Loans and Allowance for Credit Losses - Rollforward of Allowance for Credit/Loan Losses by Portfolio Segment (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 218,583,000	$ 101,788,000
Adjusted beginning balance		110,818,000
Charge-offs	(6,602,000)	(9,764,000)
Recoveries	1,292,000	2,092,000
Provision	(7,500,000)	88,000,000
Ending balance - ACL	205,773,000	191,146,000
Beginning balance - ACL on off-balance sheet	5,588,000	2,978,000
Provision	0	0
Ending balance - ACL on off-balance sheet	5,588,000	2,978,000
ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		9,030,000
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	122,700,000	63,313,000
Adjusted beginning balance		66,990,000
Charge-offs	(4,717,000)	(1,315,000)
Recoveries	126,000	1,476,000
Provision	1,459,000	55,381,000
Ending balance - ACL	119,568,000	122,532,000
Beginning balance - ACL on off-balance sheet	3,859,000	2,263,000
Ending balance - ACL on off-balance sheet	3,859,000	2,263,000
Commercial and Industrial Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		3,677,000
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	5,219,000	2,545,000
Adjusted beginning balance		2,693,000
Recoveries	115,000
Provision	(661,000)	856,000
Ending balance - ACL	4,673,000	3,549,000
Beginning balance - ACL on off-balance sheet	287,000	53,000
Ending balance - ACL on off-balance sheet	287,000	53,000
Specialty Lending Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		148,000
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	61,931,000	15,951,000
Adjusted beginning balance		16,877,000
Charge-offs		(6,062,000)
Recoveries	509,000	21,000
Provision	(2,397,000)	24,559,000
Ending balance - ACL	60,043,000	35,395,000
Beginning balance - ACL on off-balance sheet	447,000	257,000
Ending balance - ACL on off-balance sheet	447,000	257,000
Commercial Real Estate Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		926,000
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	6,586,000	2,623,000
Adjusted beginning balance		2,775,000
Charge-offs	(76,000)	(13,000)
Recoveries	59,000	14,000
Provision	(2,386,000)	1,401,000
Ending balance - ACL	4,183,000	4,177,000
Beginning balance - ACL on off-balance sheet	145,000	102,000
Ending balance - ACL on off-balance sheet	145,000	102,000
Consumer Real Estate Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		152,000
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	1,480,000	543,000
Adjusted beginning balance		574,000
Charge-offs	(109,000)	(248,000)
Recoveries	23,000	97,000
Provision	(791,000)	704,000
Ending balance - ACL	603,000	1,127,000
Beginning balance - ACL on off-balance sheet	381,000	22,000
Ending balance - ACL on off-balance sheet	381,000	22,000
Consumer Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		31,000
Credit Cards Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	15,786,000	15,739,000
Adjusted beginning balance		16,653,000
Charge-offs	(1,692,000)	(2,126,000)
Recoveries	442,000	484,000
Provision	(2,392,000)	3,812,000
Ending balance - ACL	12,144,000	18,823,000
Credit Cards Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		914,000
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	2,271,000	1,074,000
Adjusted beginning balance		1,136,000
Charge-offs	(8,000)
Recoveries	18,000
Provision	(681,000)	1,172,000
Ending balance - ACL	1,600,000	2,308,000
Beginning balance - ACL on off-balance sheet	414,000	211,000
Ending balance - ACL on off-balance sheet	414,000	211,000
Leases and Other Portfolio [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		62,000
Total - Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	215,973,000	101,788,000
Adjusted beginning balance		107,698,000
Charge-offs	(6,602,000)	(9,764,000)
Recoveries	1,292,000	2,092,000
Provision	(7,849,000)	87,885,000
Ending balance - ACL	202,814,000	187,911,000
Beginning balance - ACL on off-balance sheet	5,533,000	2,908,000
Ending balance - ACL on off-balance sheet	5,533,000	2,908,000
Total - Loans [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		5,910,000
HTM [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	2,610,000
Adjusted beginning balance		3,120,000
Provision	349,000	115,000
Ending balance - ACL	2,959,000	3,235,000
Beginning balance - ACL on off-balance sheet	55,000	70,000
Ending balance - ACL on off-balance sheet	$ 55,000	70,000
HTM [Member] | ASU 2016-13 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 2016-13 adjustment		$ 3,120,000