INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 0
Due after one year through five years	1,098
Due after five years through 10 years	272
Due after 10 years	1,792
Total perpetual securities available for sale	3,162
Due in one year or less	0
Due after one year through five years	948
Due after five years through 10 years	203
Due after 10 years	1,580
Total perpetual securities available for sale	2,731
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	5
Due after five years through 10 years	0
Due after 10 years	99
Total perpetual securities available for sale	104
Due in one year or less	0
Due after one year through five years	5
Due after five years through 10 years	0
Due after 10 years	98
Total perpetual securities available for sale	$ 103