Annual report pursuant to Section 13 and 15(d)

Securities - Available for Sale Securities, Continuous Unrealized Loss Position, Fair value (Detail)

v3.8.0.1
Securities - Available for Sale Securities, Continuous Unrealized Loss Position, Fair value (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
Security
Dec. 31, 2016
USD ($)
Security
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 2,691 $ 4,496
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 276,372 $ 320,260
Available-for-sale, Less Than 12 Months, Number of Securities | Security 93 128
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 2,593 $ 757
Available-for-sale, 12 Months or More, Estimated Fair Value $ 138,033 $ 26,991
Available-for-sale, 12 Months or More, Number of Securities | Security 67 15
Available-for-sale, Gross Unrealized Loss $ 5,284 $ 5,253
Available-for-sale, Estimated Fair Value $ 414,405 $ 347,251
Available-for-sale, Number of Securities | Security 160 143
Mortgage-backed securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 1,855 $ 1,345
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 197,621 $ 102,647
Available-for-sale, Less Than 12 Months, Number of Securities | Security 66 38
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 847 $ 112
Available-for-sale, 12 Months or More, Estimated Fair Value $ 56,998 $ 11,350
Available-for-sale, 12 Months or More, Number of Securities | Security 25 3
Available-for-sale, Gross Unrealized Loss $ 2,702 $ 1,457
Available-for-sale, Estimated Fair Value $ 254,619 $ 113,997
Available-for-sale, Number of Securities | Security 91 41
Collateralized mortgage obligations [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 773 $ 676
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 65,726 $ 60,786
Available-for-sale, Less Than 12 Months, Number of Securities | Security 20 27
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 1,125 $ 326
Available-for-sale, 12 Months or More, Estimated Fair Value $ 49,986 $ 10,579
Available-for-sale, 12 Months or More, Number of Securities | Security 32 7
Available-for-sale, Gross Unrealized Loss $ 1,898 $ 1,002
Available-for-sale, Estimated Fair Value $ 115,712 $ 71,365
Available-for-sale, Number of Securities | Security 52 34
U.S. government agency securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 15 $ 58
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 1,484 $ 7,441
Available-for-sale, Less Than 12 Months, Number of Securities | Security 1 3
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 70 $ 0
Available-for-sale, 12 Months or More, Estimated Fair Value $ 5,930 $ 0
Available-for-sale, 12 Months or More, Number of Securities | Security 2 0
Available-for-sale, Gross Unrealized Loss $ 85 $ 58
Available-for-sale, Estimated Fair Value $ 7,414 $ 7,441
Available-for-sale, Number of Securities | Security 3 3
SBA loan pool securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss   $ 0
Available-for-sale, Less Than 12 Months, Estimated Fair Value   $ 0
Available-for-sale, Less Than 12 Months, Number of Securities | Security   0
Available-for-sale, 12 Months or More, Gross Unrealized Loss   $ 210
Available-for-sale, 12 Months or More, Estimated Fair Value   $ 4,146
Available-for-sale, 12 Months or More, Number of Securities | Security   2
Available-for-sale, Gross Unrealized Loss   $ 210
Available-for-sale, Estimated Fair Value   $ 4,146
Available-for-sale, Number of Securities | Security   2
Municipal bonds-tax exempt [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 48 $ 1,995
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 11,541 $ 125,004
Available-for-sale, Less Than 12 Months, Number of Securities | Security 6 54
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 21 $ 0
Available-for-sale, 12 Months or More, Estimated Fair Value $ 2,737 $ 0
Available-for-sale, 12 Months or More, Number of Securities | Security 2 0
Available-for-sale, Gross Unrealized Loss $ 69 $ 1,995
Available-for-sale, Estimated Fair Value $ 14,278 $ 125,004
Available-for-sale, Number of Securities | Security 8 54
Municipal bonds-taxable [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss   $ 9
Available-for-sale, Less Than 12 Months, Estimated Fair Value   $ 2,904
Available-for-sale, Less Than 12 Months, Number of Securities | Security   2
Available-for-sale, 12 Months or More, Gross Unrealized Loss   $ 0
Available-for-sale, 12 Months or More, Estimated Fair Value   $ 0
Available-for-sale, 12 Months or More, Number of Securities | Security   0
Available-for-sale, Gross Unrealized Loss   $ 9
Available-for-sale, Estimated Fair Value   $ 2,904
Available-for-sale, Number of Securities | Security   2
Other securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-sale, Less Than 12 Months, Gross Unrealized Loss $ 0 $ 413
Available-for-sale, Less Than 12 Months, Estimated Fair Value $ 0 $ 21,478
Available-for-sale, Less Than 12 Months, Number of Securities | Security 0 4
Available-for-sale, 12 Months or More, Gross Unrealized Loss $ 530 $ 109
Available-for-sale, 12 Months or More, Estimated Fair Value $ 22,382 $ 916
Available-for-sale, 12 Months or More, Number of Securities | Security 6 3
Available-for-sale, Gross Unrealized Loss $ 530 $ 522
Available-for-sale, Estimated Fair Value $ 22,382 $ 22,394
Available-for-sale, Number of Securities | Security 6 7