INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 315
Due after one year through five years	1,289
Due after five years through 10 years	457
Due after 10 years	3,047
Total perpetual securities available for sale	5,108
Due in one year or less	317
Due after one year through five years	1,299
Due after five years through 10 years	461
Due after 10 years	2,488
Total perpetual securities available for sale	4,565
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	169
Total perpetual securities available for sale	174
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	162
Total perpetual securities available for sale	$ 167