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Summary of Significant Accounting Policies - Additional Information (Detail) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Aflac Japan |  |  |
Significant Accounting Policies [Line Items] |  |  |
Aflac Japan's percentage of the Company's total revenues | 69.00% | 74.00% |
Percentage of the Company Assets | 83.00% |  | 83.00%
Upper Limit |  |  |
Significant Accounting Policies [Line Items] |  |  |
Estimation of Percent of Leases Within Scope of the Guidance to Total Assets | 1.00% |  |
Estimation of Percent of Revenues Within Scope of the Guidance to Total Revenues | 1.00% |  |

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- Definition Estimation of Percent of Revenues Within Scope of the Guidance to Total Revenues + References No definition available. + Details
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- Details
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- Details
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