Quarterly report pursuant to Section 13 or 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
9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Unrealized losses impaired loans $ 15,948 $ 1,184  
Unrealized losses other real estate owned 0 $ 0  
Impaired loans | Real estate loans      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Impaired loans 12,700   $ 3,500
Impaired loans | Commercial and industrial loans      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Impaired loans 11,500   1,700
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 0   3,253
Other real estate owned 0   663
Significant Unobservable Inputs      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Impaired loans 24,264   1,957
Other real estate owned $ 330   $ 0