Noninterest Income and Expense - Components of Other Noninterest Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ 10,128	$ 9,228	$ 19,198	$ 18,584
Increase in cash value of life insurance	746	656	1,521	1,264
Asset management and commission income	739	810	1,381	1,686
Gain on sale of loans	575	666	987	1,292
Lease brokerage income	239	200	459	328
Sale of customer checks	135	138	275	239
Gain on sale of foreclosed assets	197	17	199	388
Gain (loss) on marketable equity securities	42	(23)	78	(70)
Loss on disposal of fixed assets	(42)	(41)	(80)	(54)
Other	819	523	1,327	807
Total other noninterest income	3,450	2,946	6,244	5,880
Total noninterest income	13,578	12,174	25,442	24,464
ATM and Interchange Fees [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	5,404	4,510	9,985	8,745
Service Charges on Deposit Accounts [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	4,182	3,613	8,062	7,392
Other Service Fees [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	619	630	1,390	1,344
Mortgage Banking Service Fees [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	475	511	958	1,028
Change in Value of Mortgage Servicing Rights [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Total service charges and fees	$ (552)	$ (36)	$ (1,197)	$ 75