INCOME TAXES - Components of Income Tax Expense (Benefit) Applicable to Pretax Earnings (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Provision of Income Taxes [Line Items]
Current									$ 1,663	$ 1,181	$ 1,095
Deferred									(1,060)	(730)	(118)
Income taxes	$ 21	$ 236	$ 191	$ 154	$ 342	$ (452)	$ 314	$ 247	603	451	977
Aflac Japan
Reconciliation of Provision of Income Taxes [Line Items]
Current									1,275	913	884
Deferred									(160)	200	251
Income taxes									1,115	1,113	1,135
Aflac U.S.
Reconciliation of Provision of Income Taxes [Line Items]
Current									388	268	211
Deferred									(900)	(930)	(369)
Income taxes									$ (512)	$ (662)	$ (158)