INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Aflac Japan
Available for sale:
Due in one year or less	$ 1,503
Due after one year through five years	2,195
Due after five years through 10 years	7,079
Due after 10 years	31,767
Mortgage- and asset-backed securities	892
Total fixed maturities available for sale	43,436
Held to maturity:
Due in one year or less	5,830
Due after one year through five years	679
Due after five years through 10 years	3,003
Due after 10 years	44,824
Mortgage- and asset-backed securities	90
Total fixed maturities held to maturity	54,426
Available for sale:
Due in one year or less	1,521
Due after one year through five years	2,300
Due after five years through 10 years	7,457
Due after 10 years	33,218
Mortgage- and asset-backed securities	976
Total fixed maturities available for sale	45,472
Held to maturity:
Due in one year or less	5,833
Due after one year through five years	736
Due after five years through 10 years	3,370
Due after 10 years	44,808
Mortgage- and asset-backed securities	94
Total fixed maturities held to maturity	54,841
Aflac U.S.
Available for sale:
Due in one year or less	109
Due after one year through five years	292
Due after five years through 10 years	1,183
Due after 10 years	8,219
Mortgage- and asset-backed securities	43
Total fixed maturities available for sale	9,846
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	113
Due after one year through five years	330
Due after five years through 10 years	1,399
Due after 10 years	9,728
Mortgage- and asset-backed securities	55
Total fixed maturities available for sale	11,625
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