INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 38,346	$ 33,459
Held to maturity:
Total fixed maturities held to maturity, fair value	48,796	$ 37,520
Aflac Japan
Available for sale:
Due in one year or less	305
Due after one year through five years	3,882
Due after five years through 10 years	11,905
Due after 10 years	40,332
Mortgage- and asset-backed securities	926
Total fixed maturities available for sale, amortized cost	57,350
Held to maturity:
Due in one year or less	49
Due after one year through five years	1,983
Due after five years through 10 years	2,084
Due after 10 years	34,191
Mortgage- and asset-backed securities	39
Total fixed maturities held to maturity, amortized cost	38,346
Available for sale:
Due in one year or less	312
Due after one year through five years	3,972
Due after five years through 10 years	12,101
Due after 10 years	48,573
Mortgage- and asset-backed securities	988
Total fixed maturities available for sale, fair value	65,946
Held to maturity:
Due in one year or less	49
Due after one year through five years	2,087
Due after five years through 10 years	2,283
Due after 10 years	44,336
Mortgage- and asset-backed securities	41
Total fixed maturities held to maturity, fair value	48,796
Aflac U.S.
Available for sale:
Due in one year or less	60
Due after one year through five years	722
Due after five years through 10 years	2,487
Due after 10 years	8,776
Mortgage- and asset-backed securities	34
Total fixed maturities available for sale, amortized cost	12,079
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	62
Due after one year through five years	789
Due after five years through 10 years	2,726
Due after 10 years	10,124
Mortgage- and asset-backed securities	41
Total fixed maturities available for sale, fair value	13,742
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