INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Aflac Japan
Available for sale:
Due in one year or less	$ 715
Due after one year through five years	1,963
Due after five years through 10 years	8,295
Due after 10 years	30,805
Mortgage- and asset-backed securities	813
Total fixed maturities available for sale	42,591
Held to maturity:
Due in one year or less	321
Due after one year through five years	624
Due after five years through 10 years	2,924
Due after 10 years	41,258
Mortgage- and asset-backed securities	77
Total fixed maturities held to maturity	45,204
Available for sale:
Due in one year or less	724
Due after one year through five years	2,065
Due after five years through 10 years	8,615
Due after 10 years	32,172
Mortgage- and asset-backed securities	903
Total fixed maturities available for sale	44,479
Held to maturity:
Due in one year or less	322
Due after one year through five years	672
Due after five years through 10 years	3,127
Due after 10 years	42,845
Mortgage- and asset-backed securities	81
Total fixed maturities held to maturity	47,047
Aflac U.S.
Available for sale:
Due in one year or less	107
Due after one year through five years	316
Due after five years through 10 years	1,336
Due after 10 years	8,245
Mortgage- and asset-backed securities	40
Total fixed maturities available for sale	10,044
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	110
Due after one year through five years	359
Due after five years through 10 years	1,548
Due after 10 years	9,562
Mortgage- and asset-backed securities	51
Total fixed maturities available for sale	11,630
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