Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 97,787	$ 113,031	$ 113,031
Charge-offs	(1,607)	(1,982)
Recoveries	1,385	611
Release of allowance for loan losses	(485)	(580)
Ending balance	124,166	111,080	97,787
Individually evaluated for impairment			3,970
Acquired with deteriorated credit quality			546
Collectively evaluated for impairment			93,271
Total allowance for loan losses by group	124,166	111,080	97,787
Loans ending balance:
Individually evaluated for impairment			58,204
Acquired with deteriorated credit quality			69,639
Collectively evaluated for impairment			12,153,667
Gross loans before unamortized premiums, unearned discounts and deferred fees	12,182,203		12,281,510
Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	242	494	494
Charge-offs	0	0
Recoveries	0	0
Release of allowance for loan losses	0	(121)
Ending balance	0	373	242
Individually evaluated for impairment			0
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			242
Total allowance for loan losses by group	0	373	242
Loans ending balance:
Individually evaluated for impairment			0
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			0
Gross loans before unamortized premiums, unearned discounts and deferred fees			0
Commercial Portfolio Segment \| Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	18,018	26,617	26,617
Charge-offs	(1)	0
Recoveries	250	9
Release of allowance for loan losses	(2,959)	(1,220)
Ending balance	26,841	25,406	18,018
Individually evaluated for impairment			1,540
Acquired with deteriorated credit quality			5
Collectively evaluated for impairment			16,473
Total allowance for loan losses by group	26,841	25,406	18,018
Loans ending balance:
Individually evaluated for impairment			16,145
Acquired with deteriorated credit quality			19,028
Collectively evaluated for impairment			2,925,354
Gross loans before unamortized premiums, unearned discounts and deferred fees	2,886,560		2,960,527
Commercial Portfolio Segment \| Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	52,373	54,569	54,569
Charge-offs	0	(234)
Recoveries	14	0
Release of allowance for loan losses	(1,120)	803
Ending balance	44,612	55,138	52,373
Individually evaluated for impairment			0
Acquired with deteriorated credit quality			298
Collectively evaluated for impairment			52,075
Total allowance for loan losses by group	44,612	55,138	52,373
Loans ending balance:
Individually evaluated for impairment			3,520
Acquired with deteriorated credit quality			47,553
Collectively evaluated for impairment			4,471,440
Gross loans before unamortized premiums, unearned discounts and deferred fees	4,609,824		4,522,513
Commercial Portfolio Segment \| Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,585	4,553	4,553
Charge-offs	0	0
Recoveries	0	0
Release of allowance for loan losses	344	(1,203)
Ending balance	4,414	3,350	2,585
Individually evaluated for impairment			0
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			2,585
Total allowance for loan losses by group	4,414	3,350	2,585
Loans ending balance:
Individually evaluated for impairment			0
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			222,328
Gross loans before unamortized premiums, unearned discounts and deferred fees	246,093		222,328
Commercial Portfolio Segment \| Business Banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10,983	13,152	13,152
Charge-offs	(945)	(1,384)
Recoveries	928	365
Release of allowance for loan losses	143	1,371
Ending balance	17,269	13,504	10,983
Individually evaluated for impairment			450
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			10,533
Total allowance for loan losses by group	17,269	13,504	10,983
Loans ending balance:
Individually evaluated for impairment			12,060
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			1,322,634
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,201,007		1,334,694
Residential Portfolio Segment \| Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,556	6,435	6,435
Charge-offs	0	0
Recoveries	10	10
Release of allowance for loan losses	2,188	(210)
Ending balance	22,243	6,235	6,556
Individually evaluated for impairment			1,549
Acquired with deteriorated credit quality			243
Collectively evaluated for impairment			4,764
Total allowance for loan losses by group	22,243	6,235	6,556
Loans ending balance:
Individually evaluated for impairment			22,378
Acquired with deteriorated credit quality			3,058
Collectively evaluated for impairment			1,901,374
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,936,182		1,926,810
Consumer Portfolio Segment \| Consumer home equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,722	3,744	3,744
Charge-offs	0	0
Recoveries	4	71
Release of allowance for loan losses	435	(239)
Ending balance	6,018	3,576	3,722
Individually evaluated for impairment			270
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			3,452
Total allowance for loan losses by group	6,018	3,576	3,722
Loans ending balance:
Individually evaluated for impairment			3,922
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			1,096,231
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,099,211		1,100,153
Consumer Portfolio Segment \| Other Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,308	3,467	3,467
Charge-offs	(661)	(364)
Recoveries	179	156
Release of allowance for loan losses	484	239
Ending balance	2,769	3,498	3,308
Individually evaluated for impairment			161
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			3,147
Total allowance for loan losses by group	2,769	$ 3,498	3,308
Loans ending balance:
Individually evaluated for impairment			179
Acquired with deteriorated credit quality			0
Collectively evaluated for impairment			214,306
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 203,326		$ 214,485

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Amount excluding accrued interest, of allowance for credit loss on financing receivable.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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The balance of financing receivables that were collectively evaluated for impairment.

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