Commitments and Contingencies - Summary of Off-Balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	$ 1,303,458	$ 1,305,003
Commercial mortgage loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	43,624	32,346
Commercial loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	629,729	645,924
Commercial owner-occupied commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	43,879	55,545
Commercial standby letters of credit
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	71,233	75,446
Residential mortgage loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	6,297	8,057
Consumer loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	330,929	296,010
Construction loan commitments
Financial instruments with contract amounts which represent potential credit risk:
Loan commitments	$ 177,767	$ 191,675