Quarterly report pursuant to Section 13 or 15(d)

Securities - Additional Information (Detail)

v3.21.2
Securities - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]          
Net gains in earnings resulting from sale of securities   $ 15,712,000 $ 99,000 $ 15,712,000  
Proceeds from sales of securities $ 0 495,566,000 8,035,000 495,566,000  
Net unrealized gains recorded in accumulated other comprehensive income   $ 15,300,000 142,000 $ 15,300,000  
Available for sale securities pledged as collateral $ 40,500,000   $ 40,500,000   $ 27,300,000
Minimum | U.S. Government and its Agencies          
Debt Securities, Available-for-sale [Line Items]          
Holdings of securities as percentage of share holders' equity 10.00%   10.00%