
Ending balance			7,322	8,201
Accounting Standards Update 2018-12 | Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			645		661
Effect of changes in discount rate assumptions			192
Ending balance			837	906
Accounting Standards Update 2018-12 | Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			3,594		3,818
Effect of changes in discount rate assumptions			355
Ending balance			3,949	4,389
Accounting Standards Update 2018-12 | Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			2,670		2,919
Effect of changes in discount rate assumptions			201
Ending balance			2,871	3,265
Accounting Standards Update 2018-12 | Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			13,079		13,427
Effect of changes in discount rate assumptions			2,309
Ending balance			15,388	16,733
Accounting Standards Update 2018-12 | Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			2,300		2,258
Effect of changes in discount rate assumptions			252
Ending balance			2,552	2,635
Accounting Standards Update 2018-12 | Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			549		599
Effect of changes in discount rate assumptions			67
Ending balance			$ 616	705
Accounting Standards Update 2018-12 | As Previously Reported | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					64,056
Accounting Standards Update 2018-12 | As Previously Reported | Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					34,638
Accounting Standards Update 2018-12 | As Previously Reported | Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					43,729
Accounting Standards Update 2018-12 | As Previously Reported | Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					1,562
Accounting Standards Update 2018-12 | As Previously Reported | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					7,620
Accounting Standards Update 2018-12 | As Previously Reported | Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					661
Accounting Standards Update 2018-12 | As Previously Reported | Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					3,818
Accounting Standards Update 2018-12 | As Previously Reported | Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					2,919
Accounting Standards Update 2018-12 | As Previously Reported | Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					13,427
Accounting Standards Update 2018-12 | As Previously Reported | Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					2,258
Accounting Standards Update 2018-12 | As Previously Reported | Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance					$ 599
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				18,511
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				4,980
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				4,222
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				227
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				581
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				245
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				571
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				346
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				3,306
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				377
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Effect of changes in discount rate assumptions				$ 106