DEFERRED POLICY ACQUISITION COSTS - Schedule Of Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			$ 8,758	$ 9,132	$ 9,132
Capitalization			796		1,056
Amortization expense	$ (218)	$ (214)	(655)	(638)	(851)
Foreign currency translation and other			317		(579)
Balance, end of period	9,216		9,216		8,758
Aflac Japan | Cancer
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			2,776	2,971	2,971
Capitalization			256		300
Amortization expense			(143)		(184)
Foreign currency translation and other			172		(311)
Balance, end of period	3,061		3,061		2,776
Aflac Japan | Medical and other health
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			1,833	2,041	2,041
Capitalization			67		103
Amortization expense			(75)		(100)
Foreign currency translation and other			115		(211)
Balance, end of period	1,940		1,940		1,833
Aflac Japan | Life insurance
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			441	491	491
Capitalization			24		36
Amortization expense			(25)		(34)
Foreign currency translation and other			28		(52)
Balance, end of period	468		468		441
Aflac Japan | Other
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			52	56	56
Capitalization			2		4
Amortization expense			(2)		(3)
Foreign currency translation and other			2		(5)
Balance, end of period	54		54		52
Aflac U.S. | Life insurance
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			219	172	172
Capitalization			70		77
Amortization expense			(29)		(30)
Foreign currency translation and other			0		0
Balance, end of period	260		260		219
Aflac U.S. | Accident
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			915	917	917
Capitalization			98		141
Amortization expense			(107)		(143)
Foreign currency translation and other			0		0
Balance, end of period	906		906		915
Aflac U.S. | Disability
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			636	625	625
Capitalization			91		129
Amortization expense			(91)		(118)
Foreign currency translation and other			0		0
Balance, end of period	636		636		636
Aflac U.S. | Critical Care
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			1,348	1,336	1,336
Capitalization			116		165
Amortization expense			(116)		(153)
Foreign currency translation and other			0		0
Balance, end of period	1,348		1,348		1,348
Aflac U.S. | Hospital Indemnity
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			452	436	436
Capitalization			63		89
Amortization expense			(58)		(73)
Foreign currency translation and other			0		0
Balance, end of period	457		457		452
Aflac U.S. | Dental/Vision
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			86	86	86
Capitalization			9		12
Amortization expense			(9)		(12)
Foreign currency translation and other			0		0
Balance, end of period	86		86		86
Aflac U.S. | Other
Deferred Policy Acquisition Cost [Line Items]
Balance, beginning of period			0	$ 1	1
Capitalization			0		0
Amortization expense			0		(1)
Foreign currency translation and other			0		0
Balance, end of period	$ 0		$ 0		$ 0