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Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Interest-bearing deposits maturing date | 90 days |
Transfer of assets into or out of level 3 | $ 0 | $ 0
Transfer of liabilities into or out of level 3 | 0 | 0
Collateral dependent impaired loans categorized as Level 3 | 2,054,000 | 1,745,000
Specific allocation for collateral dependent impaired loans | 31,000 | 106,000
Asset impairment charges | 0 |
Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Collateral dependent impaired loans categorized as Level 3 | $ 215,000 | $ 508,000

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- Definition Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524 + Details
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