INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 304
Due after one year through five years	1,167
Due after five years through 10 years	521
Due after 10 years	3,353
Total perpetual securities available for sale	5,345
Due in one year or less	308
Due after one year through five years	1,223
Due after five years through 10 years	551
Due after 10 years	3,089
Total perpetual securities available for sale	5,171
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	172
Total perpetual securities available for sale	177
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	176
Total perpetual securities available for sale	$ 181