Loans and Allowance for Loan Losses - Summary of the Company's Loan participations (Detail) - Loan Participations and Assignments - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 1,177,575		$ 1,132,502
Non-performing Loan Rate (%)	0.71%		0.88%
Gross Charge-offs	$ 0	$ 0
Business Banking | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 143		$ 98
Non-performing Loan Rate (%)	0.00%		0.00%
Gross Charge-offs	$ 0	0
Commercial and industrial | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 744,231		$ 732,425
Non-performing Loan Rate (%)	1.13%		1.36%
Gross Charge-offs	$ 0	0
Commercial real estate | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 390,540		$ 362,898
Non-performing Loan Rate (%)	0.00%		0.00%
Gross Charge-offs	$ 0	0
Commercial construction | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 42,661		$ 37,081
Non-performing Loan Rate (%)	0.00%		0.00%
Gross Charge-offs	$ 0	$ 0