Noninterest Income and Expense - Components of Other Noninterest Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ 10,590	$ 9,743	$ 29,788	$ 28,327
Increase in cash value of life insurance	773	732	2,294	1,996
Asset management and commission income	721	728	2,102	2,414
Gain on sale of loans	1,236	539	2,223	1,831
Lease brokerage income	172	186	631	514
Sale of customer checks	126	88	401	327
Gain on sale of investment securities	107	207	107	207
Gain (loss) on marketable equity securities	22	(22)	100	(92)
Other	361	135	1,688	942
Total other non-interest income	3,518	2,593	9,546	8,139
Total non-interest income	14,108	12,336	39,334	36,466
ATM and Interchange Fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	5,427	4,590	15,412	13,335
Service Charges on Deposit Accounts
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	4,327	4,015	12,389	11,407
Other Service Fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	808	676	2,198	2,020
Mortgage Banking Service Fees
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	483	499	1,441	1,527
Change in Value of Mortgage Servicing Rights
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ (455)	$ (37)	$ (1,652)	$ 38