Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	$ 52,429	$ 52,429	$ 48,948	$ 45,284
Allowance for credit losses - loan commitments, beginning balance	874	874	741	574
Total beginning allowance for credit losses - loans and loan commitments	53,303	53,303	49,689	45,858
Provision for loan losses		101,960	11,065	7,597
Provision for loan commitments		5,685	133	167
Total provision for credit losses - loans and loan commitments		107,645	11,198	7,764
Charge-offs		(12,535)	(12,657)	(10,567)
Recoveries		5,486	5,073	6,634
Net recoveries (charge-offs)		(7,049)	(7,584)	(3,933)
Allowance for credit losses - loans, ending balance		185,827	52,429	48,948
Allowance for credit losses - loan commitments, ending balance		9,514	874	741
Total ending allowance for credit losses - loans and loan commitments		195,341	53,303	49,689
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	14,116	14,116	12,114	9,414
Allowance for credit losses - loan commitments, beginning balance	311	311	262	173
Total beginning allowance for credit losses - loans and loan commitments	14,427	14,427	12,376	9,587
Provision for loan losses		3,918	2,714	3,430
Provision for loan commitments		693	49	89
Total provision for credit losses - loans and loan commitments		4,611	2,763	3,519
Charge-offs		(3,727)	(1,816)	(1,830)
Recoveries		1,457	1,104	1,100
Net recoveries (charge-offs)		(2,270)	(712)	(730)
Allowance for credit losses - loans, ending balance		37,850	14,116	12,114
Allowance for credit losses - loan commitments, ending balance		1,275	311	262
Total ending allowance for credit losses - loans and loan commitments		39,125	14,427	12,376
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	1,387	1,387	972	821
Total beginning allowance for credit losses - loans and loan commitments	1,387	1,387	972	821
Provision for loan losses		(376)	1,664	1,146
Total provision for credit losses - loans and loan commitments		(376)	1,664	1,146
Charge-offs		(1,011)	(1,659)	(1,374)
Recoveries		426	410	379
Net recoveries (charge-offs)		(585)	(1,249)	(995)
Allowance for credit losses - loans, ending balance		639	1,387	972
Total ending allowance for credit losses - loans and loan commitments		639	1,387	972
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	4,949	4,949	4,039	3,117
Allowance for credit losses - loan commitments, beginning balance	235	235	169	119
Total beginning allowance for credit losses - loans and loan commitments	5,184	5,184	4,208	3,236
Provision for loan losses		6,929	746	650
Provision for loan commitments		3,671	66	50
Total provision for credit losses - loans and loan commitments		10,600	812	700
Charge-offs		(51)	(107)	(137)
Recoveries		92	271	409
Net recoveries (charge-offs)		41	164	272
Allowance for credit losses - loans, ending balance		10,841	4,949	4,039
Allowance for credit losses - loan commitments, ending balance		6,508	235	169
Total ending allowance for credit losses - loans and loan commitments		17,349	5,184	4,208
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	20,293	20,293	20,848	21,166
Allowance for credit losses - loan commitments, beginning balance	22	22	33	26
Total beginning allowance for credit losses - loans and loan commitments	20,315	20,315	20,881	21,192
Provision for loan losses		78,210	2,560	(521)
Provision for loan commitments		712	(11)	7
Total provision for credit losses - loans and loan commitments		78,922	2,549	(514)
Charge-offs		(1,747)	(3,867)	(1,090)
Recoveries		796	752	1,293
Net recoveries (charge-offs)		(951)	(3,115)	203
Allowance for credit losses - loans, ending balance		110,652	20,293	20,848
Allowance for credit losses - loan commitments, ending balance		712	22	33
Total ending allowance for credit losses - loans and loan commitments		111,364	20,315	20,881
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	4,311	4,311	3,822	3,206
Allowance for credit losses - loan commitments, beginning balance	15	15	12	7
Total beginning allowance for credit losses - loans and loan commitments	4,326	4,326	3,834	3,213
Provision for loan losses		9,065	1,400	1,612
Provision for loan commitments		560	3	5
Total provision for credit losses - loans and loan commitments		9,625	1,403	1,617
Charge-offs		(1,415)	(1,276)	(1,435)
Recoveries		640	365	439
Net recoveries (charge-offs)		(775)	(911)	(996)
Allowance for credit losses - loans, ending balance		17,851	4,311	3,822
Allowance for credit losses - loan commitments, ending balance		955	15	12
Total ending allowance for credit losses - loans and loan commitments		18,806	4,326	3,834
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses - loans, beginning balance	2,951	2,951	2,797	3,063
Allowance for credit losses - loan commitments, beginning balance	41	41	39	37
Total beginning allowance for credit losses - loans and loan commitments	2,992	2,992	2,836	3,100
Provision for loan losses		2,980	1,130	1,142
Provision for loan commitments		19	2	2
Total provision for credit losses - loans and loan commitments		2,999	1,132	1,144
Charge-offs		(3,615)	(2,719)	(3,508)
Recoveries		1,574	1,743	2,100
Net recoveries (charge-offs)		(2,041)	(976)	(1,408)
Allowance for credit losses - loans, ending balance		6,507	2,951	2,797
Allowance for credit losses - loan commitments, ending balance		19	41	39
Total ending allowance for credit losses - loans and loan commitments		6,526	2,992	2,836
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	41,400	41,442
ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		22,357
ASU 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		213
ASU 2016-13 [Member] | Commercial Real Estate [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		1,524
ASU 2016-13 [Member] | Commercial Real Estate [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		13,078
ASU 2016-13 [Member] | Residential Real Estate [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		5,630
ASU 2016-13 [Member] | Consumer [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	4,422	4,422	4,356	4,497
Allowance for credit losses - loan commitments, beginning balance	250	250	226	212
Total beginning allowance for credit losses - loans and loan commitments	$ 4,672	4,672	4,582	4,709
Provision for loan losses		1,234	851	138
Provision for loan commitments		30	24	14
Total provision for credit losses - loans and loan commitments		1,264	875	152
Charge-offs		(969)	(1,213)	(1,193)
Recoveries		501	428	914
Net recoveries (charge-offs)		(468)	(785)	(279)
Allowance for credit losses - loans, ending balance		1,487	4,422	4,356
Allowance for credit losses - loan commitments, ending balance		45	250	226
Total ending allowance for credit losses - loans and loan commitments		1,532	$ 4,672	$ 4,582
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)