Revenue Recognition - Summary of Topic 606 Revenue Items (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Wealth Management fees	$ 9,746	$ 9,679	$ 18,772	$ 18,678
Services charges on deposit accounts	10,765	10,040	21,524	19,883
Debit card and ATM fees	5,080	4,436	9,945	8,672
Investment product fees	5,066	5,004	10,097	9,993
Other income:
Merchant processing fees	5,189	5,186	9,381	9,412
Gain (loss) on other real estate owned	586	(41)	721	617
Safe deposit box fees	224	207	628	514
Insurance premiums and commissions	78	160	182	267
Total	32,323	30,118	63,288	59,854
Clearing Service
Other income:
Merchant processing fees	$ 778	$ 633	$ 1,419	$ 1,230