Revenue from Contracts with Customers - Summary of Topic 606 Revenue Items (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	$ 31,007	$ 31,493
Wealth management fees
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	8,884	8,535
Service charges on deposit accounts
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	10,077	10,826
Debit card and ATM fees
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	4,998	5,503
Investment product fees
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	5,874	5,271
Merchant processing fees
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	804	707
Gain (loss) on other real estate owned
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	(56)	40
Safe deposit box fees
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	310	411
Insurance premiums and commissions
Disaggregation of Revenue [Line Items]
Noninterest income within scope of Topic 606	$ 116	$ 200