Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.8.0.1
Fair Value Measurements - Additional Information (Detail) - USD ($)
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Loans held for sale $ 6,394,000 $ 9,316,000 $ 2,874,000
Minimum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Unpaid principal balance of Non-accrual Non-PCI loans reviewed individually for amount of impairment 100,000    
Maximum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Unpaid principal balance of Non-accrual Non-PCI loans reviewed collectively for amount of impairment 100,000    
Significant Observable Inputs with No Active Market with Identical Characteristics [Member] | Non-recurring Basis [Member] | Nonperforming Loans Held For Sale [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Loans held for sale $ 0 $ 0