INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 33,350	$ 33,459
Held to maturity:
Total fixed maturities held to maturity, fair value	40,021	$ 37,520
Aflac Japan
Available for sale:
Due in one year or less	180
Due after one year through five years	3,441
Due after five years through 10 years	9,374
Due after 10 years	39,461
Mortgage- and asset-backed securities	1,144
Total fixed maturities available for sale, amortized cost	53,600
Held to maturity:
Due after one year through five years	2,009
Due after five years through 10 years	1,584
Due after 10 years	29,727
Mortgage- and asset-backed securities	30
Total fixed maturities held to maturity, amortized cost	33,350
Available for sale:
Due in one year or less	204
Due after one year through five years	3,696
Due after five years through 10 years	9,694
Due after 10 years	45,125
Mortgage- and asset-backed securities	1,184
Total fixed maturities available for sale, fair value	59,903
Held to maturity:
Due after one year through five years	2,112
Due after five years through 10 years	1,737
Due after 10 years	36,140
Mortgage- and asset-backed securities	32
Total fixed maturities held to maturity, fair value	40,021
Aflac U.S.
Available for sale:
Due in one year or less	103
Due after one year through five years	617
Due after five years through 10 years	2,860
Due after 10 years	8,545
Mortgage- and asset-backed securities	43
Total fixed maturities available for sale, amortized cost	12,168
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	105
Due after one year through five years	668
Due after five years through 10 years	3,018
Due after 10 years	9,411
Mortgage- and asset-backed securities	48
Total fixed maturities available for sale, fair value	13,250
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