DEFERRED POLICY ACQUISITION COSTS AND INSURANCE EXPENSES - Advertising Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Advertising Costs [Line Items]
Advertising expense	$ 229	$ 184	$ 219
Aflac Japan
Advertising Costs [Line Items]
Advertising expense	91	72	101
Aflac U.S.
Advertising Costs [Line Items]
Advertising expense	$ 138	$ 112	$ 118