REINSURANCE Additional Information (Detail) - 12 months ended Dec. 31, 2015 $ in Millions, ¥ in Billions	USD ($)	JPY (¥)
Aflac Japan
Effects of Reinsurance [Line Items]
Committed reinsurance facility | ¥		¥ 110
Aflac Japan | Closed Block- Tranche Three
Effects of Reinsurance [Line Items]
Coinsurance reinsurance ceded percentage	30.00%
Reinsurance assumed percentage	27.00%
Aflac Japan | Closed Medical Block - Tranche Two
Effects of Reinsurance [Line Items]
Coinsurance reinsurance ceded percentage	16.70%
Aflac Japan | Closed Medical Block - Tranche One
Effects of Reinsurance [Line Items]
Coinsurance reinsurance ceded percentage	33.30%
Aflac Japan | Closed block
Effects of Reinsurance [Line Items]
Reinsurance assumed percentage	8.35%
Reinsurance deferred profit liability	$ 786
Reinsurance recoverables	805
Letter of credit
Effects of Reinsurance [Line Items]
Collateral posted for reinsurance	$ 80