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Recent Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Thousands | 1 Months Ended | 9 Months Ended
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Mar. 31, 2017 | Sep. 30, 2018
Summary Of Significant Accounting Policies [Line Items] |  |
Corporate income tax rate |  | 21.00%
Reclassification of tax effects from AOCI due to adoption of new Tax Cuts and Job Acts |  | $ 360
Accounting Standards Update 2017-08 [Member] |  |
Summary Of Significant Accounting Policies [Line Items] |  |
Accelerated amortization expense adjustment | $ 30 |

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