Quarterly report pursuant to Section 13 or 15(d)

Securities - Summary of Debt Securities Available for Sale in an Unrealized Loss Position for Which an Allowance for Credit Losses Has Not Been Recorded (Detail)

v3.21.2
Securities - Summary of Debt Securities Available for Sale in an Unrealized Loss Position for Which an Allowance for Credit Losses Has Not Been Recorded (Detail)
$ in Thousands
Sep. 30, 2021
USD ($)
Security
Dec. 31, 2020
USD ($)
Security
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (7,517) $ (406)
Available-for-Sale Within One Year, Estimated Fair Value $ 760,074 $ 178,681
Available-for-Sale Within One Year, Number of Securities | Security 144 32
Available-for-Sale More than One Year, Gross Unrealized Loss $ (468)  
Available-for-Sale More than One Year, Estimated Fair Value $ 19,976  
Available-for-Sale More than One Year, Number of Securities | Security 3  
Available-for-Sale, Gross Unrealized Loss $ (7,985) $ (406)
Available-for-Sale, Estimated Fair Value $ 780,050 $ 178,681
Available-for-Sale, Number of Securities | Security 147 32
U.S. Treasury securities    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (3)  
Available-for-Sale Within One Year, Estimated Fair Value $ 4,945  
Available-for-Sale Within One Year, Number of Securities | Security 1  
Available-for-Sale, Gross Unrealized Loss $ (3)  
Available-for-Sale, Estimated Fair Value $ 4,945  
Available-for-Sale, Number of Securities | Security 1  
Mortgage-backed securities    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (4,954) $ (188)
Available-for-Sale Within One Year, Estimated Fair Value $ 546,307 $ 76,023
Available-for-Sale Within One Year, Number of Securities | Security 97 10
Available-for-Sale More than One Year, Gross Unrealized Loss $ (378)  
Available-for-Sale More than One Year, Estimated Fair Value $ 14,699  
Available-for-Sale More than One Year, Number of Securities | Security 2  
Available-for-Sale, Gross Unrealized Loss $ (5,332) $ (188)
Available-for-Sale, Estimated Fair Value $ 561,006 $ 76,023
Available-for-Sale, Number of Securities | Security 99 10
Collateralized mortgage obligations    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (461) $ (217)
Available-for-Sale Within One Year, Estimated Fair Value $ 47,720 $ 97,659
Available-for-Sale Within One Year, Number of Securities | Security 12 21
Available-for-Sale More than One Year, Gross Unrealized Loss $ (90)  
Available-for-Sale More than One Year, Estimated Fair Value $ 5,277  
Available-for-Sale More than One Year, Number of Securities | Security 1  
Available-for-Sale, Gross Unrealized Loss $ (551) $ (217)
Available-for-Sale, Estimated Fair Value $ 52,997 $ 97,659
Available-for-Sale, Number of Securities | Security 13 21
Debt securities    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (583) $ (1)
Available-for-Sale Within One Year, Estimated Fair Value $ 93,432 $ 4,999
Available-for-Sale Within One Year, Number of Securities | Security 17 1
Available-for-Sale, Gross Unrealized Loss $ (583) $ (1)
Available-for-Sale, Estimated Fair Value $ 93,432 $ 4,999
Available-for-Sale, Number of Securities | Security 17 1
Total U.S. government agency and sponsored agency obligations    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (5,998) $ (406)
Available-for-Sale Within One Year, Estimated Fair Value $ 687,459 $ 178,681
Available-for-Sale Within One Year, Number of Securities | Security 126 32
Available-for-Sale More than One Year, Gross Unrealized Loss $ (468)  
Available-for-Sale More than One Year, Estimated Fair Value $ 19,976  
Available-for-Sale More than One Year, Number of Securities | Security 3  
Available-for-Sale, Gross Unrealized Loss $ (6,466) $ (406)
Available-for-Sale, Estimated Fair Value $ 707,435 $ 178,681
Available-for-Sale, Number of Securities | Security 129 32
Municipal bonds-tax exempt    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ (1,516)  
Available-for-Sale Within One Year, Estimated Fair Value $ 67,670  
Available-for-Sale Within One Year, Number of Securities | Security 17  
Available-for-Sale, Gross Unrealized Loss $ (1,516)  
Available-for-Sale, Estimated Fair Value $ 67,670  
Available-for-Sale, Number of Securities | Security 17