INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 43,607	$ 54,426
Held to maturity:
Total fixed maturities held to maturity, fair value	44,756	54,841
Aflac Japan
Available for sale:
Due in one year or less	741
Due after one year through five years	2,048
Due after five years through 10 years	9,814
Due after 10 years	32,306
Mortgage- and asset-backed securities	684
Total fixed maturities available for sale, amortized cost	45,593
Held to maturity:
Due in one year or less	139
Due after one year through five years	1,142
Due after five years through 10 years	2,275
Due after 10 years	39,986
Mortgage- and asset-backed securities	65
Total fixed maturities held to maturity, amortized cost	43,607
Available for sale:
Due in one year or less	748
Due after one year through five years	2,141
Due after five years through 10 years	9,589
Due after 10 years	32,149
Mortgage- and asset-backed securities	727
Total fixed maturities available for sale, fair value	45,354
Held to maturity:
Due in one year or less	140
Due after one year through five years	1,217
Due after five years through 10 years	2,359
Due after 10 years	40,971
Mortgage- and asset-backed securities	69
Total fixed maturities held to maturity, fair value	44,756
Aflac U.S.
Available for sale:
Due in one year or less	56
Due after one year through five years	415
Due after five years through 10 years	1,458
Due after 10 years	8,555
Mortgage- and asset-backed securities	39
Total fixed maturities available for sale, amortized cost	10,523
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	56
Due after one year through five years	473
Due after five years through 10 years	1,563
Due after 10 years	9,123
Mortgage- and asset-backed securities	47
Total fixed maturities available for sale, fair value	11,262
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