Summary of Significant Accounting Policies - Additional Information (Detail) - Aflac Japan	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues	70.00%	74.00%
Percentage of the Company Assets	83.00%		82.00%