Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	$ 185,827	$ 52,429
Allowance for credit losses - loan commitments, beginning balance	9,514	874
Total beginning allowance for credit losses - loans and loan commitments	195,341	53,303
Provision for loan losses	(45,138)	84,217
Provision for loan commitments	(3,748)	6,856
Total provision for credit losses - loans and loan commitments	(48,886)	91,073
Charge-offs	(3,557)	(9,011)
Recoveries	3,598	2,353
Net (charge-offs) recoveries	41	(6,658)
Allowance for credit losses - loans, ending balance	140,730	168,475
Allowance for credit losses - loan commitments, ending balance	5,766	10,685
Total ending allowance for credit losses - loans and loan commitments	146,496	179,160
ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		41,442
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	37,850	14,116
Allowance for credit losses - loan commitments, beginning balance	1,275	311
Total beginning allowance for credit losses - loans and loan commitments	39,125	14,427
Provision for loan losses	(8,090)	10,390
Provision for loan commitments	(334)	1,280
Total provision for credit losses - loans and loan commitments	(8,424)	11,670
Charge-offs	(814)	(3,187)
Recoveries	518	227
Net (charge-offs) recoveries	(296)	(2,960)
Allowance for credit losses - loans, ending balance	29,464	43,632
Allowance for credit losses - loan commitments, ending balance	941	1,862
Total ending allowance for credit losses - loans and loan commitments	30,405	45,494
Commercial and Industrial [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		22,357
Deposit Overdrafts [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	639	1,387
Total beginning allowance for credit losses - loans and loan commitments	639	1,387
Provision for loan losses	582	(409)
Total provision for credit losses - loans and loan commitments	582	(409)
Charge-offs	(365)	(516)
Recoveries	200	254
Net (charge-offs) recoveries	(165)	(262)
Allowance for credit losses - loans, ending balance	1,056	929
Total ending allowance for credit losses - loans and loan commitments	1,056	929
Deposit Overdrafts [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		213
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	10,841	4,949
Allowance for credit losses - loan commitments, beginning balance	6,508	235
Total beginning allowance for credit losses - loans and loan commitments	17,349	5,184
Provision for loan losses	(4,740)	6,388
Provision for loan commitments	(2,929)	5,223
Total provision for credit losses - loans and loan commitments	(7,669)	11,611
Charge-offs	(22)	(1)
Recoveries	110	77
Net (charge-offs) recoveries	88	76
Allowance for credit losses - loans, ending balance	6,189	10,335
Allowance for credit losses - loan commitments, ending balance	3,579	8,060
Total ending allowance for credit losses - loans and loan commitments	9,768	18,395
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		1,524
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	110,652	20,293
Allowance for credit losses - loan commitments, beginning balance	712	22
Total beginning allowance for credit losses - loans and loan commitments	111,364	20,315
Provision for loan losses	(25,672)	58,706
Provision for loan commitments	(618)
Total provision for credit losses - loans and loan commitments	(26,290)	58,706
Charge-offs	(235)	(1,895)
Recoveries	646	396
Net (charge-offs) recoveries	411	(1,499)
Allowance for credit losses - loans, ending balance	85,391	90,600
Allowance for credit losses - loan commitments, ending balance	94
Total ending allowance for credit losses - loans and loan commitments	85,485	90,600
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		13,078
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	17,851	4,311
Allowance for credit losses - loan commitments, beginning balance	955	15
Total beginning allowance for credit losses - loans and loan commitments	18,806	4,326
Provision for loan losses	(4,535)	4,554
Provision for loan commitments	111	318
Total provision for credit losses - loans and loan commitments	(4,424)	4,872
Charge-offs	(441)	(667)
Recoveries	742	376
Net (charge-offs) recoveries	301	(291)
Allowance for credit losses - loans, ending balance	13,617	13,824
Allowance for credit losses - loan commitments, ending balance	1,066	713
Total ending allowance for credit losses - loans and loan commitments	14,683	14,537
Residential Real Estate [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		5,630
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	6,507	2,951
Allowance for credit losses - loan commitments, beginning balance	19	41
Total beginning allowance for credit losses - loans and loan commitments	6,526	2,992
Provision for loan losses	(1,964)	3,102
Provision for loan commitments	17
Total provision for credit losses - loans and loan commitments	(1,947)	3,102
Charge-offs	(1,406)	(2,183)
Recoveries	1,042	768
Net (charge-offs) recoveries	(364)	(1,415)
Allowance for credit losses - loans, ending balance	4,179	7,255
Allowance for credit losses - loan commitments, ending balance	36
Total ending allowance for credit losses - loans and loan commitments	4,215	7,255
Consumer [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		2,576
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	1,487	4,422
Allowance for credit losses - loan commitments, beginning balance	45	250
Total beginning allowance for credit losses - loans and loan commitments	1,532	4,672
Provision for loan losses	(719)	1,486
Provision for loan commitments	5	35
Total provision for credit losses - loans and loan commitments	(714)	1,521
Charge-offs	(274)	(562)
Recoveries	340	255
Net (charge-offs) recoveries	66	(307)
Allowance for credit losses - loans, ending balance	834	1,900
Allowance for credit losses - loan commitments, ending balance	50	50
Total ending allowance for credit losses - loans and loan commitments	$ 884	1,950
Home Equity [Member] | ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		$ (3,936)