INVESTMENTS - Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Aflac Japan
Available for sale:
Due in one year or less	$ 2,123
Due after one year through five years	2,223
Due after five years through 10 years	3,940
Due after 10 years	25,754
Mortgage- and asset-backed securities	1,108
Total fixed maturities available for sale	35,148
Held to maturity:
Due in one year or less	460
Due after one year through five years	1,085
Due after five years through 10 years	3,226
Due after 10 years	43,946
Mortgage- and asset-backed securities	117
Total fixed maturities held to maturity	48,834
Available for sale:
Due in one year or less	2,168
Due after one year through five years	2,330
Due after five years through 10 years	4,201
Due after 10 years	26,463
Mortgage- and asset-backed securities	1,209
Total fixed maturities available for sale	36,371
Held to maturity:
Due in one year or less	463
Due after one year through five years	1,161
Due after five years through 10 years	3,544
Due after 10 years	43,155
Mortgage- and asset-backed securities	121
Total fixed maturities held to maturity	48,444
Aflac U.S.
Available for sale:
Due in one year or less	13
Due after one year through five years	358
Due after five years through 10 years	894
Due after 10 years	7,559
Mortgage- and asset-backed securities	45
Total fixed maturities available for sale	8,869
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	0
Available for sale:
Due in one year or less	13
Due after one year through five years	387
Due after five years through 10 years	1,036
Due after 10 years	8,523
Mortgage- and asset-backed securities	56
Total fixed maturities available for sale	10,015
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	$ 0