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SHARE-BASED COMPENSATION - Assumptions Used in Valuing Options Granted (Detail)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Expected term (years) 6 years 3 months 18 days 6 years 7 months 6 days 6 years 6 months
Expected volatility 30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 34.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 38.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Annual forfeiture rate 2.70%afl_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAnnualForfeitureRate 1.60%afl_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAnnualForfeitureRate 1.60%afl_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAnnualForfeitureRate
Risk-free interest rate 2.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 2.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Dividend yield 2.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 2.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 1.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate