Quarterly report pursuant to Section 13 or 15(d)

Securities - Additional Information (Detail)

v3.19.3
Securities - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Mar. 31, 2018
Jun. 30, 2019
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Jan. 01, 2018
Debt Securities, Available-for-sale [Line Items]                
Impairment charges on securities in continuous unrealized loss position for 12 months or longer         $ 0   $ 0  
Reduction in securities available for sale $ (621,815,000)       (621,815,000)   (574,908,000)  
Reduction to retained earnings (104,927,000)       (104,927,000)   (97,539,000)  
Increase in net deferred tax asset 22,600,000       22,600,000   27,400,000  
Net gain (loss) in earnings resulting from sale of securities   $ 19,000     1,300,000 $ (870,000)    
Net unrealized gains (losses) recorded in comprehensive income 0 $ 21,000     586,000 $ 116,000    
Gross realized gains included in earnings       $ 1,400,000        
Gross realized losses included in earnings     $ 957,000          
Available for sale securities pledged as collateral $ 30,200,000       $ 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