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Summary of Significant Accounting Policies - Additional Information (Detail) (Aflac Japan)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Aflac Japan
      
Significant Accounting Policies [Line Items]      
Aflac Japan's percentage of the Company's total revenues 70.00%afl_PercentageOfCompanyRevenue
/ us-gaap_StatementBusinessSegmentsAxis
= afl_AflacJapanMember		 75.00%afl_PercentageOfCompanyRevenue
/ us-gaap_StatementBusinessSegmentsAxis
= afl_AflacJapanMember		  
Percentage of the Company Assets 82.00%afl_PercentageOfCompanyAssets
/ us-gaap_StatementBusinessSegmentsAxis
= afl_AflacJapanMember		   82.00%afl_PercentageOfCompanyAssets
/ us-gaap_StatementBusinessSegmentsAxis
= afl_AflacJapanMember