INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 34,401	$ 33,350
Held to maturity:
Total fixed maturities held to maturity, fair value	40,923	$ 40,021
Aflac Japan
Available for sale:
Due in one year or less	145
Due after one year through five years	3,561
Due after five years through 10 years	9,846
Due after 10 years	43,392
Mortgage- and asset-backed securities	316
Total fixed maturities available for sale, amortized cost	57,260
Held to maturity:
Due after one year through five years	2,086
Due after five years through 10 years	1,645
Due after 10 years	30,640
Mortgage- and asset-backed securities	30
Total fixed maturities held to maturity, amortized cost	34,401
Available for sale:
Due in one year or less	161
Due after one year through five years	3,788
Due after five years through 10 years	10,093
Due after 10 years	48,447
Mortgage- and asset-backed securities	361
Total fixed maturities available for sale, fair value	62,850
Held to maturity:
Due after one year through five years	2,193
Due after five years through 10 years	1,813
Due after 10 years	36,884
Mortgage- and asset-backed securities	33
Total fixed maturities held to maturity, fair value	40,923
Aflac U.S.
Available for sale:
Due in one year or less	74
Due after one year through five years	664
Due after five years through 10 years	3,128
Due after 10 years	8,462
Mortgage- and asset-backed securities	43
Total fixed maturities available for sale, amortized cost	12,371
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	77
Due after one year through five years	716
Due after five years through 10 years	3,324
Due after 10 years	9,421
Mortgage- and asset-backed securities	47
Total fixed maturities available for sale, fair value	13,585
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