INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 38,772	$ 33,459
Held to maturity:
Total fixed maturities held to maturity, fair value	47,937	$ 37,520
Aflac Japan
Available for sale:
Due in one year or less	393
Due after one year through five years	3,808
Due after five years through 10 years	12,340
Due after 10 years	40,610
Mortgage- and asset-backed securities	1,025
Total fixed maturities available for sale, amortized cost	58,176
Held to maturity:
Due after one year through five years	2,314
Due after five years through 10 years	1,825
Due after 10 years	34,596
Mortgage- and asset-backed securities	37
Total fixed maturities held to maturity, amortized cost	38,772
Available for sale:
Due in one year or less	403
Due after one year through five years	3,882
Due after five years through 10 years	12,616
Due after 10 years	47,945
Mortgage- and asset-backed securities	1,076
Total fixed maturities available for sale, fair value	65,922
Held to maturity:
Due after one year through five years	2,454
Due after five years through 10 years	2,030
Due after 10 years	43,414
Mortgage- and asset-backed securities	39
Total fixed maturities held to maturity, fair value	47,937
Aflac U.S.
Available for sale:
Due in one year or less	88
Due after one year through five years	686
Due after five years through 10 years	2,644
Due after 10 years	8,700
Mortgage- and asset-backed securities	34
Total fixed maturities available for sale, amortized cost	12,152
Held to maturity:
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	91
Due after one year through five years	754
Due after five years through 10 years	2,900
Due after 10 years	10,191
Mortgage- and asset-backed securities	40
Total fixed maturities available for sale, fair value	13,976
Held to maturity:
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