Non-interest Income and Expense - Components of Non-Interest Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ 10,469	$ 10,590	$ 27,763	$ 29,788
Increase in cash value of life insurance	773	773	2,203	2,294
Asset management and commission income	667	721	2,244	2,102
Gain on sale of loans	3,035	1,236	5,662	2,223
Lease brokerage income	175	172	495	631
Sale of customer checks	91	126	303	401
Gain on sale of investment securities	7	107	7	107
Gain on marketable equity securities	0	22	72	100
Other	(80)	361	(135)	1,688
Total other non-interest income	4,668	3,518	10,851	9,546
Total non-interest income	15,137	14,108	38,614	39,334
ATM and interchange fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	5,637	5,427	15,913	15,412
Service charges on deposit accounts
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	3,334	4,327	10,426	12,389
Other service fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	805	808	2,296	2,198
Mortgage banking service fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	457	483	1,386	1,441
Change in value of mortgage servicing rights
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ 236	$ (455)	$ (2,258)	$ (1,652)