SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Liability For Future Policy Benefit, Expected Future Policy Benefits, Activity (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	$ 141,463
Ending balance	123,918	$ 141,463
Net liability for future policy benefits	78,448	88,241
Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Net liability for future policy benefits			$ 115,964
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	54,766	72,747
Beginning balance at original discount rate	47,677	56,807
Effect of changes in cash flow assumptions		(148)	(721)
Effect of actual variances from expected experience		(314)	(333)
Adjusted beginning of period balance		47,215	55,753
Issuances	787	960
Interest accrual	1,116	1,599
Benefit payments	(2,245)	(3,050)
Foreign currency translation	(5,327)	(7,585)
Other	0	0
Ending balance at original discount rate	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
Net liability for future policy benefits	30,716	35,468
Less: reinsurance recoverable	1,952	0
Net liability for future policy benefits after reinsurance recoverable	28,764	35,468
Cancer | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		72,747
Beginning balance at original discount rate		56,807	64,056
Effect of changes in cash flow assumptions				$ 24
Effect of actual variances from expected experience				(149)
Adjusted beginning of period balance				63,931
Issuances			1,133
Interest accrual			2,014
Benefit payments			(3,894)
Foreign currency translation			(6,377)
Other			0
Ending balance at original discount rate			56,807
Effect of changes in discount rate assumptions			15,940
Ending balance			72,747
Net liability for future policy benefits			46,854
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			46,854
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	27,419	36,021
Beginning balance at original discount rate	27,566	31,398
Effect of changes in cash flow assumptions		(510)	352
Effect of actual variances from expected experience		(102)	83
Adjusted beginning of period balance		26,954	31,833
Issuances	295	646
Interest accrual	461	642
Benefit payments	(883)	(1,375)
Foreign currency translation	(3,064)	(4,180)
Other	0	0
Ending balance at original discount rate	23,763	27,566	31,398
Effect of changes in discount rate assumptions	(170)	(147)
Ending balance	23,593	27,419	36,021
Net liability for future policy benefits	9,699	10,705
Less: reinsurance recoverable	1,422	1,579
Net liability for future policy benefits after reinsurance recoverable	8,277	9,126
Medical and other health | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		36,021
Beginning balance at original discount rate		31,398	34,638
Effect of changes in cash flow assumptions				85
Effect of actual variances from expected experience				(458)
Adjusted beginning of period balance				34,265
Issuances			1,155
Interest accrual			769
Benefit payments			(1,313)
Foreign currency translation			(3,478)
Other			0
Ending balance at original discount rate			31,398
Effect of changes in discount rate assumptions			4,623
Ending balance			36,021
Net liability for future policy benefits			14,847
Less: reinsurance recoverable			2,150
Net liability for future policy benefits after reinsurance recoverable			12,697
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	31,954	42,720
Beginning balance at original discount rate	32,800	39,002
Effect of changes in cash flow assumptions		66	(550)
Effect of actual variances from expected experience		(43)	(91)
Adjusted beginning of period balance		32,823	38,361
Issuances	272	222
Interest accrual	472	670
Benefit payments	(1,090)	(1,248)
Foreign currency translation	(3,681)	(5,205)
Other	0	0
Ending balance at original discount rate	28,796	32,800	39,002
Effect of changes in discount rate assumptions	(868)	(846)
Ending balance	27,928	31,954	42,720
Net liability for future policy benefits	21,678	24,469
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	21,678	24,469
Life insurance | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		42,720
Beginning balance at original discount rate		39,002	43,729
Effect of changes in cash flow assumptions				31
Effect of actual variances from expected experience				(139)
Adjusted beginning of period balance				43,621
Issuances			287
Interest accrual			833
Benefit payments			(1,373)
Foreign currency translation			(4,366)
Other			0
Ending balance at original discount rate			39,002
Effect of changes in discount rate assumptions			3,718
Ending balance			42,720
Net liability for future policy benefits			31,873
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			31,873
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	1,526	1,843
Beginning balance at original discount rate	1,778	1,694
Effect of changes in cash flow assumptions		72	(1)
Effect of actual variances from expected experience		(12)	(21)
Adjusted beginning of period balance		1,838	1,672
Issuances	140	149
Interest accrual	50	62
Benefit payments	(81)	(103)
Foreign currency translation	0	0
Other	5	(2)
Ending balance at original discount rate	1,952	1,778	1,694
Effect of changes in discount rate assumptions	(344)	(252)
Ending balance	1,608	1,526	1,843
Net liability for future policy benefits	802	802
Less: reinsurance recoverable	11	9
Net liability for future policy benefits after reinsurance recoverable	791	793
Life insurance | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		1,843
Beginning balance at original discount rate		1,694	1,562
Effect of changes in cash flow assumptions				31
Effect of actual variances from expected experience				34
Adjusted beginning of period balance				1,627
Issuances			115
Interest accrual			58
Benefit payments			(107)
Foreign currency translation			0
Other			1
Ending balance at original discount rate			1,694
Effect of changes in discount rate assumptions			149
Ending balance			1,843
Net liability for future policy benefits			1,009
Less: reinsurance recoverable			10
Net liability for future policy benefits after reinsurance recoverable			999
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	5,582	7,322
Beginning balance at original discount rate	5,940	6,787
Effect of changes in cash flow assumptions		(27)	96
Effect of actual variances from expected experience		(7)	(10)
Adjusted beginning of period balance		5,906	6,873
Issuances	24	68
Interest accrual	76	106
Benefit payments	(154)	(202)
Foreign currency translation	(664)	(905)
Other	0	0
Ending balance at original discount rate	5,188	5,940	6,787
Effect of changes in discount rate assumptions	(332)	(358)
Ending balance	4,856	5,582	7,322
Net liability for future policy benefits	3,814	4,326
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	3,814	4,326
Other | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		7,322
Beginning balance at original discount rate		6,787	7,620
Effect of changes in cash flow assumptions				(11)
Effect of actual variances from expected experience				(15)
Adjusted beginning of period balance				7,594
Issuances			62
Interest accrual			129
Benefit payments			(238)
Foreign currency translation			(760)
Other			0
Ending balance at original discount rate			6,787
Effect of changes in discount rate assumptions			535
Ending balance			7,322
Net liability for future policy benefits			5,736
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			5,736
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	622	837
Beginning balance at original discount rate	624	645
Effect of changes in cash flow assumptions		(13)	(15)
Effect of actual variances from expected experience		2	7
Adjusted beginning of period balance		613	637
Issuances	76	0
Interest accrual	24	32
Benefit payments	(35)	(45)
Foreign currency translation	0	0
Other	9	0
Ending balance at original discount rate	687	624	645
Effect of changes in discount rate assumptions	(35)	(2)
Ending balance	652	622	837
Net liability for future policy benefits	480	512
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	480	512
Other | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		837
Beginning balance at original discount rate		645	661
Effect of changes in cash flow assumptions				0
Effect of actual variances from expected experience				(3)
Adjusted beginning of period balance				658
Issuances			0
Interest accrual			33
Benefit payments			(46)
Foreign currency translation			0
Other			0
Ending balance at original discount rate			645
Effect of changes in discount rate assumptions			192
Ending balance			837
Net liability for future policy benefits			684
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			684
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	3,098	3,949
Beginning balance at original discount rate	3,391	3,594
Effect of changes in cash flow assumptions		(11)	(70)
Effect of actual variances from expected experience		(61)	(177)
Adjusted beginning of period balance		3,319	3,347
Issuances	265	364
Interest accrual	95	128
Benefit payments	(340)	(456)
Foreign currency translation	0	0
Other	0	8
Ending balance at original discount rate	3,339	3,391	3,594
Effect of changes in discount rate assumptions	(375)	(293)
Ending balance	2,964	3,098	3,949
Net liability for future policy benefits	575	564
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	575	564
Accident | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		3,949
Beginning balance at original discount rate		3,594	3,818
Effect of changes in cash flow assumptions				(178)
Effect of actual variances from expected experience				(115)
Adjusted beginning of period balance				3,525
Issuances			372
Interest accrual			137
Benefit payments			(439)
Foreign currency translation			0
Other			(1)
Ending balance at original discount rate			3,594
Effect of changes in discount rate assumptions			355
Ending balance			3,949
Net liability for future policy benefits			666
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			666
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	2,445	2,871
Beginning balance at original discount rate	2,636	2,670
Effect of changes in cash flow assumptions		(59)	5
Effect of actual variances from expected experience		(21)	(48)
Adjusted beginning of period balance		2,556	2,627
Issuances	305	397
Interest accrual	72	94
Benefit payments	(349)	(483)
Foreign currency translation	0	0
Other	0	1
Ending balance at original discount rate	2,584	2,636	2,670
Effect of changes in discount rate assumptions	(233)	(191)
Ending balance	2,351	2,445	2,871
Net liability for future policy benefits	754	810
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	754	810
Disability | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		2,871
Beginning balance at original discount rate		2,670	2,919
Effect of changes in cash flow assumptions				(143)
Effect of actual variances from expected experience				(41)
Adjusted beginning of period balance				2,735
Issuances			355
Interest accrual			100
Benefit payments			(520)
Foreign currency translation			0
Other			0
Ending balance at original discount rate			2,670
Effect of changes in discount rate assumptions			201
Ending balance			2,871
Net liability for future policy benefits			1,009
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			1,009
Critical Care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	11,489	15,388
Beginning balance at original discount rate	12,846	13,079
Effect of changes in cash flow assumptions		(592)	(43)
Effect of actual variances from expected experience		(188)	(465)
Adjusted beginning of period balance		12,066	12,571
Issuances	408	550
Interest accrual	396	539
Benefit payments	(668)	(823)
Foreign currency translation	0	0
Other	1	9
Ending balance at original discount rate	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
Net liability for future policy benefits	6,599	7,003
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	6,599	7,003
Critical Care | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		15,388
Beginning balance at original discount rate		13,079	13,427
Effect of changes in cash flow assumptions				(326)
Effect of actual variances from expected experience				(304)
Adjusted beginning of period balance				12,797
Issuances			563
Interest accrual			553
Benefit payments			(834)
Foreign currency translation			0
Other			0
Ending balance at original discount rate			13,079
Effect of changes in discount rate assumptions			2,309
Ending balance			15,388
Net liability for future policy benefits			9,365
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			9,365
Hospital Indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	2,074	2,552
Beginning balance at original discount rate	2,300	2,300
Effect of changes in cash flow assumptions		(194)	40
Effect of actual variances from expected experience		(68)	(130)
Adjusted beginning of period balance		2,038	2,210
Issuances	211	282
Interest accrual	64	85
Benefit payments	(207)	(277)
Foreign currency translation	0	0
Other	0	0
Ending balance at original discount rate	2,106	2,300	2,300
Effect of changes in discount rate assumptions	(259)	(226)
Ending balance	1,847	2,074	2,552
Net liability for future policy benefits	775	854
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	775	854
Hospital Indemnity | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		2,552
Beginning balance at original discount rate		2,300	2,258
Effect of changes in cash flow assumptions				(3)
Effect of actual variances from expected experience				(36)
Adjusted beginning of period balance				2,219
Issuances			271
Interest accrual			85
Benefit payments			(275)
Foreign currency translation			0
Other			0
Ending balance at original discount rate			2,300
Effect of changes in discount rate assumptions			252
Ending balance			2,552
Net liability for future policy benefits			1,085
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			1,085
Dental/Vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	488	616
Beginning balance at original discount rate	532	549
Effect of changes in cash flow assumptions		(14)	13
Effect of actual variances from expected experience		(17)	(23)
Adjusted beginning of period balance		501	539
Issuances	33	34
Interest accrual	15	21
Benefit payments	(44)	(62)
Foreign currency translation	0	0
Other	3	0
Ending balance at original discount rate	508	532	549
Effect of changes in discount rate assumptions	(58)	(44)
Ending balance	450	488	616
Net liability for future policy benefits	256	277
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	$ 256	277
Dental/Vision | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance		616
Beginning balance at original discount rate		$ 549	599
Effect of changes in cash flow assumptions				(29)
Effect of actual variances from expected experience				(15)
Adjusted beginning of period balance				$ 555
Issuances			40
Interest accrual			23
Benefit payments			(69)
Foreign currency translation			0
Other			0
Ending balance at original discount rate			549
Effect of changes in discount rate assumptions			67
Ending balance			616
Net liability for future policy benefits			352
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			$ 352