INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 33,729	$ 34,242
Held to maturity:
Total fixed maturities held to maturity, fair value	36,948	$ 38,497
Aflac Japan
Available for sale:
Due in one year or less	246
Due after one year through five years	2,340
Due after five years through 10 years	11,299
Due after 10 years	33,384
Mortgage- and asset-backed securities	381
Total fixed maturities available for sale, amortized cost	47,650
Held to maturity:
Due in one year or less	318
Due after one year through five years	1,593
Due after five years through 10 years	1,730
Due after 10 years	30,050
Mortgage- and asset-backed securities	38
Total fixed maturities held to maturity, amortized cost	33,729
Available for sale:
Due in one year or less	262
Due after one year through five years	2,722
Due after five years through 10 years	11,576
Due after 10 years	36,760
Mortgage- and asset-backed securities	432
Total fixed maturities available for sale, fair value	51,752
Held to maturity:
Due in one year or less	324
Due after one year through five years	1,675
Due after five years through 10 years	1,825
Due after 10 years	33,084
Mortgage- and asset-backed securities	40
Total fixed maturities held to maturity, fair value	36,948
Aflac U.S.
Available for sale:
Due in one year or less	85
Due after one year through five years	641
Due after five years through 10 years	2,033
Due after 10 years	9,069
Mortgage- and asset-backed securities	36
Total fixed maturities available for sale, amortized cost	11,864
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	86
Due after one year through five years	717
Due after five years through 10 years	2,140
Due after 10 years	9,851
Mortgage- and asset-backed securities	45
Total fixed maturities available for sale, fair value	12,839
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