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Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($) | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Loss Contingencies [Line Items] |  |
Notional Amount Of Performance Standby Letters Of Credit | $ 8,100,000 |
Notional Amount Of Commercial Letters Of Credit | 0 |
Notional Amount Of Financial Standby Letters Of Credit | 0 |
Financial instrument of credit risk | 300,000 | $ 200,000
Unfunded commitment liability | 4,600,000 | $ 5,000,000
Minimum [Member] |  |
Loss Contingencies [Line Items] |  |
Loss Contingency, Estimate of Possible Loss | 0 |
Maximum [Member] |  |
Loss Contingencies [Line Items] |  |
Loss Contingency, Estimate of Possible Loss | $ 1,000,000 |

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