POLICY LIABILITIES - Additional Information (Details) - Health insurance - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (198)	$ (166)	$ (518)	$ (302)
Aflac Japan
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense			$ (220)
Percentage of total prior year claims and claims adjustment expense			42.00%
Liability for unpaid claims and claims adjustment expense, foreign currency translation gain (loss), prior year claims adjustment expense			$ (5)
Prior year claims and claims adjustment expense excluding effect of foreign currency			$ (225)
Percentage of total prior year claims and claims adjustment expense excluding effect of foreign currency			43.00%
Aflac U.S.
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense			$ (298)
Percentage of total prior year claims and claims adjustment expense			58.00%
Prior Year Claims And Claims Adjustment Expense From Refinement of Estimates			$ (125)