INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Held to maturity:
Total fixed maturities held to maturity, amortized cost	$ 34,242	$ 44,415
Held to maturity:
Total fixed maturities held to maturity, fair value	38,497	45,846
Aflac Japan
Available for sale:
Due in one year or less	369
Due after one year through five years	1,519
Due after five years through 10 years	10,351
Due after 10 years	34,018
Mortgage- and asset-backed securities	405
Total fixed maturities available for sale, amortized cost	46,662
Held to maturity:
Due after one year through five years	1,520
Due after five years through 10 years	1,937
Due after 10 years	30,742
Mortgage- and asset-backed securities	43
Total fixed maturities held to maturity, amortized cost	34,242
Available for sale:
Due in one year or less	390
Due after one year through five years	1,771
Due after five years through 10 years	10,979
Due after 10 years	38,595
Mortgage- and asset-backed securities	461
Total fixed maturities available for sale, fair value	52,196
Held to maturity:
Due after one year through five years	1,631
Due after five years through 10 years	2,130
Due after 10 years	34,690
Mortgage- and asset-backed securities	46
Total fixed maturities held to maturity, fair value	38,497
Aflac U.S.
Available for sale:
Due in one year or less	65
Due after one year through five years	628
Due after five years through 10 years	1,472
Due after 10 years	9,103
Mortgage- and asset-backed securities	36
Total fixed maturities available for sale, amortized cost	11,304
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	69
Due after one year through five years	724
Due after five years through 10 years	1,561
Due after 10 years	10,540
Mortgage- and asset-backed securities	46
Total fixed maturities available for sale, fair value	12,940
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