Quarterly report pursuant to Section 13 or 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
 9 Months Ended 12 Months Ended
Sep. 30, 2017
USD ($)
Security
Dec. 31, 2016
USD ($)
Security
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 1,463 $ 4,496
Available-for-Sale Within One Year, Estimated Fair Value $ 265,776 $ 320,260
Available-for-Sale Within One Year, Number of Securities | Security 84 128
Available-for-Sale More than One Year, Gross Unrealized Loss $ 1,274 $ 757
Available-for-Sale More than One Year, Estimated Fair Value $ 67,869 $ 26,991
Available-for-Sale More than One Year, Number of Securities | Security 43 15
Available-for-Sale, Gross Unrealized Loss $ 2,737 $ 5,253
Available-for-Sale, Estimated Fair Value $ 333,645 $ 347,251
Available-for-Sale, Number of Securities | Security 127 143
Municipal bonds-tax exempt [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 60 $ 1,995
Available-for-Sale Within One Year, Estimated Fair Value $ 3,459 $ 125,004
Available-for-Sale Within One Year, Number of Securities | Security 3 54
Available-for-Sale More than One Year, Gross Unrealized Loss $ 17 $ 0
Available-for-Sale More than One Year, Estimated Fair Value $ 1,704 $ 0
Available-for-Sale More than One Year, Number of Securities | Security 4 0
Available-for-Sale, Gross Unrealized Loss $ 77 $ 1,995
Available-for-Sale, Estimated Fair Value $ 5,163 $ 125,004
Available-for-Sale, Number of Securities | Security 7 54
Municipal bonds-taxable [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 0 $ 9
Available-for-Sale Within One Year, Estimated Fair Value $ 0 $ 2,904
Available-for-Sale Within One Year, Number of Securities | Security 0 2
Available-for-Sale More than One Year, Gross Unrealized Loss $ 0 $ 0
Available-for-Sale More than One Year, Estimated Fair Value $ 0 $ 0
Available-for-Sale More than One Year, Number of Securities | Security 0 0
Available-for-Sale, Gross Unrealized Loss $ 0 $ 9
Available-for-Sale, Estimated Fair Value $ 0 $ 2,904
Available-for-Sale, Number of Securities | Security 0 2
Mutual funds [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 254 $ 413
Available-for-Sale Within One Year, Estimated Fair Value $ 20,632 $ 21,478
Available-for-Sale Within One Year, Number of Securities | Security 2 4
Available-for-Sale More than One Year, Gross Unrealized Loss $ 126 $ 109
Available-for-Sale More than One Year, Estimated Fair Value $ 1,899 $ 916
Available-for-Sale More than One Year, Number of Securities | Security 4 3
Available-for-Sale, Gross Unrealized Loss $ 380 $ 522
Available-for-Sale, Estimated Fair Value $ 22,531 $ 22,394
Available-for-Sale, Number of Securities | Security 6 7
Mortgage-backed securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 787 $ 1,345
Available-for-Sale Within One Year, Estimated Fair Value $ 171,919 $ 102,647
Available-for-Sale Within One Year, Number of Securities | Security 53 38
Available-for-Sale More than One Year, Gross Unrealized Loss $ 367 $ 112
Available-for-Sale More than One Year, Estimated Fair Value $ 21,430 $ 11,350
Available-for-Sale More than One Year, Number of Securities | Security 9 3
Available-for-Sale, Gross Unrealized Loss $ 1,154 $ 1,457
Available-for-Sale, Estimated Fair Value $ 193,349 $ 113,997
Available-for-Sale, Number of Securities | Security 62 41
Collateralized mortgage obligations [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 320 $ 676
Available-for-Sale Within One Year, Estimated Fair Value $ 62,309 $ 60,786
Available-for-Sale Within One Year, Number of Securities | Security 23 27
Available-for-Sale More than One Year, Gross Unrealized Loss $ 624 $ 326
Available-for-Sale More than One Year, Estimated Fair Value $ 38,940 $ 10,579
Available-for-Sale More than One Year, Number of Securities | Security 24 7
Available-for-Sale, Gross Unrealized Loss $ 944 $ 1,002
Available-for-Sale, Estimated Fair Value $ 101,249 $ 71,365
Available-for-Sale, Number of Securities | Security 47 34
U.S. government agency securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale Within One Year, Gross Unrealized Loss $ 42 $ 58
Available-for-Sale Within One Year, Estimated Fair Value $ 7,457 $ 7,441
Available-for-Sale Within One Year, Number of Securities | Security 3 3
Available-for-Sale More than One Year, Gross Unrealized Loss $ 0 $ 0
Available-for-Sale More than One Year, Estimated Fair Value $ 0 $ 0
Available-for-Sale More than One Year, Number of Securities | Security 0 0
Available-for-Sale, Gross Unrealized Loss $ 42 $ 58
Available-for-Sale, Estimated Fair Value $ 7,457 $ 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 Within One Year, Gross Unrealized Loss $ 0 $ 0
Available-for-Sale Within One Year, Estimated Fair Value $ 0 $ 0
Available-for-Sale Within One Year, Number of Securities | Security 0 0
Available-for-Sale More than One Year, Gross Unrealized Loss $ 140 $ 210
Available-for-Sale More than One Year, Estimated Fair Value $ 3,896 $ 4,146
Available-for-Sale More than One Year, Number of Securities | Security 2 2
Available-for-Sale, Gross Unrealized Loss $ 140 $ 210
Available-for-Sale, Estimated Fair Value $ 3,896 $ 4,146
Available-for-Sale, Number of Securities | Security 2 2