DEFERRED POLICY ACQUISITION COSTS AND INSURANCE EXPENSES - Rollforward of Deferred Policy Acquisition Costs by Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred policy acquisition costs:
Balance, beginning of year	$ 10,441
Capitalization	1,100	$ 1,200	$ 1,500
Amortization	(1,170)	(1,214)	(1,282)
Balance, end of year	9,525	10,441
Aflac Japan
Deferred policy acquisition costs:
Balance, beginning of year	6,991	6,584
Capitalization	593	665
Amortization	(653)	(644)	(709)
Foreign currency translation and other	(698)	386
Balance, end of year	6,233	6,991	6,584
Aflac U.S.
Deferred policy acquisition costs:
Balance, beginning of year	3,450	3,544
Capitalization	470	486
Amortization	(517)	(570)	(573)
Foreign currency translation and other	(111)	(10)
Balance, end of year	$ 3,292	$ 3,450	$ 3,544