Annual report pursuant to Section 13 and 15(d)

Securities - Additional Information (Detail)

v3.10.0.1
Securities - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Jan. 01, 2018
Debt Securities, Available-for-sale [Line Items]        
Debt and equity securities OTTI charge $ 0      
Impairment charges on securities in continuous unrealized loss position for 12 months or longer 0 $ 0    
Reduction to balance of securities (574,908,000) (578,804,000)    
Reduction to retained earnings (97,539,000) (70,575,000)    
Net realized losses 870,000      
Net unrealized gains (losses) recognized in earnings resulting from the redemption of investment securities (413,000) 1,300,000 $ 314,000  
Net realized loss 957,000      
Gain (loss) on sale of securities (428,000) 1,700,000 $ 46,000  
Investment securities available-for-sale 29,900,000 $ 130,100,000    
ASU 2016-01        
Debt Securities, Available-for-sale [Line Items]        
Reduction to balance of securities       $ 529,000
Reduction to retained earnings       382,000
Increase to deferred tax assets       $ 147,000
Net unrealized gains (losses) recognized in earnings resulting from the redemption of investment securities $ (529,000)