Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale $ 753,781 $ 634,477
Derivative financial instruments, Assets 1,100  
Derivative financial instruments, Liabilities 1,100  
U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 10,132 35,206
Mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 519,241 410,801
Collateralized mortgage obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 133,601 164,592
Debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 90,807 23,878
Total U.S. government agency and sponsored agency obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 743,649 599,271
Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 753,781 634,477
Recurring Basis | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 10,132 35,205
Recurring Basis | Mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 519,241 410,800
Recurring Basis | Derivative financial instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative financial instruments, Assets 1,088  
Derivative financial instruments, Liabilities 1,149  
Recurring Basis | Collateralized mortgage obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 133,601 164,592
Recurring Basis | Debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 90,807 23,879
Recurring Basis | Total U.S. government agency and sponsored agency obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 743,649 599,272
Recurring Basis | Quoted Prices in Active Markets for Identical Assets    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 10,132 35,205
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 10,132 35,205
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | Mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | Derivative financial instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative financial instruments, Assets 0  
Derivative financial instruments, Liabilities 0  
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | Collateralized mortgage obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | Debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets | Total U.S. government agency and sponsored agency obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 743,649 599,272
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | Mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 519,241 410,800
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | Derivative financial instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative financial instruments, Assets 1,088  
Derivative financial instruments, Liabilities 1,149  
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | Collateralized mortgage obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 133,601 164,592
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | Debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 90,807 23,879
Recurring Basis | Significant Observable Inputs with No Active Market with Identical Characteristics | Total U.S. government agency and sponsored agency obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 743,649 599,272
Recurring Basis | Significant Unobservable Inputs    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Unobservable Inputs | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Unobservable Inputs | Mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Unobservable Inputs | Derivative financial instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative financial instruments, Assets 0  
Derivative financial instruments, Liabilities 0  
Recurring Basis | Significant Unobservable Inputs | Collateralized mortgage obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Unobservable Inputs | Debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale 0 0
Recurring Basis | Significant Unobservable Inputs | Total U.S. government agency and sponsored agency obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities available for sale $ 0 $ 0