DEFERRED POLICY ACQUISITION COSTS - Schedule Of Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	$ 9,132	$ 9,239	$ 9,239
Capitalization	254		1,086
Amortization expense	(215)	(205)	(816)
Foreign currency translation and other	(352)		(377)
Balance, end of period	8,819		9,132
Aflac Japan | Cancer
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	2,971	3,035	3,035
Capitalization	72		317
Amortization expense	(49)		(184)
Foreign currency translation and other	(189)		(197)
Balance, end of period	2,805		2,971
Aflac Japan | Medical and other health
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	2,041	2,161	2,161
Capitalization	29		123
Amortization expense	(25)		(105)
Foreign currency translation and other	(129)		(138)
Balance, end of period	1,916		2,041
Aflac Japan | Life insurance
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	491	525	525
Capitalization	9		33
Amortization expense	(8)		(34)
Foreign currency translation and other	(32)		(33)
Balance, end of period	460		491
Aflac Japan | Other
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	56	55	55
Capitalization	0		8
Amortization expense	(1)		(3)
Foreign currency translation and other	(2)		(4)
Balance, end of period	53		56
Aflac U.S. | Life insurance
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	172	135	135
Capitalization	19		61
Amortization expense	(7)		(24)
Foreign currency translation and other	0		0
Balance, end of period	184		172
Aflac U.S. | Accident
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	917	904	904
Capitalization	32		151
Amortization expense	(36)		(138)
Foreign currency translation and other	0		0
Balance, end of period	913		917
Aflac U.S. | Disability
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	625	613	613
Capitalization	29		125
Amortization expense	(29)		(113)
Foreign currency translation and other	0		0
Balance, end of period	625		625
Aflac U.S. | Critical Care
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	1,336	1,304	1,304
Capitalization	39		173
Amortization expense	(38)		(141)
Foreign currency translation and other	0		0
Balance, end of period	1,337		1,336
Aflac U.S. | Hospital Indemnity
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	436	418	418
Capitalization	19		84
Amortization expense	(18)		(66)
Foreign currency translation and other	0		0
Balance, end of period	437		436
Aflac U.S. | Dental/Vision
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	86	88	88
Capitalization	4		10
Amortization expense	(4)		(12)
Foreign currency translation and other	0		0
Balance, end of period	86		86
Aflac U.S. | Other
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period	1	$ 1	1
Capitalization	2		1
Amortization expense	0		4
Foreign currency translation and other	0		(5)
Balance, end of period	$ 3		$ 1