Annual report pursuant to Section 13 and 15(d)

Securities - Additional Information (Detail)

v3.19.3.a.u2
Securities - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Jan. 01, 2018
Debt Securities, Available-for-sale [Line Items]        
Reduction in securities available for sale $ (634,477,000) $ (574,908,000)    
Reduction to retained earnings (100,551,000) (97,539,000)    
Net gain (loss) in earnings resulting from sale of securities 1,295,000 (870,000) $ 1,748,000  
Net unrealized gains (losses) recorded in comprehensive income 586,000 (413,000) 1,300,000  
Gross realized losses included in earnings 64,000 957,000 $ 143,000  
Gain (Loss) on Sale of Investments   (428,000)    
Available for sale securities pledged as collateral $ 30,200,000 29,900,000    
ASU 2016-01        
Debt Securities, Available-for-sale [Line Items]        
Reduction in securities available for sale       $ 529,000
Reduction to retained earnings       382,000
Increase in net deferred tax asset       $ 147,000
Net unrealized gains (losses) recorded in comprehensive income   $ (529,000)