Policy Liabilities - Additional Information (Detail)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Liability for Future Policy Benefit, by Product Segment [Line Items]
Percentage of future policy benefits out of policy liabilities	84.00%
Percentage of unpaid policy claims out of policy liabilities	4.00%
Aflac Japan
Liability for Future Policy Benefit, by Product Segment [Line Items]
Weighted-average interest rates reflected in the consolidated statements of earnings for future policy benefits	4.00%	4.40%	4.50%
Aflac U.S.
Liability for Future Policy Benefit, by Product Segment [Line Items]
Weighted-average interest rates reflected in the consolidated statements of earnings for future policy benefits	6.00%	6.00%	6.10%

- Definition

The assumed interest rate used to determine present value of future benefits to be paid to or on behalf of policyholders and related expenses less the present value of future net premiums using assumptions such as estimates of expected investment yields, mortality, morbidity, terminations and expenses, applicable at the time the insurance contracts are made and unpaid claim costs relating to insurance contracts including estimates of costs relating to incurred but not reported claims based on the estimated ultimate cost of settling the claims (including effects of inflation and other societal and economic factors), using past experience adjusted for current trends and any other factors that would modify past experience in the year the policy went into force.

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