INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) $ in Millions	Mar. 31, 2016 USD ($)
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 322
Due after one year through five years	284
Due after 10 years	1,294
Total perpetual securities available for sale, amortized cost	1,900
Due in one year or less	284
Due after one year through five years	295
Due after 10 years	1,276
Total perpetual securities available for sale, fair value	1,855
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, amortized cost	39
Due in one year or less	0
Due after one year through five years	0
Due after 10 years	54
Total perpetual securities available for sale, fair value	$ 54