Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 113,031	$ 82,297	$ 80,655
Charge-offs	(9,002)	(9,853)	(9,499)
Recoveries	3,444	1,787	4,841
Provision (release of)	(9,686)	38,800	6,300
Ending balance	97,787	113,031	82,297
Ending balance: individually evaluated for impairment	3,970	8,054	4,669
Ending balance: acquired with deteriorated credit quality	546	2,432	1,192
Ending balance: collectively evaluated for impairment	93,271	102,545	76,436
Loans ending balance:
Individually evaluated for impairment	58,204	75,609	87,756
Acquired with deteriorated credit quality	69,639	9,297	13,451
Collectively evaluated for impairment	12,153,667	9,645,619	8,885,839
Total loans	12,281,510	9,730,525	8,987,046
Commercial and industrial | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	26,617	20,919	19,321
Charge-offs	(1,558)	(1,770)	(1,123)
Recoveries	935	778	3,748
Provision (release of)	(7,976)	6,690	(1,027)
Ending balance	18,018	26,617	20,919
Ending balance: individually evaluated for impairment	1,540	4,555	2,337
Ending balance: acquired with deteriorated credit quality	5	1,283	936
Ending balance: collectively evaluated for impairment	16,473	20,779	17,646
Loans ending balance:
Individually evaluated for impairment	16,145	17,343	32,370
Acquired with deteriorated credit quality	19,028	3,432	3,571
Collectively evaluated for impairment	2,925,354	1,974,241	1,606,243
Total loans	2,960,527	1,995,016	1,642,184
Commercial real estate | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	54,569	34,730	32,400
Charge-offs	(247)	(24)	0
Recoveries	4	230	12
Provision (release of)	(1,953)	19,633	2,318
Ending balance	52,373	54,569	34,730
Ending balance: individually evaluated for impairment	0	210	40
Ending balance: acquired with deteriorated credit quality	298	822	0
Ending balance: collectively evaluated for impairment	52,075	53,537	34,690
Loans ending balance:
Individually evaluated for impairment	3,520	4,435	7,641
Acquired with deteriorated credit quality	47,553	2,749	6,459
Collectively evaluated for impairment	4,471,440	3,566,446	3,521,341
Total loans	4,522,513	3,573,630	3,535,441
Commercial construction | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4,553	3,424	4,606
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (release of)	(1,968)	1,129	(1,182)
Ending balance	2,585	4,553	3,424
Ending balance: individually evaluated for impairment	0	0	0
Ending balance: acquired with deteriorated credit quality	0	0	0
Ending balance: collectively evaluated for impairment	2,585	4,553	3,424
Loans ending balance:
Individually evaluated for impairment	0	0	0
Acquired with deteriorated credit quality	0	0	0
Collectively evaluated for impairment	222,328	305,708	273,774
Total loans	222,328	305,708	273,774
Business Banking | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13,152	8,260	8,167
Charge-offs	(5,091)	(5,147)	(5,974)
Recoveries	1,524	292	604
Provision (release of)	1,398	9,747	5,463
Ending balance	10,983	13,152	8,260
Ending balance: individually evaluated for impairment	450	1,435	571
Ending balance: acquired with deteriorated credit quality	0	0	0
Ending balance: collectively evaluated for impairment	10,533	11,717	7,689
Loans ending balance:
Individually evaluated for impairment	12,060	21,901	11,658
Acquired with deteriorated credit quality	0	0	0
Collectively evaluated for impairment	1,322,634	1,317,263	759,840
Total loans	1,334,694	1,339,164	771,498
Residential real estate | Residential Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,435	6,380	7,059
Charge-offs	(35)	0	(66)
Recoveries	122	125	105
Provision (release of)	34	(70)	(718)
Ending balance	6,556	6,435	6,380
Ending balance: individually evaluated for impairment	1,549	1,565	1,399
Ending balance: acquired with deteriorated credit quality	243	327	256
Ending balance: collectively evaluated for impairment	4,764	4,543	4,725
Loans ending balance:
Individually evaluated for impairment	22,378	27,056	29,532
Acquired with deteriorated credit quality	3,058	3,116	3,421
Collectively evaluated for impairment	1,901,374	1,340,785	1,395,677
Total loans	1,926,810	1,370,957	1,428,630
Consumer home equity | Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,744	4,027	4,113
Charge-offs	(24)	(574)	(205)
Recoveries	185	153	52
Provision (release of)	(183)	138	67
Ending balance	3,722	3,744	4,027
Ending balance: individually evaluated for impairment	270	289	322
Ending balance: acquired with deteriorated credit quality	0	0	0
Ending balance: collectively evaluated for impairment	3,452	3,455	3,705
Loans ending balance:
Individually evaluated for impairment	3,922	4,845	6,555
Acquired with deteriorated credit quality	0	0	0
Collectively evaluated for impairment	1,096,231	863,425	926,533
Total loans	1,100,153	868,270	933,088
Other Consumer | Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,467	4,173	4,600
Charge-offs	(2,047)	(2,338)	(2,131)
Recoveries	674	209	320
Provision (release of)	1,214	1,423	1,384
Ending balance	3,308	3,467	4,173
Ending balance: individually evaluated for impairment	161	0	0
Ending balance: acquired with deteriorated credit quality	0	0	0
Ending balance: collectively evaluated for impairment	3,147	3,467	4,173
Loans ending balance:
Individually evaluated for impairment	179	29	0
Acquired with deteriorated credit quality	0	0	0
Collectively evaluated for impairment	214,306	277,751	402,431
Total loans	214,485	277,780	402,431
Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	494	384	389
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (release of)	(252)	110	(5)
Ending balance	242	494	384
Ending balance: individually evaluated for impairment	0	0	0
Ending balance: acquired with deteriorated credit quality	0	0	0
Ending balance: collectively evaluated for impairment	242	494	384
Loans ending balance:
Individually evaluated for impairment	0	0	0
Acquired with deteriorated credit quality	0	0	0
Collectively evaluated for impairment	0	0	0
Total loans	$ 0	$ 0	$ 0