INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Aflac Japan
Available for sale:
Due in one year or less	$ 1,812
Due after one year through five years	2,519
Due after five years through 10 years	4,792
Due after 10 years	32,928
Mortgage- and asset-backed securities	1,044
Total fixed maturities available for sale	43,095
Held to maturity:
Due in one year or less	6,575
Due after one year through five years	819
Due after five years through 10 years	3,371
Due after 10 years	49,180
Mortgage- and asset-backed securities	109
Total fixed maturities held to maturity	60,054
Available for sale:
Due in one year or less	1,837
Due after one year through five years	2,645
Due after five years through 10 years	5,177
Due after 10 years	34,042
Mortgage- and asset-backed securities	1,148
Total fixed maturities available for sale	44,849
Held to maturity:
Due in one year or less	6,580
Due after one year through five years	885
Due after five years through 10 years	3,778
Due after 10 years	49,900
Mortgage- and asset-backed securities	114
Total fixed maturities held to maturity	61,257
Aflac U.S.
Available for sale:
Due in one year or less	53
Due after one year through five years	336
Due after five years through 10 years	1,004
Due after 10 years	7,980
Mortgage- and asset-backed securities	44
Total fixed maturities available for sale	9,417
Held to maturity:
Due in one year or less	0
Due after one year through five years	0
Due after five years through 10 years	0
Due after 10 years	0
Mortgage- and asset-backed securities	0
Total fixed maturities held to maturity	0
Available for sale:
Due in one year or less	54
Due after one year through five years	373
Due after five years through 10 years	1,186
Due after 10 years	9,568
Mortgage- and asset-backed securities	56
Total fixed maturities available for sale	11,237
Held to maturity:
Due in one year or less	0
Due after one year through five years	0
Due after five years through 10 years	0
Due after 10 years	0
Mortgage- and asset-backed securities	0
Total fixed maturities held to maturity	$ 0