Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 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	(25,139)	28,072
Provision for loan commitments	(2,783)	1,743
Total provision for credit losses - loans and loan commitments	(27,922)	29,815
Charge-offs	(2,460)	(6,126)
Recoveries	1,812	1,410
Net charge-offs	(648)	(4,716)
Allowance for credit losses - loans, ending balance	160,040	114,272
Allowance for credit losses - loan commitments, ending balance	6,731	5,572
Total ending allowance for credit losses - loans and loan commitments	166,771	119,844
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	(4,256)	5,632
Provision for loan commitments	308	(582)
Total provision for credit losses - loans and loan commitments	(3,948)	5,050
Charge-offs	(750)	(2,714)
Recoveries	440	107
Net charge-offs	(310)	(2,607)
Allowance for credit losses - loans, ending balance	33,284	39,227
Allowance for credit losses - loan commitments, ending balance	1,583
Total ending allowance for credit losses - loans and loan commitments	34,867	39,227
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	156	(351)
Total provision for credit losses - loans and loan commitments	156	(351)
Charge-offs	(201)	(328)
Recoveries	113	143
Net charge-offs	(88)	(185)
Allowance for credit losses - loans, ending balance	707	1,064
Total ending allowance for credit losses - loans and loan commitments	707	1,064
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	(3,538)	2,564
Provision for loan commitments	(2,508)	2,274
Total provision for credit losses - loans and loan commitments	(6,046)	4,838
Charge-offs	(18)	(1)
Recoveries	55	8
Net charge-offs	37	7
Allowance for credit losses - loans, ending balance	7,340	6,442
Allowance for credit losses - loan commitments, ending balance	4,000	5,111
Total ending allowance for credit losses - loans and loan commitments	11,340	11,553
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	(11,420)	20,585
Provision for loan commitments	(504)
Total provision for credit losses - loans and loan commitments	(11,924)	20,585
Charge-offs	(19)	(1,398)
Recoveries	528	293
Net charge-offs	509	(1,105)
Allowance for credit losses - loans, ending balance	99,741	52,873
Allowance for credit losses - loan commitments, ending balance	208
Total ending allowance for credit losses - loans and loan commitments	99,949	52,873
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	(4,177)	237
Provision for loan commitments	(86)	49
Total provision for credit losses - loans and loan commitments	(4,263)	286
Charge-offs	(371)	(386)
Recoveries	135	272
Net charge-offs	(236)	(114)
Allowance for credit losses - loans, ending balance	13,438	9,684
Allowance for credit losses - loan commitments, ending balance	869	444
Total ending allowance for credit losses - loans and loan commitments	14,307	10,128
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	(1,510)	(1,241)
Provision for loan commitments	2
Total provision for credit losses - loans and loan commitments	(1,508)	(1,241)
Charge-offs	(927)	(856)
Recoveries	462	415
Net charge-offs	(465)	(441)
Allowance for credit losses - loans, ending balance	4,532	3,886
Allowance for credit losses - loan commitments, ending balance	21
Total ending allowance for credit losses - loans and loan commitments	4,553	3,886
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	(394)	646
Provision for loan commitments	5	2
Total provision for credit losses - loans and loan commitments	(389)	648
Charge-offs	(174)	(443)
Recoveries	79	172
Net charge-offs	(95)	(271)
Allowance for credit losses - loans, ending balance	998	1,096
Allowance for credit losses - loan commitments, ending balance	50	17
Total ending allowance for credit losses - loans and loan commitments	$ 1,048	1,113
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)