INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 42,718	$ 54,426
Held to maturity:
Total fixed maturities held to maturity, fair value	42,761	54,841
Aflac Japan
Available for sale:
Due in one year or less	723
Due after one year through five years	1,987
Due after five years through 10 years	9,677
Due after 10 years	31,715
Mortgage- and asset-backed securities	765
Total fixed maturities available for sale, amortized cost	44,867
Held to maturity:
Due in one year or less	77
Due after one year through five years	1,224
Due after five years through 10 years	2,256
Due after 10 years	39,094
Mortgage- and asset-backed securities	67
Total fixed maturities held to maturity, amortized cost	42,718
Available for sale:
Due in one year or less	730
Due after one year through five years	2,075
Due after five years through 10 years	9,450
Due after 10 years	31,312
Mortgage- and asset-backed securities	839
Total fixed maturities available for sale, fair value	44,406
Held to maturity:
Due in one year or less	78
Due after one year through five years	1,289
Due after five years through 10 years	2,308
Due after 10 years	39,016
Mortgage- and asset-backed securities	70
Total fixed maturities held to maturity, fair value	42,761
Aflac U.S.
Available for sale:
Due in one year or less	107
Due after one year through five years	393
Due after five years through 10 years	1,413
Due after 10 years	8,368
Mortgage- and asset-backed securities	39
Total fixed maturities available for sale, amortized cost	10,320
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, amortized cost	0
Available for sale:
Due in one year or less	108
Due after one year through five years	448
Due after five years through 10 years	1,530
Due after 10 years	9,067
Mortgage- and asset-backed securities	48
Total fixed maturities available for sale, fair value	11,201
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, fair value	$ 0