INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 289
Due after one year through five years	1,239
Due after five years through 10 years	309
Due after 10 years	2,212
Total perpetual securities available for sale	4,049
Due in one year or less	292
Due after one year through five years	1,316
Due after five years through 10 years	352
Due after 10 years	2,167
Total perpetual securities available for sale	4,127
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	159
Total perpetual securities available for sale	164
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	170
Total perpetual securities available for sale	$ 175