Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail)

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Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) - Non-recurring Basis - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Unrealized losses impaired loans $ 1,184 $ 2,730
Unrealized losses other real estate owned 0 0
Quoted Prices in Active Markets for Identical Assets    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 0 0
Other real estate owned 0 0
Significant Observable Inputs with No Active Market with Identical Characteristics    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 3,253 6,121
Other real estate owned 663 1,946
Significant Unobservable Inputs    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Impaired loans 1,957 2,436
Other real estate owned $ 0 $ 0