SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Impact from Adoption to Liability For Future Policy Benefit, Expected Net Premium (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021		Dec. 31, 2020
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	$ 16,452	$ 18,221	$ 22,470
Effect of changes in discount rate assumptions	1,057	1,077
Ending balance	17,509	19,298	25,893
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	14,040	16,195	18,681
Effect of changes in discount rate assumptions	657	519
Ending balance	14,697	16,714	21,174
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	6,258	7,284	10,064
Effect of changes in discount rate assumptions	230	201
Ending balance	6,488	7,485	10,847
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	909	799	780
Effect of changes in discount rate assumptions	(56)	(75)
Ending balance	853	724	834
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	1,069	1,242	1,461
Effect of changes in discount rate assumptions	19	14
Ending balance	1,088	1,256	1,586
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	272	118	135
Effect of changes in discount rate assumptions	5	(8)
Ending balance	277	110	153
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	2,630	2,760	2,999
Effect of changes in discount rate assumptions	(142)	(226)
Ending balance	2,488	2,534	3,283
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	1,738	1,775	1,760
Effect of changes in discount rate assumptions	(86)	(140)
Ending balance	1,652	1,635	1,862
Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	4,416	5,050	5,391
Effect of changes in discount rate assumptions	(342)	(564)
Ending balance	4,074	4,486	6,023
Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	1,193	1,365	1,380
Effect of changes in discount rate assumptions	(86)	(145)
Ending balance	1,107	1,220	1,467
Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance	217	231	241
Effect of changes in discount rate assumptions	(11)	(20)
Ending balance	$ 206	$ 211	264
Accounting Standards Update 2018-12 | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			22,470	$ 25,616	[1]
Effect of changes in discount rate assumptions			3,423
Ending balance			25,893	29,598
Accounting Standards Update 2018-12 | Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			18,681	21,276	[1]
Effect of changes in discount rate assumptions			2,493
Ending balance			21,174	23,874
Accounting Standards Update 2018-12 | Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			10,064	12,476	[1]
Effect of changes in discount rate assumptions			783
Ending balance			10,847	13,384
Accounting Standards Update 2018-12 | Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			780	705	[1]
Effect of changes in discount rate assumptions			54
Ending balance			834	783
Accounting Standards Update 2018-12 | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			1,461	1,708	[1]
Effect of changes in discount rate assumptions			125
Ending balance			1,586	1,856
Accounting Standards Update 2018-12 | Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			135	152	[1]
Effect of changes in discount rate assumptions			18
Ending balance			153	179
Accounting Standards Update 2018-12 | Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			2,999	3,350	[1]
Effect of changes in discount rate assumptions			284
Ending balance			3,283	3,829
Accounting Standards Update 2018-12 | Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			1,760	1,921	[1]
Effect of changes in discount rate assumptions			102
Ending balance			1,862	2,118
Accounting Standards Update 2018-12 | Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			5,391	5,894	[1]
Effect of changes in discount rate assumptions			632
Ending balance			6,023	6,942
Accounting Standards Update 2018-12 | Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			1,380	1,376	[1]
Effect of changes in discount rate assumptions			87
Ending balance			1,467	1,530
Accounting Standards Update 2018-12 | Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance			241	281	[1]
Effect of changes in discount rate assumptions			23
Ending balance			$ 264	322
Accounting Standards Update 2018-12 | As Reported | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						$ 25,601
Accounting Standards Update 2018-12 | As Reported | Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						21,270
Accounting Standards Update 2018-12 | As Reported | Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						12,440
Accounting Standards Update 2018-12 | As Reported | Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						710
Accounting Standards Update 2018-12 | As Reported | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						2,080
Accounting Standards Update 2018-12 | As Reported | Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						154
Accounting Standards Update 2018-12 | As Reported | Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						3,350
Accounting Standards Update 2018-12 | As Reported | Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						1,921
Accounting Standards Update 2018-12 | As Reported | Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						5,898
Accounting Standards Update 2018-12 | As Reported | Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						1,376
Accounting Standards Update 2018-12 | As Reported | Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						281
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						25,616
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						15
Effect of changes in discount rate assumptions				3,982
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]
Beginning balance						21,276
Impact of capping net premium ratio to retained earnings						(1)
Impact of deferred profit liability						7
Effect of changes in discount rate assumptions				2,598
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]
Beginning balance						12,476
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						36
Effect of changes in discount rate assumptions				908
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]
Beginning balance						705
Impact of capping net premium ratio to retained earnings						(5)
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				78
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Beginning balance						1,708
Impact of capping net premium ratio to retained earnings						(398)
Impact of deferred profit liability						26
Effect of changes in discount rate assumptions				148
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]
Beginning balance						152
Impact of capping net premium ratio to retained earnings						(2)
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				27
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]
Beginning balance						3,350
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				479
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]
Beginning balance						1,921
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				197
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]
Beginning balance						5,894
Impact of capping net premium ratio to retained earnings						(4)
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				1,048
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]
Beginning balance						1,376
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						0
Effect of changes in discount rate assumptions				154
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]
Beginning balance						281
Impact of capping net premium ratio to retained earnings						0
Impact of deferred profit liability						$ 0
Effect of changes in discount rate assumptions				$ 41

[1] Includes the adjustment for capping the Transition Date NPR.