INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 32,613	$ 33,350
Held to maturity:
Total fixed maturities held to maturity, fair value	39,307	$ 40,021
Aflac Japan
Available for sale:
Due in one year or less	140
Due after one year through five years	4,639
Due after five years through 10 years	9,668
Due after 10 years	44,106
Mortgage- and asset-backed securities	304
Total fixed maturities available for sale, amortized cost	58,857
Held to maturity:
Due in one year or less	491
Due after one year through five years	929
Due after five years through 10 years	1,648
Due after 10 years	29,516
Mortgage- and asset-backed securities	29
Total fixed maturities held to maturity, amortized cost	32,613
Available for sale:
Due in one year or less	153
Due after one year through five years	4,905
Due after five years through 10 years	10,114
Due after 10 years	49,639
Mortgage- and asset-backed securities	346
Total fixed maturities available for sale, fair value	65,157
Held to maturity:
Due in one year or less	504
Due after one year through five years	981
Due after five years through 10 years	1,826
Due after 10 years	35,965
Mortgage- and asset-backed securities	31
Total fixed maturities held to maturity, fair value	39,307
Aflac U.S.
Available for sale:
Due in one year or less	114
Due after one year through five years	639
Due after five years through 10 years	3,118
Due after 10 years	8,500
Mortgage- and asset-backed securities	40
Total fixed maturities available for sale, amortized cost	12,411
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	117
Due after one year through five years	685
Due after five years through 10 years	3,360
Due after 10 years	9,688
Mortgage- and asset-backed securities	42
Total fixed maturities available for sale, fair value	13,892
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