POLICY LIABILITIES - Additional Information (Details) - Health insurance - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (138)	$ (81)	$ (260)	$ (229)
Aflac Japan
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense			$ (166)
Percentage of total prior year claims and claims adjustment expense			64.00%
Liability for unpaid claims and claims adjustment expense, foreign currency translation gain (loss)			$ (8)
Prior year claims and claims adjustment expense excluding effect of foreign currency			$ (174)
Percentage of total prior year claims and claims adjustment expense excluding effect of foreign currency			67.00%