INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 383
Due after one year through five years	778
Due after 10 years	1,615
Total perpetual securities available for sale, amortized cost	2,776
Due in one year or less	376
Due after one year through five years	830
Due after 10 years	1,759
Total perpetual securities available for sale, fair value	2,965
Aflac U.S.
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	5
Due after one year through five years	0
Due after 10 years	39
Total perpetual securities available for sale, amortized cost	44
Due in one year or less	5
Due after one year through five years	0
Due after 10 years	56
Total perpetual securities available for sale, fair value	$ 61