Revenue from Contracts with Customers - Summary of Topic 606 Revenue Items (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	$ 130,804	$ 127,364	$ 122,416
Wealth Management Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	37,072	36,863	37,316
Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	44,915	44,026	41,331
Debit Card and ATM Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	21,652	20,216	17,676
Investment Product Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	21,785	20,539	20,977
Merchant Processing Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	3,105	2,927	2,634
Gain (Loss) on Other Real Estate Owned [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	254	1,270	939
Safe Deposit Box Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	1,206	1,124	926
Insurance Premiums and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income within scope of Topic 606	$ 815	$ 399	$ 617