Summary of Significant Accounting Policies - Additional Information (Detail) - Aflac Japan	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues	74.00%	70.00%
Percentage of the Company Assets	84.00%		83.00%