SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Signficant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Income tax expense (benefit) related to items of other comprehensive income (loss)	$ (901)	$ 1,803	$ (581)
Aflac Japan
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues	70.00%	72.00%	74.00%
Percentage of the Company assets	83.00%	82.00%
Dollar denominated investment portfolio | Aflac Japan
Significant Accounting Policies [Line Items]
Income tax expense (benefit) related to items of other comprehensive income (loss)			$ 614
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio			31.00%