INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) $ in Millions	Dec. 31, 2015 USD ($)
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 301
Due after one year through five years	292
Due after 10 years	1,209
Total perpetual securities available for sale	1,802
Due in one year or less	282
Due after one year through five years	315
Due after 10 years	1,293
Total perpetual securities available for sale	1,890
Aflac U.S.
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	0
Due after one year through five years	0
Due after 10 years	39
Total perpetual securities available for sale	39
Due in one year or less	0
Due after one year through five years	0
Due after 10 years	57
Total perpetual securities available for sale	$ 57