POLICY LIABILITIES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Health insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (208)	$ (320)
Aflac Japan | Health insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (114)
Percentage of total prior year claims and claims adjustment expense	55.00%
Liability for unpaid claims and claims adjustment expense, foreign currency translation gain (loss), prior year claims adjustment expense	$ (7)
Prior year claims and claims adjustment expense excluding effect of foreign currency	$ (122)
Percentage of total prior year claims and claims adjustment expense excluding effect of foreign currency	59.00%
Aflac U.S.
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior Year Claims And Claims Adjustment Expense From Refinement of Estimates	$ (32)
Aflac U.S. | Health insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (94)
Percentage of total prior year claims and claims adjustment expense	45.00%