Annual report pursuant to Section 13 and 15(d)

Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail)

v3.3.1.900
Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Summary of Investment Holdings [Line Items]    
Available-for-Sale Over one year through five years, Amortized Cost $ 14,303  
Available-for-Sale Over five years through ten years, Amortized Cost 152,114  
Available-for-Sale Over ten years, Amortized Cost 149,856  
Available-for-Sale, Amortized Cost 700,627 $ 1,061,703
Available-for-Sale Over one year through five years, Estimated Fair Value 14,222  
Available-for-Sale Over five years through ten years, Estimated Fair Value 152,032  
Available-for-Sale Over ten years, Estimated Fair Value 150,675  
Securities available for sale 698,296 1,060,717
Collateralized mortgage obligations [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale, Amortized Cost 97,904 188,704
Securities available for sale 96,986 188,047
Mortgage-backed securities [Member]    
Summary of Investment Holdings [Line Items]    
Available-for-Sale, Amortized Cost 286,450 571,678
Securities available for sale $ 284,381 $ 573,286