INVESTMENTS - Economic Maturities of Investments in Perpetual Securities (Detail) $ in Millions	Dec. 31, 2016 USD ($)
Aflac Japan
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	$ 87
Due after one year through five years	189
Due after 10 years	1,191
Total perpetual securities available for sale	1,467
Due in one year or less	82
Due after one year through five years	213
Due after 10 years	1,282
Total perpetual securities available for sale	1,577
Aflac U.S.
Investments Classified by Economic Maturity Date [Line Items]
Due in one year or less	0
Due after one year through five years	0
Due after 10 years	39
Total perpetual securities available for sale	39
Due in one year or less	0
Due after one year through five years	0
Due after 10 years	56
Total perpetual securities available for sale	$ 56