SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Liability For Future Policy Benefit, Expected Future Policy Benefits, Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	$ 141,463
Ending balance	132,131	$ 141,463
Liability amounts	83,718	88,241
Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Liability amounts			$ 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		(147)	(721)
Effect of actual variances from expected experience		(385)	(333)
Adjusted beginning of period balance		47,145	55,753
Issuances	1,059	960
Interest accrual	1,473	1,599
Benefit payments	(2,987)	(3,050)
Foreign currency translation	(3,064)	(7,585)
Other	0	0
Ending balance at original discount rate	43,626	47,677	56,807
Effect of changes in discount rate assumptions	6,535	7,089
Ending balance	50,161	54,766	72,747
Liability amounts	32,652	35,468
Less: reinsurance recoverable	4,135	0
Net liability for future policy benefits after reinsurance recoverable	28,517	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
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
Liability amounts			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		(507)	352
Effect of actual variances from expected experience		(154)	83
Adjusted beginning of period balance		26,905	31,833
Issuances	432	646
Interest accrual	608	642
Benefit payments	(1,153)	(1,375)
Foreign currency translation	(1,769)	(4,180)
Other	0	0
Ending balance at original discount rate	25,023	27,566	31,398
Effect of changes in discount rate assumptions	234	(147)
Ending balance	25,257	27,419	36,021
Liability amounts	10,560	10,705
Less: reinsurance recoverable	1,521	1,579
Net liability for future policy benefits after reinsurance recoverable	9,039	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
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
Liability amounts			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		65	(550)
Effect of actual variances from expected experience		(51)	(91)
Adjusted beginning of period balance		32,814	38,361
Issuances	341	222
Interest accrual	625	670
Benefit payments	(1,415)	(1,248)
Foreign currency translation	(2,109)	(5,205)
Other	0	0
Ending balance at original discount rate	30,256	32,800	39,002
Effect of changes in discount rate assumptions	(525)	(846)
Ending balance	29,731	31,954	42,720
Liability amounts	23,243	24,469
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	23,243	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
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
Liability amounts			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		(32)	(21)
Adjusted beginning of period balance		1,818	1,672
Issuances	185	149
Interest accrual	68	62
Benefit payments	(105)	(103)
Foreign currency translation	0	0
Other	5	(2)
Ending balance at original discount rate	1,971	1,778	1,694
Effect of changes in discount rate assumptions	(207)	(252)
Ending balance	1,764	1,526	1,843
Liability amounts	911	802
Less: reinsurance recoverable	15	9
Net liability for future policy benefits after reinsurance recoverable	896	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
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
Liability amounts			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		(15)	(10)
Adjusted beginning of period balance		5,898	6,873
Issuances	32	68
Interest accrual	100	106
Benefit payments	(206)	(202)
Foreign currency translation	(380)	(905)
Other	0	0
Ending balance at original discount rate	5,444	5,940	6,787
Effect of changes in discount rate assumptions	(266)	(358)
Ending balance	5,178	5,582	7,322
Liability amounts	4,090	4,326
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	4,090	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
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
Liability amounts			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		(4)	7
Adjusted beginning of period balance		607	637
Issuances	169	0
Interest accrual	33	32
Benefit payments	(48)	(45)
Foreign currency translation	0	0
Other	8	0
Ending balance at original discount rate	769	624	645
Effect of changes in discount rate assumptions	29	(2)
Ending balance	798	622	837
Liability amounts	521	512
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	521	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
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
Liability amounts			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		(75)	(177)
Adjusted beginning of period balance		3,305	3,347
Issuances	331	364
Interest accrual	127	128
Benefit payments	(464)	(456)
Foreign currency translation	0	0
Other	3	8
Ending balance at original discount rate	3,302	3,391	3,594
Effect of changes in discount rate assumptions	(193)	(293)
Ending balance	3,109	3,098	3,949
Liability amounts	621	564
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	621	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
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
Liability amounts			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		(59)	(48)
Adjusted beginning of period balance		2,518	2,627
Issuances	392	397
Interest accrual	96	94
Benefit payments	(465)	(483)
Foreign currency translation	0	0
Other	0	1
Ending balance at original discount rate	2,541	2,636	2,670
Effect of changes in discount rate assumptions	(119)	(191)
Ending balance	2,422	2,445	2,871
Liability amounts	770	810
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	770	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
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
Liability amounts			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		(271)	(465)
Adjusted beginning of period balance		11,983	12,571
Issuances	505	550
Interest accrual	524	539
Benefit payments	(893)	(823)
Foreign currency translation	0	0
Other	1	9
Ending balance at original discount rate	12,120	12,846	13,079
Effect of changes in discount rate assumptions	(830)	(1,357)
Ending balance	11,290	11,489	15,388
Liability amounts	7,216	7,003
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	7,216	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
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
Liability amounts			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		(99)	(130)
Adjusted beginning of period balance		2,007	2,210
Issuances	258	282
Interest accrual	84	85
Benefit payments	(274)	(277)
Foreign currency translation	0	0
Other	1	0
Ending balance at original discount rate	2,076	2,300	2,300
Effect of changes in discount rate assumptions	(133)	(226)
Ending balance	1,943	2,074	2,552
Liability amounts	836	854
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	836	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
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
Liability amounts			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		(22)	(23)
Adjusted beginning of period balance		496	539
Issuances	46	34
Interest accrual	21	21
Benefit payments	(59)	(62)
Foreign currency translation	0	0
Other	2	0
Ending balance at original discount rate	506	532	549
Effect of changes in discount rate assumptions	(28)	(44)
Ending balance	478	488	616
Liability amounts	272	277
Less: reinsurance recoverable	0	0
Net liability for future policy benefits after reinsurance recoverable	$ 272	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
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
Liability amounts			352
Less: reinsurance recoverable			0
Net liability for future policy benefits after reinsurance recoverable			$ 352