Annual report pursuant to Section 13 and 15(d)

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

v3.8.0.1
Securities - Summary of Investment Securities Available for Sale (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 581,992 $ 521,053
Gross Unrealized Gain 2,096 1,164
Gross Unrealized Loss 5,284 5,253
Estimated Fair Value 578,804 516,964
Collateralized mortgage obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 119,658 77,447
Gross Unrealized Gain 8 6
Gross Unrealized Loss 1,898 1,002
Estimated Fair Value 117,768 76,451
Mortgage-backed securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 306,166 230,489
Gross Unrealized Gain 145 598
Gross Unrealized Loss 2,702 1,457
Estimated Fair Value 303,609 229,630
U.S. government agency securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 7,499 7,499
Gross Unrealized Gain 0 0
Gross Unrealized Loss 85 58
Estimated Fair Value 7,414 7,441
SBA loan pool securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost   4,356
Gross Unrealized Gain   0
Gross Unrealized Loss   210
Estimated Fair Value   4,146
Municipal bonds-tax exempt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 125,601 159,789
Gross Unrealized Gain 1,943 236
Gross Unrealized Loss 69 1,995
Estimated Fair Value 127,475 158,030
Municipal bonds-taxable [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost   13,391
Gross Unrealized Gain   319
Gross Unrealized Loss   9
Estimated Fair Value   13,701
Corporate bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost   5,010
Gross Unrealized Gain   5
Gross Unrealized Loss   0
Estimated Fair Value   5,015
U.S. treasury securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 152 156
Gross Unrealized Gain 0 0
Gross Unrealized Loss 0 0
Estimated Fair Value 152 156
Other securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 22,916 22,916
Gross Unrealized Gain 0 0
Gross Unrealized Loss 530 522
Estimated Fair Value $ 22,386 $ 22,394