DEFERRED POLICY ACQUISITION COSTS AND INSURANCE EXPENSES - Advertising Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Advertising Costs [Line Items]
Advertising expense	$ 188	$ 204	$ 229
Aflac Japan
Advertising Costs [Line Items]
Advertising expense	58	77	91
Aflac U.S.
Advertising Costs [Line Items]
Advertising expense	$ 130	$ 127	$ 138