POLICY LIABILITIES - Schedule of Changes in Present Value of Expected Net Premiums and Expected Future Policy Benefits (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2025	Dec. 31, 2024	Dec. 31, 2023
Present value of expected future policy benefits:
Beginning balance		$ 111,508
Ending balance		107,596	$ 111,508
Net liability for future policy benefits		67,143	70,381
Aflac Japan | Cancer
Present value of expected future net premiums:
Beginning balance		14,184	17,509
Beginning balance at original discount rate		14,008	16,452
Effect of changes in cash flow assumptions			(661)	$ (625)
Effect of actual variances from expected experience			(277)	(71)
Adjusted beginning of period balance			13,070	15,756
Issuances		836	983
Interest accrual		276	378
Net premiums collected	[1]	(1,054)	(1,453)
Foreign currency translation		879	(1,655)
Other		(2)	(1)
Ending balance at original discount rate		14,005	14,008
Effect of changes in discount rate assumptions		(716)	176
Ending balance		13,289	14,184
Present value of expected future policy benefits:
Beginning balance		40,781	50,161
Beginning balance at original discount rate		37,856	43,626
Effect of changes in cash flow assumptions			(1,130)	(815)
Effect of actual variances from expected experience			(311)	(117)
Adjusted beginning of period balance			36,415	42,694
Issuances		849	1,004
Interest accrual		986	1,356
Benefit payments		(2,046)	(2,773)
Foreign currency translation		2,370	(4,425)
Other		0	0
Ending balance at original discount rate		38,574	37,856
Effect of changes in discount rate assumptions		(313)	2,925
Ending balance		38,261	40,781
Net liability for future policy benefits		24,972	26,597
Less: reinsurance recoverable		4,840	5,085
Net liability for future policy benefits after reinsurance recoverable		20,132	21,512
Aflac Japan | Medical and other health
Present value of expected future net premiums:
Beginning balance		11,817	14,697
Beginning balance at original discount rate		11,845	14,040
Effect of changes in cash flow assumptions			136	(154)
Effect of actual variances from expected experience			(83)	(164)
Adjusted beginning of period balance			11,898	13,722
Issuances		204	361
Interest accrual		221	302
Net premiums collected	[1]	(818)	(1,135)
Foreign currency translation		744	(1,405)
Other		(1)	0
Ending balance at original discount rate		12,248	11,845
Effect of changes in discount rate assumptions		(903)	(28)
Ending balance		11,345	11,817
Present value of expected future policy benefits:
Beginning balance		20,606	25,257
Beginning balance at original discount rate		21,957	25,023
Effect of changes in cash flow assumptions			108	(228)
Effect of actual variances from expected experience			(101)	(193)
Adjusted beginning of period balance			21,964	24,602
Issuances		209	373
Interest accrual		425	570
Benefit payments		(781)	(1,033)
Foreign currency translation		1,372	(2,555)
Other		0	0
Ending balance at original discount rate		23,189	21,957
Effect of changes in discount rate assumptions		(3,798)	(1,351)
Ending balance		19,391	20,606
Net liability for future policy benefits		8,046	8,789
Less: reinsurance recoverable		1,165	1,245
Net liability for future policy benefits after reinsurance recoverable		6,881	7,544
Aflac Japan | Life insurance
Present value of expected future net premiums:
Beginning balance		5,156	6,488
Beginning balance at original discount rate		5,084	6,258
Effect of changes in cash flow assumptions			(40)	(190)
Effect of actual variances from expected experience			(40)	(97)
Adjusted beginning of period balance			5,004	5,971
Issuances		277	478
Interest accrual		84	110
Net premiums collected	[1]	(608)	(862)
Foreign currency translation		318	(613)
Other		0	0
Ending balance at original discount rate		5,075	5,084
Effect of changes in discount rate assumptions		(156)	72
Ending balance		4,919	5,156
Present value of expected future policy benefits:
Beginning balance		24,265	29,731
Beginning balance at original discount rate		26,330	30,256
Effect of changes in cash flow assumptions			(102)	(302)
Effect of actual variances from expected experience			(40)	(110)
Adjusted beginning of period balance			26,188	29,844
Issuances		282	488
Interest accrual		431	582
Benefit payments		(1,366)	(1,510)
Foreign currency translation		1,648	(3,074)
Other		0	0
Ending balance at original discount rate		27,183	26,330
Effect of changes in discount rate assumptions		(4,425)	(2,065)
Ending balance		22,758	24,265
Net liability for future policy benefits		17,839	19,109
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		17,839	19,109
Aflac Japan | Other
Present value of expected future net premiums:
Beginning balance		846	1,088
Beginning balance at original discount rate		864	1,069
Effect of changes in cash flow assumptions			5	(19)
Effect of actual variances from expected experience			(7)	(14)
Adjusted beginning of period balance			862	1,036
Issuances		7	16
Interest accrual		12	17
Net premiums collected	[1]	(72)	(101)
Foreign currency translation		54	(104)
Other		0	0
Ending balance at original discount rate		863	864
Effect of changes in discount rate assumptions		(61)	(18)
Ending balance		802	846
Present value of expected future policy benefits:
Beginning balance		4,225	5,178
Beginning balance at original discount rate		4,765	5,444
Effect of changes in cash flow assumptions			75	(7)
Effect of actual variances from expected experience			(14)	(24)
Adjusted beginning of period balance			4,826	5,413
Issuances		11	22
Interest accrual		69	93
Benefit payments		(165)	(208)
Foreign currency translation		296	(555)
Other		0	0
Ending balance at original discount rate		5,037	4,765
Effect of changes in discount rate assumptions		(1,012)	(540)
Ending balance		4,025	4,225
Net liability for future policy benefits		3,223	3,379
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		3,223	3,379
Aflac U.S. | Life insurance
Present value of expected future net premiums:
Beginning balance		909	853
Beginning balance at original discount rate		976	909
Effect of changes in cash flow assumptions			(5)	(5)
Effect of actual variances from expected experience			(27)	(29)
Adjusted beginning of period balance			944	875
Issuances		182	226
Interest accrual		31	37
Net premiums collected	[1]	(128)	(157)
Foreign currency translation		0	0
Other		(3)	(5)
Ending balance at original discount rate		1,026	976
Effect of changes in discount rate assumptions		(32)	(67)
Ending balance		994	909
Present value of expected future policy benefits:
Beginning balance		1,847	1,764
Beginning balance at original discount rate		2,126	1,971
Effect of changes in cash flow assumptions			(17)	(3)
Effect of actual variances from expected experience			(41)	(43)
Adjusted beginning of period balance			2,068	1,925
Issuances		188	231
Interest accrual		65	78
Benefit payments		(82)	(108)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		2,239	2,126
Effect of changes in discount rate assumptions		(207)	(279)
Ending balance		2,032	1,847
Net liability for future policy benefits		1,038	938
Less: reinsurance recoverable		23	18
Net liability for future policy benefits after reinsurance recoverable		1,015	920
Aflac U.S. | Accident
Present value of expected future net premiums:
Beginning balance		2,497	2,488
Beginning balance at original discount rate		2,687	2,630
Effect of changes in cash flow assumptions			18	65
Effect of actual variances from expected experience			24	66
Adjusted beginning of period balance			2,729	2,761
Issuances		235	307
Interest accrual		83	106
Net premiums collected	[1]	(365)	(479)
Foreign currency translation		0	0
Other		(5)	(8)
Ending balance at original discount rate		2,677	2,687
Effect of changes in discount rate assumptions		(113)	(190)
Ending balance		2,564	2,497
Present value of expected future policy benefits:
Beginning balance		3,127	3,109
Beginning balance at original discount rate		3,386	3,302
Effect of changes in cash flow assumptions			47	109
Effect of actual variances from expected experience			22	91
Adjusted beginning of period balance			3,455	3,502
Issuances		240	311
Interest accrual		103	133
Benefit payments		(398)	(560)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		3,400	3,386
Effect of changes in discount rate assumptions		(165)	(259)
Ending balance		3,235	3,127
Net liability for future policy benefits		671	630
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		671	630
Aflac U.S. | Disability
Present value of expected future net premiums:
Beginning balance		1,635	1,652
Beginning balance at original discount rate		1,726	1,738
Effect of changes in cash flow assumptions			(22)	(47)
Effect of actual variances from expected experience			1	12
Adjusted beginning of period balance			1,705	1,703
Issuances		273	364
Interest accrual		51	66
Net premiums collected	[1]	(301)	(401)
Foreign currency translation		0	0
Other		(4)	(6)
Ending balance at original discount rate		1,724	1,726
Effect of changes in discount rate assumptions		(44)	(91)
Ending balance		1,680	1,635
Present value of expected future policy benefits:
Beginning balance		2,330	2,422
Beginning balance at original discount rate		2,466	2,541
Effect of changes in cash flow assumptions			(46)	(73)
Effect of actual variances from expected experience			(13)	(16)
Adjusted beginning of period balance			2,407	2,452
Issuances		284	381
Interest accrual		74	98
Benefit payments		(356)	(465)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		2,409	2,466
Effect of changes in discount rate assumptions		(68)	(136)
Ending balance		2,341	2,330
Net liability for future policy benefits		661	695
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		661	695
Aflac U.S. | Critical Care
Present value of expected future net premiums:
Beginning balance		3,901	4,074
Beginning balance at original discount rate		4,340	4,416
Effect of changes in cash flow assumptions			(163)	(106)
Effect of actual variances from expected experience			8	(100)
Adjusted beginning of period balance			4,185	4,210
Issuances		404	543
Interest accrual		133	173
Net premiums collected	[1]	(442)	(578)
Foreign currency translation		0	0
Other		(5)	(8)
Ending balance at original discount rate		4,275	4,340
Effect of changes in discount rate assumptions		(293)	(439)
Ending balance		3,982	3,901
Present value of expected future policy benefits:
Beginning balance		10,701	11,290
Beginning balance at original discount rate		12,013	12,120
Effect of changes in cash flow assumptions			(219)	(112)
Effect of actual variances from expected experience			(3)	(144)
Adjusted beginning of period balance			11,791	11,864
Issuances		418	559
Interest accrual		387	515
Benefit payments		(736)	(925)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		11,860	12,013
Effect of changes in discount rate assumptions		(929)	(1,312)
Ending balance		10,931	10,701
Net liability for future policy benefits		6,949	6,800
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		6,949	6,800
Aflac U.S. | Hospital Indemnity
Present value of expected future net premiums:
Beginning balance		1,122	1,107
Beginning balance at original discount rate		1,221	1,193
Effect of changes in cash flow assumptions			(8)	(21)
Effect of actual variances from expected experience			17	21
Adjusted beginning of period balance			1,230	1,193
Issuances		171	231
Interest accrual		37	46
Net premiums collected	[1]	(190)	(244)
Foreign currency translation		0	0
Other		(3)	(5)
Ending balance at original discount rate		1,245	1,221
Effect of changes in discount rate assumptions		(61)	(99)
Ending balance		1,184	1,122
Present value of expected future policy benefits:
Beginning balance		1,897	1,943
Beginning balance at original discount rate		2,073	2,076
Effect of changes in cash flow assumptions			(4)	(31)
Effect of actual variances from expected experience			12	21
Adjusted beginning of period balance			2,081	2,066
Issuances		176	237
Interest accrual		65	84
Benefit payments		(236)	(314)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		2,086	2,073
Effect of changes in discount rate assumptions		(114)	(176)
Ending balance		1,972	1,897
Net liability for future policy benefits		788	775
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		788	775
Aflac U.S. | Dental/Vision
Present value of expected future net premiums:
Beginning balance		196	206
Beginning balance at original discount rate		209	217
Effect of changes in cash flow assumptions			(10)	(17)
Effect of actual variances from expected experience			(8)	(12)
Adjusted beginning of period balance			191	188
Issuances		38	52
Interest accrual		7	9
Net premiums collected	[1]	(29)	(39)
Foreign currency translation		0	0
Other		0	(1)
Ending balance at original discount rate		207	209
Effect of changes in discount rate assumptions		(6)	(13)
Ending balance		201	196
Present value of expected future policy benefits:
Beginning balance		441	478
Beginning balance at original discount rate		477	506
Effect of changes in cash flow assumptions			(15)	(28)
Effect of actual variances from expected experience			(10)	(16)
Adjusted beginning of period balance			452	462
Issuances		39	55
Interest accrual		15	20
Benefit payments		(45)	(60)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		461	477
Effect of changes in discount rate assumptions		(20)	(36)
Ending balance		441	441
Net liability for future policy benefits		240	245
Less: reinsurance recoverable		0	0
Net liability for future policy benefits after reinsurance recoverable		240	245
Aflac U.S. | Other
Present value of expected future net premiums:
Beginning balance		826	277
Beginning balance at original discount rate		824	272
Effect of changes in cash flow assumptions			386	(8)
Effect of actual variances from expected experience			70	13
Adjusted beginning of period balance			1,280	277
Issuances		402	592
Interest accrual		48	25
Net premiums collected	[1]	(93)	(53)
Foreign currency translation		0	0
Other		(25)	(17)
Ending balance at original discount rate		1,612	824
Effect of changes in discount rate assumptions		116	2
Ending balance		1,728	826
Present value of expected future policy benefits:
Beginning balance		1,288	798
Beginning balance at original discount rate		1,293	769
Effect of changes in cash flow assumptions			399	(12)
Effect of actual variances from expected experience			69	(7)
Adjusted beginning of period balance			1,761	$ 750
Issuances		405	597
Interest accrual		66	50
Benefit payments		(148)	(104)
Foreign currency translation		0	0
Other		0	0
Ending balance at original discount rate		2,084	1,293
Effect of changes in discount rate assumptions		125	(5)
Ending balance		2,209	1,288
Net liability for future policy benefits		481	462
Less: reinsurance recoverable		14	0
Net liability for future policy benefits after reinsurance recoverable		$ 467	$ 462

[1] Net premiums collected represent the portion of gross premiums collected from policyholders that is used to fund expected future benefit payments.