Contractual Maturities of Investments in Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Aflac Japan
Available for sale:
Due in one year or less	$ 1,877
Due after one year through five years	3,170
Due after five years through 10 years	3,855
Due after 10 years	26,418
Mortgage- and asset-backed securities	1,177
Total fixed maturities available for sale	36,497
Held to maturity:
Due in one year or less	488
Due after one year through five years	1,148
Due after five years through 10 years	3,539
Due after 10 years	41,704
Mortgage- and asset-backed securities	130
Total fixed maturities held to maturity	47,009
Available for sale:
Due in one year or less	1,902
Due after one year through five years	3,300
Due after five years through 10 years	4,086
Due after 10 years	26,905
Mortgage- and asset-backed securities	1,280
Total fixed maturities available for sale	37,473
Held to maturity:
Due in one year or less	495
Due after one year through five years	1,230
Due after five years through 10 years	3,855
Due after 10 years	40,668
Mortgage- and asset-backed securities	135
Total fixed maturities held to maturity	46,383
Aflac U.S.
Available for sale:
Due in one year or less	12
Due after one year through five years	301
Due after five years through 10 years	890
Due after 10 years	7,491
Mortgage- and asset-backed securities	45
Total fixed maturities available for sale	8,739
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	12
Due after one year through five years	328
Due after five years through 10 years	1,020
Due after 10 years	8,544
Mortgage- and asset-backed securities	57
Total fixed maturities available for sale	9,961
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