Annual report pursuant to Section 13 and 15(d)

Securities - Summary of Investment Securities Available for Sale (Detail)

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Securities - Summary of Investment Securities Available for Sale (Detail) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 629,725 $ 583,444
Gross Unrealized Gain 5,553 401
Gross Unrealized Loss (801) (8,937)
Estimated Fair Value 634,477 574,908
Municipal bonds-tax exempt    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost   110,670
Gross Unrealized Gain   197
Gross Unrealized Loss   (517)
Estimated Fair Value   110,350
U.S. Treasury securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 34,946 39,768
Gross Unrealized Gain 259 69
Gross Unrealized Loss   (7)
Estimated Fair Value 35,205 39,830
Mortgage-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 406,813 300,957
Gross Unrealized Gain 4,334 61
Gross Unrealized Loss (347) (5,984)
Estimated Fair Value 410,800 295,034
Collateralized mortgage obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 164,232 124,550
Gross Unrealized Gain 792 74
Gross Unrealized Loss (432) (2,332)
Estimated Fair Value 164,592 122,292
Debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 23,733 7,499
Gross Unrealized Gain 168  
Gross Unrealized Loss (22) (97)
Estimated Fair Value 23,879 7,402
Total U.S. government agency and sponsored agency obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 594,778 433,006
Gross Unrealized Gain 5,294 135
Gross Unrealized Loss (801) (8,413)
Estimated Fair Value $ 599,272 $ 424,728