INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 35,515	$ 33,459
Held to maturity:
Total fixed maturities held to maturity, fair value	42,807	$ 37,520
Aflac Japan
Available for sale:
Due in one year or less	182
Due after one year through five years	3,305
Due after five years through 10 years	11,490
Due after 10 years	36,829
Mortgage- and asset-backed securities	388
Total fixed maturities available for sale, amortized cost	52,194
Held to maturity:
Due in one year or less	222
Due after one year through five years	1,811
Due after five years through 10 years	1,904
Due after 10 years	31,541
Mortgage- and asset-backed securities	37
Total fixed maturities held to maturity, amortized cost	35,515
Available for sale:
Due in one year or less	192
Due after one year through five years	3,560
Due after five years through 10 years	11,675
Due after 10 years	42,681
Mortgage- and asset-backed securities	444
Total fixed maturities available for sale, fair value	58,552
Held to maturity:
Due in one year or less	223
Due after one year through five years	1,904
Due after five years through 10 years	2,038
Due after 10 years	38,602
Mortgage- and asset-backed securities	40
Total fixed maturities held to maturity, fair value	42,807
Aflac U.S.
Available for sale:
Due in one year or less	74
Due after one year through five years	712
Due after five years through 10 years	2,222
Due after 10 years	8,885
Mortgage- and asset-backed securities	35
Total fixed maturities available for sale, amortized cost	11,928
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	76
Due after one year through five years	768
Due after five years through 10 years	2,381
Due after 10 years	9,763
Mortgage- and asset-backed securities	41
Total fixed maturities available for sale, fair value	13,029
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