Commitments and Contingencies - Summary of Off-Balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	$ 2,351,630	$ 2,104,096
Commercial mortgage loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	100,729	106,626
Commercial loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	1,083,512	919,353
Commercial owner-occupied commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	70,155	57,144
Commercial standby letters of credit
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	95,897	148,131
Residential mortgage loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	2,842	5,317
Consumer loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	591,856	506,544
Construction loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	$ 406,639	$ 360,981