INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 34,262	$ 34,242
Held to maturity:
Total fixed maturities held to maturity, fair value	38,102	38,497
Aflac Japan
Available for sale:
Due in one year or less	311
Due after one year through five years	2,173
Due after five years through 10 years	10,658
Due after 10 years	34,092
Mortgage- and asset-backed securities	397
Total fixed maturities available for sale, amortized cost	47,631
Held to maturity:
Due in one year or less	109
Due after one year through five years	1,374
Due after five years through 10 years	2,151
Due after 10 years	30,587
Mortgage- and asset-backed securities	41
Total fixed maturities held to maturity, amortized cost	34,262
Available for sale:
Due in one year or less	339
Due after one year through five years	2,539
Due after five years through 10 years	11,346
Due after 10 years	38,783
Mortgage- and asset-backed securities	451
Total fixed maturities available for sale, fair value	53,458
Held to maturity:
Due in one year or less	114
Due after one year through five years	1,472
Due after five years through 10 years	2,341
Due after 10 years	34,131
Mortgage- and asset-backed securities	44
Total fixed maturities held to maturity, fair value	38,102
Aflac U.S.
Available for sale:
Due in one year or less	65
Due after one year through five years	626
Due after five years through 10 years	1,666
Due after 10 years	9,108
Mortgage- and asset-backed securities	37
Total fixed maturities available for sale, amortized cost	11,502
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	68
Due after one year through five years	725
Due after five years through 10 years	1,803
Due after 10 years	10,721
Mortgage- and asset-backed securities	46
Total fixed maturities available for sale, fair value	13,363
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