BENEFIT PLANS - Fair Value Hierarchy Levels of Funded Pension Plans' Assets (Detail) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Japan
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 335	$ 415	$ 416
U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	659	885	$ 824
Japanese equity securities | Japan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	20	21
International equity securities | Japan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	57	86
Japanese bonds | Japan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	20	22
International bonds | Japan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	210	252
Insurance contracts | Japan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	28	34
U.S. large cap equity securities | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0	297
U.S. mid cap equity securities | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0	25
International equity funds | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0	208
Fixed income bond funds | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	641	346
Aflac Incorporated common stock | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0	7
Cash and cash equivalents | U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 18	$ 2