INCOME TAXES - Components of Income Tax Expense (Benefit) Applicable to Pretax Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Provision of Income Taxes [Line Items]
Current	$ 1,095	$ 794	$ 806
Deferred	(98)	(1,413)	335
Total income tax expense	997	(619)	1,141
Aflac Japan
Reconciliation of Provision of Income Taxes [Line Items]
Current	884	822	737
Deferred	251	(28)	183
Total income tax expense	1,135	794	920
Aflac U.S.
Reconciliation of Provision of Income Taxes [Line Items]
Current	211	(28)	69
Deferred	(349)	(1,385)	152
Total income tax expense	$ (138)	$ (1,413)	$ 221