Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Securities - Summary of Investment Securities Available for Sale (Detail) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 588,097 $ 581,992
Gross Unrealized Gain 66 2,096
Gross Unrealized Loss 15,927 5,284
Estimated Fair Value 572,236 578,804
Mortgage-backed securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 308,054 306,166
Gross Unrealized Gain 51 145
Gross Unrealized Loss 9,719 2,702
Estimated Fair Value 298,386 303,609
Collateralized mortgage obligations [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 121,541 119,658
Gross Unrealized Gain 6 8
Gross Unrealized Loss 3,892 1,898
Estimated Fair Value 117,655 117,768
U.S. government agency securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 7,499 7,499
Gross Unrealized Gain 0 0
Gross Unrealized Loss 147 85
Estimated Fair Value 7,352 7,414
Municipal bonds-tax exempt [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 111,328 125,601
Gross Unrealized Gain 9 1,943
Gross Unrealized Loss 2,059 69
Estimated Fair Value 109,278 127,475
U.S treasury securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 39,675 152
Gross Unrealized Gain 0 0
Gross Unrealized Loss 110 0
Estimated Fair Value $ 39,565 152
Mutual funds [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost   22,916
Gross Unrealized Gain   0
Gross Unrealized Loss   530
Estimated Fair Value   $ 22,386