Eastern Bankshares (EBC) 10-Q 10 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Nov. 09, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-39610
Entity Registrant Name	Eastern Bankshares, Inc.
Entity Incorporation, State or Country Code	MA
Entity Tax Identification Number	84-4199750
Entity Address, Address Line One	265 Franklin Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02110
City Area Code	800
Local Phone Number	327-8376
Title of 12(b) Security	Common Stock
Trading Symbol	EBC
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		186,758,154
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001810546
Current Fiscal Year End Date	--12-31

Unaudited Consolidated Balance

Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
ASSETS
Cash and due from banks	$ 78,805	$ 116,591
Short-term investments	1,172,956	1,937,479
Cash and cash equivalents	1,251,761	2,054,070
Available for sale securities	5,689,312	3,183,861
Loans held for sale	1,757	1,140
Loans:
Total loans	9,504,562	9,730,525
Less: allowance for loan losses	(103,398)	(113,031)
Less: unamortized premiums, net of unearned discounts and deferred fees	(23,104)	(23,536)
Net loans	9,378,060	9,593,958
Federal Home Loan Bank stock, at cost	10,601	8,805
Premises and equipment	44,048	49,398
Bank-owned life insurance	79,259	78,561
Goodwill and other intangibles, net	379,772	376,534
Deferred income taxes, net	34,135	13,229
Prepaid expenses	148,180	148,680
Other assets	444,338	455,954
Total assets	17,461,223	15,964,190
Deposits:
Demand	5,484,126	4,910,794
Interest checking accounts	2,693,276	2,380,497
Savings accounts	1,444,928	1,256,736
Money market investment	3,802,319	3,348,898
Certificates of deposit	225,315	258,859
Total deposits	13,649,964	12,155,784
Borrowed funds:
Federal Home Loan Bank advances	14,172	14,624
Escrow deposits of borrowers	15,900	13,425
Total borrowed funds	30,072	28,049
Other liabilities	351,895	352,305
Total liabilities	14,031,931	12,536,138
Commitments and contingencies
Shareholders’ equity
Common shares, $0.01 par value, 1,000,000,000 shares authorized, 186,758,154 shares issued and outstanding at both September 30, 2021 and December 31, 2020	1,868	1,868
Additional paid in capital	1,857,165	1,854,068
Unallocated common shares held by the Employee Stock Ownership Plan	(143,966)	(147,725)
Retained earnings	1,747,300	1,665,607
Accumulated other comprehensive income, net of tax	(33,075)	54,234
Total shareholders’ equity	3,429,292	3,428,052
Total liabilities and shareholders’ equity	17,461,223	15,964,190
Commercial and industrial
Loans:
Total loans	1,652,447	1,995,016
Commercial real estate
Loans:
Total loans	3,825,186	3,573,630
Commercial construction
Loans:
Total loans	243,146	305,708
Business banking
Loans:
Total loans	1,225,538	1,339,164
Residential real estate
Loans:
Total loans	1,491,269	1,370,957
Consumer home equity
Loans:
Total loans	848,570	868,270
Other consumer
Loans:
Total loans	$ 218,406	$ 277,780

Unaudited Consolidated Balanc_2

Unaudited Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock issued (in shares)	186,758,154	186,758,154
Common stock outstanding (in shares)	186,758,154	186,758,154

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest and dividend income:
Interest and fees on loans	$ 86,735	$ 90,704	$ 266,310	$ 278,385
Taxable interest and dividends on available for sale securities	14,314	7,554	36,977	23,332
Non-taxable interest and dividends on available for sale securities	1,848	1,883	5,561	5,709
Interest on federal funds sold and other short-term investments	571	372	1,434	1,173
Interest and dividends on trading securities	0	0	0	6
Total interest and dividend income	103,468	100,513	310,282	308,605
Interest expense:
Interest on deposits	736	1,727	2,769	10,245
Interest on borrowings	41	44	123	717
Total interest expense	777	1,771	2,892	10,962
Net interest income	102,691	98,742	307,390	297,643
(Release of) provision for allowance for loan losses	(1,488)	700	(5,368)	37,900
Net interest income after provision for loan losses	104,179	98,042	312,758	259,743
Noninterest income:
Insurance commissions	21,956	21,884	73,767	72,058
Service charges on deposit accounts	5,935	5,052	17,010	15,514
Trust and investment advisory fees	6,310	5,311	18,047	15,600
Debit card processing fees	3,030	2,721	8,949	7,528
Interest rate swap income (losses)	881	1,319	5,122	(3,919)
(Losses) income from investments held in rabbi trusts	(289)	3,800	5,773	4,802
Losses on trading securities, net	0	0	0	(3)
Gains on sales of mortgage loans held for sale, net	717	2,219	3,044	3,732
Gains on sales of securities available for sale, net	1	0	1,166	285
Other	4,668	5,403	11,276	13,138
Total noninterest income	43,209	47,709	144,154	128,735
Noninterest expense:
Salaries and employee benefits	66,238	66,593	199,554	191,517
Office occupancy and equipment	7,960	8,294	24,271	25,598
Data processing	12,191	11,721	37,892	33,905
Professional services	4,024	5,510	14,611	13,595
Charitable contributions	0	0	0	3,984
Marketing	1,598	1,943	6,786	6,056
Loan expenses	1,586	1,554	5,287	4,702
FDIC insurance	1,056	938	2,989	2,788
Amortization of intangible assets	629	699	1,786	2,102
Other	3,688	12,565	7,178	21,507
Total noninterest expense	98,970	109,817	300,354	305,754
Income before income tax expense	48,418	35,934	156,558	82,724
Income tax expense	11,312	7,429	36,980	15,924
Net income	$ 37,106	$ 28,505	$ 119,578	$ 66,800
Basic earnings per share (in dollars per share)	$ 0.22	$ 0	$ 0.69	$ 0
Diluted earnings per share (in dollars per share)	$ 0.22	$ 0	$ 0.69	$ 0

Unaudited Consolidated Statem_2

Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 37,106	$ 28,505	$ 119,578	$ 66,800
Other comprehensive income (loss), net of tax:
Net change in fair value of securities available for sale	(21,610)	(4,321)	(71,086)	22,158
Net change in fair value of cash flow hedges	(5,644)	(6,144)	(17,501)	20,286
Net change in other comprehensive income for defined benefit postretirement plans	426	1,702	1,278	5,106
Total other comprehensive (loss) income	(26,828)	(8,763)	(87,309)	47,550
Total comprehensive income	$ 10,278	$ 19,742	$ 32,269	$ 114,350

Unaudited Consolidated Statem_3

Unaudited Consolidated Statements of Changes in Shareholders Equity - USD ($) $ in Thousands		Total	Cumulative effect accounting adjustment	[1]	Common Stock	Additional Paid in Capital	Retained Earnings	Retained EarningsCumulative effect accounting adjustment	[1]	Accumulated Other Comprehensive Income (Loss)	Unallocated Common Stock Held by ESOP
Beginning balance (in shares) at Dec. 31, 2019					0
Beginning Balance at Dec. 31, 2019		$ 1,600,153	$ (1,131)		$ 0	$ 0	$ 1,644,000	$ (1,131)		$ (43,847)	$ 0
Net income		66,800					66,800
Other comprehensive income (loss), net of tax		47,550								47,550
Ending balance (in shares) at Sep. 30, 2020					0
Ending balance at Sep. 30, 2020		1,713,372			$ 0	0	1,709,669			3,703	0
Beginning balance (in shares) at Jun. 30, 2020					0
Beginning Balance at Jun. 30, 2020		1,693,630			$ 0	0	1,681,164			12,466	0
Net income		28,505					28,505
Other comprehensive income (loss), net of tax		(8,763)								(8,763)
Ending balance (in shares) at Sep. 30, 2020					0
Ending balance at Sep. 30, 2020		$ 1,713,372			$ 0	0	1,709,669			3,703	0
Beginning balance (in shares) at Dec. 31, 2020		186,758,154			186,758,154,000
Beginning Balance at Dec. 31, 2020		$ 3,428,052			$ 1,868	1,854,068	1,665,607			54,234	(147,725)
Dividends to common shareholders	[2]	(37,885)					(37,885)
Net income		119,578					119,578
Other comprehensive income (loss), net of tax		(87,309)								(87,309)
ESOP shares committed to be released		$ 6,856				3,097					3,759
Ending balance (in shares) at Sep. 30, 2021		186,758,154			186,758,154,000
Ending balance at Sep. 30, 2021		$ 3,429,292			$ 1,868	1,857,165	1,747,300			(33,075)	(143,966)
Beginning balance (in shares) at Jun. 30, 2021					186,758,154,000
Beginning Balance at Jun. 30, 2021		3,430,622			$ 1,868	1,856,241	1,723,979			(6,247)	(145,219)
Dividends to common shareholders	[3]	(13,785)					(13,785)
Net income		37,106					37,106
Other comprehensive income (loss), net of tax		(26,828)								(26,828)
ESOP shares committed to be released		$ 2,177				924					1,253
Ending balance (in shares) at Sep. 30, 2021		186,758,154			186,758,154,000
Ending balance at Sep. 30, 2021		$ 3,429,292			$ 1,868	$ 1,857,165	$ 1,747,300			$ (33,075)	$ (143,966)
[1]	Represents cumulative impact on retained earnings pursuant to the Company’s (as defined herein) adoption of Accounting Standards Update 2016-02 Leases . The transition adjustment to the opening balance of retained earnings on January 1, 2020 amounted to $1.1 million, net of tax, related to an incremental accrued rent adjustment calculated as a result of electing the hindsight practical expedient.
[2]	The Company declared and paid quarterly cash dividends of $0.06, $0.08 and $0.08 per share of common stock during the three months ended March 31, 2021, June 30, 2021 and September 30, 2021, respectively.
[3]	The Company declared and paid a quarterly cash dividend of $0.08 per share of common stock during the three months ended September 30, 2021.

Unaudited Consolidated Statem_4

Unaudited Consolidated Statements of Changes in Shareholders Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021
Cumulative effect of accounting adjustments	$ 3,429,292	$ 3,430,622
Dividends (in dollars per share)	$ 0.08	$ 0.08	$ 0.06

Unaudited Consolidated Statem_5

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net income	$ 119,578	$ 66,800
Adjustments to reconcile net income to net cash provided by operating activities
(Release of) provision for loan losses	(5,368)	37,900
Depreciation and amortization	9,932	12,246
Accretion of deferred loan fees and premiums, net	(19,126)	(5,582)
Deferred income tax expense (benefit)	5,606	(7,511)
Amortization of investment security premiums and discounts	11,084	3,057
Right-of-use asset amortization	9,172	9,086
Increase in cash surrender value of bank-owned life insurance	(1,598)	(1,685)
Gain on sale of securities available for sale, net	(1,166)	(285)
Amortization of gains from terminated interest rate swaps	(24,344)	(7,409)
Employee Stock Ownership Plan expense	6,856	0
Other	(755)	(672)
Change in:
Trading securities	0	961
Loans held for sale	(610)	(4,644)
Prepaid pension expense	2,515	(26,391)
Other assets	34,227	(122,883)
Other liabilities	(18,904)	61,326
Net cash provided by operating activities	127,099	14,314
Investing activities
Proceeds from sales of securities available for sale	23,237	9,097
Proceeds from maturities and principal paydowns of securities available for sale	573,135	289,151
Purchases of securities available for sale	(3,202,995)	(971,990)
Proceeds from sale of Federal Home Loan Bank stock	0	749
Purchases of Federal Home Loan Bank stock	(1,796)	(527)
Contributions to low income housing tax credit investments	(10,168)	(9,614)
Contributions to other equity investments	(2,294)	(1,631)
Distributions from other equity investments	258	54
Net decrease (increase) in outstanding loans	240,354	(929,237)
Acquisitions, net of cash and cash equivalents acquired	(4,354)	0
Purchased banking premises and equipment, net	(3,791)	(3,386)
Proceeds from sale of premises held for sale	736	0
Proceeds from sale of other real estate owned	125	546
Net cash used in investing activities	(2,387,553)	(1,616,788)
Financing activities
Net increase in demand, savings, interest checking, and money market investment deposit accounts	1,527,724	3,830,588
Net decrease in time deposits	(33,544)	(49,395)
Net increase (decrease) in borrowed funds	2,023	(205,958)
Contingent consideration paid	(173)	(165)
Payment of deferred offering costs	0	(7,114)
Dividends declared and paid to common shareholders	(37,885)	0
Net cash provided by financing activities	1,458,145	3,567,956
Net (decrease) increase in cash, cash equivalents, and restricted cash	(802,309)	1,965,482
Cash, cash equivalents, and restricted cash at beginning of period	2,054,070	362,602
Cash, cash equivalents, and restricted cash at end of period	1,251,761	2,328,084
Cash paid during the period for:
Interest paid	2,943	12,546
Income taxes	42,432	35,126
Non-cash activities
Net increase in capital commitments relating to low income housing tax credit projects	28,291	25,816
Initial recognition of operating lease right-of-use assets upon adoption of Accounting Standards Update 2016-02	0	92,948
Initial recognition of operating lease liabilities upon adoption of Accounting Standards Update 2016-02	$ 0	$ 96,426

Corporate Structure and Nature

Corporate Structure and Nature of Operations; Basis of Presentation	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Corporate Structure and Nature of Operations; Basis of Presentation	Corporate Structure and Nature of Operations; Basis of Presentation Corporate Structure and Nature of Operations Eastern Bankshares, Inc., a Massachusetts corporation (the “Company”), is a bank holding company. Through its wholly-owned subsidiaries, Eastern Bank (the “Bank”) and Eastern Insurance Group LLC (“Eastern Insurance Group”), the Company provides a variety of banking, trust and investment, and insurance services, through its full-service bank branches and insurance offices, located primarily in Eastern Massachusetts, southern and coastal New Hampshire and Rhode Island. Eastern Insurance Group LLC is a wholly-owned subsidiary of the Bank. The activities of the Company are subject to the regulatory supervision of the Board of Governors of the Federal Reserve System (“Federal Reserve”). The activities of the Bank are subject to the regulatory supervision of the Massachusetts Commissioner of Banks, the Federal Deposit Insurance Corporation (“FDIC”) and the Consumer Financial Protection Bureau. The Company and the activities of the Bank and Eastern Insurance Group are also subject to various Massachusetts, New Hampshire and Rhode Island business and banking regulations. Basis of Presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) as set forth by the Financial Accounting Standards Board (“FASB”) and its Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) as well as the rules and interpretive releases of the Securities and Exchange Commission (“SEC”) under the authority of federal securities laws. The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries and entities in which it holds a controlling financial interest through being the primary beneficiary or through holding a majority of the voting interest. All intercompany accounts and transactions have been eliminated in consolidation. Certain previously reported amounts have been reclassified to conform to the current period’s presentation. The accompanying consolidated balance sheet as of September 30, 2021, the consolidated statements of income and comprehensive income and of changes in equity for the three and nine months ended September 30, 2021 and 2020 and statement of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The consolidated balance sheet as of December 31, 2020 was derived from the audited consolidated financial statements as of that date. The interim consolidated financial statements and the accompanying notes should be read in conjunction with the annual consolidated financial statements and the accompanying notes contained within the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 (“2020 Form 10-K”), as filed with the SEC. In the opinion of management, the Company’s consolidated financial statements reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The following describes the Company’s use of estimates as well as relevant accounting pronouncements that were recently issued but not yet adopted as of September 30, 2021 and those that were adopted during the nine months ended September 30, 2021. For a full discussion of significant accounting policies, refer to the notes included within the Company’s 2020 Form 10-K. Use of Estimates In preparing the Consolidated Financial Statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheets and income and expenses for the periods reported. Actual results could differ from those estimates based on changing conditions, including economic conditions and future events. Material estimates that are particularly susceptible to change relate to the determination of the allowance for loan losses, valuation and fair value measurements, other-than-temporary impairment on investment securities, the liabilities for benefit obligations (particularly pensions), the provision for income taxes and impairment of goodwill and other intangibles. Recent Accounting Pronouncements The Company qualifies as an emerging growth company under the Jumpstart Our Business Act of 2012 (“JOBS Act”) and has elected to defer the adoption of new or revised accounting standards until the nonpublic company effective dates. Relevant standards that were recently issued but not yet adopted as of September 30, 2021: In March 2020, the FASB issued ASU 2020-4, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”). This update addresses optional expedients and exceptions for applying GAAP to certain contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The new guidance applies only to contracts, hedging relationships, and other transactions that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued because of reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made and hedging relationships existing as of December 31, 2022, that an entity has elected certain optional expedients for and that are retained through the end of the hedging relationship. For public and nonpublic entities, the guidance is effective as of March 12, 2020 through December 31, 2022 and does not apply to contract modifications made after December 31, 2022. The Company will adopt this standard on the nonpublic company effective date and is currently in the process of reviewing its contracts and existing processes in order to assess the risks and potential impact of the transition away from LIBOR. In June 2016, the FASB issued ASU 2016-13, Financial Instruments–Credit Losses on Financial Instruments and relevant amendments (Topic 326) (“ASU 2016-13”). This update was created to replace the current GAAP method of calculating credit losses. Specifically, the standard replaces the existing incurred loss impairment guidance by requiring immediate recognition of expected credit losses. For financial assets carried at amortized cost that are held at the reporting date (including trade and other receivables, loans and commitments, held-to-maturity debt securities and other financial assets), credit losses are measured based on historical experience, current conditions and reasonable supportable forecasts. The standard also amends existing impairment guidance for available for sale securities, in which credit losses will be recorded as an allowance versus a write-down of the amortized cost basis of the security. It will also allow for a reversal of impairment loss when the credit of the issuer improves. The guidance requires a cumulative effect of the initial application to be recognized in retained earnings at the date of initial application. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments – Credit Losses (“ASU 2018-19”). The amendments in ASU 2018-19 were intended to clarify that receivables arising from operating leases are not within the scope of Subtopic 326-20. Instead, impairment of receivables arising from operating leases should be accounted for in accordance with Topic 842, Leases . In November 2019, the FASB issued ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments – Credit Losses . This update requires entities to include expected recoveries of the amortized cost basis previously written off or expected to be written off in the valuation account for purchased financial assets with credit deterioration. In addition, the amendments in this update clarify and improve various aspects of the guidance for ASU 2016-13. For public entities that meet the definition of an SEC filer (excluding smaller reporting entities) the guidance is effective for annual reporting periods beginning after December 15, 2019. Early adoption is permitted for all entities as of the fiscal years beginning after December 15, 2018. For all other entities, the guidance is effective for annual reporting periods beginning after December 15, 2022, including interim periods within those fiscal years. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was enacted in response to the COVID-19 pandemic in the United States. to provide economic relief measures including the option to defer adoption of ASU 2016-13 to the earlier of the ending of the national emergency declaration related to the COVID-19 crisis or December 31, 2020. On December 27, 2020, the Consolidated Appropriations Act (the “Appropriations Act”) was enacted to fund the federal government through their fiscal year, extend certain expiring tax provisions and provide additional emergency relief to individuals and businesses related to the COVID-19 pandemic in the United States. Included within the provisions of the Appropriations Act is an extension of the adoption date for ASU 2016-13 from December 31, 2020 to the earlier of January 1, 2022 or 60 days after the date on which the COVID-19 national emergency terminates. To address the impact of ASU 2016-13, the Company has formed a committee, which members include the Chief Credit Officer, the Chief Financial Officer, and Chief Information Officer, to assist in identifying, implementing, and evaluating the impact of the required changes to loan loss estimation models and processes. The Company has concluded on segmentation, methodologies and other assumptions used for modeling and is currently working with third parties in validation efforts, model methodology documentation, project management and governance implementation. The Company is currently assessing the impact of the new standard on its consolidated financial statements and will adopt the standard effective January 1, 2022. Additionally, the Company is focused on the expected impact of its pending acquisition of Century Bancorp, Inc. (“Century”) on the adoption process. In August 2018, the FASB issued ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20) Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”). This update modifies the disclosure requirements for employers that sponsor defined benefit pension and/or other postretirement benefit plans. The guidance eliminates requirements for certain disclosures that are no longer considered cost beneficial and requires new ones that the FASB considers pertinent. For public companies, ASU 2018-14 is effective for fiscal years ending after December 15, 2020. For nonpublic companies, ASU 2018-14 is effective for fiscal years ending after December 15, 2021. Early adoption is permitted. The Company will adopt this standard on the nonpublic company effective date. The Company expects the adoption of this standard will not have a material impact on its consolidated financial statements. In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (“ASU 2021-08”). This update modifies how an acquiring entity measures contract assets and contract liabilities of an acquiree in a business combination in accordance with Topic 606. The amendments in this update require the acquiring entity in a business combination to account for revenue contracts as if they had originated the contract an assess how the acquiree accounted for the contract under Topic 606. ASU 2021-08 improves comparability of recognition and measurement of revenue contracts with customers both before and after a business combination. For public business entities, the amendments in this update are effective for fiscal years beginning after December 15, 2022. For all other entities, the amendments are effective for fiscal years beginning after December 15, 2023. The amendments in this update should be applied prospectively to business combinations occurring on or after the effective date of the amendments with early adoption permitted. The Company expects the adoption of this standard will not have a material impact on its consolidated financial statements. Relevant standards that were adopted during the nine months ended September 30, 2021: In August 2018, the FASB issued ASU 2018-15, Intangibles–Goodwill and Other–Internal-use software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract (“ASU 2018-15”). This update addresses accounting for fees paid by a customer for implementation, set-up and other upfront costs incurred in a cloud computing arrangement that is hosted by the vendor (i.e., a service contract). The new guidance aligns treatment for capitalization of implementation costs with guidance on internal-use software. For public entities, the guidance is effective for annual reporting periods beginning after December 15, 2019. For nonpublic entities, the guidance is effective for annual reporting periods beginning after December 15, 2020, and for all interim periods beginning after December 15, 2021. The adoption of this standard on January 1, 2021 did not have a material impact on the Company’s consolidated financial statements. In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848) (“ASU 2021-01”) which expands the scope of guidance in ASC 848 so that companies can apply the optional expedients to derivative instruments affected by the clearing house changes. ASU 2021-01 also clarifies and updates several items in ASU 2020-04 as part of the FASB’s monitoring of global reference rate reform activities. ASU 2021-01 permits entities to elect certain optional expedients and exceptions to modifications of interest rate indexes used for computing when accounting derivative contracts and certain hedging relationships impacted by changes in interest rates used for discounting, margining, or contract price alignment. ASU 2021-01 clarifies other aspects of the guidance in ASC 848 and provides new guidance on how to address the effects of the cash compensation adjustment that is provided as part of the above change on certain aspects of hedge accounting. The guidance was effective upon issuance and allows for retrospective or prospective application with certain conditions. The Company did not elect retrospective application. The adoption of this update did not have a material impact on the Company’s consolidated financial statements.

Securities

Securities	9 Months Ended
	Sep. 30, 2021
Debt Securities [Abstract]
Securities	SecuritiesAvailable for Sale Securities The amortized cost, gross unrealized gains and losses, and fair value of available for sale securities as of September 30, 2021 and December 31, 2020 were as follows: As of September 30, 2021 Amortized Unrealized Unrealized Fair (In thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 4,097,006 $ 20,437 $ (44,075) $ 4,073,368 Government-sponsored commercial mortgage-backed securities 436,748 — (5,739) 431,009 U.S. Agency bonds 860,595 — (19,312) 841,283 U.S. Treasury securities 69,419 16 (253) 69,182 State and municipal bonds and obligations 258,121 16,349 — 274,470 $ 5,721,889 $ 36,802 $ (69,379) $ 5,689,312 As of December 31, 2020 Amortized Unrealized Unrealized Fair (In thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 2,106,658 $ 42,142 $ — $ 2,148,800 Government-sponsored commercial mortgage-backed securities 17,054 27 — 17,081 U.S. Agency bonds 670,468 113 (3,872) 666,709 U.S. Treasury securities 70,106 263 — 70,369 State and municipal bonds and obligations 260,898 20,004 — 280,902 $ 3,125,184 $ 62,549 $ (3,872) $ 3,183,861 The amortized cost and estimated fair value of available for sale securities by contractual maturities as of September 30, 2021 and December 31, 2020 are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without prepayment penalties. The scheduled contractual maturities of available for sale securities as of the dates indicated were as follows: As of September 30, 2021 Due in one year or less Due after one year to five years Due after five to ten years Due after ten years Total Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value (In thousands) Government-sponsored residential mortgage-backed securities $ — $ — $ 16,131 $ 17,151 $ 924,290 $ 923,300 $ 3,156,585 $ 3,132,917 $ 4,097,006 $ 4,073,368 Government-sponsored commercial mortgage-backed securities — — 71,814 71,256 364,934 359,753 — — 436,748 431,009 U.S. Agency bonds — — 243,920 240,554 616,675 600,729 — — 860,595 841,283 U.S. Treasury securities 20,029 20,045 49,390 49,137 — — — — 69,419 69,182 State and municipal bonds and obligations 485 486 31,324 32,381 72,039 75,293 154,273 166,310 258,121 274,470 Total $ 20,514 $ 20,531 $ 412,579 $ 410,479 $ 1,977,938 $ 1,959,075 $ 3,310,858 $ 3,299,227 $ 5,721,889 $ 5,689,312 As of December 31, 2020 Due in one year or less Due after one year to five years Due after five to ten years Due after ten years Total Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value (In thousands) Government-sponsored residential mortgage-backed securities $ — $ — $ 46,293 $ 48,925 $ 96,338 $ 100,278 $ 1,964,027 $ 1,999,597 $ 2,106,658 $ 2,148,800 Government-sponsored commercial mortgage-backed securities — — — — 17,054 17,081 — — 17,054 17,081 U.S. Agency bonds — — 99,772 99,834 570,696 566,875 — — 670,468 666,709 U.S. Treasury securities 50,023 50,251 20,083 20,118 — — — — 70,106 70,369 State and municipal bonds and obligations 406 408 20,511 21,431 74,980 79,635 165,001 179,428 260,898 280,902 Total $ 50,429 $ 50,659 $ 186,659 $ 190,308 $ 759,068 $ 763,869 $ 2,129,028 $ 2,179,025 $ 3,125,184 $ 3,183,861 Gross realized gains from sales of available for sale securities during the three months ended September 30, 2021 were less than $100 thousand. There were no gross realized gains from sales of available for sale securities during the three months ended September 30, 2020. Gross realized gains from sales of available for sale securities during the nine months ended September 30, 2021 and 2020 were $1.2 million and $0.3 million, respectively. The Company had no significant gross realized losses from sales of securities available for sale during both the nine months ended September 30, 2021 and 2020. There was no other-than-temporary impairment (“OTTI”) recorded during the nine months ended September 30, 2021 and 2020. Management prepares an estimate of the expected cash flows for investment securities available for sale that potentially may be deemed to have been an OTTI. This estimate begins with the contractual cash flows of the security. This amount is then reduced by an estimate of probable credit losses associated with the security. When estimating the extent of probable losses on the securities, management considers the credit quality and the ability to pay of the underlying issuers. Indicators of diminished credit quality of the issuers include defaults, interest deferrals, or “payments in kind.” Management also considers those factors listed in the “Investments – Debt and Equity Securities” topic of the FASB ASC when estimating the ultimate realizability of the cash flows for each individual security. The resulting estimate of cash flows after considering credit is then subject to a present value computation using a discount rate equal to the current yield used to accrete the beneficial interest or the effective interest rate implicit in the security at the date of acquisition. If the present value of the estimated cash flows is less than the current amortized cost basis, an OTTI is considered to have occurred and the security is written down to the fair value indicated by the cash flow analysis. As part of the analysis, management considers whether it intends to sell the security or whether it is more than likely that it would be required to sell the security before the expected recovery of its amortized cost basis. Information pertaining to available for sale securities with gross unrealized losses as of September 30, 2021 and December 31, 2020, which the Company has not deemed to be OTTI, aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: As of September 30, 2021 Less than 12 Months 12 Months or Longer Total # of Gross Fair Gross Fair Gross Fair (Dollars in thousands) Government-sponsored residential mortgage-backed securities 30 $ 44,075 $ 3,443,757 $ — $ — $ 44,075 $ 3,443,757 Government-sponsored commercial mortgage-backed securities 17 5,739 431,009 — — 5,739 431,009 U.S. Agency bonds 13 10,010 529,855 9,302 311,428 19,312 841,283 U.S. Treasury securities 1 253 49,137 — — 253 49,137 61 $ 60,077 $ 4,453,758 $ 9,302 $ 311,428 $ 69,379 $ 4,765,186 As of December 31, 2020 Less than 12 Months 12 Months or Longer Total # of Gross Fair Gross Fair Gross Fair (Dollars in thousands) U.S. Agency bonds 6 $ 3,872 $ 416,824 $ — $ — $ 3,872 $ 416,824 6 $ 3,872 $ 416,824 $ — $ — $ 3,872 $ 416,824 The Company does not intend to sell these investments and has determined based upon available evidence that it is more likely than not that the Company will not be required to sell each security before the expected recovery of its amortized cost basis. As a result, the Company does not consider these investments with gross unrealized losses to be OTTI. The Company made this determination by reviewing various qualitative and quantitative factors regarding each investment category, such as current market conditions, extent and nature of changes in fair value, issuer rating changes and trends, and volatility of earnings. As a result of the Company’s review of these qualitative and quantitative factors, the causes of the impairments listed in the tables above by category are as follows as of September 30, 2021 and December 31, 2020: • Government-sponsored residential mortgage-backed securities – The securities with unrealized losses in this portfolio have contractual terms that generally do not permit the issuer to settle the security at a price less than the current par value of the investment. The decline in market value of these securities is attributable to changes in interest rates and not credit quality. Additionally, these securities are implicitly guaranteed by the U.S. government or one of its agencies. • Government-sponsored commercial mortgage-backed securities – The securities with unrealized losses in this portfolio have contractual terms that generally do not permit the issuer to settle the security at a price less than the current par value of the investment. The decline in market value of these securities is attributable to changes in interest rates and not credit quality. Additionally, these securities are implicitly guaranteed by the U.S. government or one of its agencies. • U.S. Agency bonds – The securities with unrealized losses in this portfolio have contractual terms that generally do not permit the issuer to settle the security at a price less than the current par value of the investment. The decline in market value of these securities is attributable to changes in interest rates and not credit quality. Additionally, these securities are implicitly guaranteed by the U.S. government or one of its agencies. • U.S. Treasury securities – The security with unrealized losses in this portfolio has contractual terms that generally do not permit the issuer to settle the security at a price less than the current par value of the investment. The decline in market value of this security is attributable to changes in interest rates and not credit quality. Additionally, this security is implicitly guaranteed by the U.S. government or one of its agencies.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2021
Receivables [Abstract]
Loans and Allowance for Loan Losses	Loans and Allowance for Loan Losses Loans The following table provides a summary of the Company’s loan portfolio as of the dates indicated: At September 30, At December 31, 2021 2020 (In thousands) Commercial and industrial $ 1,652,447 $ 1,995,016 Commercial real estate 3,825,186 3,573,630 Commercial construction 243,146 305,708 Business banking 1,225,538 1,339,164 Residential real estate 1,491,269 1,370,957 Consumer home equity 848,570 868,270 Other consumer (1) 218,406 277,780 Gross loans before unamortized premiums, unearned discounts and deferred fees 9,504,562 9,730,525 Allowance for loan losses (103,398) (113,031) Unamortized premiums, net of unearned discounts and deferred fees (23,104) (23,536) Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees $ 9,378,060 $ 9,593,958 (1) Automobile loans are included in the other consumer portfolio above and amounted to $67.1 million and $126.7 million at September 30, 2021 and December 31, 2020, respectively. There are no other loan categories that exceed 10% of total loans not already reflected in the preceding table. The Company’s lending activities are conducted principally in the New England area with the exception of its Shared National Credit Program (“SNC Program”) portfolio. The Company participates in the SNC Program in an effort to improve its industry and geographical diversification. The SNC Program portfolio is included in the Company’s commercial and industrial, commercial real estate and commercial construction portfolios. The SNC Program portfolio is defined as loan syndications with exposure over $100 million and with three or more lenders participating. Most loans originated by the Company are either collateralized by real estate or other assets or guaranteed by federal and local governmental authorities. The ability and willingness of the single-family residential and consumer borrowers to honor their repayment commitments is generally dependent on the level of overall economic activity within the borrowers’ geographic areas and real estate values. The ability and willingness of commercial real estate, commercial and industrial, and construction loan borrowers to honor their repayment commitments is generally dependent on the health of the real estate economy in the borrowers’ geographic areas and the general economy. Loans Pledged as Collateral The carrying value of loans pledged to secure advances from the Federal Home Loan Bank (“FHLB”) of Boston (“FHLBB”) were $2.4 billion at both September 30, 2021 and December 31, 2020. The balance of funds borrowed from the FHLBB were $14.2 million and $14.6 million at September 30, 2021 and December 31, 2020, respectively. The carrying value of loans pledged to secure advances from the Federal Reserve Bank (“FRB”) were $761.8 million and $884.1 million at September 30, 2021 and December 31, 2020, respectively. There were no funds borrowed from the FRB outstanding at September 30, 2021 and December 31, 2020. Serviced Loans At September 30, 2021 and December 31, 2020, mortgage loans partially or wholly-owned by others and serviced by the Company amounted to approximately $12.0 million and $13.5 million, respectively. Allowance for Loan Losses The allowance for loan losses is established to provide for probable losses incurred in the Company’s loan portfolio at the balance sheet date and is established through a provision for loan losses charged to net income. Charge-offs, net of recoveries, are charged directly to the allowance. Commercial and residential loans are charged-off in the period in which they are deemed uncollectible. Delinquent loans in these product types are subject to ongoing review and analysis to determine if a charge-off in the current period is appropriate. For consumer loans, policies and procedures exist that require charge-off consideration upon a certain triggering event depending on the product type. The following tables summarize the changes in the allowance for loan losses by loan category for the periods indicated: For the Three Months Ended September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 22,596 $ 52,759 $ 3,446 $ 12,705 $ 6,478 $ 3,588 $ 3,626 $ 439 $ 105,637 Charge-offs — (8) — (867) — — (742) — (1,617) Recoveries 40 — — 469 88 63 206 — 866 (Release of) provision (2,007) 1,435 (44) (929) (136) (16) 297 (88) (1,488) Ending balance $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 For the Three Months Ended September 30, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 33,229 $ 54,228 $ 4,816 $ 9,805 $ 6,569 $ 3,875 $ 3,762 $ 352 $ 116,636 Charge-offs (140) — — (1,179) — (22) (1,077) — (2,418) Recoveries 306 4 — 91 43 31 39 — 514 Provision (release of) (3,281) 1,350 (540) 2,711 (261) (76) 834 (37) 700 Ending balance $ 30,114 $ 55,582 $ 4,276 $ 11,428 $ 6,351 $ 3,808 $ 3,558 $ 315 $ 115,432 For the Nine Months Ended September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 26,617 $ 54,569 $ 4,553 $ 13,152 $ 6,435 $ 3,744 $ 3,467 $ 494 $ 113,031 Charge-offs (550) (242) — (4,089) — — (1,381) — (6,262) Recoveries 62 4 — 1,125 115 137 554 — 1,997 (Release of) provision (5,500) (145) (1,151) 1,190 (120) (246) 747 (143) (5,368) Ending balance $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 For the Nine Months Ended September 30, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 20,919 $ 34,730 $ 3,424 $ 8,260 $ 6,380 $ 4,027 $ 4,173 $ 384 $ 82,297 Charge-offs (167) (24) — (3,714) — (495) (1,625) — (6,025) Recoveries 686 10 — 245 116 53 150 — 1,260 Provision (release of) 8,676 20,866 852 6,637 (145) 223 860 (69) 37,900 Ending balance $ 30,114 $ 55,582 $ 4,276 $ 11,428 $ 6,351 $ 3,808 $ 3,558 $ 315 $ 115,432 The following tables bifurcate the amount of loans and the allowance allocated to each loan category based on the type of impairment analysis as of the dates indicated: As of September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses ending balance: Individually evaluated for impairment $ 4,287 $ — $ — $ 669 $ 1,462 $ 256 $ 200 $ — $ 6,874 Acquired with deteriorated credit quality — — — — 293 — — — 293 Collectively evaluated for impairment 16,342 54,186 3,402 10,709 4,675 3,379 3,187 351 96,231 Total allowance for loan losses by group $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 Loans ending balance: Individually evaluated for impairment $ 21,580 $ 3,793 $ — $ 15,141 $ 23,494 $ 4,023 $ 222 $ — $ 68,253 Acquired with deteriorated credit quality 1,546 — — — 2,880 — — — 4,426 Collectively evaluated for impairment 1,629,321 3,821,393 243,146 1,210,397 1,464,895 844,547 218,184 — 9,431,883 Total loans by group $ 1,652,447 $ 3,825,186 $ 243,146 $ 1,225,538 $ 1,491,269 $ 848,570 $ 218,406 $ — $ 9,504,562 As of December 31, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses ending balance: Individually evaluated for impairment $ 4,555 $ 210 $ — $ 1,435 $ 1,565 $ 289 $ — $ — $ 8,054 Acquired with deteriorated credit quality 1,283 822 — — 327 — — — 2,432 Collectively evaluated for impairment 20,779 53,537 4,553 11,717 4,543 3,455 3,467 494 102,545 Total allowance for loan losses by group $ 26,617 $ 54,569 $ 4,553 $ 13,152 $ 6,435 $ 3,744 $ 3,467 $ 494 $ 113,031 Loans ending balance: Individually evaluated for impairment $ 17,343 $ 4,435 $ — $ 21,901 $ 27,056 $ 4,845 $ 29 $ — $ 75,609 Acquired with deteriorated credit quality 3,432 2,749 — — 3,116 — — — 9,297 Collectively evaluated for impairment 1,974,241 3,566,446 305,708 1,317,263 1,340,785 863,425 277,751 — 9,645,619 Total loans by group $ 1,995,016 $ 3,573,630 $ 305,708 $ 1,339,164 $ 1,370,957 $ 868,270 $ 277,780 $ — $ 9,730,525 Management uses a methodology to systematically estimate the amount of loss incurred in the portfolio. Commercial real estate, commercial and industrial, commercial construction and business banking loans are evaluated using a loan rating system, historical losses and other factors which form the basis for estimating incurred losses. Portfolios of more homogeneous populations of loans, including residential mortgages and consumer loans, are analyzed as groups taking into account delinquency ratios, historical loss experience and charge-offs. For the purpose of estimating the allowance for loan losses, management segregates the loan portfolio into the categories noted in the above tables. Each of these loan categories possesses unique risk characteristics such as the purpose of the loan, repayment source, and collateral. These characteristics are considered when determining the appropriate level of the allowance for each category. Some examples of these risk characteristics unique to each loan category include: Commercial Lending Commercial and industrial : The primary risk associated with commercial and industrial loans is the ability of borrowers to achieve business results consistent with those projected at origination. Collateral frequently consists of a first lien position on business assets including, but not limited to accounts receivable, inventory, airplanes and equipment. The primary repayment source is operating cash flow and, secondarily, the liquidation of assets. The Company often obtains personal guarantees from individuals holding material ownership in the borrowing entity. Commercial real estate : Collateral values are established by independent third-party appraisals and evaluations. Primary repayment sources include operating income generated by the real estate, permanent debt refinancing, sale of the real estate and, secondarily, liquidation of the collateral. The Company often obtains personal guarantees from individuals holding material ownership in the borrowing entity. Commercial construction : These loans are generally considered to present a higher degree of risk than other real estate loans and may be affected by a variety of factors, such as adverse changes in interest rates and the borrower’s ability to control costs and adhere to time schedules. Construction loans are underwritten utilizing feasibility studies, independent appraisal reviews, sensitivity analysis of absorption and lease rates and financial analysis of the developers and property owners. Construction loans are generally based upon estimates of costs and value associated with the completed project. Construction loan repayment is substantially dependent on the ability of the borrower to complete the project and obtain permanent financing. Business banking : These loans are typically secured by all business assets or commercial real estate. Business banking originations include traditionally underwritten loans as well as partially automated scored loans. Business banking scored loans are determined by utilizing the Company’s proprietary decision matrix that has a number of quantitative factors including, but not limited to, a guarantor’s credit score, industry risk, and time in business. The Company also engages in Small Business Association (“SBA”) lending, both in the business banking and commercial banking divisions. The SBA guarantees reduce the Company’s loss due to default and are considered a credit enhancement to the loan structure. Residential Lending Residential real estate : These loans are made to borrowers who demonstrate the ability to repay principal and interest on a monthly basis. Underwriting considerations include, among others, income sources and their reliability, willingness to repay as evidenced by credit repayment history, financial resources (including cash reserves) and the value of the collateral. The Company maintains policy standards for minimum credit score and cash reserves and maximum loan to value consistent with a “prime” portfolio. Collateral consists of mortgage liens on 1-4 family residential dwellings. The Company does not originate or purchase sub-prime or other high-risk loans. Residential loans are originated either for sale to investors or retained in the Company’s loan portfolio. Decisions about whether to sell or retain residential loans are made based on the interest rate characteristics, pricing for loans in the secondary mortgage market, competitive factors and the Company’s capital needs. Consumer Lending Consumer home equity : Home equity lines of credit are granted for ten years with monthly interest-only repayment requirements. Full principal repayment is required at the end of the ten-year draw period. Home equity loans are term loans that require the monthly payment of principal and interest such that the loan will be fully amortized at maturity. Underwriting considerations are materially consistent with those utilized in residential real estate. Collateral consists of a senior or subordinate lien on owner-occupied residential property. Other consumer : The Company’s policy and underwriting in this category, which is comprised primarily of home improvement and automobile loans, include the following factors, among others: income sources and reliability, credit histories, term of repayment, and collateral value, as applicable. These are typically granted on an unsecured basis, with the exception of airplane and automobile loans. Credit Quality Commercial Lending Credit Quality The Company monitors credit quality indicators and utilizes portfolio scorecards to assess the risk of its commercial portfolio. Specifically, the Company utilizes a 15-point credit risk-rating system to manage risk and identify potential problem loans. Prior to December 31, 2020, the Company utilized a 12-point credit risk-rating system to manage risk and identify potential problem loans. In the fourth quarter of 2020, the Company realigned its credit risk-rating system, transitioning to a 15-point credit risk-rating system. The Company believes that the expansion from the prior 12-point scale provides more refinement in the pass grade categories; new pass grades are 0-10. There are no changes to non-pass categories, which continue to align with regulatory guidelines and are found in ratings: special mention (11), substandard (12), doubtful (13) and loss (14). The Company believes that increasing granularity of the risk rating system allows for more robust portfolio management and increased precision and effectiveness of credit risk identification. Under both point systems, risk-rating assignments are based upon a number of quantitative and qualitative factors that are under continual review. Factors include cash flow, collateral coverage, liquidity, leverage, position within the industry, internal controls and management, financial reporting, and other considerations. The risk-rating categories under the new 15-point credit risk-rating system are defined as follows: 0 Risk Rating - Unrated Certain segments of the portfolios are not rated. These segments include airplane loans, business banking scored loan products, and other commercial loans managed by exception. Loans within this unrated loan segment are monitored by delinquency status; and for lines of credit greater than $100,000 in exposure, an annual review is conducted. The Company supplements performance data with current business credit scores for the business banking portfolio on a quarterly basis. Unrated commercial and business banking loans are generally restricted to commercial exposure of less than $1 million. Loans included in this category have qualification requirements that include a risk rating of 10 or better at the time of recommendation for unrated status, acceptable management of deposit accounts, and no known negative changes in management, operations or financial performance. For purposes of estimating the allowance for loan losses, unrated loans are considered in the same manner as pass rated loans. 1-10 Risk Rating – Pass Loans with a risk rating of 1-10 are classified as “Pass” and are comprised of loans that range from “substantially risk free” which indicates borrowers of unquestioned credit standing, well-established national companies with a very strong financial condition, and loans fully secured by policy conforming cash levels, through “low pass” which indicates acceptable rated loans that may be experiencing weak cash flow, impending lease rollover or minor liquidity concerns. 11 Risk Rating – Special Mention (Potential Weakness) Loans to borrowers in this category exhibit potential weaknesses or downward trends deserving management’s close attention. While potentially weak, no loss of principal or interest is envisioned. Included in this category are borrowers who are performing as agreed, are weak when compared to industry standards, may be experiencing an interim loss and may be in declining industries. An element of asset quality, financial flexibility or management is below average. The Company does not consider borrowers within this category as new business prospects. Borrowers rated special mention may find it difficult to obtain alternative financing from traditional bank sources. 12 Risk Rating – Substandard (Well-Defined Weakness) Loans with a risk-rating of 12 exhibit well-defined weaknesses that, if not corrected, may jeopardize the orderly liquidation of the debt. A loan is classified as substandard if it is inadequately protected by the repayment capacity of the obligor or by the collateral pledged. Specifically, repayment under market rates and terms, or by the requirements under the existing loan documents, is in jeopardy, but no loss of principal or interest is envisioned. There is a possibility that a partial loss of principal and/or interest will occur in the future if the deficiencies are not corrected. Loss potential, while existing in the aggregate portfolio of substandard assets, does not have to exist in individual assets classified as substandard. Non-accrual is possible, but not mandatory, in this class. 13 Risk Rating – Doubtful (Loss Probable) Loans classified as doubtful have comparable weaknesses as found in the loans classified as substandard, with the added provision that such weaknesses make collection of the debt in full (based on currently existing facts, conditions and values) highly questionable and improbable. Serious problems exist such that a partial loss of principal is likely. The probability of loss exists, however, because of reasonable specific pending factors that may work to strengthen the credit, estimated losses are deferred until a more exact status can be determined. Specific reserves will be the amount identified after specific review. Non-accrual is mandatory in this class. 14 Risk Rating – Loss Loans to borrowers in this category are deemed incapable of repayment. Loans to such borrowers are considered uncollectible and of such little value that continuance as active assets of the Company is not warranted. This classification does not mean that the loans have no recovery or salvage value, but rather, it is not practical or desirable to defer writing off these assets even though partial recovery may occur in the future. Loans in this category have a recorded investment of $0 at the time of the downgrade. The credit quality of the commercial loan portfolio is actively monitored and supported by a comprehensive credit approval process; and all large dollar transactions are sent for approval to a committee of seasoned business line and credit professionals. Risk ratings are periodically reviewed and the Company maintains an independent credit risk review function that reports directly to the Risk Management Committee of the Board of Directors. Credits that demonstrate significant deterioration in credit quality are transferred to a specialized group of experienced officers for individual attention. The following tables detail the internal risk-rating categories for the Company’s commercial and industrial, commercial real estate, commercial construction and business banking portfolios: As of September 30, 2021 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 278,093 $ 4,196 $ 138 $ 763,573 $ 1,046,000 Pass 1,302,413 3,524,607 224,770 389,812 5,441,602 Special mention 13,959 124,618 9,611 54,592 202,780 Substandard 41,459 171,765 8,627 16,478 238,329 Doubtful 16,523 — — 1,083 17,606 Loss — — — — — Total $ 1,652,447 $ 3,825,186 $ 243,146 $ 1,225,538 $ 6,946,317 As of December 31, 2020 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 655,346 $ 6,585 $ — $ 918,921 $ 1,580,852 Pass 1,199,522 3,256,697 280,792 336,657 5,073,668 Special mention 78,117 134,562 10,330 57,092 280,101 Substandard 47,525 173,308 14,586 24,788 260,207 Doubtful 14,506 2,478 — 1,706 18,690 Loss — — — — — Total $ 1,995,016 $ 3,573,630 $ 305,708 $ 1,339,164 $ 7,213,518 Paycheck Protection Program (“PPP”) loans are included within the unrated category of the commercial and industrial and business banking portfolios in the tables above. Commercial and industrial PPP loans and business banking PPP loans amounted to $215.7 million and $318.3 million, respectively, at September 30, 2021 and $568.8 million and $457.4 million respectively, at December 31, 2020. The Company does not have an allowance for loan losses for PPP loans as they are 100% guaranteed by the SBA. Residential and Consumer Lending Credit Quality For the Company’s residential and consumer portfolios, the quality of the loan is best indicated by the repayment performance of an individual borrower. Updated appraisals, broker opinions of value and other collateral valuation methods are employed in the residential and consumer portfolios, typically for credits that are deteriorating. Delinquency status is determined using payment performance, while accrual status may be determined using a combination of payment performance, expected borrower viability and collateral value. Delinquent consumer loans are handled by a team of seasoned collection specialists. Asset Quality In response to the novel coronavirus (“COVID-19”) pandemic, the Company has granted loan modifications to allow deferral of payments for borrowers negatively impacted by the COVID-19 pandemic. Modifications granted to customers allowed for full payment deferrals (principal and interest) or deferral of only principal payments. The balance of loans which underwent a modification and have not yet resumed payment as of September 30, 2021 and December 31, 2020 was $110.6 million and $332.7 million, respectively. The Company defines a modified loan to have resumed payment if it is one month past the modification end date and not more than 30 days past due. These modifications with active deferrals met the criteria of either Section 4013 of the CARES Act or the Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus (Revised) and therefore are not deemed troubled debt restructurings, referred to as TDRs (as defined below). Additionally, loans that are performing in accordance with the contractual terms of the modification are not reflected as being past due and therefore are not impacting non-accrual or delinquency totals as of September 30, 2021 and December 31, 2020. The Company continued to accrue interest on these COVID-19 modified loans and evaluated the deferred interest for collectability as of September 30, 2021 and December 31, 2020. The Appropriations Act, which was enacted on December 27, 2020, extends certain provisions related to the COVID-19 pandemic in the United States (which were due to expire) and provides additional emergency relief to individuals and businesses. Included within the provisions of the Appropriations Act is the extension of Section 4013 of the CARES Act to January 1, 2022. As such, the Company intends to apply the TDR relief granted pursuant to such section to any qualifying loan modifications executed during the allowable time period. The Company manages its loan portfolio with careful monitoring. As a general rule, loans more than 90 days past due with respect to principal and interest are classified as non-accrual loans. Exceptions may be made if management believes that collateral held by the Company is clearly sufficient and in full satisfaction of both principal and interest, or the loan is accounted for as a purchased credit impaired (“PCI”) loan. In addition, as permitted by banking regulations, certain consumer loans past due 90 days or more may continue to accrue interest. The Company may also use discretion regarding other loans over 90 days delinquent if the loan is well secured and in the process of collection. Non-accrual loans and loans that are more than 90 days past due but still accruing interest are considered non-performing loans. Non-accrual loans may be returned to an accrual status when principal and interest payments are no longer delinquent, and the risk characteristics of the loan have improved to the extent that there no longer exists a concern as to the collectability of principal and interest. Loans are considered past due based upon the number of days delinquent according to their contractual terms. A loan is expected to remain on non-accrual status until it becomes current with respect to principal and interest, the loan is liquidated, or the loan is determined to be uncollectible and is charged-off against the allowance for loan losses. The following is a summary pertaining to the breakdown of the Company’s non-accrual loans: As of September 30, As of December 31, 2021 2020 (In thousands) Commercial and industrial $ 17,640 $ 11,714 Commercial real estate 272 915 Business banking 11,254 17,430 Residential real estate 7,185 6,815 Consumer home equity 3,491 3,602 Other consumer 771 529 Total non-accrual loans $ 40,613 $ 41,005 The following tables show the age analysis of past due loans as of the dates indicated: As of September 30, 2021 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 529 $ 2,068 $ 2,043 $ 4,640 $ 1,647,807 $ 1,652,447 $ — Commercial real estate — — 1,171 1,171 3,824,015 3,825,186 1,171 Commercial construction — — — — 243,146 243,146 — Business banking 3,351 634 5,497 9,482 1,216,056 1,225,538 — Residential real estate 9,014 2,426 5,515 16,955 1,474,314 1,491,269 278 Consumer home equity 2,319 415 3,111 5,845 842,725 848,570 9 Other consumer 1,107 362 771 2,240 216,166 218,406 — Total $ 16,320 $ 5,905 $ 18,108 $ 40,333 $ 9,464,229 $ 9,504,562 $ 1,458 As of December 31, 2020 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 4 $ 268 $ 1,924 $ 2,196 $ 1,992,820 $ 1,995,016 $ 848 Commercial real estate — 556 1,545 2,101 3,571,529 3,573,630 1,111 Commercial construction — — — — 305,708 305,708 — Business banking 5,279 3,311 10,196 18,786 1,320,378 1,339,164 — Residential real estate 9,184 2,517 4,904 16,605 1,354,352 1,370,957 279 Consumer home equity 1,806 364 3,035 5,205 863,065 868,270 9 Other consumer 1,978 234 517 2,729 275,051 277,780 — Total $ 18,251 $ 7,250 $ 22,121 $ 47,622 $ 9,682,903 $ 9,730,525 $ 2,247 In the normal course of business, the Company may become aware of possible credit problems in which borrowers exhibit potential for the inability to comply with the contractual terms of their loans, but which currently do not yet meet the criteria for classification as non-performing loans (which consist of non-accrual loans and loans that are more than 90 days past due but still accruing interest). Based upon the Company’s past experiences, some of these loans with potential weaknesses will ultimately be restructured or placed in non-accrual status. As of both September 30, 2021 and December 31, 2020, we are unable to reasonably estimate the amount of these loans that will be restructured or placed on non-accrual status. Troubled Debt Restructurings (“TDR”) In cases where a borrower experiences financial difficulty and the Company makes certain concessionary modifications to contractual terms, the loan is classified as a troubled debt restructured loan. The objective is to aid in the resolution of non-performing loans by modifying the contractual obligation to avoid the possibility of foreclosure. All TDR loans are considered impaired and therefore are subject to a specific review for impairment loss. The amount of impairment loss, if any, is recorded as a specific loss allocation to each individual loan in the allowance for loan losses. Commercial loans and residential loans that have been classified as TDRs and which subsequently default are reviewed to determine if the loan should be deemed collateral dependent. In such an instance, any shortfall between the value of the collateral and the book value of the loan is determined by measuring the recorded investment in the loan against the fair value of the collateral less costs to sell. The Company’s policy is to have any TDR loans which are on non-accrual status prior to being modified remain on non-accrual status for approximately six months subsequent to being modified before management considers its return to accrual status. If the TDR loan is on accrual status prior to being modified, it is reviewed to determine if the modified loan should remain on accrual status. The following tables show the TDR loans on accrual and non-accrual status as of the dates indicated: As of September 30, 2021 TDRs on Accrual Status TDRs on Non-Accrual Status Total TDRs Number of Loans Balance of Number of Balance of Number of Balance of (Dollars in thousands) Commercial and industrial 1 $ 3,940 6 $ 10,944 7 $ 14,884 Commercial real estate 1 3,520 — — 1 3,520 Business banking 5 3,888 5 1,262 10 5,150 Residential real estate 127 20,092 26 3,135 153 23,227 Consumer home equity 73 3,280 16 744 89 4,024 Other consumer 2 3 1 18 3 21 Total 209 $ 34,723 54 $ 16,103 263 $ 50,826 As of December 31, 2020 TDRs on Accrual Status TDRs on Non-Accrual Status Total TDRs Number of Loans Balance of Number of Loans Balance of Number of Loans Balance of (Dollars in thousands) Commercial and industrial 1 $ 5,628 7 $ 6,819 8 $ 12,447 Commercial real estate 1 3,521 1 480 2 4,001 Business banking 6 4,471 6 722 12 5,193 Residential real estate 146 23,416 27 3,273 173 26,689 Consumer home equity 91 4,030 12 815 103 4,845 Other consumer 3 29 — — 3 29 Total 248 $ 41,095 53 $ 12,109 301 $ 53,204 The amount of specific reserve associated with the TDRs was $3.1 million and $3.5 million at September 30, 2021 and December 31, 2020, respectively. There were additional commitments to lend of $0.5 million to borrowers who have been a party to a TDR as of September 30, 2021. There were no additional commitments to lend to borrowers who have been party to a TDR as of December 31, 2020. The following tables show the modifications which occurred during the periods and the change in the recorded investment subsequent to the modifications occurring: For the Three Months Ended September 30, 2021 For the Nine Months Ended September 30, 2021 Number Pre- Post- Number Pre-Modification Post- (Dollars in thousands) Business banking — $ — $ — 1 $ 462 $ 462 Residential real estate — — — 1 295 295 Consumer home equity 2 200 200 2 200 200 Total 2 $ 200 $ 200 4 $ 957 $ 957 (1) The post-modification balances represent the balance of the loan on the date of modification. These amounts may show an increase when modification includes capitalization of interest. For the Three Months Ended September 30, 2020 For the Nine Months Ended September 30, 2020 Number Pre- Post- Number Pre-Modification Post- (Dollars in thousands) Commercial and industrial — $ — $ — 1 $ 140 $ 140 Commercial real estate — — — 2 632 632 Business banking — — — 3 1,040 1,040 Residential real estate — — — 3 399 399 Consumer home equity — — — 12 527 531 Other consumer 3 35 35 4 58 58 Total 3 $ 35 $ 35 25 $ 2,796 $ 2,800 (1) The post-modification balances represent the balance of the loan on the date of modification. These amounts may show an increase when modification includes capitalization of interest. At September 30, 2021 and December 31, 2020, the outstanding recorded investment of loans that were new TDR loans during the nine months ended September 30, 2021 and the year ended December 31, 2020 was $1.0 million and $3.9 million, r

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	LeasesThe Company leases certain office space and equipment under various non-cancelable operating leases. These leases have original terms ranging from 1 year to 25 years. Operating lease liabilities and right-of-use (“ROU”) assets are recognized at the lease commencement date based upon the present value of the future minimum lease payments over the lease term. Operating lease liabilities are recorded within other liabilities and ROU assets are recorded within other assets in the Company’s consolidated balance sheet. As of the dates indicated, the Company had the following related to operating leases: As of September 30, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 75,196 $ 81,596 Lease liabilities 79,187 85,330 Finance leases are not material. Finance lease liabilities are recorded within other liabilities and finance ROU assets are recorded within other assets in the Company’s consolidated balance sheets. The following tables are a summary of the Company’s components of net lease cost for the periods indicated: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 (In thousands) Operating lease cost $ 3,478 $ 10,560 Finance lease cost 50 116 Variable lease cost 617 1,564 Total lease cost $ 4,145 $ 12,240 Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 (In thousands) Operating lease cost $ 3,596 $ 10,810 Finance lease cost 24 43 Variable lease cost 509 1,479 Total lease cost $ 4,129 $ 12,332 During the three and nine months ended September 30, 2021 the Company made $3.5 million and $10.6 million respectively, in cash payments for operating and finance lease payments. During the three and nine months ended September 30, 2020 the Company made $3.6 million and $10.6 million, respectively, in cash payments for operating and finance lease payments. Supplemental balance sheet information related to operating leases are as follows: As of September 30, 2021 As of December 31, 2020 Weighted-average remaining lease term (in years) 7.96 8.50 Weighted-average discount rate 2.62 % 2.65 %
Leases	LeasesThe Company leases certain office space and equipment under various non-cancelable operating leases. These leases have original terms ranging from 1 year to 25 years. Operating lease liabilities and right-of-use (“ROU”) assets are recognized at the lease commencement date based upon the present value of the future minimum lease payments over the lease term. Operating lease liabilities are recorded within other liabilities and ROU assets are recorded within other assets in the Company’s consolidated balance sheet. As of the dates indicated, the Company had the following related to operating leases: As of September 30, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 75,196 $ 81,596 Lease liabilities 79,187 85,330 Finance leases are not material. Finance lease liabilities are recorded within other liabilities and finance ROU assets are recorded within other assets in the Company’s consolidated balance sheets. The following tables are a summary of the Company’s components of net lease cost for the periods indicated: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 (In thousands) Operating lease cost $ 3,478 $ 10,560 Finance lease cost 50 116 Variable lease cost 617 1,564 Total lease cost $ 4,145 $ 12,240 Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 (In thousands) Operating lease cost $ 3,596 $ 10,810 Finance lease cost 24 43 Variable lease cost 509 1,479 Total lease cost $ 4,129 $ 12,332 During the three and nine months ended September 30, 2021 the Company made $3.5 million and $10.6 million respectively, in cash payments for operating and finance lease payments. During the three and nine months ended September 30, 2020 the Company made $3.6 million and $10.6 million, respectively, in cash payments for operating and finance lease payments. Supplemental balance sheet information related to operating leases are as follows: As of September 30, 2021 As of December 31, 2020 Weighted-average remaining lease term (in years) 7.96 8.50 Weighted-average discount rate 2.62 % 2.65 %

Goodwill and Other Intangibles

Goodwill and Other Intangibles	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other IntangiblesThe following tables set forth the carrying amount of goodwill and other intangible assets, net of accumulated amortization by reporting unit at the dates indicated below: As of September 30, 2021 Banking Insurance Net (In thousands) Balances not subject to amortization Goodwill $ 298,611 $ 73,861 $ 372,472 Balances subject to amortization Insurance agency (1) — 7,234 7,234 Core deposit intangible 66 — 66 Total other intangible assets 66 7,234 7,300 Total goodwill and other intangible assets $ 298,677 $ 81,095 $ 379,772 (1) Insurance agency intangible assets include customer list, non-compete agreement and supplier relationship intangible assets. As of December 31, 2020 Banking Insurance Net (In thousands) Balances not subject to amortization Goodwill $ 298,611 $ 70,866 $ 369,477 Balances subject to amortization Insurance agency (1) — 6,899 6,899 Core deposit intangible 158 — 158 Total other intangible assets 158 6,899 7,057 Total goodwill and other intangible assets $ 298,769 $ 77,765 $ 376,534 (1) Insurance agency intangible assets include customer list, non-compete agreement and supplier relationship intangible assets. The Company acquired two insurance agencies during the nine months ended September 30, 2021. The aggregate purchase price and goodwill recorded as a result of the acquisitions were not material. The Company quantitatively assesses goodwill for impairment at the reporting unit level on an annual basis or sooner if an event occurs or circumstances change which might indicate that the fair value of a reporting unit is below its carrying amount. The Company has identified and assigned goodwill to two reporting units - the banking business and insurance agency business. The quantitative assessments for both the banking business and insurance agency business were most recently performed as of September 30, 2021. The assessment for the banking business included a market capitalization analysis, as well as a comparison of the banking business’ book value to the implied fair value using a pricing multiple of the Company’s tangible book value. The assessment for insurance agency business included a price-to-earnings analysis, as well as an EBITDA multiplier valuation based upon recent and observed agency mergers and acquisitions. The Company considered the economic conditions for the period including the potential impact of the COVID-19 pandemic as it pertains to the goodwill above and determined that there was no indication of impairment related to goodwill as of September 30, 2021 or December 31, 2020. Other intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. The Company also considered the impact of the COVID-19 pandemic as it pertains to these intangible assets and determined that there was no indication of impairment related to other intangible assets as of September 30, 2021 or December 31, 2020.

Earnings Per Share ("EPS")

Earnings Per Share ("EPS")	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings Per Share ("EPS")	Earnings Per Share (“EPS”) Basic EPS represents income available to common shareholders divided by the weighted-average number of common shares outstanding during the period. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common shares (such as stock options) were exercised or converted into additional common shares that would then share in the earnings of the entity. Diluted EPS is computed by dividing net income attributable to common shareholders by the weighted-average number of common shares outstanding for the period, plus the effect of potential dilutive common share equivalents computed using the treasury stock method. There were no securities that had a dilutive effect during the three and nine months ended September 30, 2021, and therefore the weighted-average common shares outstanding used to calculate both basic and diluted EPS are the same. Shares held by the Employee Stock Ownership Plan (“ESOP”) that have not been allocated to employees in accordance with the terms of the ESOP, referred to as “unallocated ESOP shares,” are not deemed outstanding for earnings per share calculations. Earnings per share data is not applicable for the three and nine months ended September 30, 2020 as the Company had no shares outstanding. For the Three Months Ended September 30, 2021 For the Nine Months Ended September 30, 2021 (Dollars in thousands, except per share data) Net income applicable to common shares $ 37,106 $ 119,578 Average number of common shares outstanding 186,758,154 186,758,154 Less: Average unallocated ESOP shares (14,459,539) (14,583,685) Average number of common shares outstanding used to calculate basic earnings per common share 172,298,615 172,174,469 Common stock equivalents — — Average number of common shares outstanding used to calculate diluted earnings per common share 172,298,615 172,174,469 Earnings per common share Basic and diluted $ 0.22 $ 0.69 All unallocated ESOP shares have been excluded from the calculation of basic and diluted EPS.

Low Income Housing Tax Credits

Low Income Housing Tax Credits and Other Tax Credit Investments	9 Months Ended
	Sep. 30, 2021
Investments in Affordable Housing Projects [Abstract]
Low Income Housing Tax Credits and Other Tax Credit Investments	Low Income Housing Tax Credits and Other Tax Credit Investments The Community Reinvestment Act (“CRA”) encourages banks to meet the credit needs of their communities for housing and other purposes, particularly in neighborhoods with low or moderate income. The Company has primarily invested in separate Low Income Housing Tax Credits (“LIHTC”) projects, also referred to as qualified affordable housing projects, which provide the Company with tax credits and operating loss tax benefits over a period of approximately 15 years. The return on these investments is generally generated through tax credits and tax losses. In addition to LIHTC projects, the Company invests in new markets tax credit projects that qualify for CRA credits and eligible projects that qualify for renewable energy and historic tax credits. As of September 30, 2021 and December 31, 2020, the Company had $85.5 million and $59.8 million, respectively, in tax credit investments that were included in other assets in the consolidated balance sheets. When permissible, the Company accounts for its investments in LIHTC projects using the proportional amortization method, under which it amortizes the initial cost of the investment in proportion to the amount of the tax credits and other tax benefits received and recognizes that amortization as a component of income tax expense. The net investment in the housing projects is included in other assets. The Company will continue to use the proportional amortization method on any new qualifying LIHTC investments. The following table presents the Company’s investments in low income housing projects accounted for using the proportional amortization method for the periods indicated: As of September 30, 2021 As of December 31, 2020 (In thousands) Current recorded investment included in other assets $ 82,533 $ 58,504 Commitments to fund qualified affordable housing projects included in recorded investment noted above 49,611 31,487 The following table presents additional information related to the Company's investments in LIHTC projects for the period indicated: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Tax credits and benefits recognized $ 1,730 $ 1,539 $ 4,717 $ 4,597 Amortization expense included in income tax expense 1,496 1,263 4,255 3,715 The Company accounts for certain other investments in renewable energy projects using the equity method of accounting. These investments in renewable energy projects are included in other assets on the consolidated balance sheet and totaled $3.0 million and $1.2 million as of September 30, 2021 and December 31, 2020, respectively. There were no outstanding commitments related to these investments as of September 30, 2021. There was $1.7 million in outstanding commitments related to these investments as of December 31, 2020. During the three months ended September 30, 2020, in reviewing its tax credit equity investments for impairment, the Company identified an immaterial correction to the investment balances primarily related to prior periods. Accordingly, during the three months ended September 30, 2020, the Company wrote off $7.6 million of the tax credit equity investment balances as a component of noninterest expense and other assets to reflect the remaining benefits from these investments. Management evaluated the correction in relation to the three and nine months ended September 30, 2020, as well as the preceding periods in which it originated and believes this correction is immaterial to both the consolidated quarterly and previous annual financial statements. During the three and nine months ended September 30, 2021, the Company performed a similar review and, accordingly, recorded an impairment and (recovery of) impairment as a result of management’s review of its tax credit equity investments for impairment of $1.1 million and $(0.3) million, respectively.

Employee Benefits

Employee Benefits	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Conversion of Defined Benefit Pension Plan and Benefit Equalization Plan to Cash Balance Plan Design Effective November 1, 2020, the Qualified Defined Benefit Pension Plan (“Defined Benefit Plan”) and the Non-Qualified Benefit Equalization Plan (“BEP”) sponsored by the Company were amended to convert the plans from a traditional final average earnings plan design to a cash balance plan design. Benefits earned under the final average earnings plan design were frozen at October 31, 2020. Starting November 1, 2020, future benefits are earned under the cash balance plan design. Under the cash balance plan design, hypothetical account balances are established for each participant and pension benefits are generally stated as the lump sum amount in that hypothetical account. Contribution credits equal to a percentage of a participant’s annual compensation (if the participant works at least 1,000 hours during the year) and interest credits equal to the greater of the 30-Year Treasury rate for September preceding the current plan year or 3.5% are added to a participant’s account each year. For employees hired prior to November 1, 2020, annual contribution credits generally increase as the participant remains employed with the Company. Employees hired on and after November 1, 2020 receive annual contribution credits equal to 5% of annual compensation, with no future increases. Notwithstanding the preceding sentence, since a cash balance plan is a defined benefit plan, the annual retirement benefit payable at normal retirement (age 65) is an annuity, which is the actuarial equivalent of the participant’s account balance under the cash balance plan design, plus their frozen benefit under the final average earnings plan design. However, under the Defined Benefit Plan, participants may elect, with the consent of their spouses if they are married, to have the benefits distributed as a lump sum rather than an annuity. The lump sum is equal to the sum of the actuarial equivalent of their frozen benefit under the final average earnings plan design, plus their cash balance account. Under the BEP, benefits are generally only payable as a lump sum, which is equal to the sum of the actuarial equivalent of their frozen benefit under the final average earnings plan design, plus their cash balance account. Pension Plans The Company provides pension benefits for its employees through membership in the Savings Banks Employees’ Retirement Association. The plan through which benefits are provided is a noncontributory, qualified defined benefit plan. The Company’s annual contribution to the Defined Benefit Plan is based upon standards established by the Pension Protection Act. The contribution is based on an actuarial method intended to provide not only for benefits attributable to service to date, but also for those expected to be earned in the future. The Defined Benefit Plan has a plan year end of October 31. The Company has an unfunded Defined Benefit Supplemental Executive Retirement Plan (“DB SERP”) that provides certain retired and currently employed officers with defined pension benefits in excess of qualified plan limits imposed by U.S. federal tax law. The DB SERP has a plan year end of December 31. In addition, the Company has an unfunded Benefit Equalization Plan, the aforementioned BEP, to provide retirement benefits to certain employees whose retirement benefits under the qualified pension plan are limited per the Internal Revenue Code. The BEP has a plan year end of October 31. The Company also has an unfunded Outside Directors’ Retainer Continuance Plan (“ODRCP”) that provides pension benefits to outside directors who retire from service. The ODRCP has a plan year end of December 31. Effective December 31, 2020, the Company closed the ODRCP to new participants and froze benefit accruals for active participants. Components of Net Periodic Benefit Cost The components of net pension expense for the plans for the periods indicated are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Components of net periodic benefit cost: Service cost $ 7,896 $ 6,231 $ 23,690 $ 18,694 Interest cost 1,269 2,617 3,805 7,849 Expected return on plan assets (8,141) (7,427) (24,424) (22,277) Past service cost (2,945) 7 (8,835) 19 Recognized net actuarial loss 3,537 2,361 10,612 7,082 Net periodic benefit cost $ 1,616 $ 3,789 $ 4,848 $ 11,367 Service costs for the Defined Benefit Plan, the BEP, and the DB SERP are recognized within salaries and employee benefits in the statement of income. Service costs for the ODRCP are recognized within professional services in the statement of income. The remaining components of net periodic benefit cost are recognized in other noninterest expense in the statement of income. The Company’s non-service cost expenses for the Defined Benefit Plan and the BEP decreased by $3.8 million for the three months ended September 30, 2021 compared to the three months ended September 30, 2020 and decreased by $11.5 million for the nine months ended September 30, 2021 compared to the nine months ended September 30, 2020. This was primarily due to the conversion of the Company's Defined Benefit Plan and BEP from a traditional final average earnings plan design to a cash balance plan design. In accordance with the Pension Protection Act, the Company was not required to make any contributions to the Defined Benefit Plan for the plan year beginning November 1, 2020, and did not make any contributions to the Defined Benefit Plan during the nine months ended September 30, 2021. During the three months ended September 30, 2020, there were no contributions made to the Defined Benefit Plan. During the nine months ended September 30, 2020, the Company made contributions to the Defined Benefit Plan of $32.5 million. Rabbi Trust Variable Interest Entity The Company established a rabbi trust to meet its obligations under certain executive non-qualified retirement benefits and deferred compensation plans and to mitigate the expense volatility of the aforementioned retirement plans. The rabbi trust is considered a variable interest entity (“VIE”) as the equity investment at risk is insufficient to permit the trust to finance its activities without additional subordinated financial support from the Company. The Company is considered the primary beneficiary of the rabbi trust as it has the power to direct the activities of the rabbi trust that significantly affect the rabbi trust’s economic performance and it has the obligation to absorb losses of the rabbi trust that could potentially be significant to the rabbi trust by virtue of its contingent call options on the rabbi trust’s assets in the event of the Company’s bankruptcy. As the primary beneficiary of this VIE, the Company consolidates the rabbi trust investments. In general, the rabbi trust investments and any earnings received thereon are accumulated, reinvested and used exclusively for trust purposes. These rabbi trust investments consist primarily of cash and cash equivalents, U.S. government agency obligations, equity securities, mutual funds and other exchange-traded funds, and are recorded at fair value in other assets in the Company's consolidated balance sheet. Changes in fair value are recorded in noninterest income. At September 30, 2021 and December 31, 2020 the amount of rabbi trust investments at fair value were $98.2 million and $91.7 million, respectively. Investments in rabbi trust accounts are recorded at fair value within the Company's consolidated balance sheets with changes in fair value recorded through noninterest income. The following table presents the book value, mark-to-market, and fair value of assets held in rabbi trust accounts by asset type: As of September 30, 2021 As of December 31, 2020 Book Value Mark-to-Market Fair Value Book Value Mark-to-Market Fair Value Asset Type (In thousands) Cash and cash equivalents $ 4,476 $ — $ 4,476 $ 5,157 $ — $ 5,157 Equities 65,670 19,880 85,550 59,235 19,492 78,727 Fixed income 7,976 172 8,148 7,441 358 7,799 Total assets $ 78,122 $ 20,052 $ 98,174 $ 71,833 $ 19,850 $ 91,683

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Financial Instruments with Off-Balance Sheet Risk In order to meet the financing needs of its customers and to reduce its own exposure to fluctuations in interest rates, the Company is party to financial instruments with off-balance sheet risk in the normal course of business. These financial instruments include commitments to extend credit, standby letters of credit, and forward commitments to sell loans, all of which involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the consolidated balance sheets. The contract or notional amounts of those instruments reflect the extent of involvement the Company has in each particular class of financial instruments. Substantially all of the Company’s commitments to extend credit, which normally have fixed expiration dates or termination clauses, are contingent upon customers maintaining specific credit standards at the time of loan funding. Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. In the event the customer does not perform in accordance with the terms of agreement with the third party, the Company would be required to fund the commitment. The maximum potential amount of future payments the Company could be required to make is represented by the contractual amount of the commitment. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. For forward loan sale commitments, the contract or notional amount does not represent exposure to credit loss. The Company does not sell loans with recourse. The following table summarizes the above financial instruments as of the dates indicated: As of September 30, 2021 As of December 31, 2020 (In thousands) Commitments to extend credit $ 4,387,306 $ 3,818,952 Standby letters of credit 58,734 60,221 Forward commitments to sell loans 49,105 41,160 Other Contingencies The Company has been named a defendant in various legal proceedings arising in the normal course of business. Set out below are descriptions of significant legal matters involving the Company and its subsidiaries. In the opinion of management, based on the advice of legal counsel, the ultimate resolution of these proceedings will not have a material effect on the Company’s consolidated financial statements. In the second quarter of 2021, the Company entered into a preliminary settlement of two purported class action matters concerning overdraft and nonsufficient funds fees. The matters were filed in the Massachusetts Superior Court in November 2019 and April 2021, respectively, and are expected to be consolidated into one matter for final settlement purposes. As of September 30, 2021, the Company estimated the settlement expense, including related costs, to be $3.3 million. As a member of the Federal Reserve System, the Bank is required to maintain certain reserves of vault cash and/or deposits with the Federal Reserve Bank of Boston (the “FRBB”). However, in response to the COVID-19 pandemic, the Federal Reserve temporarily eliminated reserve requirements and therefore there was no minimum reserve requirement as of either September 30, 2021 or December 31, 2020.

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2021
Summary of Derivative Instruments [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Company uses derivative financial instruments to manage its interest rate risk resulting from the differences in the amount, timing, and duration of known or expected cash receipts and known or expected cash payments. Additionally, the Company enters into interest rate derivatives and foreign exchange contracts to accommodate the business requirements of its customers (“customer-related positions”) and risk participation agreements entered into as financial guarantees of performance on customer-related interest rate swap derivatives. Derivative instruments are carried at fair value in the Company’s financial statements. The accounting for changes in the fair value of a derivative instrument is dependent upon whether or not the instrument qualifies as a hedge for accounting purposes, and further, by the type of hedging relationship. By using derivatives, the Company is exposed to credit risk to the extent that counterparties to the derivative contracts do not perform as required. Should a counterparty fail to perform under the terms of a derivative contract, the Company’s credit exposure on interest rate swaps is limited to the net positive fair value and accrued interest of all swaps with each counterparty plus any initial margin collateral posted. The Company seeks to minimize counterparty credit risk through credit approvals, limits, monitoring procedures, and obtaining collateral, where appropriate. As such, management believes the risk of incurring credit losses on derivative contracts with those counterparties is remote. Interest Rate Positions An interest rate swap is an agreement whereby one party agrees to pay a floating rate of interest on a notional principal amount in exchange for receiving a fixed rate of interest on the same notional amount, for a predetermined period of time, from a second party. The amounts relating to the notional principal amount are not actually exchanged. The Company may enter into interest rate swaps in which it pays floating and receives fixed interest in order to manage its interest rate risk exposure to the variability in interest cash flows on certain floating-rate commercial loans. For interest rate swaps that are accounted for as cash flow hedges, changes in fair value are included in other comprehensive income and reclassified into net income in the same period or periods during which the hedged forecasted transaction affects net income. As of September 30, 2021 and December 31, 2020, the Company does not have any active interest rate swaps which qualify as cash flow hedges for accounting purposes. Due to the phase-out, and eventual discontinuation, of the LIBOR, central clearinghouses have begun to transition to alternative rates for valuation purposes. As of October 16, 2020, the Company changed its valuation methodology to reflect changes made by the Chicago Mercantile Exchange (“CME”), through which the Company clears derivative financial instruments that are eligible for clearing. The changes from the CME changed the discounting methodology and interest calculation of cash margin from overnight index swap to secured overnight financing rate (also known as SOFR) for U.S. dollar cleared interest rate swaps. The Company believes that its improvements to its valuation methodology will result in valuations for cleared interest rate swaps that better reflect prices obtainable in the markets in which the Company transacts. The changes in valuation methodology were applied prospectively as a change in accounting estimate and are immaterial to the Company’s financial statements. The following table presents the pre-tax impact of terminated cash flow hedges on accumulated other comprehensive income (“AOCI”) for the three and nine months ended September 30, 2021 and September 30, 2020: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Unrealized gains on terminated hedges included in AOCI – beginning of respective period $ 24,980 $ 30,579 $ 41,473 $ — Unrealized gains on terminated hedges arising during the period — 26,410 — 57,362 Reclassification adjustments for amortization of unrealized (gains) into net income (7,851) (7,036) (24,344) (7,409) Unrealized gains on terminated hedges included in AOCI – September 30 $ 17,129 $ 49,953 $ 17,129 $ 49,953 The balance of terminated cash flow hedges in AOCI will be amortized into earnings through January 2023. The Company expects approximately $16.5 million to be reclassified into interest income from other comprehensive income related to the Company’s terminated cash flow hedges in the next 12 months as of September 30, 2021. Customer-Related Positions Interest rate swaps offered to commercial customers do not qualify as hedges for accounting purposes. These swaps allow the Company to retain variable rate commercial loans while allowing the commercial customer to synthetically fix the loan rate by entering into a variable-to-fixed rate interest rate swap. The Company believes that its exposure to commercial customer derivatives is limited to nonperformance by either the customer or the dealer because these contracts are simultaneously matched at inception with an offsetting transaction. Risk participation agreements are entered into as financial guarantees of performance on interest rate swap derivatives. The purchased (asset) or sold (liability) guarantee allow the Company to participate-out (fee paid) or participate-in (fee received) the risk associated with certain derivative positions executed with the borrower by the lead bank in a customer-related interest rate swap derivative. Foreign exchange contracts consist of those offered to commercial customers and those entered into to hedge the Company’s foreign currency risk associated with a foreign-currency loan. Neither qualifies as a hedge for accounting purposes. These commercial customer derivatives are offset with matching derivatives with correspondent-bank counterparties in order to minimize foreign exchange rate risk to the Company. Exposure with respect to these derivatives is largely limited to nonperformance by either the customer or the other counterparty. Neither the Company nor the correspondent-bank counterparty are required to post collateral but each has established foreign-currency transaction limits to manage the exposure risk. The Company requires its customers to post collateral to minimize risk exposure. The following tables present the Company’s customer-related derivative positions as of the dates indicated below for those derivatives not designated as hedging. September 30, 2021 Number of Positions Total Notional (Dollars in thousands) Interest rate swaps 510 $ 3,169,358 Risk participation agreements 66 263,847 Foreign exchange contracts: Matched commercial customer book 52 6,516 Foreign currency loan 4 9,977 December 31, 2020 Number of Positions Total Notional (Dollars in thousands) Interest rate swaps 576 $ 3,652,385 Risk participation agreements 70 287,732 Foreign exchange contracts: Matched commercial customer book 40 4,242 Foreign currency loan 3 10,798 The level of interest rate swaps, risk participation agreements and foreign currency exchange contracts at the end of each period noted above was commensurate with the activity throughout those periods. The table below presents the fair value of the Company’s derivative financial instruments, as well as their classification on the consolidated balance sheet for the periods indicated. There were no derivatives designated as hedging instruments at September 30, 2021 or December 31, 2020. Asset Derivatives Liability Derivatives Balance Fair Value at September 30, Fair Value at December 31, Balance Sheet Fair Value at September 30, Fair Value at December 31, (In thousands) Derivatives not designated as hedging instruments Customer-related positions: Interest rate swaps Other assets $ 80,102 $ 141,822 Other liabilities $ 25,274 $ 42,600 Risk participation agreements Other assets 347 722 Other liabilities 594 1,230 Foreign currency exchange contracts - matched customer book Other assets 44 90 Other liabilities 31 77 Foreign currency exchange contracts - foreign currency loan Other assets 120 9 Other liabilities — 69 Total $ 80,613 $ 142,643 $ 25,899 $ 43,976 The table below presents the net effect of the Company’s derivative financial instruments on the consolidated income statements as well as the effect of the Company’s derivative financial instruments included in other comprehensive income (“OCI”) as follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 (In thousands) Derivatives designated as hedges: (Loss) gain in OCI on derivatives $ — $ (142) $ — $ 46,869 Gain reclassified from OCI into interest income (effective portion) $ 7,851 $ 8,405 $ 24,344 $ 18,651 Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test) Interest income — — — — Other income — — — — Total $ — $ — $ — $ — Derivatives not designated as hedges: Customer-related positions: Gain (loss) recognized in interest rate swap income $ 832 $ 904 $ 4,596 $ (6,063) (Loss) gain recognized in interest rate swap income for risk participation agreements (4) 11 260 (370) Gain (loss) recognized in other income for foreign currency exchange contracts: Matched commercial customer book 8 (86) — (17) Foreign currency loan 72 149 181 179 Total gain (loss) for derivatives not designated as hedges $ 908 $ 978 $ 5,037 $ (6,271) The Company has agreements with its customer-related interest rate swap derivative counterparties that contain a provision whereby if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations. The Company also has agreements with certain of its customer-related interest rate swap derivative correspondent-bank counterparties that contain a provision whereby if the Company fails to maintain its status as a well-capitalized institution, then the counterparty could terminate the derivative positions and the Company would be required to settle its obligations under the agreements. The Company’s exposure related to its customer-related interest rate swap derivatives consists of exposure on cleared derivative transactions and exposure on non-cleared derivative transactions. Cleared derivative transactions are with CME and exposure is settled to market daily, with additional credit exposure related to initial-margin collateral pledged to CME at trade execution. At September 30, 2021, the Company had no exposure to CME for settled variation margin in excess of the customer-related interest rate swap termination values. At December 31, 2020, the Company’s exposure to CME for settled variation margin in excess of the customer-related interest rate swap termination values was less than $0.1 million. In addition, at September 30, 2021 and December 31, 2020, the Company had posted initial-margin collateral in the form of a U.S. Treasury note amounting to $49.4 million and $60.4 million, respectively, to CME for these derivatives. The U.S. Treasury note was considered a restricted asset and was included in available for sale securities within the Company's consolidated balance sheets. At September 30, 2021 and December 31, 2020 the fair value of all customer-related interest rate swap derivatives with credit-risk related contingent features that were in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, totaled $21.7 million and $42.6 million, respectively. The Company has minimum collateral posting thresholds with its customer-related interest rate swap derivative correspondent-bank counterparties to the extent that the Company has a liability position with the correspondent-bank counterparties. At September 30, 2021 and December 31, 2020, the Company had posted collateral in the form of cash amounting to $27.8 million and $49.2 million, respectively, which was considered to be a restricted asset and was included in other short-term investments within the Company's consolidated balance sheets. If the Company had breached any of these provisions at September 30, 2021 or December 31, 2020, it would have been required to settle its obligations under the agreements at the termination value. In

Balance Sheet Offsetting

Balance Sheet Offsetting	9 Months Ended
	Sep. 30, 2021
Offsetting [Abstract]
Balance Sheet Offsetting	Balance Sheet Offsetting Certain financial instruments, including derivatives, may be eligible for offset in the consolidated balance sheets and/or subject to master netting arrangements or similar agreements. The Company’s derivative transactions with upstream financial institution counterparties are generally executed under International Swaps and Derivative Association master agreements which include “right of set-off” provisions. In such cases there is generally a legally enforceable right to offset recognized amounts. However, the Company does not offset fair value amounts recognized for derivative instruments. The Company nets the amount recognized for the right to reclaim cash collateral against the obligation to return cash collateral arising from derivative instruments executed with the same counterparty under a master netting arrangement. Collateral legally required to be maintained at dealer banks by the Company is monitored and adjusted as necessary. As of September 30, 2021 and December 31, 2020, it was determined that no additional collateral would have to be posted to immediately settle these instruments. The following tables present the Company’s asset and liability positions that were eligible for offset and the potential effect of netting arrangements on its consolidated balance sheet, as of the dates indicated: As of September 30, 2021 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Customer-related positions: Interest rate swaps $ 80,102 $ — $ 80,102 $ 859 $ — $ 79,243 Risk participation agreements 347 — 347 — — 347 Foreign currency exchange contracts – matched customer book 44 — 44 — — 44 Foreign currency exchange contracts – foreign currency loan 120 — 120 — — 120 $ 80,613 $ — $ 80,613 $ 859 $ — $ 79,754 Derivative Liabilities Customer-related positions: Interest rate swaps $ 25,274 $ — $ 25,274 $ 859 $ 24,415 $ — Risk participation agreements 594 — 594 — — 594 Foreign currency exchange contracts – matched customer book 31 — 31 — — 31 Foreign currency exchange contracts – foreign currency loan — — — — — — $ 25,899 $ — $ 25,899 $ 859 $ 24,415 $ 625 As of December 31, 2020 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Customer-related positions: Interest rate swaps $ 141,822 $ — $ 141,822 $ 48 $ — $ 141,774 Risk participation agreements 722 — 722 — — 722 Foreign currency exchange contracts – matched customer book 90 — 90 — (1) 89 Foreign currency exchange contracts – foreign currency loan 9 — 9 — — 9 $ 142,643 $ — $ 142,643 $ 48 $ (1) $ 142,594 Derivative Liabilities Customer-related positions: Interest rate swaps $ 42,600 $ — $ 42,600 $ 48 $ 42,552 $ — Risk participation agreements 1,230 — 1,230 — — 1,230 Foreign currency exchange contracts – matched customer book 77 — 77 — — 77 Foreign currency exchange contracts – foreign currency loan 69 — 69 — — 69 $ 43,976 $ — $ 43,976 $ 48 $ 42,552 $ 1,376

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities The Company uses fair value measurements to record adjustments to certain assets and liabilities and to determine fair value disclosures. The fair value of a financial instrument is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various financial instruments. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument. Fair value is a market-based measure considered from the perspective of a market participant rather than an entity-specific measure. Therefore, even when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that the Company believes market participants would use in pricing the asset or liability at the measurement date. The Company uses prices and inputs that are current as of the measurement date, including during periods of market dislocation. In periods of market dislocation, the observability of prices and inputs may be reduced for many instruments. This condition could cause an instrument to be reclassified from Level 1 to Level 2 or from Level 2 to Level 3. Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Because no active market exists for a portion of the Company’s financial instruments, fair value estimates are based on judgements regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgement, and therefore cannot be determined with precision. Changes in assumptions could significantly affect these estimates. The following methods and assumptions were used by the Company in estimating fair value disclosures: Cash and Cash Equivalents For these financial instruments, which have original maturities of 90 days or less, their carrying amounts reported in the consolidated balance sheets approximate fair value. Available for Sale Securities Available for sale securities recorded at fair value consisted of U.S. Treasury securities, U.S. government-sponsored residential and commercial mortgage-backed securities, U.S. Agency bonds, and state and municipal bonds. The Company’s U.S. Treasury securities are traded on active markets and therefore these securities were classified as Level 1. The fair value of U.S. Agency bonds are evaluated using relevant trade data, benchmark quotes and spreads obtained from publicly available trade data, and generated on a price, yield or spread basis as determined by the observed market data. Therefore, these securities were categorized as Level 2 given the use of observable inputs. The fair value of U.S. government-sponsored residential and commercial mortgage-backed securities were estimated using either a matrix or benchmarks. The inputs used include benchmark yields, reported trades, broker/dealer quotes, and issuer spreads. Therefore, these securities were categorized as Level 2 given the use of observable inputs. The fair value of state and municipal bonds were estimated by a third-party pricing vendor using a valuation matrix with inputs including observable bond interest rate tables, recent transactions, and yield relationships. Therefore, these securities were categorized as Level 2 given the use of observable inputs. Fair value was based on the value of one unit without regard to any premium or discount that may result from concentrations of ownership of a financial instrument, possible tax ramifications, or estimated transaction costs. The estimated fair value of the Company’s securities available for sale, by type, is disclosed in the Securities footnote. Loans Held for Sale The fair value of loans held for sale, whose carrying amounts approximate fair value, was estimated using the anticipated market price based upon pricing indications provided by investor banks. These assets were classified as Level 2 given the use of observable inputs. Loans The fair value of commercial construction, commercial and industrial lines of credit, and certain other consumer loans was estimated by discounting the contractual cash flows using interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. For commercial, commercial real estate, residential real estate, automobile, and consumer home equity loans, fair value was estimated by discounting contractual cash flows adjusted for prepayment estimates using interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The fair value of PPP loans, which are fully guaranteed by the SBA, approximates the carrying amount. Loans that are deemed to be impaired were recorded at the fair value of the underlying collateral, if the loan is collateral-dependent, or at a carrying value based upon expected cash flows discounted using the loan’s effective interest rate. Loans are classified as Level 3 since the valuation methodology utilizes significant unobservable inputs. FHLB Stock The fair value of FHLB stock approximates the carrying amount based on the redemption provisions of the FHLB. These assets were classified as Level 2. Rabbi Trust Investments Rabbi trust investments consisted primarily of cash and cash equivalents, U.S. government agency obligations, equity securities, mutual funds and other exchange-traded funds, and were recorded at fair value and included in other assets. The purpose of these rabbi trust investments is to fund certain executive non-qualified retirement benefits and deferred compensation. The fair value of other U.S. government agency obligations was estimated using either a matrix or benchmarks. The inputs used include benchmark yields, reported trades, broker/dealer quotes, and issuer spreads. These securities were categorized as Level 2 given the use of observable inputs. The equity securities, mutual funds and other exchange-traded funds were valued based on quoted prices from the market. The equities, mutual funds and exchange-traded funds traded in an active market were categorized as Level 1 as they were valued based upon quoted prices from the market. Mutual funds at net asset value amounted to $55.1 million at September 30, 2021 and $53.9 million at December 31, 2020. There were no redemption restrictions on these mutual funds at the end of any period presented. Bank-Owned Life Insurance The fair value of bank-owned life insurance was based upon quotations received from bank-owned life insurance dealers. These assets were classified as Level 2 given the use of observable inputs. Deposits The fair value of deposits with no stated maturity, such as noninterest-bearing demand deposits, savings and interest checking accounts, and money market accounts, was equal to their carrying amount. The fair value of time deposits was based on the discounted value of contractual cash flows using current market interest rates. Deposits were classified as Level 2 given the use of observable market inputs. The fair value estimates of deposits do not include the benefit that results from the low-cost funding provided by the deposit liabilities compared to the cost of borrowing funds in the wholesale market (core deposit intangibles). FHLB Advances The fair value of FHLB advances was based on the discounted value of contractual cash flows. The discount rates used are representative of approximate rates currently offered on instruments with similar remaining maturities. FHLB advances were classified as Level 2. Escrow Deposits of Borrowers The fair value of escrow deposits of borrowers, which have no stated maturity, approximates the carrying amount. Escrow deposits of borrowers were classified as Level 2. Interest Rate Swaps The fair value of interest rate swaps was determined using discounted cash flow analysis on the expected cash flows of the interest rate swaps. This analysis reflects the contractual terms of the interest rate swaps, including the period of maturity, and uses observable market-based inputs, including interest rate curves and implied volatility. In addition, for customer-related interest rate swaps, the analysis reflects a credit valuation adjustment to reflect the Company’s own non-performance risk and the respective counterparty’s non-performance risk in the fair value measurements. The majority of inputs used to value its interest rate swaps fall within Level 2 of the fair value hierarchy, but the credit valuation adjustments associated with the interest rate swaps utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. However, at September 30, 2021 and December 31, 2020, the impact of the Level 3 inputs on the overall valuation of the interest rate swaps was deemed insignificant to the overall valuation. As a result, the interest rate swaps were categorized as Level 2 within the fair value hierarchy. Risk Participations The fair value of risk participations was determined based upon the total expected exposure of the derivative which considers the present value of cash flows discounted using market-based inputs and were therefore categorized as Level 2 within the fair value hierarchy. The fair value also included a credit valuation adjustment which evaluates the credit risk of its counterparties by considering factors such as the likelihood of default by the counterparties, its net exposures, the remaining contractual life, as well as the amount of collateral securing the position. The change in value of derivative assets and liabilities attributable to credit risk was not significant during the reported periods. Foreign Currency Forward Contracts The fair values of foreign currency forward contracts were based upon the remaining expiration period of the contracts and bid quotations received from foreign exchange contract dealers and were categorized as Level 2 within the fair value hierarchy. Fair Value of Assets and Liabilities Measured on a Recurring Basis The following tables present the balances of assets and liabilities measured at fair value on a recurring basis as of September 30, 2021 and December 31, 2020: Fair Value Measurements at Reporting Date Using Balance as of September 30, 2021 Quoted Prices in Significant Significant Description (In thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 4,073,368 $ — $ 4,073,368 $ — Government-sponsored commercial mortgage-backed securities 431,009 — 431,009 — U.S. Agency bonds 841,283 — 841,283 — U.S. Treasury securities 69,182 69,182 — — State and municipal bonds and obligations 274,470 — 274,470 — Rabbi trust investments 98,174 90,026 8,148 — Loans held for sale 1,757 — 1,757 — Interest rate swap contracts Customer-related positions 80,102 — 80,102 — Risk participation agreements 347 — 347 — Foreign currency forward contracts Matched customer book 44 — 44 — Foreign currency loan 120 — 120 — Total $ 5,869,856 $ 159,208 $ 5,710,648 $ — Liabilities Interest rate swap contracts Customer-related positions $ 25,274 $ — $ 25,274 $ — Risk participation agreements 594 — 594 — Foreign currency forward contracts Matched customer book 31 — 31 — Foreign currency loan — — — — Total $ 25,899 $ — $ 25,899 $ — Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices in Significant Significant (In thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 2,148,800 $ — $ 2,148,800 $ — Government-sponsored commercial mortgage-backed securities 17,081 — 17,081 — U.S. Agency bonds 666,709 — 666,709 — U.S. Treasury securities 70,369 70,369 — — State and municipal bonds and obligations 280,902 — 280,902 — Rabbi trust investments 91,683 83,884 7,799 — Loans held for sale 1,140 — 1,140 — Interest rate swap contracts Customer-related positions 141,822 — 141,822 — Risk participation agreements 722 — 722 — Foreign currency forward contracts Matched customer book 90 — 90 — Foreign currency loan 9 — 9 — Total $ 3,419,327 $ 154,253 $ 3,265,074 $ — Liabilities Interest rate swap contracts Customer-related positions $ 42,600 $ — $ 42,600 $ — Risk participation agreements 1,230 — 1,230 — Foreign currency forward contracts Matched customer book 77 — 77 — Foreign currency loan 69 — 69 — Total $ 43,976 $ — $ 43,976 $ — There were no transfers to or from Level 1, 2 and 3 during the nine months ended September 30, 2021 and year ended December 31, 2020. The Company held no assets or liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) as of September 30, 2021 or December 31, 2020. Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis The Company may also be required, from time to time, to measure certain other assets on a nonrecurring basis in accordance with generally accepted accounting principles. The following tables summarize the fair value of assets and liabilities measured at fair value on a nonrecurring basis, as of September 30, 2021 and December 31, 2020. Fair Value Measurements at Reporting Date Using Description Balance as of September 30, 2021 Quoted Prices Significant Significant (In thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 15,484 $ — $ — $ 15,484 Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices Significant Significant (In thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 11,036 $ — $ — 11,036 For the valuation of the collateral-dependent impaired loans, the Company relies primarily on third-party valuation information from certified appraisers and values are generally based upon recent appraisals of the underlying collateral, brokers’ opinions based upon recent sales of comparable properties, estimated equipment auction or liquidation values, income capitalization, or a combination of income capitalization and comparable sales. Depending on the type of underlying collateral, valuations may be adjusted by management for qualitative factors such as economic factors and estimated liquidation expenses. The range of these possible adjustments may vary. Impaired loans in which a reserve was established based upon expected cash flows discounted at the loan’s effective interest rate are not deemed to be measured at fair value. Disclosures about Fair Value of Financial Instruments The estimated fair values and related carrying amounts for assets and liabilities for which fair value is only disclosed are shown below as of the dates indicated: Fair Value Measurements at Reporting Date Using Description Carrying Value as of September 30, 2021 Fair Value as of September 30, 2021 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,378,060 $ 9,512,887 $ — $ — $ 9,512,887 FHLB stock 10,601 10,601 — 10,601 — Bank-owned life insurance 79,259 79,259 — 79,259 — Liabilities Deposits $ 13,649,964 $ 13,649,818 $ — $ 13,649,818 $ — FHLB advances 14,172 13,728 — 13,728 — Escrow deposits from borrowers 15,900 15,900 — 15,900 — Fair Value Measurements at Reporting Date Using Description Carrying Value as of December 31, 2020 Fair Value as of December 31, 2020 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,593,958 $ 9,779,195 $ — $ — $ 9,779,195 FHLB stock 8,805 8,805 — 8,805 — Bank-owned life insurance 78,561 78,561 — 78,561 — Liabilities Deposits $ 12,155,784 $ 12,155,843 $ — $ 12,155,843 $ — FHLB advances 14,624 14,434 — 14,434 — Escrow deposits from borrowers 13,425 13,425 — 13,425 — This summary excludes certain financial assets and liabilities for which the carrying value approximates fair value. For financial assets, these may include cash and due from banks, federal funds sold and short-term investments. For financial liabilities, these may include federal funds purchased. These instruments would all be considered to be classified as Level 1 within the fair value hierarchy. Also excluded from the summary are financial instruments measured at fair value on a recurring and nonrecurring basis, as previously described.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers Revenue from contracts with customers within the scope of ASC 606, Revenue from Contracts with Customers (Topic 606) (“ASC 606”) is recognized when control of goods or services is transferred to the customer, in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company considers the terms of the contract and all relevant facts and circumstances when applying this guidance. The Company measures revenue and timing of recognition by applying the following five steps: 1. Identify the contract(s) with the customers 2. Identify the performance obligations 3. Determine the transaction price 4. Allocate the transaction price to the performance obligations 5. Recognize revenue when (or as) the entity satisfies a performance obligation The Company accounts for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance and collectability of consideration is probable. Performance obligations The Company’s performance obligations are generally satisfied either at a point in time or over time, as services are rendered. Unsatisfied performance obligations at the report date are not material to the Company’s consolidated financial statements. A portion of the Company's noninterest income is derived from contracts with customers within the scope of ASC 606. The Company has disaggregated such revenues by type of service, as presented in the table below. These categories reflect how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Insurance commissions $ 21,956 $ 21,884 $ 73,767 $ 72,058 Service charges on deposit accounts 5,935 5,052 17,010 15,514 Trust and investment advisory fees 6,310 5,311 18,047 15,600 Debit card processing fees 3,030 2,721 8,949 7,528 Other noninterest income 2,318 1,689 6,233 5,226 Total noninterest income in-scope of ASC 606 39,549 36,657 124,006 115,926 Total noninterest income out-of-scope of ASC 606 3,660 11,052 20,148 12,809 Total noninterest income $ 43,209 $ 47,709 $ 144,154 $ 128,735 Additional information related to each of the revenue streams is further noted below. Insurance Commissions The Company acts as an agent in offering property, casualty, and life and health insurance to both commercial and consumer customers though Eastern Insurance Group. The Company earns a fixed commission on the sales of these products and services. The Company may also earn bonus commissions based upon meeting certain volume thresholds. In general, the Company recognizes commission revenues when earned based upon the effective date of the policy. For certain insurance products, the Company may also earn and recognize annual residual commissions commensurate with annual premiums being paid. The Company also earns profit-sharing, or contingency revenues, from the insurers with whom the Company places business. These profit-sharing revenues are performance bonuses from the insurers based upon certain performance metrics such as floors on written premiums, loss rates, and growth rates. Because the Company’s expectation of the ultimate profit-sharing revenue amounts to be earned can vary from period to period, the Company does not recognize this revenue until it has concluded that, based on all the facts and information available, it is probable that a significant revenue reversal will not occur in future periods. Insurance commissions earned but not yet received amounted to $14.0 million as of September 30, 2021, and $15.8 million as of December 31, 2020, and were included in other assets. Deposit Service Charges The Company offers various deposit account products to its customers governed by specific deposit agreements applicable to either personal customers or business customers. These agreements identify the general conditions and obligations of both parties and include standard information regarding deposit account-related fees. Deposit account services include providing access to deposit accounts as well as access to the various deposit transactional services of the Company. These transactional services are primarily those that are identified in the standard fee schedule, and include, but are not limited to, services such as overdraft protection, wire transfer, and check collection. The Company may charge monthly fixed service fees associated with the customer having access to the deposit account as well as separate fixed fees associated with and at the time specific transactions are entered into by the customer. As such, the Company considers that its performance obligations are fulfilled when customers are provided deposit account access or when the requested deposit transaction is completed. Cash management services are a subset of the deposit service charges revenue stream. These services include automated clearing house, or ACH, transaction processing, positive pay, lockbox, and remote deposit services. These services are also governed by separate agreements entered into by the customer. The fee arrangement for these services is structured as a fixed fee per transaction which may be offset by earnings credits. An earnings credit is a discount that a customer receives based upon the investable balance in the applicable covered deposit account(s) for a given month. Earnings credits are only good for the given month. That is, if cash management fees for a given month are less than the month’s earnings credit, the remainder of the credit does not carry over to the following month. Cash management fees are recognized as revenue in the month that the services are provided. Cash management fees earned but not yet received amounted to $0.9 million and $1.0 million as of September 30, 2021 and December 31, 2020 and were included in other assets. Trust and Investment Advisory Fees The Company offers investment management and trust services to individuals, institutions, small businesses and charitable institutions. Each investment management product is governed by its own contract along with a separate identifiable fee schedule unique to that product. The Company also offers additional services, such as estate settlement, financial planning, tax services, and other special services quoted at the customer’s request. The asset management and/or custody fees are primarily based upon a percentage of the monthly valuation of the principal assets in the customer’s account. Customers are also charged a base fee which is prorated over a 12-month period. Fees for additional or special services are generally fixed in nature and are charged as services are rendered. All revenue is recognized in correlation to the monthly management fee determinations or as transactional services are provided. Debit Card Processing Fees The Company provides debit cards to its customers which are authorized and settled through various card payment networks, and in exchange, the Company earns revenue as determined by each payment network’s interchange program. Regardless of the network that is utilized to authorize and settle the payment, the merchant that provides the product or service to the debit card holder is ultimately responsible for the interchange payment to the Company. Debit card processing fees are recognized as card transactions are settled within each network. Debit card processing fees earned but not yet received amounted to $0.3 million as of both September 30, 2021 and December 31, 2020 and were included in other assets. Other Noninterest Income The Company earns various types of other noninterest income that have been aggregated into one general revenue stream in the table noted above. Noninterest income includes, but is not limited to, the following types of revenue with customers: safe deposit rent, ATM surcharge fees and customer checkbook fees. Individually, these sources of noninterest income are immaterial.

Other Comprehensive Income

Other Comprehensive Income	9 Months Ended
	Sep. 30, 2021
Statement of Other Comprehensive Income [Abstract]
Other Comprehensive Income	Other Comprehensive Income The following tables present a reconciliation of the changes in the components of other comprehensive (loss) income for the dates indicated including the amount of income tax (expense) benefit allocated to each component of other comprehensive (loss) income: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Pre Tax Tax After Tax Pre Tax Tax After Tax (In thousands) Unrealized losses on securities available for sale: Change in fair value of securities available for sale $ (27,741) $ 6,132 $ (21,609) $ (90,088) $ 19,911 $ (70,177) Less: reclassification adjustment for gains included in net income 1 — 1 1,166 (257) 909 Net change in fair value of securities available for sale (27,742) 6,132 (21,610) (91,254) 20,168 (71,086) Unrealized gains (losses) on cash flow hedges: Change in fair value of cash flow hedges — — — — — — Less: net cash flow hedge gains reclassified into interest income (1) 7,851 (2,207) 5,644 24,344 (6,843) 17,501 Net change in fair value of cash flow hedges (7,851) 2,207 (5,644) (24,344) 6,843 (17,501) Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (3,537) 994 (2,543) (10,612) 2,983 (7,629) Less: accretion of prior service cost 2,945 (828) 2,117 8,835 (2,484) 6,351 Net change in other comprehensive income for defined benefit postretirement plans 592 (166) 426 1,777 (499) 1,278 Total other comprehensive loss $ (35,001) $ 8,173 $ (26,828) $ (113,821) $ 26,512 $ (87,309) (1) Represents amortization of realized gains on terminated cash flow hedges for the three and nine months ended September 30, 2021. The total realized gain of $41.2 million, net of tax, will be recognized in earnings through January 2023. The balance of this gain had amortized to $12.3 million, net of tax, at September 30, 2021. Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Pre Tax Tax After Tax Pre Tax Tax After Tax (In thousands) Unrealized (losses) gains on securities available for sale: Change in fair value of securities available for sale $ (5,563) $ 1,242 $ (4,321) $ 28,750 $ (6,370) $ 22,380 Less: reclassification adjustment for gains included in net income — — — 285 (63) 222 Net change in fair value of securities available for sale (5,563) 1,242 (4,321) 28,465 (6,307) 22,158 Unrealized (losses) gains on cash flow hedges: Change in fair value of cash flow hedges (142) 40 (102) 46,869 (13,175) 33,694 Less: net cash flow hedge gains reclassified into interest income (1) 8,405 (2,363) 6,042 18,651 (5,243) 13,408 Net change in fair value of cash flow hedges (8,547) 2,403 (6,144) 28,218 (7,932) 20,286 Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (2,361) 664 (1,697) (7,082) 1,990 (5,092) Less: amortization of prior service cost (7) 2 (5) (19) 5 (14) Net change in other comprehensive income for defined benefit postretirement plans 2,368 (666) 1,702 7,101 (1,995) 5,106 Total other comprehensive (loss) income $ (11,742) $ 2,979 $ (8,763) $ 63,784 $ (16,234) $ 47,550 (1) Includes amortization of $5.1 million and $5.3 million of the remaining balance of realized but unrecognized gains, net of tax, on terminated cash flow hedges for the three and nine months ended September 30, 2020, respectively. The original realized gain of $41.2 million, net of tax, will be recognized in earnings through January 2023. The balance of this gain had amortized to $35.9 million, net of tax, at September 30, 2020. The following table illustrates the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax: Unrealized Unrealized Defined Benefit Total (In thousands) Beginning Balance: January 1, 2021 $ 45,672 $ 29,815 $ (21,253) $ 54,234 Other comprehensive loss before reclassifications (70,177) — — (70,177) Less: Amounts reclassified from accumulated other comprehensive income 909 17,501 (1,278) 17,132 Net current-period other comprehensive (loss) income (71,086) (17,501) 1,278 (87,309) Ending Balance: September 30, 2021 $ (25,414) $ 12,314 $ (19,975) $ (33,075) Beginning Balance: January 1, 2020 $ 21,798 $ 15,624 $ (81,269) $ (43,847) Other comprehensive income before reclassifications 22,380 33,694 — 56,074 Less: Amounts reclassified from accumulated other comprehensive income (loss) 222 13,408 (5,106) 8,524 Net current-period other comprehensive income 22,158 20,286 5,106 47,550 Ending Balance: September 30, 2020 $ 43,956 $ 35,910 $ (76,163) $ 3,703

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s primary reportable segment is its banking business, which offers a range of commercial, retail, wealth management and banking services, and consists primarily of attracting deposits from the general public and investing those deposits, together with borrowings and funds generated from operations, to originate loans in a variety of sectors and to invest in securities. Revenue from the banking business consists primarily of interest earned on loans and investment securities. In addition to its banking business reportable segment, the Company has an insurance agency business reportable segment, which consists of insurance-related activities, acting as an independent agent in offering commercial, personal and employee benefits insurance products to individual and commercial clients. Revenue from the insurance agency business consists primarily of commissions on sales of insurance products and services. Results of operations and selected financial information by segment and reconciliation to the consolidated financial statements as of and for the three months ended September 30, 2021 and 2020, and for the nine months ended September 30, 2021 and 2020, was as follows: As of and for the three months ended September 30, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 102,691 $ — $ — $ 102,691 $ 98,742 $ — $ — $ 98,742 (Release of) provision for loan losses (1,488) — — (1,488) 700 — — 700 Net interest income after provision for loan losses 104,179 — — 104,179 98,042 — — 98,042 Noninterest income 20,783 22,508 (82) 43,209 25,288 22,571 (150) 47,709 Noninterest expense 80,474 19,538 (1,042) 98,970 91,509 19,506 (1,198) 109,817 Income before provision for income taxes 44,488 2,970 960 48,418 31,821 3,065 1,048 35,934 Income tax provision 10,471 841 — 11,312 6,561 868 — 7,429 Net income $ 34,017 $ 2,129 $ 960 $ 37,106 $ 25,260 $ 2,197 $ 1,048 $ 28,505 Total assets $ 17,324,816 $ 207,996 $ (71,589) $ 17,461,223 $ 15,332,420 $ 202,319 $ (74,145) $ 15,460,594 Total liabilities $ 14,051,100 $ 52,420 $ (71,589) $ 14,031,931 $ 13,761,414 $ 59,953 $ (74,145) $ 13,747,222 For the nine months ended September 30, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 307,390 $ — $ — $ 307,390 $ 297,643 $ — $ — $ 297,643 (Release of) provision for loan losses (5,368) — — (5,368) 37,900 — — 37,900 Net interest income after provision for loan losses 312,758 — — 312,758 259,743 — — 259,743 Noninterest income 69,308 74,959 (113) 144,154 55,935 72,979 (179) 128,735 Noninterest expense 243,549 59,844 (3,039) 300,354 251,688 57,231 (3,165) 305,754 Income before provision for income taxes 138,517 15,115 2,926 156,558 63,990 15,748 2,986 82,724 Income tax provision 32,728 4,252 — 36,980 11,468 4,456 — 15,924 Net income $ 105,789 $ 10,863 $ 2,926 $ 119,578 $ 52,522 $ 11,292 $ 2,986 $ 66,800

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Equity Incentive Plan On October 1, 2021, our Board of Directors approved the Eastern Bankshares Inc. 2021 Equity Incentive Plan (the “2021 Equity Plan”). The 2021 Equity Plan will become effective on November 29, 2021 if shareholders approve the 2021 Equity Plan at the special meeting of shareholders to be held on that date. The 2021 Equity Plan provides for the grant of restricted stock, restricted stock units, non-qualified stock options, and incentive stock options, any or all of which can be granted with performance-based vesting conditions. Incentive stock options may only be granted to employees of the Company’s subsidiaries and affiliates. No awards have been made under the 2021 Equity Plan. However, initial awards to our non-employee directors are set forth in the 2021 Equity Plan and will be self-executing on the day following the approval of the Plan by shareholders, if such approval is received. The estimated aggregate amount of the initial grants to non-employee directors is approximately $13.75 million which is comprised of an individual grant amount to each non-employee director that is not to exceed $1.25 million. These amounts are based upon the fair market value of the Company’s common stock on October 1, 2021. The actual value of the awards, and the number of shares underlying such awards, is not determinable as their value will depend upon the fair market value of the Company’s common stock on the date of the grant. Share Repurchases On October 28, 2021, the Company announced that its Board of Directors has approved a stock repurchase program pursuant to which the Company may purchase up to 9,337,900 shares, or 5% of the Company’s outstanding shares of common stock over a 12-month period. The authorization is contingent upon the non-objection from the Federal Reserve. The Company’s request for non-objection is pending. The Company is unable to predict whether the Federal Reserve will permit the Company to implement the proposed repurchase program in whole or part, whether the Federal Reserve will impose one or more related conditions on the Company, or the timing of such non-objection, if granted. If non-objection is granted by the Federal Reserve, repurchases will be made at management’s discretion from time to time at prices management considers to be attractive and in the best interests of both the Company and its shareholders, subject to the availability of shares, general market conditions, the trading price of the shares, alternative uses for capital, and the Company’s financial performance. Repurchases may be suspended, terminated or modified by the Company at any time for any reason.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) as set forth by the Financial Accounting Standards Board (“FASB”) and its Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) as well as the rules and interpretive releases of the Securities and Exchange Commission (“SEC”) under the authority of federal securities laws. The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries and entities in which it holds a controlling financial interest through being the primary beneficiary or through holding a majority of the voting interest. All intercompany accounts and transactions have been eliminated in consolidation. Certain previously reported amounts have been reclassified to conform to the current period’s presentation. The accompanying consolidated balance sheet as of September 30, 2021, the consolidated statements of income and comprehensive income and of changes in equity for the three and nine months ended September 30, 2021 and 2020 and statement of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The consolidated balance sheet as of December 31, 2020 was derived from the audited consolidated financial statements as of that date. The interim consolidated financial statements and the accompanying notes should be read in conjunction with the annual consolidated financial statements and the accompanying notes contained within the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 (“2020 Form 10-K”), as filed with the SEC. In the opinion of management, the Company’s consolidated financial statements reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.
Use of Estimates	Use of EstimatesIn preparing the Consolidated Financial Statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheets and income and expenses for the periods reported. Actual results could differ from those estimates based on changing conditions, including economic conditions and future events. Material estimates that are particularly susceptible to change relate to the determination of the allowance for loan losses, valuation and fair value measurements, other-than-temporary impairment on investment securities, the liabilities for benefit obligations (particularly pensions), the provision for income taxes and impairment of goodwill and other intangibles.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Company qualifies as an emerging growth company under the Jumpstart Our Business Act of 2012 (“JOBS Act”) and has elected to defer the adoption of new or revised accounting standards until the nonpublic company effective dates. Relevant standards that were recently issued but not yet adopted as of September 30, 2021: In March 2020, the FASB issued ASU 2020-4, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”). This update addresses optional expedients and exceptions for applying GAAP to certain contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The new guidance applies only to contracts, hedging relationships, and other transactions that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued because of reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made and hedging relationships existing as of December 31, 2022, that an entity has elected certain optional expedients for and that are retained through the end of the hedging relationship. For public and nonpublic entities, the guidance is effective as of March 12, 2020 through December 31, 2022 and does not apply to contract modifications made after December 31, 2022. The Company will adopt this standard on the nonpublic company effective date and is currently in the process of reviewing its contracts and existing processes in order to assess the risks and potential impact of the transition away from LIBOR. In June 2016, the FASB issued ASU 2016-13, Financial Instruments–Credit Losses on Financial Instruments and relevant amendments (Topic 326) (“ASU 2016-13”). This update was created to replace the current GAAP method of calculating credit losses. Specifically, the standard replaces the existing incurred loss impairment guidance by requiring immediate recognition of expected credit losses. For financial assets carried at amortized cost that are held at the reporting date (including trade and other receivables, loans and commitments, held-to-maturity debt securities and other financial assets), credit losses are measured based on historical experience, current conditions and reasonable supportable forecasts. The standard also amends existing impairment guidance for available for sale securities, in which credit losses will be recorded as an allowance versus a write-down of the amortized cost basis of the security. It will also allow for a reversal of impairment loss when the credit of the issuer improves. The guidance requires a cumulative effect of the initial application to be recognized in retained earnings at the date of initial application. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments – Credit Losses (“ASU 2018-19”). The amendments in ASU 2018-19 were intended to clarify that receivables arising from operating leases are not within the scope of Subtopic 326-20. Instead, impairment of receivables arising from operating leases should be accounted for in accordance with Topic 842, Leases . In November 2019, the FASB issued ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments – Credit Losses . This update requires entities to include expected recoveries of the amortized cost basis previously written off or expected to be written off in the valuation account for purchased financial assets with credit deterioration. In addition, the amendments in this update clarify and improve various aspects of the guidance for ASU 2016-13. For public entities that meet the definition of an SEC filer (excluding smaller reporting entities) the guidance is effective for annual reporting periods beginning after December 15, 2019. Early adoption is permitted for all entities as of the fiscal years beginning after December 15, 2018. For all other entities, the guidance is effective for annual reporting periods beginning after December 15, 2022, including interim periods within those fiscal years. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was enacted in response to the COVID-19 pandemic in the United States. to provide economic relief measures including the option to defer adoption of ASU 2016-13 to the earlier of the ending of the national emergency declaration related to the COVID-19 crisis or December 31, 2020. On December 27, 2020, the Consolidated Appropriations Act (the “Appropriations Act”) was enacted to fund the federal government through their fiscal year, extend certain expiring tax provisions and provide additional emergency relief to individuals and businesses related to the COVID-19 pandemic in the United States. Included within the provisions of the Appropriations Act is an extension of the adoption date for ASU 2016-13 from December 31, 2020 to the earlier of January 1, 2022 or 60 days after the date on which the COVID-19 national emergency terminates. To address the impact of ASU 2016-13, the Company has formed a committee, which members include the Chief Credit Officer, the Chief Financial Officer, and Chief Information Officer, to assist in identifying, implementing, and evaluating the impact of the required changes to loan loss estimation models and processes. The Company has concluded on segmentation, methodologies and other assumptions used for modeling and is currently working with third parties in validation efforts, model methodology documentation, project management and governance implementation. The Company is currently assessing the impact of the new standard on its consolidated financial statements and will adopt the standard effective January 1, 2022. Additionally, the Company is focused on the expected impact of its pending acquisition of Century Bancorp, Inc. (“Century”) on the adoption process. In August 2018, the FASB issued ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20) Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”). This update modifies the disclosure requirements for employers that sponsor defined benefit pension and/or other postretirement benefit plans. The guidance eliminates requirements for certain disclosures that are no longer considered cost beneficial and requires new ones that the FASB considers pertinent. For public companies, ASU 2018-14 is effective for fiscal years ending after December 15, 2020. For nonpublic companies, ASU 2018-14 is effective for fiscal years ending after December 15, 2021. Early adoption is permitted. The Company will adopt this standard on the nonpublic company effective date. The Company expects the adoption of this standard will not have a material impact on its consolidated financial statements. In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (“ASU 2021-08”). This update modifies how an acquiring entity measures contract assets and contract liabilities of an acquiree in a business combination in accordance with Topic 606. The amendments in this update require the acquiring entity in a business combination to account for revenue contracts as if they had originated the contract an assess how the acquiree accounted for the contract under Topic 606. ASU 2021-08 improves comparability of recognition and measurement of revenue contracts with customers both before and after a business combination. For public business entities, the amendments in this update are effective for fiscal years beginning after December 15, 2022. For all other entities, the amendments are effective for fiscal years beginning after December 15, 2023. The amendments in this update should be applied prospectively to business combinations occurring on or after the effective date of the amendments with early adoption permitted. The Company expects the adoption of this standard will not have a material impact on its consolidated financial statements. Relevant standards that were adopted during the nine months ended September 30, 2021: In August 2018, the FASB issued ASU 2018-15, Intangibles–Goodwill and Other–Internal-use software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract (“ASU 2018-15”). This update addresses accounting for fees paid by a customer for implementation, set-up and other upfront costs incurred in a cloud computing arrangement that is hosted by the vendor (i.e., a service contract). The new guidance aligns treatment for capitalization of implementation costs with guidance on internal-use software. For public entities, the guidance is effective for annual reporting periods beginning after December 15, 2019. For nonpublic entities, the guidance is effective for annual reporting periods beginning after December 15, 2020, and for all interim periods beginning after December 15, 2021. The adoption of this standard on January 1, 2021 did not have a material impact on the Company’s consolidated financial statements. In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848) (“ASU 2021-01”) which expands the scope of guidance in ASC 848 so that companies can apply the optional expedients to derivative instruments affected by the clearing house changes. ASU 2021-01 also clarifies and updates several items in ASU 2020-04 as part of the FASB’s monitoring of global reference rate reform activities. ASU 2021-01 permits entities to elect certain optional expedients and exceptions to modifications of interest rate indexes used for computing when accounting derivative contracts and certain hedging relationships impacted by changes in interest rates used for discounting, margining, or contract price alignment. ASU 2021-01 clarifies other aspects of the guidance in ASC 848 and provides new guidance on how to address the effects of the cash compensation adjustment that is provided as part of the above change on certain aspects of hedge accounting. The guidance was effective upon issuance and allows for retrospective or prospective application with certain conditions. The Company did not elect retrospective application. The adoption of this update did not have a material impact on the Company’s consolidated financial statements.

Securities (Tables)

Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Securities [Abstract]
Summary Of Debt Securities	The amortized cost, gross unrealized gains and losses, and fair value of available for sale securities as of September 30, 2021 and December 31, 2020 were as follows: As of September 30, 2021 Amortized Unrealized Unrealized Fair (In thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 4,097,006 $ 20,437 $ (44,075) $ 4,073,368 Government-sponsored commercial mortgage-backed securities 436,748 — (5,739) 431,009 U.S. Agency bonds 860,595 — (19,312) 841,283 U.S. Treasury securities 69,419 16 (253) 69,182 State and municipal bonds and obligations 258,121 16,349 — 274,470 $ 5,721,889 $ 36,802 $ (69,379) $ 5,689,312 As of December 31, 2020 Amortized Unrealized Unrealized Fair (In thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 2,106,658 $ 42,142 $ — $ 2,148,800 Government-sponsored commercial mortgage-backed securities 17,054 27 — 17,081 U.S. Agency bonds 670,468 113 (3,872) 666,709 U.S. Treasury securities 70,106 263 — 70,369 State and municipal bonds and obligations 260,898 20,004 — 280,902 $ 3,125,184 $ 62,549 $ (3,872) $ 3,183,861
Summary Of Fair Value Of Available For Sale Securities By Contractual Maturities	The amortized cost and estimated fair value of available for sale securities by contractual maturities as of September 30, 2021 and December 31, 2020 are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without prepayment penalties. The scheduled contractual maturities of available for sale securities as of the dates indicated were as follows: As of September 30, 2021 Due in one year or less Due after one year to five years Due after five to ten years Due after ten years Total Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value (In thousands) Government-sponsored residential mortgage-backed securities $ — $ — $ 16,131 $ 17,151 $ 924,290 $ 923,300 $ 3,156,585 $ 3,132,917 $ 4,097,006 $ 4,073,368 Government-sponsored commercial mortgage-backed securities — — 71,814 71,256 364,934 359,753 — — 436,748 431,009 U.S. Agency bonds — — 243,920 240,554 616,675 600,729 — — 860,595 841,283 U.S. Treasury securities 20,029 20,045 49,390 49,137 — — — — 69,419 69,182 State and municipal bonds and obligations 485 486 31,324 32,381 72,039 75,293 154,273 166,310 258,121 274,470 Total $ 20,514 $ 20,531 $ 412,579 $ 410,479 $ 1,977,938 $ 1,959,075 $ 3,310,858 $ 3,299,227 $ 5,721,889 $ 5,689,312 As of December 31, 2020 Due in one year or less Due after one year to five years Due after five to ten years Due after ten years Total Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value (In thousands) Government-sponsored residential mortgage-backed securities $ — $ — $ 46,293 $ 48,925 $ 96,338 $ 100,278 $ 1,964,027 $ 1,999,597 $ 2,106,658 $ 2,148,800 Government-sponsored commercial mortgage-backed securities — — — — 17,054 17,081 — — 17,054 17,081 U.S. Agency bonds — — 99,772 99,834 570,696 566,875 — — 670,468 666,709 U.S. Treasury securities 50,023 50,251 20,083 20,118 — — — — 70,106 70,369 State and municipal bonds and obligations 406 408 20,511 21,431 74,980 79,635 165,001 179,428 260,898 280,902 Total $ 50,429 $ 50,659 $ 186,659 $ 190,308 $ 759,068 $ 763,869 $ 2,129,028 $ 2,179,025 $ 3,125,184 $ 3,183,861
Summary Of Government-Sponsored Residential Mortgage-Backed Securities With Gross Unrealized Losses	Information pertaining to available for sale securities with gross unrealized losses as of September 30, 2021 and December 31, 2020, which the Company has not deemed to be OTTI, aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: As of September 30, 2021 Less than 12 Months 12 Months or Longer Total # of Gross Fair Gross Fair Gross Fair (Dollars in thousands) Government-sponsored residential mortgage-backed securities 30 $ 44,075 $ 3,443,757 $ — $ — $ 44,075 $ 3,443,757 Government-sponsored commercial mortgage-backed securities 17 5,739 431,009 — — 5,739 431,009 U.S. Agency bonds 13 10,010 529,855 9,302 311,428 19,312 841,283 U.S. Treasury securities 1 253 49,137 — — 253 49,137 61 $ 60,077 $ 4,453,758 $ 9,302 $ 311,428 $ 69,379 $ 4,765,186 As of December 31, 2020 Less than 12 Months 12 Months or Longer Total # of Gross Fair Gross Fair Gross Fair (Dollars in thousands) U.S. Agency bonds 6 $ 3,872 $ 416,824 $ — $ — $ 3,872 $ 416,824 6 $ 3,872 $ 416,824 $ — $ — $ 3,872 $ 416,824

Loans and Allowance for Loan _2

Loans and Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2021
Receivables [Abstract]
Summary of financing receivable composition of loan portfolio	The following table provides a summary of the Company’s loan portfolio as of the dates indicated: At September 30, At December 31, 2021 2020 (In thousands) Commercial and industrial $ 1,652,447 $ 1,995,016 Commercial real estate 3,825,186 3,573,630 Commercial construction 243,146 305,708 Business banking 1,225,538 1,339,164 Residential real estate 1,491,269 1,370,957 Consumer home equity 848,570 868,270 Other consumer (1) 218,406 277,780 Gross loans before unamortized premiums, unearned discounts and deferred fees 9,504,562 9,730,525 Allowance for loan losses (103,398) (113,031) Unamortized premiums, net of unearned discounts and deferred fees (23,104) (23,536) Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees $ 9,378,060 $ 9,593,958 (1) Automobile loans are included in the other consumer portfolio above and amounted to $67.1 million and $126.7 million at September 30, 2021 and December 31, 2020, respectively.
Summary of allowance for credit losses on financing receivables by loan category	The following tables summarize the changes in the allowance for loan losses by loan category for the periods indicated: For the Three Months Ended September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 22,596 $ 52,759 $ 3,446 $ 12,705 $ 6,478 $ 3,588 $ 3,626 $ 439 $ 105,637 Charge-offs — (8) — (867) — — (742) — (1,617) Recoveries 40 — — 469 88 63 206 — 866 (Release of) provision (2,007) 1,435 (44) (929) (136) (16) 297 (88) (1,488) Ending balance $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 For the Three Months Ended September 30, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 33,229 $ 54,228 $ 4,816 $ 9,805 $ 6,569 $ 3,875 $ 3,762 $ 352 $ 116,636 Charge-offs (140) — — (1,179) — (22) (1,077) — (2,418) Recoveries 306 4 — 91 43 31 39 — 514 Provision (release of) (3,281) 1,350 (540) 2,711 (261) (76) 834 (37) 700 Ending balance $ 30,114 $ 55,582 $ 4,276 $ 11,428 $ 6,351 $ 3,808 $ 3,558 $ 315 $ 115,432 For the Nine Months Ended September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 26,617 $ 54,569 $ 4,553 $ 13,152 $ 6,435 $ 3,744 $ 3,467 $ 494 $ 113,031 Charge-offs (550) (242) — (4,089) — — (1,381) — (6,262) Recoveries 62 4 — 1,125 115 137 554 — 1,997 (Release of) provision (5,500) (145) (1,151) 1,190 (120) (246) 747 (143) (5,368) Ending balance $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 For the Nine Months Ended September 30, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses: Beginning balance $ 20,919 $ 34,730 $ 3,424 $ 8,260 $ 6,380 $ 4,027 $ 4,173 $ 384 $ 82,297 Charge-offs (167) (24) — (3,714) — (495) (1,625) — (6,025) Recoveries 686 10 — 245 116 53 150 — 1,260 Provision (release of) 8,676 20,866 852 6,637 (145) 223 860 (69) 37,900 Ending balance $ 30,114 $ 55,582 $ 4,276 $ 11,428 $ 6,351 $ 3,808 $ 3,558 $ 315 $ 115,432 The following tables bifurcate the amount of loans and the allowance allocated to each loan category based on the type of impairment analysis as of the dates indicated: As of September 30, 2021 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses ending balance: Individually evaluated for impairment $ 4,287 $ — $ — $ 669 $ 1,462 $ 256 $ 200 $ — $ 6,874 Acquired with deteriorated credit quality — — — — 293 — — — 293 Collectively evaluated for impairment 16,342 54,186 3,402 10,709 4,675 3,379 3,187 351 96,231 Total allowance for loan losses by group $ 20,629 $ 54,186 $ 3,402 $ 11,378 $ 6,430 $ 3,635 $ 3,387 $ 351 $ 103,398 Loans ending balance: Individually evaluated for impairment $ 21,580 $ 3,793 $ — $ 15,141 $ 23,494 $ 4,023 $ 222 $ — $ 68,253 Acquired with deteriorated credit quality 1,546 — — — 2,880 — — — 4,426 Collectively evaluated for impairment 1,629,321 3,821,393 243,146 1,210,397 1,464,895 844,547 218,184 — 9,431,883 Total loans by group $ 1,652,447 $ 3,825,186 $ 243,146 $ 1,225,538 $ 1,491,269 $ 848,570 $ 218,406 $ — $ 9,504,562 As of December 31, 2020 Commercial Commercial Commercial Business Residential Consumer Other Other Total (In thousands) Allowance for loan losses ending balance: Individually evaluated for impairment $ 4,555 $ 210 $ — $ 1,435 $ 1,565 $ 289 $ — $ — $ 8,054 Acquired with deteriorated credit quality 1,283 822 — — 327 — — — 2,432 Collectively evaluated for impairment 20,779 53,537 4,553 11,717 4,543 3,455 3,467 494 102,545 Total allowance for loan losses by group $ 26,617 $ 54,569 $ 4,553 $ 13,152 $ 6,435 $ 3,744 $ 3,467 $ 494 $ 113,031 Loans ending balance: Individually evaluated for impairment $ 17,343 $ 4,435 $ — $ 21,901 $ 27,056 $ 4,845 $ 29 $ — $ 75,609 Acquired with deteriorated credit quality 3,432 2,749 — — 3,116 — — — 9,297 Collectively evaluated for impairment 1,974,241 3,566,446 305,708 1,317,263 1,340,785 863,425 277,751 — 9,645,619 Total loans by group $ 1,995,016 $ 3,573,630 $ 305,708 $ 1,339,164 $ 1,370,957 $ 868,270 $ 277,780 $ — $ 9,730,525
Summary of details the internal risk-rating categories for the Company's commercial and industrial, commercial real estate, commercial construction and business banking portfolios	The following tables detail the internal risk-rating categories for the Company’s commercial and industrial, commercial real estate, commercial construction and business banking portfolios: As of September 30, 2021 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 278,093 $ 4,196 $ 138 $ 763,573 $ 1,046,000 Pass 1,302,413 3,524,607 224,770 389,812 5,441,602 Special mention 13,959 124,618 9,611 54,592 202,780 Substandard 41,459 171,765 8,627 16,478 238,329 Doubtful 16,523 — — 1,083 17,606 Loss — — — — — Total $ 1,652,447 $ 3,825,186 $ 243,146 $ 1,225,538 $ 6,946,317 As of December 31, 2020 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 655,346 $ 6,585 $ — $ 918,921 $ 1,580,852 Pass 1,199,522 3,256,697 280,792 336,657 5,073,668 Special mention 78,117 134,562 10,330 57,092 280,101 Substandard 47,525 173,308 14,586 24,788 260,207 Doubtful 14,506 2,478 — 1,706 18,690 Loss — — — — — Total $ 1,995,016 $ 3,573,630 $ 305,708 $ 1,339,164 $ 7,213,518
Summary pertaining to the breakdown of the Company's nonaccrual loans	The following is a summary pertaining to the breakdown of the Company’s non-accrual loans: As of September 30, As of December 31, 2021 2020 (In thousands) Commercial and industrial $ 17,640 $ 11,714 Commercial real estate 272 915 Business banking 11,254 17,430 Residential real estate 7,185 6,815 Consumer home equity 3,491 3,602 Other consumer 771 529 Total non-accrual loans $ 40,613 $ 41,005
Summary of age analysis of past due loans	The following tables show the age analysis of past due loans as of the dates indicated: As of September 30, 2021 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 529 $ 2,068 $ 2,043 $ 4,640 $ 1,647,807 $ 1,652,447 $ — Commercial real estate — — 1,171 1,171 3,824,015 3,825,186 1,171 Commercial construction — — — — 243,146 243,146 — Business banking 3,351 634 5,497 9,482 1,216,056 1,225,538 — Residential real estate 9,014 2,426 5,515 16,955 1,474,314 1,491,269 278 Consumer home equity 2,319 415 3,111 5,845 842,725 848,570 9 Other consumer 1,107 362 771 2,240 216,166 218,406 — Total $ 16,320 $ 5,905 $ 18,108 $ 40,333 $ 9,464,229 $ 9,504,562 $ 1,458 As of December 31, 2020 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 4 $ 268 $ 1,924 $ 2,196 $ 1,992,820 $ 1,995,016 $ 848 Commercial real estate — 556 1,545 2,101 3,571,529 3,573,630 1,111 Commercial construction — — — — 305,708 305,708 — Business banking 5,279 3,311 10,196 18,786 1,320,378 1,339,164 — Residential real estate 9,184 2,517 4,904 16,605 1,354,352 1,370,957 279 Consumer home equity 1,806 364 3,035 5,205 863,065 868,270 9 Other consumer 1,978 234 517 2,729 275,051 277,780 — Total $ 18,251 $ 7,250 $ 22,121 $ 47,622 $ 9,682,903 $ 9,730,525 $ 2,247
Summary of TDR loans on accrual and nonaccrual status	The following tables show the TDR loans on accrual and non-accrual status as of the dates indicated: As of September 30, 2021 TDRs on Accrual Status TDRs on Non-Accrual Status Total TDRs Number of Loans Balance of Number of Balance of Number of Balance of (Dollars in thousands) Commercial and industrial 1 $ 3,940 6 $ 10,944 7 $ 14,884 Commercial real estate 1 3,520 — — 1 3,520 Business banking 5 3,888 5 1,262 10 5,150 Residential real estate 127 20,092 26 3,135 153 23,227 Consumer home equity 73 3,280 16 744 89 4,024 Other consumer 2 3 1 18 3 21 Total 209 $ 34,723 54 $ 16,103 263 $ 50,826 As of December 31, 2020 TDRs on Accrual Status TDRs on Non-Accrual Status Total TDRs Number of Loans Balance of Number of Loans Balance of Number of Loans Balance of (Dollars in thousands) Commercial and industrial 1 $ 5,628 7 $ 6,819 8 $ 12,447 Commercial real estate 1 3,521 1 480 2 4,001 Business banking 6 4,471 6 722 12 5,193 Residential real estate 146 23,416 27 3,273 173 26,689 Consumer home equity 91 4,030 12 815 103 4,845 Other consumer 3 29 — — 3 29 Total 248 $ 41,095 53 $ 12,109 301 $ 53,204
Summary of the modifications which occurred during the periods and the change in the recorded investment subsequent to the modifications occurring	The following tables show the modifications which occurred during the periods and the change in the recorded investment subsequent to the modifications occurring: For the Three Months Ended September 30, 2021 For the Nine Months Ended September 30, 2021 Number Pre- Post- Number Pre-Modification Post- (Dollars in thousands) Business banking — $ — $ — 1 $ 462 $ 462 Residential real estate — — — 1 295 295 Consumer home equity 2 200 200 2 200 200 Total 2 $ 200 $ 200 4 $ 957 $ 957 (1) The post-modification balances represent the balance of the loan on the date of modification. These amounts may show an increase when modification includes capitalization of interest. For the Three Months Ended September 30, 2020 For the Nine Months Ended September 30, 2020 Number Pre- Post- Number Pre-Modification Post- (Dollars in thousands) Commercial and industrial — $ — $ — 1 $ 140 $ 140 Commercial real estate — — — 2 632 632 Business banking — — — 3 1,040 1,040 Residential real estate — — — 3 399 399 Consumer home equity — — — 12 527 531 Other consumer 3 35 35 4 58 58 Total 3 $ 35 $ 35 25 $ 2,796 $ 2,800 (1) The post-modification balances represent the balance of the loan on the date of modification. These amounts may show an increase when modification includes capitalization of interest.
Summary of postmodification balance of troubled debt restructuring listed by type of modification	The following table shows the Company’s post-modification balance of TDRs listed by type of modification during the periods indicated: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Interest only/principal deferred $ — $ — $ — $ 1,305 Extended maturity 200 — 200 35 Extended maturity and interest only/principal deferred — — — 427 Court-ordered concession — 35 295 1,033 Other — — 462 — Total $ 200 $ 35 $ 957 $ 2,800
Summary of troubled debt restructurings on financing receivables loans modified as Tdrs in the past twelve months that have subsequently defaulted	The following table shows the number of loans and the recorded investment amount of those loans, as of the respective date, that have been modified during the prior 12 months which have subsequently defaulted during the periods indicated. The Company considers a loan to have defaulted when it reaches 90 days past due or is transferred to non-accrual: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 Number of Recorded Number of Recorded Number of Recorded Number of Recorded (Dollars in thousands) Troubled debt restructurings that subsequently defaulted (1): Business banking — $ — — $ — 1 $ 404 — $ — Consumer home equity — — 1 40 1 56 1 40 Total — $ — 1 $ 40 2 $ 460 1 $ 40
Summary of company's impaired loans by loan portfolio	The following table summarizes the Company’s impaired loans by loan portfolio as of the dates indicated: As of September 30, 2021 As of December 31, 2020 Recorded Unpaid Related Recorded Unpaid Related (In thousands) With no related allowance recorded: Commercial and industrial $ 13,807 $ 15,188 $ — $ 9,182 $ 11,212 $ — Commercial real estate 3,793 3,832 — 3,955 3,974 — Business banking 3,557 4,564 — 5,250 7,659 — Residential real estate 11,352 12,727 — 14,730 17,010 — Consumer home equity 1,895 1,895 — 2,571 2,571 — Other consumer 22 22 — 29 29 — Sub-total 34,426 38,228 — 35,717 42,455 — With an allowance recorded: Commercial and industrial 7,773 8,350 4,287 8,161 8,432 4,555 Commercial real estate — — — 480 497 210 Business banking 11,584 15,978 669 16,651 21,146 1,435 Residential real estate 12,142 12,142 1,462 12,326 12,326 1,565 Consumer home equity 2,128 2,128 256 2,274 2,274 289 Other consumer 200 200 200 — — — Sub-total 33,827 38,798 6,874 39,892 44,675 8,054 Total $ 68,253 $ 77,026 $ 6,874 $ 75,609 $ 87,130 $ 8,054
Summary of information regarding interest income recognized on impaired loans	The following tables display information regarding interest income recognized on impaired loans, by portfolio, for the periods indicated: For the Three Months Ended September 30, 2021 For the Nine Months Ended September 30, 2021 Average Total Average Total (In thousands) With no related allowance recorded: Commercial and industrial $ 12,517 $ 39 $ 11,405 $ 131 Commercial real estate 3,909 45 4,047 133 Business banking 3,988 25 4,586 75 Residential real estate 11,561 113 12,349 344 Consumer home equity 1,877 13 1,988 47 Other consumer 22 — 24 — Sub-total 33,874 235 34,399 730 With an allowance recorded: Commercial and industrial 7,808 — 7,849 — Commercial real estate — — 271 — Business banking 12,642 14 14,560 43 Residential real estate 12,290 127 13,093 387 Consumer home equity 2,108 15 2,232 53 Other consumer 67 — 22 — Sub-total 34,915 156 38,027 483 Total $ 68,789 $ 391 $ 72,426 $ 1,213 For the Three Months Ended September 30, 2020 For the Nine Months Ended September 30, 2020 Average Total Average Total (In thousands) With no related allowance recorded: Commercial and industrial $ 9,273 $ 48 $ 14,152 $ 167 Commercial real estate 4,408 45 5,433 134 Commercial construction 280 — 125 — Business banking 3,298 30 2,659 66 Residential real estate 13,513 129 13,141 399 Consumer home equity 3,034 21 3,287 61 Other consumer 53 1 33 1 Sub-total 33,859 274 38,830 828 With an allowance recorded: Commercial and industrial 6,229 — 8,168 — Commercial real estate 1,017 — 625 — Business banking 17,452 15 13,063 44 Residential real estate 14,165 144 13,708 446 Consumer home equity 2,417 23 2,692 69 Sub-total 41,280 182 38,256 559 Total $ 75,139 $ 456 $ 77,086 $ 1,387
Summary of outstanding and carrying amounts of Purchased credit impaired loans	The following table displays the outstanding and carrying amounts of PCI loans as of the dates indicated: September 30, December 31, 2021 2020 (In thousands) Outstanding balance $ 4,484 $ 9,982 Carrying amount 4,426 9,297
Summary of activity in the accretable yield for the PCI loan portfolio	The following table summarizes activity in the accretable yield for the PCI loan portfolio: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Balance at beginning of period $ 2,981 $ 2,994 $ 2,495 $ 3,923 Accretion (245) (298) (877) (1,058) Other change in expected cash flows (1,161) (44) (1,370) (209) Reclassification from (to) non-accretable difference for loans with improved (deteriorated) cash flows — — 1,327 (4) Balance at end of period $ 1,575 $ 2,652 $ 1,575 $ 2,652
Summary of the Company's loan participations	The following table summarizes the Company’s loan participations: As of and for the Nine Months Ended September 30, 2021 As of and for the Year Ended December 31, 2020 Balance Non-performing Impaired Gross Balance Non-performing Impaired Gross (Dollars in thousands) Commercial and industrial $ 632,229 1.73 % 1.73 % $ — $ 598,873 1.11 % 1.11 % $ — Commercial real estate 385,782 0.00 % 0.00 % — 306,202 0.00 % 0.00 % — Commercial construction 72,374 0.00 % 0.00 % — 119,600 0.00 % 0.00 % — Business banking 104 0.00 % 0.00 % — 34 0.00 % 0.00 % 15 Total loan participations $ 1,090,489 1.00 % 1.00 % $ — $ 1,024,709 0.65 % 0.65 % $ 15

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Summary of Lease Cost	As of the dates indicated, the Company had the following related to operating leases: As of September 30, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 75,196 $ 81,596 Lease liabilities 79,187 85,330 The following tables are a summary of the Company’s components of net lease cost for the periods indicated: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 (In thousands) Operating lease cost $ 3,478 $ 10,560 Finance lease cost 50 116 Variable lease cost 617 1,564 Total lease cost $ 4,145 $ 12,240 Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 (In thousands) Operating lease cost $ 3,596 $ 10,810 Finance lease cost 24 43 Variable lease cost 509 1,479 Total lease cost $ 4,129 $ 12,332
Summary of Other Information Related to Leases	Supplemental balance sheet information related to operating leases are as follows: As of September 30, 2021 As of December 31, 2020 Weighted-average remaining lease term (in years) 7.96 8.50 Weighted-average discount rate 2.62 % 2.65 %

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Goodwill and Other Intangible Assets	The following tables set forth the carrying amount of goodwill and other intangible assets, net of accumulated amortization by reporting unit at the dates indicated below: As of September 30, 2021 Banking Insurance Net (In thousands) Balances not subject to amortization Goodwill $ 298,611 $ 73,861 $ 372,472 Balances subject to amortization Insurance agency (1) — 7,234 7,234 Core deposit intangible 66 — 66 Total other intangible assets 66 7,234 7,300 Total goodwill and other intangible assets $ 298,677 $ 81,095 $ 379,772 (1) Insurance agency intangible assets include customer list, non-compete agreement and supplier relationship intangible assets. As of December 31, 2020 Banking Insurance Net (In thousands) Balances not subject to amortization Goodwill $ 298,611 $ 70,866 $ 369,477 Balances subject to amortization Insurance agency (1) — 6,899 6,899 Core deposit intangible 158 — 158 Total other intangible assets 158 6,899 7,057 Total goodwill and other intangible assets $ 298,769 $ 77,765 $ 376,534 (1) Insurance agency intangible assets include customer list, non-compete agreement and supplier relationship intangible assets.

Earnings Per Share ("EPS") (Tab

Earnings Per Share ("EPS") (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	For the Three Months Ended September 30, 2021 For the Nine Months Ended September 30, 2021 (Dollars in thousands, except per share data) Net income applicable to common shares $ 37,106 $ 119,578 Average number of common shares outstanding 186,758,154 186,758,154 Less: Average unallocated ESOP shares (14,459,539) (14,583,685) Average number of common shares outstanding used to calculate basic earnings per common share 172,298,615 172,174,469 Common stock equivalents — — Average number of common shares outstanding used to calculate diluted earnings per common share 172,298,615 172,174,469 Earnings per common share Basic and diluted $ 0.22 $ 0.69 All unallocated ESOP shares have been excluded from the calculation of basic and diluted EPS.

Low Income Housing Tax Credit_2

Low Income Housing Tax Credits and Other Tax Credit Investments (Tables)	9 Months Ended
	Sep. 30, 2021
Investments in Affordable Housing Projects [Abstract]
Summary of the Company's Investments in Low Income Housing Projects Accounted for Using the Proportional Amortization Method	The following table presents the Company’s investments in low income housing projects accounted for using the proportional amortization method for the periods indicated: As of September 30, 2021 As of December 31, 2020 (In thousands) Current recorded investment included in other assets $ 82,533 $ 58,504 Commitments to fund qualified affordable housing projects included in recorded investment noted above 49,611 31,487 The following table presents additional information related to the Company's investments in LIHTC projects for the period indicated: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Tax credits and benefits recognized $ 1,730 $ 1,539 $ 4,717 $ 4,597 Amortization expense included in income tax expense 1,496 1,263 4,255 3,715

Employee Benefits (Tables)

Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Summary of Components of Net Pension Expense	The components of net pension expense for the plans for the periods indicated are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Components of net periodic benefit cost: Service cost $ 7,896 $ 6,231 $ 23,690 $ 18,694 Interest cost 1,269 2,617 3,805 7,849 Expected return on plan assets (8,141) (7,427) (24,424) (22,277) Past service cost (2,945) 7 (8,835) 19 Recognized net actuarial loss 3,537 2,361 10,612 7,082 Net periodic benefit cost $ 1,616 $ 3,789 $ 4,848 $ 11,367
Schedule of Assets Held in Rabbi Trust	Investments in rabbi trust accounts are recorded at fair value within the Company's consolidated balance sheets with changes in fair value recorded through noninterest income. The following table presents the book value, mark-to-market, and fair value of assets held in rabbi trust accounts by asset type: As of September 30, 2021 As of December 31, 2020 Book Value Mark-to-Market Fair Value Book Value Mark-to-Market Fair Value Asset Type (In thousands) Cash and cash equivalents $ 4,476 $ — $ 4,476 $ 5,157 $ — $ 5,157 Equities 65,670 19,880 85,550 59,235 19,492 78,727 Fixed income 7,976 172 8,148 7,441 358 7,799 Total assets $ 78,122 $ 20,052 $ 98,174 $ 71,833 $ 19,850 $ 91,683

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Summary of Financial Instruments as of the Dates Indicated	The following table summarizes the above financial instruments as of the dates indicated: As of September 30, 2021 As of December 31, 2020 (In thousands) Commitments to extend credit $ 4,387,306 $ 3,818,952 Standby letters of credit 58,734 60,221 Forward commitments to sell loans 49,105 41,160

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Summary of Derivative Instruments [Abstract]
Schedule of Pre-tax Impact of Terminated Cash Flow Hedges on AOCI	The following table presents the pre-tax impact of terminated cash flow hedges on accumulated other comprehensive income (“AOCI”) for the three and nine months ended September 30, 2021 and September 30, 2020: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Unrealized gains on terminated hedges included in AOCI – beginning of respective period $ 24,980 $ 30,579 $ 41,473 $ — Unrealized gains on terminated hedges arising during the period — 26,410 — 57,362 Reclassification adjustments for amortization of unrealized (gains) into net income (7,851) (7,036) (24,344) (7,409) Unrealized gains on terminated hedges included in AOCI – September 30 $ 17,129 $ 49,953 $ 17,129 $ 49,953
Derivatives Not Designated as Hedging Instruments	The following tables present the Company’s customer-related derivative positions as of the dates indicated below for those derivatives not designated as hedging. September 30, 2021 Number of Positions Total Notional (Dollars in thousands) Interest rate swaps 510 $ 3,169,358 Risk participation agreements 66 263,847 Foreign exchange contracts: Matched commercial customer book 52 6,516 Foreign currency loan 4 9,977 December 31, 2020 Number of Positions Total Notional (Dollars in thousands) Interest rate swaps 576 $ 3,652,385 Risk participation agreements 70 287,732 Foreign exchange contracts: Matched commercial customer book 40 4,242 Foreign currency loan 3 10,798
Schedule of Derivative Financial Instruments	The table below presents the fair value of the Company’s derivative financial instruments, as well as their classification on the consolidated balance sheet for the periods indicated. There were no derivatives designated as hedging instruments at September 30, 2021 or December 31, 2020. Asset Derivatives Liability Derivatives Balance Fair Value at September 30, Fair Value at December 31, Balance Sheet Fair Value at September 30, Fair Value at December 31, (In thousands) Derivatives not designated as hedging instruments Customer-related positions: Interest rate swaps Other assets $ 80,102 $ 141,822 Other liabilities $ 25,274 $ 42,600 Risk participation agreements Other assets 347 722 Other liabilities 594 1,230 Foreign currency exchange contracts - matched customer book Other assets 44 90 Other liabilities 31 77 Foreign currency exchange contracts - foreign currency loan Other assets 120 9 Other liabilities — 69 Total $ 80,613 $ 142,643 $ 25,899 $ 43,976
Schedule of Derivative Financial Instruments On The Consolidated Income Statements	The table below presents the net effect of the Company’s derivative financial instruments on the consolidated income statements as well as the effect of the Company’s derivative financial instruments included in other comprehensive income (“OCI”) as follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 (In thousands) Derivatives designated as hedges: (Loss) gain in OCI on derivatives $ — $ (142) $ — $ 46,869 Gain reclassified from OCI into interest income (effective portion) $ 7,851 $ 8,405 $ 24,344 $ 18,651 Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test) Interest income — — — — Other income — — — — Total $ — $ — $ — $ — Derivatives not designated as hedges: Customer-related positions: Gain (loss) recognized in interest rate swap income $ 832 $ 904 $ 4,596 $ (6,063) (Loss) gain recognized in interest rate swap income for risk participation agreements (4) 11 260 (370) Gain (loss) recognized in other income for foreign currency exchange contracts: Matched commercial customer book 8 (86) — (17) Foreign currency loan 72 149 181 179 Total gain (loss) for derivatives not designated as hedges $ 908 $ 978 $ 5,037 $ (6,271)

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	9 Months Ended
	Sep. 30, 2021
Offsetting [Abstract]
Disclosure Detail Of Balance Sheet Offsetting Of Financial Assets And Liabilities	The following tables present the Company’s asset and liability positions that were eligible for offset and the potential effect of netting arrangements on its consolidated balance sheet, as of the dates indicated: As of September 30, 2021 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Customer-related positions: Interest rate swaps $ 80,102 $ — $ 80,102 $ 859 $ — $ 79,243 Risk participation agreements 347 — 347 — — 347 Foreign currency exchange contracts – matched customer book 44 — 44 — — 44 Foreign currency exchange contracts – foreign currency loan 120 — 120 — — 120 $ 80,613 $ — $ 80,613 $ 859 $ — $ 79,754 Derivative Liabilities Customer-related positions: Interest rate swaps $ 25,274 $ — $ 25,274 $ 859 $ 24,415 $ — Risk participation agreements 594 — 594 — — 594 Foreign currency exchange contracts – matched customer book 31 — 31 — — 31 Foreign currency exchange contracts – foreign currency loan — — — — — — $ 25,899 $ — $ 25,899 $ 859 $ 24,415 $ 625 As of December 31, 2020 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Customer-related positions: Interest rate swaps $ 141,822 $ — $ 141,822 $ 48 $ — $ 141,774 Risk participation agreements 722 — 722 — — 722 Foreign currency exchange contracts – matched customer book 90 — 90 — (1) 89 Foreign currency exchange contracts – foreign currency loan 9 — 9 — — 9 $ 142,643 $ — $ 142,643 $ 48 $ (1) $ 142,594 Derivative Liabilities Customer-related positions: Interest rate swaps $ 42,600 $ — $ 42,600 $ 48 $ 42,552 $ — Risk participation agreements 1,230 — 1,230 — — 1,230 Foreign currency exchange contracts – matched customer book 77 — 77 — — 77 Foreign currency exchange contracts – foreign currency loan 69 — 69 — — 69 $ 43,976 $ — $ 43,976 $ 48 $ 42,552 $ 1,376

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary Of The Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis	The following tables present the balances of assets and liabilities measured at fair value on a recurring basis as of September 30, 2021 and December 31, 2020: Fair Value Measurements at Reporting Date Using Balance as of September 30, 2021 Quoted Prices in Significant Significant Description (In thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 4,073,368 $ — $ 4,073,368 $ — Government-sponsored commercial mortgage-backed securities 431,009 — 431,009 — U.S. Agency bonds 841,283 — 841,283 — U.S. Treasury securities 69,182 69,182 — — State and municipal bonds and obligations 274,470 — 274,470 — Rabbi trust investments 98,174 90,026 8,148 — Loans held for sale 1,757 — 1,757 — Interest rate swap contracts Customer-related positions 80,102 — 80,102 — Risk participation agreements 347 — 347 — Foreign currency forward contracts Matched customer book 44 — 44 — Foreign currency loan 120 — 120 — Total $ 5,869,856 $ 159,208 $ 5,710,648 $ — Liabilities Interest rate swap contracts Customer-related positions $ 25,274 $ — $ 25,274 $ — Risk participation agreements 594 — 594 — Foreign currency forward contracts Matched customer book 31 — 31 — Foreign currency loan — — — — Total $ 25,899 $ — $ 25,899 $ — Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices in Significant Significant (In thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 2,148,800 $ — $ 2,148,800 $ — Government-sponsored commercial mortgage-backed securities 17,081 — 17,081 — U.S. Agency bonds 666,709 — 666,709 — U.S. Treasury securities 70,369 70,369 — — State and municipal bonds and obligations 280,902 — 280,902 — Rabbi trust investments 91,683 83,884 7,799 — Loans held for sale 1,140 — 1,140 — Interest rate swap contracts Customer-related positions 141,822 — 141,822 — Risk participation agreements 722 — 722 — Foreign currency forward contracts Matched customer book 90 — 90 — Foreign currency loan 9 — 9 — Total $ 3,419,327 $ 154,253 $ 3,265,074 $ — Liabilities Interest rate swap contracts Customer-related positions $ 42,600 $ — $ 42,600 $ — Risk participation agreements 1,230 — 1,230 — Foreign currency forward contracts Matched customer book 77 — 77 — Foreign currency loan 69 — 69 — Total $ 43,976 $ — $ 43,976 $ —
Summary Of The Fair Value Of Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis	The following tables summarize the fair value of assets and liabilities measured at fair value on a nonrecurring basis, as of September 30, 2021 and December 31, 2020. Fair Value Measurements at Reporting Date Using Description Balance as of September 30, 2021 Quoted Prices Significant Significant (In thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 15,484 $ — $ — $ 15,484 Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices Significant Significant (In thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 11,036 $ — $ — 11,036
Fair Value, by Balance Sheet Grouping	The estimated fair values and related carrying amounts for assets and liabilities for which fair value is only disclosed are shown below as of the dates indicated: Fair Value Measurements at Reporting Date Using Description Carrying Value as of September 30, 2021 Fair Value as of September 30, 2021 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,378,060 $ 9,512,887 $ — $ — $ 9,512,887 FHLB stock 10,601 10,601 — 10,601 — Bank-owned life insurance 79,259 79,259 — 79,259 — Liabilities Deposits $ 13,649,964 $ 13,649,818 $ — $ 13,649,818 $ — FHLB advances 14,172 13,728 — 13,728 — Escrow deposits from borrowers 15,900 15,900 — 15,900 — Fair Value Measurements at Reporting Date Using Description Carrying Value as of December 31, 2020 Fair Value as of December 31, 2020 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,593,958 $ 9,779,195 $ — $ — $ 9,779,195 FHLB stock 8,805 8,805 — 8,805 — Bank-owned life insurance 78,561 78,561 — 78,561 — Liabilities Deposits $ 12,155,784 $ 12,155,843 $ — $ 12,155,843 $ — FHLB advances 14,624 14,434 — 14,434 — Escrow deposits from borrowers 13,425 13,425 — 13,425 —

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue from External Customers by Products and Services	The Company has disaggregated such revenues by type of service, as presented in the table below. These categories reflect how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Insurance commissions $ 21,956 $ 21,884 $ 73,767 $ 72,058 Service charges on deposit accounts 5,935 5,052 17,010 15,514 Trust and investment advisory fees 6,310 5,311 18,047 15,600 Debit card processing fees 3,030 2,721 8,949 7,528 Other noninterest income 2,318 1,689 6,233 5,226 Total noninterest income in-scope of ASC 606 39,549 36,657 124,006 115,926 Total noninterest income out-of-scope of ASC 606 3,660 11,052 20,148 12,809 Total noninterest income $ 43,209 $ 47,709 $ 144,154 $ 128,735

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2021
Statement of Other Comprehensive Income [Abstract]
Comprehensive Income (Loss)	The following tables present a reconciliation of the changes in the components of other comprehensive (loss) income for the dates indicated including the amount of income tax (expense) benefit allocated to each component of other comprehensive (loss) income: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Pre Tax Tax After Tax Pre Tax Tax After Tax (In thousands) Unrealized losses on securities available for sale: Change in fair value of securities available for sale $ (27,741) $ 6,132 $ (21,609) $ (90,088) $ 19,911 $ (70,177) Less: reclassification adjustment for gains included in net income 1 — 1 1,166 (257) 909 Net change in fair value of securities available for sale (27,742) 6,132 (21,610) (91,254) 20,168 (71,086) Unrealized gains (losses) on cash flow hedges: Change in fair value of cash flow hedges — — — — — — Less: net cash flow hedge gains reclassified into interest income (1) 7,851 (2,207) 5,644 24,344 (6,843) 17,501 Net change in fair value of cash flow hedges (7,851) 2,207 (5,644) (24,344) 6,843 (17,501) Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (3,537) 994 (2,543) (10,612) 2,983 (7,629) Less: accretion of prior service cost 2,945 (828) 2,117 8,835 (2,484) 6,351 Net change in other comprehensive income for defined benefit postretirement plans 592 (166) 426 1,777 (499) 1,278 Total other comprehensive loss $ (35,001) $ 8,173 $ (26,828) $ (113,821) $ 26,512 $ (87,309) (1) Represents amortization of realized gains on terminated cash flow hedges for the three and nine months ended September 30, 2021. The total realized gain of $41.2 million, net of tax, will be recognized in earnings through January 2023. The balance of this gain had amortized to $12.3 million, net of tax, at September 30, 2021. Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Pre Tax Tax After Tax Pre Tax Tax After Tax (In thousands) Unrealized (losses) gains on securities available for sale: Change in fair value of securities available for sale $ (5,563) $ 1,242 $ (4,321) $ 28,750 $ (6,370) $ 22,380 Less: reclassification adjustment for gains included in net income — — — 285 (63) 222 Net change in fair value of securities available for sale (5,563) 1,242 (4,321) 28,465 (6,307) 22,158 Unrealized (losses) gains on cash flow hedges: Change in fair value of cash flow hedges (142) 40 (102) 46,869 (13,175) 33,694 Less: net cash flow hedge gains reclassified into interest income (1) 8,405 (2,363) 6,042 18,651 (5,243) 13,408 Net change in fair value of cash flow hedges (8,547) 2,403 (6,144) 28,218 (7,932) 20,286 Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (2,361) 664 (1,697) (7,082) 1,990 (5,092) Less: amortization of prior service cost (7) 2 (5) (19) 5 (14) Net change in other comprehensive income for defined benefit postretirement plans 2,368 (666) 1,702 7,101 (1,995) 5,106 Total other comprehensive (loss) income $ (11,742) $ 2,979 $ (8,763) $ 63,784 $ (16,234) $ 47,550 (1) Includes amortization of $5.1 million and $5.3 million of the remaining balance of realized but unrecognized gains, net of tax, on terminated cash flow hedges for the three and nine months ended September 30, 2020, respectively. The original realized gain of $41.2 million, net of tax, will be recognized in earnings through January 2023. The balance of this gain had amortized to $35.9 million, net of tax, at September 30, 2020.
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table illustrates the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax: Unrealized Unrealized Defined Benefit Total (In thousands) Beginning Balance: January 1, 2021 $ 45,672 $ 29,815 $ (21,253) $ 54,234 Other comprehensive loss before reclassifications (70,177) — — (70,177) Less: Amounts reclassified from accumulated other comprehensive income 909 17,501 (1,278) 17,132 Net current-period other comprehensive (loss) income (71,086) (17,501) 1,278 (87,309) Ending Balance: September 30, 2021 $ (25,414) $ 12,314 $ (19,975) $ (33,075) Beginning Balance: January 1, 2020 $ 21,798 $ 15,624 $ (81,269) $ (43,847) Other comprehensive income before reclassifications 22,380 33,694 — 56,074 Less: Amounts reclassified from accumulated other comprehensive income (loss) 222 13,408 (5,106) 8,524 Net current-period other comprehensive income 22,158 20,286 5,106 47,550 Ending Balance: September 30, 2020 $ 43,956 $ 35,910 $ (76,163) $ 3,703

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Schedule Of Segment Reporting Information, By Segment	Results of operations and selected financial information by segment and reconciliation to the consolidated financial statements as of and for the three months ended September 30, 2021 and 2020, and for the nine months ended September 30, 2021 and 2020, was as follows: As of and for the three months ended September 30, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 102,691 $ — $ — $ 102,691 $ 98,742 $ — $ — $ 98,742 (Release of) provision for loan losses (1,488) — — (1,488) 700 — — 700 Net interest income after provision for loan losses 104,179 — — 104,179 98,042 — — 98,042 Noninterest income 20,783 22,508 (82) 43,209 25,288 22,571 (150) 47,709 Noninterest expense 80,474 19,538 (1,042) 98,970 91,509 19,506 (1,198) 109,817 Income before provision for income taxes 44,488 2,970 960 48,418 31,821 3,065 1,048 35,934 Income tax provision 10,471 841 — 11,312 6,561 868 — 7,429 Net income $ 34,017 $ 2,129 $ 960 $ 37,106 $ 25,260 $ 2,197 $ 1,048 $ 28,505 Total assets $ 17,324,816 $ 207,996 $ (71,589) $ 17,461,223 $ 15,332,420 $ 202,319 $ (74,145) $ 15,460,594 Total liabilities $ 14,051,100 $ 52,420 $ (71,589) $ 14,031,931 $ 13,761,414 $ 59,953 $ (74,145) $ 13,747,222 For the nine months ended September 30, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 307,390 $ — $ — $ 307,390 $ 297,643 $ — $ — $ 297,643 (Release of) provision for loan losses (5,368) — — (5,368) 37,900 — — 37,900 Net interest income after provision for loan losses 312,758 — — 312,758 259,743 — — 259,743 Noninterest income 69,308 74,959 (113) 144,154 55,935 72,979 (179) 128,735 Noninterest expense 243,549 59,844 (3,039) 300,354 251,688 57,231 (3,165) 305,754 Income before provision for income taxes 138,517 15,115 2,926 156,558 63,990 15,748 2,986 82,724 Income tax provision 32,728 4,252 — 36,980 11,468 4,456 — 15,924 Net income $ 105,789 $ 10,863 $ 2,926 $ 119,578 $ 52,522 $ 11,292 $ 2,986 $ 66,800

Securities - Summary Of Debt Se

Securities - Summary Of Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,721,889	$ 3,125,184
Unrealized Gains	36,802	62,549
Unrealized Losses	(69,379)	(3,872)
Fair Value	5,689,312	3,183,861
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,097,006	2,106,658
Unrealized Gains	20,437	42,142
Unrealized Losses	(44,075)	0
Fair Value	4,073,368	2,148,800
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	436,748	17,054
Unrealized Gains	0	27
Unrealized Losses	(5,739)	0
Fair Value	431,009	17,081
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	860,595	670,468
Unrealized Gains	0	113
Unrealized Losses	(19,312)	(3,872)
Fair Value	841,283	666,709
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	69,419	70,106
Unrealized Gains	16	263
Unrealized Losses	(253)	0
Fair Value	69,182	70,369
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	258,121	260,898
Unrealized Gains	16,349	20,004
Unrealized Losses	0	0
Fair Value	$ 274,470	$ 280,902

Securities - Summary Of Fair Va

Securities - Summary Of Fair Value Of Available For Sale Securities By Contractual Maturities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	$ 20,514	$ 50,429
Due in one year or less, Fair value	20,531	50,659
Due after one year to five years, Amortized Cost	412,579	186,659
Due after one year to five years, Fair value	410,479	190,308
Due after five to ten years, Amortized Cost	1,977,938	759,068
Due after five to ten years, Fair value	1,959,075	763,869
Due after ten years, Amortized Cost	3,310,858	2,129,028
Due after ten years, Fair value	3,299,227	2,179,025
Amortized Cost	5,721,889	3,125,184
Available for sale securities	5,689,312	3,183,861
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	0	0
Due in one year or less, Fair value	0	0
Due after one year to five years, Amortized Cost	16,131	46,293
Due after one year to five years, Fair value	17,151	48,925
Due after five to ten years, Amortized Cost	924,290	96,338
Due after five to ten years, Fair value	923,300	100,278
Due after ten years, Amortized Cost	3,156,585	1,964,027
Due after ten years, Fair value	3,132,917	1,999,597
Amortized Cost	4,097,006	2,106,658
Available for sale securities	4,073,368	2,148,800
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	0	0
Due in one year or less, Fair value	0	0
Due after one year to five years, Amortized Cost	71,814	0
Due after one year to five years, Fair value	71,256	0
Due after five to ten years, Amortized Cost	364,934	17,054
Due after five to ten years, Fair value	359,753	17,081
Due after ten years, Amortized Cost	0	0
Due after ten years, Fair value	0	0
Amortized Cost	436,748	17,054
Available for sale securities	431,009	17,081
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	0	0
Due in one year or less, Fair value	0	0
Due after one year to five years, Amortized Cost	243,920	99,772
Due after one year to five years, Fair value	240,554	99,834
Due after five to ten years, Amortized Cost	616,675	570,696
Due after five to ten years, Fair value	600,729	566,875
Due after ten years, Amortized Cost	0	0
Due after ten years, Fair value	0	0
Amortized Cost	860,595	670,468
Available for sale securities	841,283	666,709
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	20,029	50,023
Due in one year or less, Fair value	20,045	50,251
Due after one year to five years, Amortized Cost	49,390	20,083
Due after one year to five years, Fair value	49,137	20,118
Due after five to ten years, Amortized Cost	0	0
Due after five to ten years, Fair value	0	0
Due after ten years, Amortized Cost	0	0
Due after ten years, Fair value	0	0
Amortized Cost	69,419	70,106
Available for sale securities	69,182	70,369
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	485	406
Due in one year or less, Fair value	486	408
Due after one year to five years, Amortized Cost	31,324	20,511
Due after one year to five years, Fair value	32,381	21,431
Due after five to ten years, Amortized Cost	72,039	74,980
Due after five to ten years, Fair value	75,293	79,635
Due after ten years, Amortized Cost	154,273	165,001
Due after ten years, Fair value	166,310	179,428
Amortized Cost	258,121	260,898
Available for sale securities	$ 274,470	$ 280,902

Securities - Additional Informa

Securities - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Securities [Abstract]
Gross realized gains from sales of available for sale securities (less than for the three months ended June 30, 2021)	$ 100,000	$ 0	$ 1,200,000	$ 300,000
Gross realized losses from sales of available for sale securities			0	0
Other-than-temporary impairment was recorded			$ 0	$ 0

Securities - Summary Of Governm

Securities - Summary Of Government-Sponsored Residential Mortgage-Backed Securities With Gross Unrealized Losses (Detail) $ in Thousands	Sep. 30, 2021USD ($)holding	Dec. 31, 2020USD ($)holding
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | holding	61	6
Less than 12 Months, Gross Unrealized Losses	$ 60,077	$ 3,872
Less than 12 Months, Fair Value	4,453,758	416,824
12 Months or Longer, Gross Unrealized Losses	9,302	0
12 Months or Longer, Fair Value	311,428	0
Gross Unrealized Losses	69,379	3,872
Fair Value	$ 4,765,186	$ 416,824
Government-sponsored residential mortgage-backed securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | holding	30
Less than 12 Months, Gross Unrealized Losses	$ 44,075
Less than 12 Months, Fair Value	3,443,757
12 Months or Longer, Gross Unrealized Losses	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	44,075
Fair Value	$ 3,443,757
Government-sponsored commercial mortgage-backed securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | holding	17
Less than 12 Months, Gross Unrealized Losses	$ 5,739
Less than 12 Months, Fair Value	431,009
12 Months or Longer, Gross Unrealized Losses	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	5,739
Fair Value	$ 431,009
U.S. Agency bonds
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | holding	13	6
Less than 12 Months, Gross Unrealized Losses	$ 10,010	$ 3,872
Less than 12 Months, Fair Value	529,855	416,824
12 Months or Longer, Gross Unrealized Losses	9,302	0
12 Months or Longer, Fair Value	311,428	0
Gross Unrealized Losses	19,312	3,872
Fair Value	$ 841,283	$ 416,824
U.S. Treasury securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | holding	1
Less than 12 Months, Gross Unrealized Losses	$ 253
Less than 12 Months, Fair Value	49,137
12 Months or Longer, Gross Unrealized Losses	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	253
Fair Value	$ 49,137

Loans and Allowance for Loan _3

Loans and Allowance for Loan Losses - Summary of Company's Loan Portfolio as of the Dates Indicated (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 9,504,562		$ 9,730,525
Allowance for loan losses	(103,398)	$ (105,637)	(113,031)	$ (115,432)	$ (116,636)	$ (82,297)
Unamortized premiums, net of unearned discounts and deferred fees	(23,104)		(23,536)
Net loans	9,378,060		9,593,958
Commercial and Industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,652,447		1,995,016
Allowance for loan losses	(20,629)	(22,596)	(26,617)	(30,114)	(33,229)	(20,919)
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,825,186		3,573,630
Allowance for loan losses	(54,186)	(52,759)	(54,569)	(55,582)	(54,228)	(34,730)
Commercial Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	243,146		305,708
Allowance for loan losses	(3,402)	(3,446)	(4,553)	(4,276)	(4,816)	(3,424)
Business Banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,225,538		1,339,164
Allowance for loan losses	(11,378)	(12,705)	(13,152)	(11,428)	(9,805)	(8,260)
Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,491,269		1,370,957
Allowance for loan losses	(6,430)	(6,478)	(6,435)	(6,351)	(6,569)	(6,380)
Consumer Home Equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	848,570		868,270
Allowance for loan losses	(3,635)	(3,588)	(3,744)	(3,808)	(3,875)	(4,027)
Other Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	218,406		277,780
Allowance for loan losses	(3,387)	$ (3,626)	(3,467)	$ (3,558)	$ (3,762)	$ (4,173)
Other Consumer, Automobile Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 67,100		$ 126,700

Loans and Allowance for Loan _4

Loans and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Changes in lines of credit,resrticted to commercial exposure
Loan syndications, amount	$ 100,000,000		$ 100,000,000
Mortgage loans partially or wholly-owned by others and serviced by the Company	12,000,000		12,000,000		$ 13,500,000
Loans, net of allowance for loan losses	9,378,060,000		9,378,060,000		9,593,958,000
Total loans	9,504,562,000		$ 9,504,562,000		9,730,525,000
Maximum number of days required for special mention			90 days
Amount of specific reserve associated with the TDR	3,100,000		$ 3,100,000		3,500,000
Amount of additional commitments to lend to borrowers who have been a party to a TDR	500,000		500,000		0
Outstanding recorded investment of loans that were new to troubled debt restructuring	1,000,000		1,000,000		3,900,000
Amounts charged-off on TDRs	0	$ 200,000	0	$ 600,000
CARES Act | Payment Deferral
Changes in lines of credit,resrticted to commercial exposure
Loans which underwent a modification, CARES Act			110,600,000		332,700,000
Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,652,447,000		1,652,447,000		1,995,016,000
Business Banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,225,538,000		1,225,538,000		1,339,164,000
Federal Home Loan Bank Advances
Changes in lines of credit,resrticted to commercial exposure
Carrying value of loans pledged to secure advances from federal banks	2,400,000,000		2,400,000,000		2,400,000,000
Funds borrowed from federal banks	14,200,000		14,200,000		14,600,000
Federal Reserve Bank Advances
Changes in lines of credit,resrticted to commercial exposure
Carrying value of loans pledged to secure advances from federal banks	761,800,000		761,800,000		884,100,000
Funds borrowed from federal banks	0		0		0
Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	6,946,317,000		6,946,317,000		7,213,518,000
Nonperforming Loans | Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,652,447,000		1,652,447,000		1,995,016,000
Nonperforming Loans | Business Banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,225,538,000		1,225,538,000		1,339,164,000
Unrated
Changes in lines of credit,resrticted to commercial exposure
Lines of credit, exposure	100,000		100,000
Unrated | Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,046,000,000		1,046,000,000		1,580,852,000
Unrated | Nonperforming Loans | Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	278,093,000		278,093,000		655,346,000
Unrated | Nonperforming Loans | Business Banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	763,573,000		763,573,000		918,921,000
Unrated | Nonperforming Loans | Paycheck Protection Program | Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	215,700,000		215,700,000		568,800,000
Unrated | Nonperforming Loans | Paycheck Protection Program | Business Banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	318,300,000		318,300,000		457,400,000
Unrated | Line of Credit | Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Lines of credit, exposure	1,000,000		1,000,000
Unrated | Line of Credit | Business Banking
Changes in lines of credit,resrticted to commercial exposure
Lines of credit, exposure	1,000,000		1,000,000
Loss
Changes in lines of credit,resrticted to commercial exposure
Loans, net of allowance for loan losses	0		0
Loss | Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	0		0		0
Loss | Nonperforming Loans | Commercial and Industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	0		0		0
Loss | Nonperforming Loans | Business Banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	$ 0		$ 0		$ 0

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 105,637	$ 116,636	$ 113,031	$ 82,297	$ 82,297
Charge-offs	(1,617)	(2,418)	(6,262)	(6,025)
Recoveries	866	514	1,997	1,260
(Release of) provision	(1,488)	700	(5,368)	37,900
Ending balance	103,398	115,432	103,398	115,432	113,031
Allowance for loan losses ending balance:
Individually evaluated for impairment	6,874		6,874		8,054
Acquired with deteriorated credit quality	293		293		2,432
Collectively evaluated for impairment			96,231		102,545
Total allowance for loan losses by group	103,398	115,432	103,398	115,432	113,031
Loans ending balance:
Individually evaluated for impairment			68,253		75,609
Acquired with deteriorated credit quality	4,426		4,426		9,297
Collectively evaluated for impairment	9,431,883		9,431,883		9,645,619
Gross loans before unamortized premiums, unearned discounts and deferred fees	9,504,562		9,504,562		9,730,525
Commercial and Industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	22,596	33,229	26,617	20,919	20,919
Charge-offs	0	(140)	(550)	(167)
Recoveries	40	306	62	686
(Release of) provision	(2,007)	(3,281)	(5,500)	8,676
Ending balance	20,629	30,114	20,629	30,114	26,617
Allowance for loan losses ending balance:
Individually evaluated for impairment	4,287		4,287		4,555
Acquired with deteriorated credit quality	0		0		1,283
Collectively evaluated for impairment			16,342		20,779
Total allowance for loan losses by group	20,629	30,114	20,629	30,114	26,617
Loans ending balance:
Individually evaluated for impairment			21,580		17,343
Acquired with deteriorated credit quality	1,546		1,546		3,432
Collectively evaluated for impairment	1,629,321		1,629,321		1,974,241
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,652,447		1,652,447		1,995,016
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	52,759	54,228	54,569	34,730	34,730
Charge-offs	(8)	0	(242)	(24)
Recoveries	0	4	4	10
(Release of) provision	1,435	1,350	(145)	20,866
Ending balance	54,186	55,582	54,186	55,582	54,569
Allowance for loan losses ending balance:
Individually evaluated for impairment	0		0		210
Acquired with deteriorated credit quality	0		0		822
Collectively evaluated for impairment			54,186		53,537
Total allowance for loan losses by group	54,186	55,582	54,186	55,582	54,569
Loans ending balance:
Individually evaluated for impairment			3,793		4,435
Acquired with deteriorated credit quality	0		0		2,749
Collectively evaluated for impairment	3,821,393		3,821,393		3,566,446
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,825,186		3,825,186		3,573,630
Commercial Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,446	4,816	4,553	3,424	3,424
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
(Release of) provision	(44)	(540)	(1,151)	852
Ending balance	3,402	4,276	3,402	4,276	4,553
Allowance for loan losses ending balance:
Individually evaluated for impairment	0		0		0
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment			3,402		4,553
Total allowance for loan losses by group	3,402	4,276	3,402	4,276	4,553
Loans ending balance:
Individually evaluated for impairment			0		0
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment	243,146		243,146		305,708
Gross loans before unamortized premiums, unearned discounts and deferred fees	243,146		243,146		305,708
Business Banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	12,705	9,805	13,152	8,260	8,260
Charge-offs	(867)	(1,179)	(4,089)	(3,714)
Recoveries	469	91	1,125	245
(Release of) provision	(929)	2,711	1,190	6,637
Ending balance	11,378	11,428	11,378	11,428	13,152
Allowance for loan losses ending balance:
Individually evaluated for impairment	669		669		1,435
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment			10,709		11,717
Total allowance for loan losses by group	11,378	11,428	11,378	11,428	13,152
Loans ending balance:
Individually evaluated for impairment			15,141		21,901
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment	1,210,397		1,210,397		1,317,263
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,225,538		1,225,538		1,339,164
Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,478	6,569	6,435	6,380	6,380
Charge-offs	0	0	0	0
Recoveries	88	43	115	116
(Release of) provision	(136)	(261)	(120)	(145)
Ending balance	6,430	6,351	6,430	6,351	6,435
Allowance for loan losses ending balance:
Individually evaluated for impairment	1,462		1,462		1,565
Acquired with deteriorated credit quality	293		293		327
Collectively evaluated for impairment			4,675		4,543
Total allowance for loan losses by group	6,430	6,351	6,430	6,351	6,435
Loans ending balance:
Individually evaluated for impairment			23,494		27,056
Acquired with deteriorated credit quality	2,880		2,880		3,116
Collectively evaluated for impairment	1,464,895		1,464,895		1,340,785
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,491,269		1,491,269		1,370,957
Consumer Home Equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,588	3,875	3,744	4,027	4,027
Charge-offs	0	(22)	0	(495)
Recoveries	63	31	137	53
(Release of) provision	(16)	(76)	(246)	223
Ending balance	3,635	3,808	3,635	3,808	3,744
Allowance for loan losses ending balance:
Individually evaluated for impairment	256		256		289
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment			3,379		3,455
Total allowance for loan losses by group	3,635	3,808	3,635	3,808	3,744
Loans ending balance:
Individually evaluated for impairment			4,023		4,845
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment	844,547		844,547		863,425
Gross loans before unamortized premiums, unearned discounts and deferred fees	848,570		848,570		868,270
Other Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,626	3,762	3,467	4,173	4,173
Charge-offs	(742)	(1,077)	(1,381)	(1,625)
Recoveries	206	39	554	150
(Release of) provision	297	834	747	860
Ending balance	3,387	3,558	3,387	3,558	3,467
Allowance for loan losses ending balance:
Individually evaluated for impairment	200		200		0
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment			3,187		3,467
Total allowance for loan losses by group	3,387	3,558	3,387	3,558	3,467
Loans ending balance:
Individually evaluated for impairment			222		29
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment	218,184		218,184		277,751
Gross loans before unamortized premiums, unearned discounts and deferred fees	218,406		218,406		277,780
Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	439	352	494	384	384
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
(Release of) provision	(88)	(37)	(143)	(69)
Ending balance	351	315	351	315	494
Allowance for loan losses ending balance:
Individually evaluated for impairment	0		0		0
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment			351		494
Total allowance for loan losses by group	351	$ 315	351	$ 315	494
Loans ending balance:
Individually evaluated for impairment			0		0
Acquired with deteriorated credit quality	0		0		0
Collectively evaluated for impairment	0		0		0
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 0		$ 0		$ 0

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Summary of Internal Risk-rating Categories (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 9,504,562	$ 9,730,525
Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	6,946,317	7,213,518
Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,046,000	1,580,852
Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	5,441,602	5,073,668
Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	202,780	280,101
Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	238,329	260,207
Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	17,606	18,690
Loss | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,652,447	1,995,016
Commercial and Industrial | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,652,447	1,995,016
Commercial and Industrial | Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	278,093	655,346
Commercial and Industrial | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,302,413	1,199,522
Commercial and Industrial | Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	13,959	78,117
Commercial and Industrial | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	41,459	47,525
Commercial and Industrial | Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	16,523	14,506
Commercial and Industrial | Loss | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,825,186	3,573,630
Commercial Real Estate | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,825,186	3,573,630
Commercial Real Estate | Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	4,196	6,585
Commercial Real Estate | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,524,607	3,256,697
Commercial Real Estate | Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	124,618	134,562
Commercial Real Estate | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	171,765	173,308
Commercial Real Estate | Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	2,478
Commercial Real Estate | Loss | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Commercial Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	243,146	305,708
Commercial Construction | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	243,146	305,708
Commercial Construction | Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	138	0
Commercial Construction | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	224,770	280,792
Commercial Construction | Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	9,611	10,330
Commercial Construction | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	8,627	14,586
Commercial Construction | Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Commercial Construction | Loss | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Business Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,225,538	1,339,164
Business Banking | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,225,538	1,339,164
Business Banking | Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	763,573	918,921
Business Banking | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	389,812	336,657
Business Banking | Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	54,592	57,092
Business Banking | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	16,478	24,788
Business Banking | Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,083	1,706
Business Banking | Loss | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 0	$ 0

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Summary Pertaining to the Breakdown of the Company's Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	$ 40,613	$ 41,005
Commercial and Industrial
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	17,640	11,714
Commercial Real Estate
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	272	915
Business banking
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	11,254	17,430
Residential real estate
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	7,185	6,815
Consumer home equity
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	3,491	3,602
Other Consumer
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	$ 771	$ 529

Loans and Allowance for Loan _8

Loans and Allowance for Loan Losses - Summary of Shows the Age Analysis of Past Due Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans	$ 9,504,562	$ 9,730,525
Recorded Investment > 90 Days Past Due and Accruing	1,458	2,247
Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	40,333	47,622
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	16,320	18,251
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	5,905	7,250
90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	18,108	22,121
Current
Financing Receivable, Past Due [Line Items]
Total loans	9,464,229	9,682,903
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total loans	1,652,447	1,995,016
Recorded Investment > 90 Days Past Due and Accruing	0	848
Commercial and Industrial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	4,640	2,196
Commercial and Industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	529	4
Commercial and Industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	2,068	268
Commercial and Industrial | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	2,043	1,924
Commercial and Industrial | Current
Financing Receivable, Past Due [Line Items]
Total loans	1,647,807	1,992,820
Commercial Real Estate
Financing Receivable, Past Due [Line Items]
Total loans	3,825,186	3,573,630
Recorded Investment > 90 Days Past Due and Accruing	1,171	1,111
Commercial Real Estate | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	1,171	2,101
Commercial Real Estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Real Estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	556
Commercial Real Estate | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	1,171	1,545
Commercial Real Estate | Current
Financing Receivable, Past Due [Line Items]
Total loans	3,824,015	3,571,529
Commercial Construction
Financing Receivable, Past Due [Line Items]
Total loans	243,146	305,708
Recorded Investment > 90 Days Past Due and Accruing	0	0
Commercial Construction | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Construction | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Construction | Current
Financing Receivable, Past Due [Line Items]
Total loans	243,146	305,708
Business banking
Financing Receivable, Past Due [Line Items]
Total loans	1,225,538	1,339,164
Recorded Investment > 90 Days Past Due and Accruing	0	0
Business banking | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	9,482	18,786
Business banking | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	3,351	5,279
Business banking | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	634	3,311
Business banking | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	5,497	10,196
Business banking | Current
Financing Receivable, Past Due [Line Items]
Total loans	1,216,056	1,320,378
Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans	1,491,269	1,370,957
Recorded Investment > 90 Days Past Due and Accruing	278	279
Residential real estate | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	16,955	16,605
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	9,014	9,184
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	2,426	2,517
Residential real estate | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	5,515	4,904
Residential real estate | Current
Financing Receivable, Past Due [Line Items]
Total loans	1,474,314	1,354,352
Consumer home equity
Financing Receivable, Past Due [Line Items]
Total loans	848,570	868,270
Recorded Investment > 90 Days Past Due and Accruing	9	9
Consumer home equity | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	5,845	5,205
Consumer home equity | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	2,319	1,806
Consumer home equity | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	415	364
Consumer home equity | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	3,111	3,035
Consumer home equity | Current
Financing Receivable, Past Due [Line Items]
Total loans	842,725	863,065
Other Consumer
Financing Receivable, Past Due [Line Items]
Total loans	218,406	277,780
Recorded Investment > 90 Days Past Due and Accruing	0	0
Other Consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans	2,240	2,729
Other Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	1,107	1,978
Other Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	362	234
Other Consumer | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	771	517
Other Consumer | Current
Financing Receivable, Past Due [Line Items]
Total loans	$ 216,166	$ 275,051

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Summary of TDR Loans on Accrual and Nonaccrual (Detail) $ in Thousands	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2021USD ($)contract	Sep. 30, 2020contract	Sep. 30, 2021USD ($)loan	Sep. 30, 2021USD ($)contract	Sep. 30, 2020contract	Dec. 31, 2020USD ($)loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	2	3	263	4	25	301
Balance of Loans	$ 50,826		$ 50,826	$ 50,826		$ 53,204
TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			209			248
Balance of Loans	34,723		$ 34,723	34,723		$ 41,095
TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			54			53
Balance of Loans	16,103		$ 16,103	16,103		$ 12,109
Commercial and Industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans		0	7		1	8
Balance of Loans	14,884		$ 14,884	14,884		$ 12,447
Commercial and Industrial | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			1
Balance of Loans	3,940		$ 3,940	3,940		$ 5,628
Commercial and Industrial | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			6			7
Balance of Loans	10,944		$ 10,944	10,944		$ 6,819
Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans		0	1		2	2
Balance of Loans	3,520		$ 3,520	3,520		$ 4,001
Commercial Real Estate | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			1
Balance of Loans	3,520		$ 3,520	3,520		$ 3,521
Commercial Real Estate | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			0			1
Balance of Loans	$ 0		$ 0	$ 0		$ 480
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	0	0	10	1	3	12
Balance of Loans	$ 5,150		$ 5,150	$ 5,150		$ 5,193
Business banking | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			5			6
Balance of Loans	3,888		$ 3,888	3,888		$ 4,471
Business banking | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			5			6
Balance of Loans	$ 1,262		$ 1,262	$ 1,262		$ 722
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	0	0	153	1	3	173
Balance of Loans	$ 23,227		$ 23,227	$ 23,227		$ 26,689
Residential real estate | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			127			146
Balance of Loans	20,092		$ 20,092	20,092		$ 23,416
Residential real estate | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			26			27
Balance of Loans	$ 3,135		$ 3,135	$ 3,135		$ 3,273
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	2	0	89	2	12	103
Balance of Loans	$ 4,024		$ 4,024	$ 4,024		$ 4,845
Consumer home equity | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			73			91
Balance of Loans	3,280		$ 3,280	3,280		$ 4,030
Consumer home equity | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			16			12
Balance of Loans	744		$ 744	744		$ 815
Other Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans		3	3		4	3
Balance of Loans	21		$ 21	21		$ 29
Other Consumer | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			2			3
Balance of Loans	3		$ 3	3		$ 29
Other Consumer | TDRs on Non-Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			0
Balance of Loans	$ 18		$ 18	$ 18		$ 0

Loans and Allowance for Loan_10

Loans and Allowance for Loan Losses - Summary of the Modifications Which Occurred During the Periods and the Change in the Recorded Investment Subsequent to the Modifications Occurring (Detail) $ in Thousands	3 Months Ended		9 Months Ended				12 Months Ended
	Sep. 30, 2021USD ($)contract	Sep. 30, 2020USD ($)contract	Sep. 30, 2021loan	Sep. 30, 2021contract	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)contract	Dec. 31, 2020loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	2	3	263	4		25	301
Pre- Modification Outstanding Recorded Investment	$ 200	$ 35			$ 957	$ 2,796
Post-Modification Modification Outstanding Recorded Investment	$ 200	$ 35			957	$ 2,800
Commercial and Industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts		0	7			1	8
Pre- Modification Outstanding Recorded Investment		$ 0				$ 140
Post-Modification Modification Outstanding Recorded Investment		$ 0				$ 140
Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts		0	1			2	2
Pre- Modification Outstanding Recorded Investment		$ 0				$ 632
Post-Modification Modification Outstanding Recorded Investment		$ 0				$ 632
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	0	0	10	1		3	12
Pre- Modification Outstanding Recorded Investment	$ 0	$ 0			462	$ 1,040
Post-Modification Modification Outstanding Recorded Investment	$ 0	$ 0			462	$ 1,040
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	0	0	153	1		3	173
Pre- Modification Outstanding Recorded Investment	$ 0	$ 0			295	$ 399
Post-Modification Modification Outstanding Recorded Investment	$ 0	$ 0			295	$ 399
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	2	0	89	2		12	103
Pre- Modification Outstanding Recorded Investment	$ 200	$ 0			200	$ 527
Post-Modification Modification Outstanding Recorded Investment	$ 200	$ 0			$ 200	$ 531
Other Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts		3	3			4	3
Pre- Modification Outstanding Recorded Investment		$ 35				$ 58
Post-Modification Modification Outstanding Recorded Investment		$ 35				$ 58

Loans and Allowance for Loan_11

Loans and Allowance for Loan Losses - Summary of Post-modification Balance of TDRs listed by Type of Modification (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	$ 200	$ 35	$ 957	$ 2,800
Interest only/principal deferred
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	0	0	0	1,305
Extended maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	200	0	200	35
Extended maturity and interest only/principal deferred
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	0	0	0	427
Court-ordered concession
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	0	35	295	1,033
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	$ 0	$ 0	$ 462	$ 0

Loans and Allowance for Loan_12

Loans and Allowance for Loan Losses - Summary of Subsequent Default (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)loan	Sep. 30, 2020USD ($)loan	Sep. 30, 2021USD ($)loan	Sep. 30, 2020USD ($)loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | loan	0	1	2	1
Recorded Investment | $	$ 0	$ 40	$ 460	$ 40
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | loan	0	0	1	0
Recorded Investment | $	$ 0	$ 0	$ 404	$ 0
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | loan	0	1	1	1
Recorded Investment | $	$ 0	$ 40	$ 56	$ 40

Loans and Allowance for Loan_13

Loans and Allowance for Loan Losses - Summary of Company's Impaired Loans by Loan Portfolio (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	$ 34,426	$ 35,717
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	38,228	42,455
Impaired financing receivable, with no related allowance, Recorded Investment	33,827	39,892
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	38,798	44,675
Impaired financing receivable, Related Allowance	6,874	8,054
Impaired financing receivable, Recorded Investment	68,253	75,609
Impaired financing receivable, Unpaid Principal Balance	77,026	87,130
Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	13,807	9,182
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	15,188	11,212
Impaired financing receivable, with no related allowance, Recorded Investment	7,773	8,161
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	8,350	8,432
Impaired financing receivable, Related Allowance	4,287	4,555
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	3,793	3,955
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	3,832	3,974
Impaired financing receivable, with no related allowance, Recorded Investment	0	480
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	0	497
Impaired financing receivable, Related Allowance	0	210
Business banking
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	3,557	5,250
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	4,564	7,659
Impaired financing receivable, with no related allowance, Recorded Investment	11,584	16,651
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	15,978	21,146
Impaired financing receivable, Related Allowance	669	1,435
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	11,352	14,730
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	12,727	17,010
Impaired financing receivable, with no related allowance, Recorded Investment	12,142	12,326
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	12,142	12,326
Impaired financing receivable, Related Allowance	1,462	1,565
Consumer home equity
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	1,895	2,571
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	1,895	2,571
Impaired financing receivable, with no related allowance, Recorded Investment	2,128	2,274
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	2,128	2,274
Impaired financing receivable, Related Allowance	256	289
Other Consumer
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	22	29
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	22	29
Impaired financing receivable, with no related allowance, Recorded Investment	200	0
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	200	0
Impaired financing receivable, Related Allowance	$ 200	$ 0

Loans and Allowance for Loan_14

Loans and Allowance for Loan Losses - Summary of Information Regarding Interest Income Recognized on Impaired Loans, by Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	$ 33,874	$ 33,859	$ 34,399	$ 38,830
Impaired financing receivable, with no related allowance, Total Interest Recognized	235	274	730	828
Impaired financing receivable, with related allowance, Average Recorded Investment	34,915	41,280	38,027	38,256
Impaired financing receivable, with related allowance, Total Interest Recognized	156	182	483	559
Impaired financing receivable, Average Recorded Investment	68,789	75,139	72,426	77,086
Impaired financing receivable, Total Interest Recognized	391	456	1,213	1,387
Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	12,517	9,273	11,405	14,152
Impaired financing receivable, with no related allowance, Total Interest Recognized	39	48	131	167
Impaired financing receivable, with related allowance, Average Recorded Investment	7,808	6,229	7,849	8,168
Impaired financing receivable, with related allowance, Total Interest Recognized	0	0	0	0
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	3,909	4,408	4,047	5,433
Impaired financing receivable, with no related allowance, Total Interest Recognized	45	45	133	134
Impaired financing receivable, with related allowance, Average Recorded Investment	0	1,017	271	625
Impaired financing receivable, with related allowance, Total Interest Recognized	0	0	0	0
Commercial Construction
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment		280		125
Impaired financing receivable, with no related allowance, Total Interest Recognized		0		0
Business banking
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	3,988	3,298	4,586	2,659
Impaired financing receivable, with no related allowance, Total Interest Recognized	25	30	75	66
Impaired financing receivable, with related allowance, Average Recorded Investment	12,642	17,452	14,560	13,063
Impaired financing receivable, with related allowance, Total Interest Recognized	14	15	43	44
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	11,561	13,513	12,349	13,141
Impaired financing receivable, with no related allowance, Total Interest Recognized	113	129	344	399
Impaired financing receivable, with related allowance, Average Recorded Investment	12,290	14,165	13,093	13,708
Impaired financing receivable, with related allowance, Total Interest Recognized	127	144	387	446
Consumer home equity
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	1,877	3,034	1,988	3,287
Impaired financing receivable, with no related allowance, Total Interest Recognized	13	21	47	61
Impaired financing receivable, with related allowance, Average Recorded Investment	2,108	2,417	2,232	2,692
Impaired financing receivable, with related allowance, Total Interest Recognized	15	23	53	69
Other Consumer
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	22	53	24	33
Impaired financing receivable, with no related allowance, Total Interest Recognized	0	$ 1	0	$ 1
Impaired financing receivable, with related allowance, Average Recorded Investment	67		22
Impaired financing receivable, with related allowance, Total Interest Recognized	$ 0		$ 0

Loans and Allowance for Loan_15

Loans and Allowance for Loan Losses - Summary of Outstanding and Carrying Amounts of PCI Loans (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	$ 68,253	$ 75,609
Outstanding balance
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	4,484	9,982
Carrying amount
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	$ 4,426	$ 9,297

Loans and Allowance for Loan_16

Loans and Allowance for Loan Losses - Summary of Activity in the Accretable Yield for the PCI Loan Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 2,981	$ 2,994	$ 2,495	$ 3,923
Accretion	(245)	(298)	(877)	(1,058)
Other change in expected cash flows	(1,161)	(44)	(1,370)	(209)
Reclassification from (to) non-accretable difference for loans with improved (deteriorated) cash flows	0	0	1,327	(4)
Balance at end of period	$ 1,575	$ 2,652	$ 1,575	$ 2,652

Loans and Allowance for Loan_17

Loans and Allowance for Loan Losses - Summary of the Company's Loan participations (Detail) - Loan Participations and Assignments - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 1,090,489	$ 1,024,709
Non-performing Loan Rate (%)	1.00%	0.65%
Impaired (%)	1.00%	0.65%
Gross Charge-offs	$ 0	$ 15
Commercial and Industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 632,229	$ 598,873
Non-performing Loan Rate (%)	1.73%	1.11%
Impaired (%)	1.73%	1.11%
Gross Charge-offs	$ 0	$ 0
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 385,782	$ 306,202
Non-performing Loan Rate (%)	0.00%	0.00%
Impaired (%)	0.00%	0.00%
Gross Charge-offs	$ 0	$ 0
Commercial Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 72,374	$ 119,600
Non-performing Loan Rate (%)	0.00%	0.00%
Impaired (%)	0.00%	0.00%
Gross Charge-offs	$ 0	$ 0
Business banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 104	$ 34
Non-performing Loan Rate (%)	0.00%	0.00%
Impaired (%)	0.00%	0.00%
Gross Charge-offs	$ 0	$ 15

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disclosure of Leases [Line Items]
Payment of lease payments	$ 3.5	$ 3.6	$ 10.6	$ 10.6
Minimum
Disclosure of Leases [Line Items]
Operating lease remaining lease term	1 year		1 year
Maximum
Disclosure of Leases [Line Items]
Operating lease remaining lease term	25 years		25 years

Leases - Summary of Information

Leases - Summary of Information Relating to Operating Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Right-of-use assets	$ 75,196	$ 81,596
Lease liabilities	$ 79,187	$ 85,330

Leases - Summary of Net Lease C

Leases - Summary of Net Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 3,478	$ 3,596	$ 10,560	$ 10,810
Finance lease cost	50	24	116	43
Variable lease cost	617	509	1,564	1,479
Total lease cost	$ 4,145	$ 4,129	$ 12,240	$ 12,332

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information Related to Operating Leases (Detail)	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted-average remaining lease term (in years)	7 years 11 months 15 days	8 years 6 months
Weighted-average discount rate	2.62%	2.65%

Goodwill and Other Intangible_2

Goodwill and Other Intangibles - Summary of Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balances not subject to amortization
Goodwill	$ 372,472	$ 369,477
Balances subject to amortization
Total other intangible assets	7,300	7,057
Total goodwill and other intangible assets	379,772	376,534
Insurance agency
Balances subject to amortization
Balances subject to amortization	7,234	6,899
Core deposit intangible
Balances subject to amortization
Balances subject to amortization	66	158
Banking Business
Balances not subject to amortization
Goodwill	298,611	298,611
Balances subject to amortization
Total other intangible assets	66	158
Total goodwill and other intangible assets	298,677	298,769
Banking Business | Insurance agency
Balances subject to amortization
Balances subject to amortization	0	0
Banking Business | Core deposit intangible
Balances subject to amortization
Balances subject to amortization	66	158
Insurance Agency Business
Balances not subject to amortization
Goodwill	73,861	70,866
Balances subject to amortization
Total other intangible assets	7,234	6,899
Total goodwill and other intangible assets	81,095	77,765
Insurance Agency Business | Insurance agency
Balances subject to amortization
Balances subject to amortization	7,234	6,899
Insurance Agency Business | Core deposit intangible
Balances subject to amortization
Balances subject to amortization	$ 0	$ 0

Goodwill and Other Intangible_3

Goodwill and Other Intangibles - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021agencyreporting_unit
Business Acquisition [Line Items]
Number of reporting units | reporting_unit	2
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Number of insurance agencies acquired | agency	2

Earnings Per Share ("EPS") (Det

Earnings Per Share ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income applicable to common shares	$ 37,106		$ 119,578
Average number of common shares outstanding (in shares)	186,758,154		186,758,154
Less: Average unallocated ESOP shares (in shares)	(14,459,539)		(14,583,685)
Average number of common shares outstanding used to calculate basic earnings per common share (in shares)	172,298,615		172,174,469
Common stock equivalents (in shares)	0		0
Average number of common shares outstanding used to calculate diluted earnings per common share (in shares)	172,298,615		172,174,469
Earnings per common share
Basic earnings per share (in dollars per share)	$ 0.22	$ 0	$ 0.69	$ 0
Diluted earnings per share (in dollars per share)	$ 0.22	$ 0	$ 0.69	$ 0

Low Income Housing Tax Credit_3

Low Income Housing Tax Credits and Other Tax Credit Investments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Investments In Affordable Housing Projects [Line Items]
Tax credit investment			$ 85,500,000	$ 59,800,000
Renewable Energy Program
Investments In Affordable Housing Projects [Line Items]
Equity investments	$ 3,000,000		3,000,000	1,200,000
Outstanding investment commitments	0		$ 0	$ 1,700,000
Low income housing tax credit and other tax credit investments
Investments In Affordable Housing Projects [Line Items]
Tax credit period of benefits			15 years
Operating loss tax benefits period			15 years
Tax credit write off		$ 7,600,000
Impairment (recovery) as a result of management's review of tax credit equity investments	$ 1,100,000		$ (300,000)

Low Income Housing Tax Credit_4

Low Income Housing Tax Credits and Other Tax Credit Investments - Summary of the Company's Investments in Low Income Housing Projects Accounted for Using the Proportional Amortization Method (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Investments in Affordable Housing Projects [Abstract]
Current recorded investment included in other assets	$ 82,533		$ 82,533		$ 58,504
Commitments to fund qualified affordable housing projects included in recorded investment noted above	49,611		49,611		$ 31,487
Tax credits and benefits recognized	1,730	$ 1,539	4,717	$ 4,597
Amortization expense included in income tax expense	$ 1,496	$ 1,263	$ 4,255	$ 3,715

Employee Benefits - Narrative (

Employee Benefits - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Nov. 01, 2020	Oct. 31, 2020
Primary Beneficiary
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments	$ 98,174		$ 98,174		$ 91,683
Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Decrease in non-service cost expense	$ 3,800		$ 11,500
Discretionary employer contributions to defined benefit plans		$ 0		$ 32,500
Qualified Plan | Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Contribution credits rate							3.50%
Nonqualified Plan | Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Contribution credits rate						5.00%

Employee Benefits - Summary of

Employee Benefits - Summary of Components of Net Pension Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Components of net periodic benefit cost:
Service cost	$ 7,896	$ 6,231	$ 23,690	$ 18,694
Interest cost	1,269	2,617	3,805	7,849
Expected return on plan assets	(8,141)	(7,427)	(24,424)	(22,277)
Past service cost	(2,945)	7	(8,835)	19
Recognized net actuarial loss	3,537	2,361	10,612	7,082
Net periodic benefit cost	$ 1,616	$ 3,789	$ 4,848	$ 11,367

Employee Benefits - Asset Held

Employee Benefits - Asset Held in Rabbi Trust by Plan Type (Details) - Primary Beneficiary - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Book Value	$ 78,122	$ 71,833
Mark-to-Market	20,052	19,850
Fair Value	98,174	91,683
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Book Value	4,476	5,157
Fair Value	4,476	5,157
Equities
Defined Benefit Plan Disclosure [Line Items]
Book Value	65,670	59,235
Mark-to-Market	19,880	19,492
Fair Value	85,550	78,727
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Book Value	7,976	7,441
Mark-to-Market	172	358
Fair Value	$ 8,148	$ 7,799

Commitments and Contingencies -

Commitments and Contingencies - Summary of Financial Instruments as of the Dates Indicated (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Commitments to extend credit
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	$ 4,387,306	$ 3,818,952
Standby letters of credit
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	58,734	60,221
Forward commitments to sell loans
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	$ 49,105	$ 41,160

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Jun. 30, 2021settlement	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Disclosure of Commitments and Contingencies [Line Items]
Number of legal settlements | settlement	2
Estimates of the settlement		$ 3,300,000
Cash and Cash Equivalents
Disclosure of Commitments and Contingencies [Line Items]
Other contingencies		$ 0	$ 0

Derivative Financial Instrume_3

Derivative Financial Instruments - Pre-tax Impact of Terminated Cash Flow Hedges on AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning Balance	$ 3,430,622	$ 1,693,630	$ 3,428,052	$ 1,600,153
Unrealized gains on terminated hedges arising during the period	0	26,410	0	57,362
Reclassification adjustments for amortization of unrealized (gains) into net income	(7,851)	(7,036)	(24,344)	(7,409)
Ending balance	3,429,292	1,713,372	3,429,292	1,713,372
Accumulated Gain (Loss), Net, Terminated Cash Flow Hedge, Parent
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning Balance	24,980	30,579	41,473	0
Ending balance	$ 17,129	$ 49,953	$ 17,129	$ 49,953

Derivative Financial Instrume_4

Derivative Financial Instruments - Additional information (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Credit exposure to settled variation margin in excess of customer related interest rate swap (less than)	$ 0	$ 0.1
Non Cleared Derivative Transactions | Customer Related Interest Rate Swap Derivatives
Derivative [Line Items]
Fair value of interest rate swap liabilities that are net in a net liability position	21.7	42.6
Cash and Cash Equivalents | Non Cleared Derivative Transactions | Customer Related Interest Rate Swap Derivatives
Derivative [Line Items]
Additional collateral posted	27.8
Available-for-sale Securities | Non Cleared Derivative Transactions | Customer Related Interest Rate Swap Derivatives
Derivative [Line Items]
Additional collateral posted		49.2
Restricted Assets | Cash and Cash Equivalents | Cleared Derivative Transaction
Derivative [Line Items]
Additional collateral posted	49.4
Restricted Assets | Available-for-sale Securities | Cleared Derivative Transaction
Derivative [Line Items]
Additional collateral posted		$ 60.4
Interest Income | Termination Of Cash Flow Hedges
Derivative [Line Items]
Interest rate swap cash flow hedges amount expected to reclassified from other comprehensive income to income statement in the next twelve months	$ 16.5

Derivative Financial Instrume_5

Derivative Financial Instruments - Customer-related derivative positions (Detail) - Not Designated as Hedging Instrument $ in Thousands	Sep. 30, 2021USD ($)position	Dec. 31, 2020USD ($)position
Interest rate swaps
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions | position	510	576
Total Notional | $	$ 3,169,358	$ 3,652,385
Risk participation agreements
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions | position	66	70
Total Notional | $	$ 263,847	$ 287,732
Matched commercial customer book
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions | position	52	40
Total Notional | $	$ 6,516	$ 4,242
Foreign currency loan
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions | position	4	3
Total Notional | $	$ 9,977	$ 10,798

Derivative Financial Instrume_6

Derivative Financial Instruments - Classification on the balance sheet for the periods indicated (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Asset Derivatives
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Interest rate swaps, Other assets	$ 80,102	$ 141,822
Derivatives not designated as hedging instruments, Other assets	80,613	142,643
Asset Derivatives | Risk participation agreements
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	347	722
Asset Derivatives | Foreign currency exchange contracts - matched customer book
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	44	90
Asset Derivatives | Foreign currency exchange contracts - foreign currency loan
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	120	9
Liability Derivatives
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivative not designated as hedging instruments, Interest rate swaps, Other liabilities	25,274	42,600
Derivatives not designated as hedging instruments, Other liabilities	25,899	43,976
Liability Derivatives | Risk participation agreements
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	594	1,230
Liability Derivatives | Foreign currency exchange contracts - matched customer book
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	31	77
Liability Derivatives | Foreign currency exchange contracts - foreign currency loan
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	$ 0	$ 69

Derivative Financial Instrume_7

Derivative Financial Instruments - Company's derivative financial instruments included in OCI as follows (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain in OCI on derivatives	$ 0	$ (142)	$ 0	$ 46,869
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
Gain (loss) recognized in other income for foreign currency exchange contracts:	908	978	5,037	(6,271)
Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain reclassified from OCI into interest income (effective portion)	7,851	8,405	24,344	18,651
Interest Income | Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
Interest Income | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Customer-related positions:	832	904	4,596	(6,063)
Interest Income | Risk participation agreements
Derivative Instruments, Gain (Loss) [Line Items]
Customer-related positions:	(4)	11	260	(370)
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
Other Income | Foreign currency exchange contracts - matched customer book
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other income for foreign currency exchange contracts:	8	(86)	0	(17)
Other Income | Foreign currency exchange contracts - foreign currency loan
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other income for foreign currency exchange contracts:	$ 72	$ 149	$ 181	$ 179

Balance Sheet Offsetting - Disc

Balance Sheet Offsetting - Disclosure Detail Of Balance Sheet Offsetting Of Financial Assets And Liabilities (Detail) - Customer-related positions - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Derivative Assets
Gross Amounts Recognized	$ 80,613	$ 142,643
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	80,613	142,643
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	859	48
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	(1)
Net Amount	79,754	142,594
Derivative Liabilities
Gross Amounts Recognized	25,899	43,976
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	25,899	43,976
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	859	48
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	24,415	42,552
Net Amount	625	1,376
Interest rate swaps
Derivative Assets
Gross Amounts Recognized	80,102	141,822
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	80,102	141,822
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	859	48
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	79,243	141,774
Derivative Liabilities
Gross Amounts Recognized	25,274	42,600
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	25,274	42,600
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	859	48
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	24,415	42,552
Net Amount	0	0
Risk participation agreements
Derivative Assets
Gross Amounts Recognized	347	722
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	347	722
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	347	722
Derivative Liabilities
Gross Amounts Recognized	594	1,230
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	594	1,230
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	594	1,230
Foreign currency exchange contracts - matched customer book
Derivative Assets
Gross Amounts Recognized	44	90
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	44	90
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	(1)
Net Amount	44	89
Derivative Liabilities
Gross Amounts Recognized	31	77
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	31	77
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	31	77
Foreign currency exchange contracts - foreign currency loan
Derivative Assets
Gross Amounts Recognized	120	9
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	120	9
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	120	9
Derivative Liabilities
Gross Amounts Recognized	0	69
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts Presented in the Consolidated Balance Sheet	0	69
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Collateral Pledged (Received)	0	0
Net Amount	$ 0	$ 69

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Additional information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer from level one to level two fair value assets	$ 0	$ 0
Transfer from level two to level one fair value assets	0	0
Transfer from level one to level three fair value assets		0
Transfer from level three to level one fair value assets		0
Transfer from level one to level two fair value liabilities	0	0
Transfer from level two to level one fair value liabilities	0	0
Transfer from level one to level three fair value liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer from level one to level three fair value assets	0
Transfer from level three to level one fair value assets	0
Transfer from level one to level three fair value liabilities	0	0
Transfer from level three to level one fair value liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in mutual funds	55,100,000	53,900,000
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer from level one to level three fair value assets	0
Transfer from level three to level one fair value assets	0	0
Transfer from level one to level three fair value liabilities	0	0
Transfer from level three to level one fair value liabilities	$ 0	$ 0
Carrying amount | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments original maturity	90 days

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Summary Of The Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Available for sale securities	$ 5,689,312	$ 3,183,861
Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	4,073,368	2,148,800
Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	431,009	17,081
U.S. Agency bonds
Assets
Available for sale securities	841,283	666,709
U.S. Treasury securities
Assets
Available for sale securities	69,182	70,369
Fair Value, Recurring
Assets
Rabbi trust investments	98,174	91,683
Loans held for sale	1,757	1,140
Customer-related positions	80,102	141,822
Risk participation agreements	347	722
Matched customer book	44	90
Foreign currency loan	120	9
Total	5,869,856	3,419,327
Liabilities
Customer-related positions	25,274	42,600
Risk participation agreements	594	1,230
Matched customer book	31	77
Foreign currency loan	0	69
Total	25,899	43,976
Fair Value, Recurring | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	4,073,368	2,148,800
Fair Value, Recurring | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	431,009	17,081
Fair Value, Recurring | U.S. Agency bonds
Assets
Available for sale securities	841,283	666,709
Fair Value, Recurring | U.S. Treasury securities
Assets
Available for sale securities	69,182	70,369
Fair Value, Recurring | State and municipal bonds and obligations
Assets
Available for sale securities	274,470	280,902
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Rabbi trust investments	90,026	83,884
Loans held for sale	0	0
Customer-related positions	0	0
Risk participation agreements	0	0
Matched customer book	0	0
Foreign currency loan	0	0
Total	159,208	154,253
Liabilities
Customer-related positions	0	0
Risk participation agreements	0	0
Matched customer book	0	0
Foreign currency loan	0	0
Total	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Agency bonds
Assets
Available for sale securities	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Assets
Available for sale securities	69,182	70,369
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal bonds and obligations
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Assets
Rabbi trust investments	8,148	7,799
Loans held for sale	1,757	1,140
Customer-related positions	80,102	141,822
Risk participation agreements	347	722
Matched customer book	44	90
Foreign currency loan	120	9
Total	5,710,648	3,265,074
Liabilities
Customer-related positions	25,274	42,600
Risk participation agreements	594	1,230
Matched customer book	31	77
Foreign currency loan	0	69
Total	25,899	43,976
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	4,073,368	2,148,800
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	431,009	17,081
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Agency bonds
Assets
Available for sale securities	841,283	666,709
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | State and municipal bonds and obligations
Assets
Available for sale securities	274,470	280,902
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Assets
Rabbi trust investments	0	0
Loans held for sale	0	0
Customer-related positions	0	0
Risk participation agreements	0	0
Matched customer book	0	0
Foreign currency loan	0	0
Total	0	0
Liabilities
Customer-related positions	0	0
Risk participation agreements	0	0
Matched customer book	0	0
Foreign currency loan	0	0
Total	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Agency bonds
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities
Assets
Available for sale securities	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | State and municipal bonds and obligations
Assets
Available for sale securities	$ 0	$ 0

Fair Value of Assets and Liab_5

Fair Value of Assets and Liabilities - Summary Of The Fair Value Of Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis (Detail) - Fair Value, Nonrecurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Collateral-dependent impaired loans whose fair value is based upon appraisals	$ 15,484	$ 11,036
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Collateral-dependent impaired loans whose fair value is based upon appraisals	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Collateral-dependent impaired loans whose fair value is based upon appraisals	0	0
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Collateral-dependent impaired loans whose fair value is based upon appraisals	$ 15,484	$ 11,036

Fair Value of Assets and Liab_6

Fair Value of Assets and Liabilities - Schedule of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	$ 9,378,060	$ 9,593,958
FHLB stock	10,601	8,805
Bank-owned life insurance	79,259	78,561
Deposits	13,649,964	12,155,784
Federal Home Loan Bank advances	14,172	14,624
Escrow deposits of borrowers	15,900	13,425
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	0	0
FHLB stock	0	0
Bank-owned life insurance	0	0
Deposits	0	0
Federal Home Loan Bank advances	0	0
Escrow deposits of borrowers	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	0	0
FHLB stock	10,601	8,805
Bank-owned life insurance	79,259	78,561
Deposits	13,649,818	12,155,843
Federal Home Loan Bank advances	13,728	14,434
Escrow deposits of borrowers	15,900	13,425
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	9,512,887	9,779,195
FHLB stock	0	0
Bank-owned life insurance	0	0
Deposits	0	0
Federal Home Loan Bank advances	0	0
Escrow deposits of borrowers	0	0
Carrying Value
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	9,378,060	9,593,958
FHLB stock	10,601	8,805
Bank-owned life insurance	79,259	78,561
Deposits	13,649,964	12,155,784
Federal Home Loan Bank advances	14,172	14,624
Escrow deposits of borrowers	15,900	13,425
Outstanding balance
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for loan losses	9,512,887	9,779,195
FHLB stock	10,601	8,805
Bank-owned life insurance	79,259	78,561
Deposits	13,649,818	12,155,843
Federal Home Loan Bank advances	13,728	14,434
Escrow deposits of borrowers	$ 15,900	$ 13,425

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Revenue from External Customers by Products and Services (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	$ 39,549	$ 36,657	$ 124,006	$ 115,926
Total noninterest income out-of-scope of ASC 606	3,660	11,052	20,148	12,809
Total noninterest income	43,209	47,709	144,154	128,735
Insurance commissions
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	21,956	21,884	73,767	72,058
Service charges on deposit accounts
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	5,935	5,052	17,010	15,514
Trust and investment advisory fees
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	6,310	5,311	18,047	15,600
Debit card processing fees
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	3,030	2,721	8,949	7,528
Other noninterest income
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	$ 2,318	$ 1,689	$ 6,233	$ 5,226

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Additional information (Detail) - Other Assets - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Insurance commission earned but not yet received	$ 14	$ 15.8
Cash Management Fees
Disaggregation of Revenue [Line Items]
Fess earned but not yet received	0.9	1
Debit Card
Disaggregation of Revenue [Line Items]
Fess earned but not yet received	$ 0.3	$ 0.3

Other Comprehensive Income - Co

Other Comprehensive Income - Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pre Tax Amount
Net change	$ (35,001)	$ (11,742)	$ (113,821)	$ 63,784
Tax Benefit (Expense)
Net change	8,173	2,979	26,512	(16,234)
After Tax Amount
Change in fair value			(70,177)	56,074
Less: Amounts reclassified from accumulated other comprehensive income			17,132	8,524
Total other comprehensive (loss) income	(26,828)	(8,763)	(87,309)	47,550
Amortization of gains from terminated interest rate swaps			(24,344)	(7,409)
Total realized gain, net of tax	41,200	41,200	41,200	41,200
Balance of gain after amortization, net of tax	12,300	35,900	12,300	35,900
Unrealized Gains and (Losses) on Available for Sale Securities
Pre Tax Amount
Change in fair value	(27,741)	(5,563)	(90,088)	28,750
Other comprehensive loss before reclassifications	1	0	1,166	285
Net change	(27,742)	(5,563)	(91,254)	28,465
Tax Benefit (Expense)
Change in fair value	6,132	1,242	19,911	(6,370)
Less: amortization	0	0	(257)	(63)
Net change	6,132	1,242	20,168	(6,307)
After Tax Amount
Change in fair value	(21,609)	(4,321)	(70,177)	22,380
Less: Amounts reclassified from accumulated other comprehensive income	1	0	909	222
Total other comprehensive (loss) income	(21,610)	(4,321)	(71,086)	22,158
Unrealized Gains and (Losses) on Cash Flow Hedges
Pre Tax Amount
Change in fair value	0	(142)	0	46,869
Other comprehensive loss before reclassifications	7,851	8,405	24,344	18,651
Net change	(7,851)	(8,547)	(24,344)	28,218
Tax Benefit (Expense)
Change in fair value	0	40	0	(13,175)
Less: amortization	(2,207)	(2,363)	(6,843)	(5,243)
Net change	2,207	2,403	6,843	(7,932)
After Tax Amount
Change in fair value	0	(102)	0	33,694
Less: Amounts reclassified from accumulated other comprehensive income	5,644	6,042	17,501	13,408
Total other comprehensive (loss) income	(5,644)	(6,144)	(17,501)	20,286
Defined benefit pension plans
Pre Tax Amount
Net change	592	2,368	1,777	7,101
Tax Benefit (Expense)
Net change	(166)	(666)	(499)	(1,995)
After Tax Amount
Total other comprehensive (loss) income	426	1,702	1,278	5,106
Defined Benefit Pension Plans
Pre Tax Amount
Change in fair value	0	0	0	0
Tax Benefit (Expense)
Change in fair value	0	0	0	0
After Tax Amount
Change in fair value	0	0	0	0
Less: Amounts reclassified from accumulated other comprehensive income			(1,278)	(5,106)
Defined benefit pension plans, actuarial loss
Pre Tax Amount
Other comprehensive loss before reclassifications	(3,537)	(2,361)	(10,612)	(7,082)
Tax Benefit (Expense)
Less: amortization	994	664	2,983	1,990
After Tax Amount
Less: Amounts reclassified from accumulated other comprehensive income	(2,543)	(1,697)	(7,629)	(5,092)
Defined benefit pension plans, prior service cost
Pre Tax Amount
Other comprehensive loss before reclassifications	2,945	(7)	8,835	(19)
Tax Benefit (Expense)
Less: amortization	(828)	2	(2,484)	5
After Tax Amount
Less: Amounts reclassified from accumulated other comprehensive income	$ 2,117	(5)	$ 6,351	(14)
Interest rate swaps
After Tax Amount
Amortization of gains from terminated interest rate swaps		$ 5,100		$ 5,300

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 3,430,622	$ 1,693,630	$ 3,428,052	$ 1,600,153
Other comprehensive loss before reclassifications			(70,177)	56,074
Less: Amounts reclassified from accumulated other comprehensive income			17,132	8,524
Net change in fair value			(87,309)	47,550
Ending balance	3,429,292	1,713,372	3,429,292	1,713,372
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(6,247)	12,466	54,234	(43,847)
Ending balance	(33,075)	3,703	(33,075)	3,703
Unrealized Gains and (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			45,672	21,798
Other comprehensive loss before reclassifications	(21,609)	(4,321)	(70,177)	22,380
Less: Amounts reclassified from accumulated other comprehensive income	1	0	909	222
Net change in fair value			(71,086)	22,158
Ending balance	(25,414)	43,956	(25,414)	43,956
Unrealized Gains and (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			29,815	15,624
Other comprehensive loss before reclassifications	0	(102)	0	33,694
Less: Amounts reclassified from accumulated other comprehensive income	5,644	6,042	17,501	13,408
Net change in fair value			(17,501)	20,286
Ending balance	12,314	35,910	12,314	35,910
Defined Benefit Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			(21,253)	(81,269)
Other comprehensive loss before reclassifications	0	0	0	0
Less: Amounts reclassified from accumulated other comprehensive income			(1,278)	(5,106)
Net change in fair value			1,278	5,106
Ending balance	$ (19,975)	$ (76,163)	$ (19,975)	$ (76,163)

Segment Reporting - Schedule Of

Segment Reporting - Schedule Of Segment Reporting Information, By Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income	$ 102,691	$ 98,742	$ 307,390	$ 297,643
(Release of) provision	(1,488)	700	(5,368)	37,900
Net interest income after provision for loan losses	104,179	98,042	312,758	259,743
Total noninterest income	43,209	47,709	144,154	128,735
Noninterest expense	98,970	109,817	300,354	305,754
Income before income tax expense	48,418	35,934	156,558	82,724
Income tax provision	11,312	7,429	36,980	15,924
Net income	37,106	28,505	119,578	66,800
Total assets	17,461,223	15,460,594	17,461,223	15,460,594	$ 15,964,190
Total liabilities	14,031,931	13,747,222	14,031,931	13,747,222	$ 12,536,138
Other/Eliminations
Segment Reporting Information [Line Items]
Net interest income	0	0	0	0
(Release of) provision	0	0	0	0
Net interest income after provision for loan losses	0	0	0	0
Total noninterest income	(82)	(150)	(113)	(179)
Noninterest expense	(1,042)	(1,198)	(3,039)	(3,165)
Income before income tax expense	960	1,048	2,926	2,986
Income tax provision	0	0	0	0
Net income	960	1,048	2,926	2,986
Total assets	(71,589)	(74,145)	(71,589)	(74,145)
Total liabilities	(71,589)	(74,145)	(71,589)	(74,145)
Business Banking | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	102,691	98,742	307,390	297,643
(Release of) provision	(1,488)	700	(5,368)	37,900
Net interest income after provision for loan losses	104,179	98,042	312,758	259,743
Total noninterest income	20,783	25,288	69,308	55,935
Noninterest expense	80,474	91,509	243,549	251,688
Income before income tax expense	44,488	31,821	138,517	63,990
Income tax provision	10,471	6,561	32,728	11,468
Net income	34,017	25,260	105,789	52,522
Total assets	17,324,816	15,332,420	17,324,816	15,332,420
Total liabilities	14,051,100	13,761,414	14,051,100	13,761,414
Insurance Agency Business | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	0	0	0	0
(Release of) provision	0	0	0	0
Net interest income after provision for loan losses	0	0	0	0
Total noninterest income	22,508	22,571	74,959	72,979
Noninterest expense	19,538	19,506	59,844	57,231
Income before income tax expense	2,970	3,065	15,115	15,748
Income tax provision	841	868	4,252	4,456
Net income	2,129	2,197	10,863	11,292
Total assets	207,996	202,319	207,996	202,319
Total liabilities	$ 52,420	$ 59,953	$ 52,420	$ 59,953

Subsequent Events (Detail)

Subsequent Events (Detail) - Subsequent Event - USD ($) $ in Thousands	Oct. 28, 2021	Oct. 01, 2021
Subsequent Event [Line Items]
Number of shares authorized to be repurchased (in shares)	9,337,900
Percentage of shares authorized (in percent)	5.00%
Purchase period	12 months
Non-Employee Director
Subsequent Event [Line Items]
Initial grant		$ 13,750
Individual grant amount to each non-employee director		$ 1,250

Uncategorized Items - ebc-20210

Label	Element	Value
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-02 [Member]