Eastern Bankshares (EBC) 10-Q 14 May 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	May 13, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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 Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		186,758,154
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001810546
Current Fiscal Year End Date	--12-31

Unaudited Consolidated Balance

Unaudited Consolidated Balance sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Cash and due from banks	$ 79,497	$ 116,591
Short-term investments	1,780,835	1,937,479
Cash and cash equivalents	1,860,332	2,054,070
Available for sale securities	3,986,253	3,183,861
Loans held for sale	2,022	1,140
Loans:
Total loans	9,916,475	9,730,525
Less: allowance for loan losses	(111,080)	(113,031)
Less: unamortized premiums, net of unearned discounts and deferred fees	(32,673)	(23,536)
Net loans	9,772,722	9,593,958
Federal Home Loan Bank stock, at cost	8,805	8,805
Premises and equipment	46,619	49,398
Bank-owned life insurance	79,110	78,561
Goodwill and other intangibles, net	376,002	376,534
Deferred income taxes, net	31,508	13,229
Prepaid expenses	150,453	148,680
Other assets	412,969	455,954
Total assets	16,726,795	15,964,190
Deposits:
Demand	5,369,164	4,910,794
Interest checking accounts	2,482,731	2,380,497
Savings accounts	1,362,463	1,256,736
Money market investment	3,522,990	3,348,898
Certificates of deposit	243,527	258,859
Total deposits	12,980,875	12,155,784
Borrowed funds:
Federal Home Loan Bank advances	14,473	14,624
Escrow deposits of borrowers	14,878	13,425
Total borrowed funds	29,351	28,049
Other liabilities	329,524	352,305
Total liabilities	13,339,750	12,536,138
Commitments and contingencies (see footnote 11)	0	0
Common shares, $0.01 par value, 1,000,000,000 shares authorized, 186,758,154 and 186,758,154 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	1,868	1,868
Additional paid in capital	1,854,895	1,854,068
Unallocated common shares held by the Employee Stock Ownership Plan	(146,472)	(147,725)
Retained earnings	1,702,946	1,665,607
Accumulated other comprehensive income, net of tax	(26,192)	54,234
Total shareholders’ equity	3,387,045	3,428,052
Total liabilities and shareholders’ equity	16,726,795	15,964,190
Commercial and industrial
Loans:
Total loans	1,986,366	1,995,016
Commercial real estate
Loans:
Total loans	3,676,941	3,573,630
Commercial construction
Loans:
Total loans	249,416	305,708
Business banking
Loans:
Total loans	1,513,051	1,339,164
Residential real estate
Loans:
Total loans	1,406,510	1,370,957
Consumer home equity
Loans:
Total loans	832,466	868,270
Other consumer
Loans:
Total loans	$ 251,725	$ 277,780

Unaudited Consolidated Balanc_2

Unaudited Consolidated Balance sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, 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
	Mar. 31, 2021	Mar. 31, 2020
Interest and dividend income:
Interest and fees on loans	$ 88,639	$ 95,538
Taxable interest and dividends on available for sale securities	10,206	8,178
Non-taxable interest and dividends on available for sale securities	1,856	1,921
Interest on federal funds sold and other short-term investments	432	517
Interest and dividends on trading securities	0	5
Total interest and dividend income	101,133	106,159
Interest expense:
Interest on deposits	1,002	5,414
Interest on borrowings	40	599
Total interest expense	1,042	6,013
Net interest income	100,091	100,146
(Release of) provision for allowance for loan losses	(580)	28,600
Net interest income after provision for loan losses	100,671	71,546
Noninterest income:
Insurance commissions	28,147	27,477
Service charges on deposit accounts	5,367	6,098
Trust and investment advisory fees	5,663	5,095
Debit card processing fees	2,749	2,470
Interest rate swap income (losses)	5,405	(6,009)
Income (losses) from investments held in rabbi trusts	1,846	(6,743)
Losses on trading securities, net	0	(2)
Gains on sales of mortgage loans held for sale, net	1,479	93
Gains on sales of securities available for sale, net	1,164	122
Other	3,392	4,768
Total noninterest income	55,212	33,369
Noninterest expense:
Salaries and employee benefits	64,040	61,589
Office occupancy and equipment	8,217	8,689
Data processing	12,129	10,004
Professional services	4,148	3,689
Charitable contributions	0	1,187
Marketing	1,691	2,468
Loan expenses	1,847	1,112
FDIC insurance	948	906
Amortization of intangible assets	532	702
Other	497	4,826
Total noninterest expense	94,049	95,172
Income before income tax expense	61,834	9,743
Income tax expense	14,171	1,298
Net income	$ 47,663	$ 8,445
Basic earnings per share (in dollars per share)	$ 0.28	$ 0
Diluted earnings per share (in dollars per share)	$ 0.28	$ 0

Unaudited Consolidated Statem_2

Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 47,663	$ 8,445
Other comprehensive income, net of tax:
Net change in fair value of securities available for sale	(74,904)	26,192
Net change in fair value of cash flow hedges	(5,948)	29,075
Net change in other comprehensive income for defined benefit postretirement plans	426	0
Total other comprehensive (loss) income	(80,426)	55,267
Total comprehensive (loss) income	$ (32,763)	$ 63,712

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	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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		8,445					8,445
Other comprehensive income, net of tax		55,267								55,267
Ending balance (in shares) at Mar. 31, 2020					0
Ending balance at Mar. 31, 2020		$ 1,662,734			$ 0	0	1,651,314			11,420	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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		47,663					47,663
Other comprehensive income, net of tax		(80,426)								(80,426)
Dividends to common shareholders	[2]	(10,324)					(10,324)
ESOP shares committed to be released		$ 2,080				827					1,253
Ending balance (in shares) at Mar. 31, 2021		186,758,154			186,758,154,000
Ending balance at Mar. 31, 2021		$ 3,387,045			$ 1,868	$ 1,854,895	$ 1,702,946			$ (26,192)	$ (146,472)
[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 a quarterly cash dividend of $0.06 per share of common stock during the three months ended March 31, 2021.

Unaudited Consolidated Statem_4

Unaudited Consolidated Statements of Changes In Shareholders' Equity - Parenthetical $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)$ / shares
Cumulative effect of accounting adjustments | $	$ 3,387,045
Dividends (in dollars per share) | $ / shares	$ 0.06

Unaudited Consolidated Statem_5

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net income	$ 47,663	$ 8,445
Adjustments to reconcile net income to net cash provided by operating activities
(Release of) provision for loan losses	(580)	28,600
Depreciation and amortization	3,283	4,318
(Accretion) amortization of net loan costs and premiums, net	(6,859)	795
Deferred income tax expense	5,118	4,641
Amortization of investment security premiums and discounts	3,277	791
Right-of-use asset amortization	2,862	3,615
Net gain on sale of securities available for sale	(1,164)	(122)
Amortization of gains from terminated interest rate swaps	(8,274)	0
Employee Stock Ownership Plan expense	2,080	0
Other	(557)	(576)
Trading securities	0	309
Loans held for sale	(863)	(2,866)
Prepaid pension expense	838	(30,473)
Other assets	43,683	(61,071)
Other liabilities	(25,597)	12,043
Net cash provided by (used in) operating activities	64,910	(31,551)
Investing activities
Proceeds from sales of securities available for sale	23,236	5,600
Proceeds from maturities and principal paydowns of securities available for sale	214,085	56,021
Purchases of securities available for sale	(1,137,969)	(70,301)
Proceeds from sale of Federal Home Loan Bank stock	0	749
Purchases of Federal Home Loan Bank stock	0	(527)
Contributions to low income housing tax credit investments	(2,727)	(5,177)
Contributions to other equity investments	0	(137)
Distributions from equity investments	7	13
Net increase in outstanding loans	(171,325)	(101,856)
Purchased banking premises and equipment, net	(719)	(1,029)
Proceeds from sale of premises held for sale	736	0
Net cash used in investing activities	(1,074,676)	(116,644)
Financing activities
Net increase in demand, savings, interest checking, and money market investment deposit accounts	840,423	762,049
Net decrease in time deposits	(15,332)	(4,430)
Net decrease (increase) in borrowed funds	1,302	(203,968)
Contingent consideration paid	(41)	(92)
Payment of initial public offering costs	0	(1,517)
Dividends declared and paid to common shareholders	(10,324)	0
Net cash provided by financing activities	816,028	552,042
Net (decrease) increase in cash, cash equivalents, and restricted cash	(193,738)	403,847
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	1,860,332	766,449
Supplemental Cash Flow Information [Abstract]
Interest paid	1,049	6,908
Income taxes	4,858	5,361
Noncash Investing and Financing Items [Abstract]
Net increase in capital commitments relating to low income housing tax credit projects	2,943	5,000
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	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Corporate Structure and Nature of Operations; Conversion and Reorganization; 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 services, 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 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 Update (“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 year's presentation. The accompanying consolidated balance sheet as of March 31, 2021, the consolidated statements of income and comprehensive income and of changes in shareholders’ equity for the three months ended March 31, 2021 and 2020 and statement of cash flows for the three months ended March 31, 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 months ended March 31, 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	3 Months Ended
	Mar. 31, 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 March 31, 2021 and those that were adopted during the three months ended March 31, 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 March 31, 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. The Company anticipates deferring adoption of this standard to January 1, 2022. To address the impact of ASU 2016-13, the Company has formed a committee, including 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 evaluated portfolio segmentation, methodologies and economic forecasting inputs to the process and continues to design the control environment under the new standard. A third party has been engaged to assist the Company in project management, documentation, model governance and related internal controls implementation. The Company is currently assessing the impact of the new standard on its consolidated financial statements. 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. Relevant standards that were adopted during the period ended March 31, 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 Board’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	3 Months Ended
	Mar. 31, 2021
Debt Securities [Abstract]
Securities	Securities Available for Sale Securities The amortized cost, gross unrealized gains and losses, and fair value of available for sale securities as of March 31, 2021 and December 31, 2020 were as follows: As of March 31, 2021 Amortized Unrealized Unrealized Fair (In Thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 2,713,898 $ 23,199 $ (45,395) $ 2,691,702 Government-sponsored commercial mortgage-backed securities 119,064 — (2,793) 116,271 U.S. Agency bonds 860,554 — (28,882) 831,672 U.S. Treasury securities 69,385 30 (325) 69,090 State and municipal bonds and obligations 260,818 16,700 — 277,518 $ 4,023,719 $ 39,929 $ (77,395) $ 3,986,253 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 March 31, 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 March 31, 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 $ — $ — $ 20,503 $ 21,777 $ 87,383 $ 91,340 $ 2,606,012 $ 2,578,585 $ 2,713,898 $ 2,691,702 Government-sponsored commercial mortgage-backed securities — — 24,090 23,771 94,974 92,500 — — 119,064 116,271 U.S. Agency bonds — — 99,784 98,111 760,770 733,561 — — 860,554 831,672 U.S. Treasury securities 10,065 10,095 59,320 58,995 — — — — 69,385 69,090 State and municipal bonds and obligations 405 406 25,244 26,220 72,587 76,077 162,582 174,815 260,818 277,518 Total $ 10,470 $ 10,501 $ 228,941 $ 228,874 $ 1,015,714 $ 993,478 $ 2,768,594 $ 2,753,400 $ 4,023,719 $ 3,986,253 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 March 31, 2021 and 2020 were $1.2 million and $0.1 million, respectively. There were no significant gross realized losses from sales of securities available for sale during the three months ended March 31, 2021 and 2020. There was no other-than-temporary impairment (“OTTI”) recorded during the three months ended March 31, 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 March 31, 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 March 31, 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 18 $ 45,395 $ 2,004,883 $ — $ — $ 45,395 $ 2,004,883 Government-sponsored commercial mortgage-backed securities 7 2,793 116,271 — — 2,793 116,271 U.S. Agency bonds 13 28,882 831,672 — — 28,882 831,672 U.S. Treasury securities 2 325 58,995 — — 325 58,995 40 $ 77,395 $ 3,011,821 $ — $ — $ 77,395 $ 3,011,821 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 March 31, 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. The securities in a loss position as of December 31, 2020 remain in a loss position as of March 31, 2021 but have not yet been held for a period of 12 months or longer as of March 31, 2021. Additionally, these securities are implicitly guaranteed by the U.S. government or one of its agencies. • U.S. Treasury securities – The securities with unrealized losses in this portfolio have contractual terms that generally do not permit the issuer to settle the securities at a price less than the current par value of the investments. 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.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	3 Months Ended
	Mar. 31, 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: As of March 31, As of December 31, 2021 2020 (In thousands) Commercial and industrial $ 1,986,366 $ 1,995,016 Commercial real estate 3,676,941 3,573,630 Commercial construction 249,416 305,708 Business banking 1,513,051 1,339,164 Residential real estate 1,406,510 1,370,957 Consumer home equity 832,466 868,270 Other consumer 251,725 277,780 Gross loans before unamortized premiums, unearned discounts and deferred fees 9,916,475 9,730,525 Allowance for credit losses (111,080) (113,031) Unamortized premiums, net of unearned discounts and deferred fees (32,673) (23,536) Loans after the allowance for credit losses, unamortized premiums, unearned discounts and deferred fees $ 9,772,722 $ 9,593,958 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 March 31, 2021 and December 31, 2020. The balance of funds borrowed from the FHLBB were $14.5 million and $14.6 million at March 31, 2021 and December 31, 2020, respectively. The carrying value of loans pledged to secure advances from the Federal Reserve Bank (“FRB”) were $832.4 million and $884.1 million at March 31, 2021 and December 31, 2020, respectively. There were no funds borrowed from the FRB outstanding at March 31, 2021 and December 31, 2020. Serviced Loans At March 31, 2021 and December 31, 2020, mortgage loans partially or wholly-owned by others and serviced by the Company amounted to approximately $12.9 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 table summarizes the changes in the allowance for loan losses for the periods indicated: For the Three Months Ended March 31, 2021 2020 (In thousands) Balance at the beginning of period $ 113,031 $ 82,297 Loans charged off (1,982) (2,343) Recoveries 611 584 (Release of) provision for loan losses (580) 28,600 Balance at end of period $ 111,080 $ 109,138 The following tables summarize changes in the allowance for loan losses by loan category and bifurcates the amount of allowance allocated to each loan category based on collective impairment analysis and loans evaluated individually for impairment: For the Three Months Ended March 31, 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 — (234) — (1,384) — — (364) — (1,982) Recoveries 9 — — 365 10 71 156 — 611 (Release of) provision (1,220) 803 (1,203) 1,371 (210) (239) 239 (121) (580) Ending balance $ 25,406 $ 55,138 $ 3,350 $ 13,504 $ 6,235 $ 3,576 $ 3,498 $ 373 $ 111,080 Ending balance: individually evaluated for impairment $ 4,761 $ 210 $ — $ 1,387 $ 1,516 $ 263 $ — $ — $ 8,137 Ending balance: acquired with deteriorated credit quality $ 1,283 $ 822 $ — $ — $ 327 $ — $ — $ — $ 2,432 Ending balance: collectively evaluated for impairment $ 19,362 $ 54,106 $ 3,350 $ 12,117 $ 4,392 $ 3,313 $ 3,498 $ 373 $ 100,511 Loans ending balance: Individually evaluated for impairment $ 17,907 $ 4,536 $ — $ 21,001 $ 26,459 $ 4,461 $ 26 $ — $ 74,390 Acquired with deteriorated credit quality 2,944 1,554 — — 3,119 — — — 7,617 Collectively evaluated for impairment 1,965,515 3,670,851 249,416 1,492,050 1,376,932 828,005 251,699 — 9,834,468 Total loans by group $ 1,986,366 $ 3,676,941 $ 249,416 $ 1,513,051 $ 1,406,510 $ 832,466 $ 251,725 $ — $ 9,916,475 For the Three Months Ended March 31, 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 — — — (1,337) — (473) (533) — (2,343) Recoveries 322 1 — 127 60 14 60 — 584 Provision (release of) 9,290 14,496 1,288 3,131 (212) 345 319 (57) 28,600 Ending balance $ 30,531 $ 49,227 $ 4,712 $ 10,181 $ 6,228 $ 3,913 $ 4,019 $ 327 $ 109,138 Ending balance: individually evaluated for impairment $ 4,037 $ 270 $ — $ 453 $ 1,275 $ 221 $ — $ — $ 6,256 Ending balance: acquired with deteriorated credit quality $ — $ 936 $ — $ — $ 256 $ — $ — $ — $ 1,192 Ending balance: collectively evaluated for impairment $ 26,494 $ 48,021 $ 4,712 $ 9,728 $ 4,697 $ 3,692 $ 4,019 $ 327 $ 101,690 Loans ending balance: Individually evaluated for impairment $ 32,423 $ 8,054 $ — $ 10,258 $ 29,393 $ 6,280 $ 23 $ — $ 86,431 Acquired with deteriorated credit quality 3,939 5,780 — — 3,424 — — — 13,143 Collectively evaluated for impairment 1,734,760 3,509,887 293,135 769,658 1,387,186 923,274 369,629 — 8,987,529 Total loans by group $ 1,771,122 $ 3,523,721 $ 293,135 $ 779,916 $ 1,420,003 $ 929,554 $ 369,652 $ — $ 9,087,103 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 airplane 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 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 less than $1 million. Loans included in this category have qualification requirements that include risk rating of 10 or better at 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 March 31, 2021 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 684,938 $ 6,318 $ — $ 1,079,605 $ 1,770,861 Pass 1,171,994 3,353,758 232,981 347,867 5,106,600 Special mention 68,826 127,751 10,345 57,387 264,309 Substandard 45,573 186,707 6,090 26,492 264,862 Doubtful 15,035 2,407 — 1,700 19,142 Loss — — — — — Total $ 1,986,366 $ 3,676,941 $ 249,416 $ 1,513,051 $ 7,425,774 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 and business banking PPP loans amounted to $609.9 million and $628.2 million, respectively, at March 31, 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 March 31, 2021 and December 31, 2020 was $178.4 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 TDRs (as defined herein). 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 March 31, 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 March 31, 2021 and December 31, 2020. 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. Therefore, 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. Specifically, non-accrual residential loans that have been restructured must perform for a period of six months before being considered for accrual status. 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 March 31, As of December 31, 2021 2020 (In Thousands) Commercial and industrial $ 12,266 $ 11,714 Commercial real estate 1,016 915 Business banking 16,993 17,430 Residential real estate 8,127 6,815 Consumer home equity 3,524 3,602 Other consumer 349 529 Total non-accrual loans $ 42,275 $ 41,005 The following tables show the age analysis of past due loans as of the dates indicated: As of March 31, 2021 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 9,460 $ 3 $ 1,174 $ 10,637 $ 1,975,729 $ 1,986,366 $ 252 Commercial real estate 3,225 — 1,403 4,628 3,672,313 3,676,941 1,138 Commercial construction — — — — 249,416 249,416 — Business banking 13,299 1,404 8,513 23,216 1,489,835 1,513,051 — Residential real estate 5,738 857 6,271 12,866 1,393,644 1,406,510 280 Consumer home equity 1,416 496 3,006 4,918 827,548 832,466 9 Other consumer 975 419 349 1,743 249,982 251,725 — Total $ 34,113 $ 3,179 $ 20,716 $ 58,008 $ 9,858,467 $ 9,916,475 $ 1,679 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. However, based upon the Company’s past experiences, some of these loans with potential weaknesses will ultimately be restructured or placed in 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 table shows the TDR loans on accrual and nonaccrual status as of the dates indicated: As of March 31, 2021 TDRs on Accrual Status TDRs on Nonaccrual Status Total TDRs Number of Loans Balance of Number of Balance of Number of Balance of (Dollars in thousands) Commercial and industrial 1 $ 5,641 6 $ 7,583 7 $ 13,224 Commercial real estate 1 3,520 1 468 2 3,988 Business banking 5 4,008 6 1,075 11 5,083 Residential real estate 140 22,565 30 3,557 170 26,122 Consumer home equity 79 3,607 14 854 93 4,461 Other consumer 3 26 — — 3 26 Total 229 $ 39,367 57 $ 13,537 286 $ 52,904 As of December 31, 2020 TDRs on Accrual Status TDRs on Nonaccrual Status Total TDRs Number of Loans Balance of Number of Loans Balance 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 reserves associated with the TDRs was $4.1 million and $3.5 million at March 31, 2021 and December 31, 2020, respectively. There were no additional commitments to lend to borrowers who have been a party to a TDR as of both March 31, 2021 and 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 March 31, 2021 For the Three Months Ended March 31, 2020 Number Pre- Post- Number Pre- Post- (Dollars in thousands) Business banking — $ — $ — 1 $ 244 $ 244 Residential real estate 1 295 295 8 414 419 Consumer home equity — — — 1 24 24 Total 1 $ 295 $ 295 10 $ 682 $ 687 (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 March 31, 2021 and December 31, 2020, the outstanding recorded investment of loans that were new TDRs were $0.3 million and $3.9 million, respectively. 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 March 31, 2021 2020 (In thousands) Extended maturity and interest only/principal deferred $ — $ 46 Court-ordered concession 295 — Other — 641 Total $ 295 $ 687 The following table shows the loans 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 nonaccrual: For the Three Months Ended March 31, 2021 2020 Number of Recorded Number of Recorded (Dollars in thousands) Troubled debt restructurings that subsequently defaulted (1): Commercial and industrial — $ — 2 $ 4,613 Business banking 1 419 — — Consumer home equity 1 59 1 1,335 Total 2 $ 478 3 $ 5,948 (1) This table does not reflect any TDRs which were fully charged off, paid off, or otherwise settled during the period. During the three months ended March 31, 2021 and 2020 the amounts charged-off on TDRs modified in the prior 12 months were $0 and $0.4 million, respectively. Impaired Loans Impaired loans consist of all loans for which management has determined it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the loan agreements. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. The Company measures impairment of loans using a discounted cash flow method, the loan’s observable market price, or the fair value of the collateral if the loan is collateral dependent. The Company has defined the population of impaired loans to include certain non-accrual loans, TDR loans, and residential and home equity loans that have been partially charged off. The following table summarizes the Company’s impaired loans by loan portfolio as of the dates indicated: As of March 31, 2021 As of December 31, 2020 Recorded Unpaid Related Recorded Unpaid Related (In thousands) With no related allowance recorded: Commercial and industrial $ 10,071 $ 11,312 $ — $ 9,182 $ 11,212 $ — Commercial real estate 4,068 4,113 — 3,955 3,974 — Business banking 4,961 7,260 — 5,250 7,659 — Residential real estate 14,408 16,714 — 14,730 17,010 — Consumer home equity 2,370 2,370 — 2,571 2,571 — Other consumer 26 26 — 29 29 — Sub-total 35,904 41,795 — 35,717 42,455 — With an allowance recorded: Commercial and industrial 7,836 8,147 4,761 8,161 8,432 4,555 Commercial real estate 468 489 210 480 497 210 Business banking 16,040 20,925 1,387 16,651 21,146 1,435 Residential real estate 12,051 12,051 1,516 12,326 12,326 1,565 Consumer home equity 2,091 2,091 263 2,274 2,274 289 Sub-total 38,486 43,703 8,137 39,892 44,675 8,054 Total $ 74,390 $

Goodwill and Other Intangibles

Goodwill and Other Intangibles	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles 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 March 31, 2021 Banking Insurance Net (In Thousands) Balances not subject to amortization Goodwill $ 298,611 $ 70,866 $ 369,477 Balances subject to amortization Insurance agency — 6,398 6,398 Core deposits 127 — 127 Total other intangible assets 127 6,398 6,525 Total goodwill and other intangible assets $ 298,738 $ 77,264 $ 376,002 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 — 6,899 6,899 Core deposits 158 — 158 Total other intangible assets 158 6,899 7,057 Total goodwill and other intangible assets $ 298,769 $ 77,765 $ 376,534 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 quantitative assessment was most recently performed as of September 30, 2020. During the three months ended December 31, 2020 and the three months ended March 31, 2021 there were no events or changes in circumstances not already considered in the Company's annual assessment. 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 March 31, 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 March 31, 2021 or December 31, 2020.

Earnings Per Share ("EPS")

Earnings Per Share ("EPS")	3 Months Ended
	Mar. 31, 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 quarter ended March 31, 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 quarter ended March 31, 2020 as the Company had no shares outstanding. For the Three Months Ended March 31, 2021 (Dollars in thousands, except per share data) Net income applicable to common shares $ 47,663 Average number of common shares outstanding 186,758,154 Less: Average unallocated ESOP shares (14,709,110) Average number of common shares outstanding used to calculate basic earnings per common share 172,049,044 Common stock equivalents — Average number of common shares outstanding used to calculate diluted earnings per common share 172,049,044 Earnings per common share Basic and diluted $ 0.28 All unallocated ESOP shares have been excluded from the calculation of basic and diluted EPS.

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	Leases The 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 March 31, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 79,163 $ 81,596 Lease liabilities 82,910 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 sheet. The following table is a summary of the Company’s components of net lease cost for the periods indicated: For the Three Months Ended March 31, 2021 2020 (In thousands) Operating lease cost $ 3,561 $ 3,613 Finance lease cost 31 2 Variable lease cost 490 522 Total lease cost $ 4,082 $ 4,137 During the three months ended March 31, 2021 and 2020, the Company made $3.6 million and $3.5 million, respectively, in cash payments for operating and finance lease payments. Supplemental balance sheet information related to operating leases are as follows: As of March 31, 2021 As of As of December 31, 2020 Weighted-average remaining lease term (in years) 8.33 8.50 Weighted-average discount rate 2.63 % 2.65 %
Leases	Leases The 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 March 31, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 79,163 $ 81,596 Lease liabilities 82,910 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 sheet. The following table is a summary of the Company’s components of net lease cost for the periods indicated: For the Three Months Ended March 31, 2021 2020 (In thousands) Operating lease cost $ 3,561 $ 3,613 Finance lease cost 31 2 Variable lease cost 490 522 Total lease cost $ 4,082 $ 4,137 During the three months ended March 31, 2021 and 2020, the Company made $3.6 million and $3.5 million, respectively, in cash payments for operating and finance lease payments. Supplemental balance sheet information related to operating leases are as follows: As of March 31, 2021 As of As of December 31, 2020 Weighted-average remaining lease term (in years) 8.33 8.50 Weighted-average discount rate 2.63 % 2.65 %

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table sets forth information regarding the Company’s tax provision and applicable tax rates for the periods indicated: For the Three Months Ended March 31, 2021 2020 (Dollars in thousands) Combined federal and state income tax provisions $ 14,171 $ 1,298 Effective income tax rates 22.9 % 13.3 % The Company’s provision for income taxes was $14.2 million and $1.3 million for the three months ended March 31, 2021 and 2020, respectively. The increase in income tax expense was due primarily to higher pre-tax income during the three months ended March 31, 2021 compared to the three months ended March 31, 2020, decreasing the impact on the effective rate related to net favorable permanent differences, including investment tax credits and tax exempt income. The Company assesses the realizability of deferred tax assets and whether it is more likely than not that all or a portion of the deferred tax assets will be realized. The Company considers projections of future taxable income during the periods in which deferred tax assets and liabilities are scheduled to reverse. Additionally, in determining the availability of operating loss carrybacks and other tax attributes, both projected future taxable income and tax planning strategies are considered in making this assessment. As of March 31, 2021 and December 31, 2020, the Company had a valuation allowance of $12.0 million related to the 2020 stock donation of $91.3 million and cash contribution of $3.7 million to the Eastern Bank Charitable Foundation (the “Foundation”). Based upon the level of available historical taxable income and projections for future taxable income over the periods which the deferred tax assets are realizable, the Company believes it is more likely than not that the Company will realize the remainder of the net deferred tax assets as of March 31, 2021. The Company files tax returns in the U.S. federal jurisdiction and various states. As of March 31, 2021, the Company is no longer subject to exam for tax years before 2017 by the Internal Revenue Service (“IRS”) and state tax authorities. The Company believes that its income tax returns have been filed based upon applicable statutes, regulations and case law in effect at the time of filing, however the IRS and/or state jurisdiction, upon examination, could disagree with the Company’s interpretation. Management has performed an evaluation of the Company’s tax positions and determined that a reserve for unrecognized tax benefits at March 31, 2021 and December 31, 2020 was not needed.

Low Income Housing Tax Credits

Low Income Housing Tax Credits and Other Tax Credit Investments	3 Months Ended
	Mar. 31, 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 March 31, 2021 and December 31, 2020, the Company had $64.1 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 LIHTC projects using the proportional amortization method for the periods indicated: Three Months Ended Year Ended December 31, 2020 (In thousands) Current recorded investment included in other assets $ 62,904 $ 58,504 Commitments to fund qualified affordable housing projects included in recorded investment noted above 34,430 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 March 31, 2021 2020 (In thousands) Tax credits and benefits recognized $ 1,464 $ 1,519 Amortization expense included in income tax expense 1,264 1,191

Employee Benefits

Employee Benefits	3 Months Ended
	Mar. 31, 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 will generally increase as the participant remains employed with the Company. Employees hired on and after November 1, 2020 will 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 (“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: For the Three Months Ended March 31, 2021 2020 (In Thousands) Components of net periodic benefit cost: Service cost $ 7,896 $ 6,232 Interest cost 1,269 2,616 Expected return on plan assets (8,141) (7,425) Prior service (credit) cost (2,946) 6 Recognized net actuarial loss 3,538 2,361 Net periodic benefit cost $ 1,616 $ 3,790 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 March 31, 2021 compared to the three months ended March 31, 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 three months ended March 31, 2021. During the three months ended March 31, 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 on the Company's consolidated balance sheet. Changes in fair value are recorded in noninterest income. At March 31, 2021 and December 31, 2020 the amount of rabbi trust investments at fair value were $94.0 million and $91.7 million, respectively. Investments in rabbi trust accounts are recorded at fair value within the Company's consolidated balance sheet 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 March 31, 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 $ 5,230 $ — $ 5,230 $ 5,157 $ — $ 5,157 Equities 61,662 18,828 80,490 59,235 19,492 78,727 Fixed income 8,110 175 8,285 7,441 358 7,799 Total assets $ 75,002 $ 19,003 $ 94,005 $ 71,833 $ 19,850 $ 91,683

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 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 March 31, 2021 As of December 31, 2020 (In Thousands) Commitments to extend credit $ 3,959,011 $ 3,818,952 Standby letters of credit 63,986 60,221 Forward commitments to sell loans 35,564 41,160 Other Contingencies The Company has been named a defendant in various legal proceedings arising in the normal course of business. 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. 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 March 31, 2021 or December 31, 2020.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2021
Summary of Derivative Instruments [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Company uses derivative financial instruments to manage the Company’s 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 they pay floating and receive 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 March 31, 2021 and December 31, 2020, the Company did 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 months ended March 31, 2021: For the Three Months Ended (In thousands) Unrealized gains on terminated hedges included in AOCI - January 1 $ 41,473 Unrealized gains on terminated hedges arising during the period — Reclassification adjustments for amortization of unrealized (gains) into net income (8,274) Unrealized gains on terminated hedges included in AOCI - March 31 $ 33,199 There were no unrealized gains or losses on terminated hedges during the three months ended March 31, 2020. The balance of terminated cash flow hedges in AOCI will be amortized into earnings through January 2023. The Company expects approximately $28.3 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 March 31, 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 non-performance by either the customer or the dealer because these contracts are simultaneously matched at inception with an offsetting dealer transaction. Risk participation agreements are entered into as financial guarantees of performance on interest rate swap derivatives. The purchased (asset) or sold (liability) guarantee allows 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 non-performance 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: As of March 31, 2021 Number of Positions Total Notional (Dollars in Thousands) Interest rate swaps 562 $ 3,571,918 Risk participation agreements 70 288,803 Foreign exchange contracts: Matched commercial customer book 74 8,428 Foreign currency loan 3 7,988 As of 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 balance sheet for the periods indicated. There were no derivatives designated as hedging instruments at March 31, 2021 or December 31, 2020. Asset Derivatives Liability Derivatives Balance Fair Value at March 31, Fair Value at December 31, 2020 Balance Sheet Fair Value at March 31, Fair Value at December 31, 2020 (Dollars in thousands) Derivatives not designated as hedging instruments Customer-related positions: Interest rate swaps Other assets $ 90,748 $ 141,822 Other liabilities $ 33,620 $ 42,600 Risk participation agreements Other assets 391 722 Other liabilities 530 1,230 Foreign currency exchange contracts - matched customer book Other assets 81 90 Other liabilities 61 77 Foreign currency exchange contracts - foreign currency loan Other assets 18 9 Other liabilities 5 69 Total $ 91,238 $ 142,643 $ 34,216 $ 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: For the Three Months Ended March 31, 2021 2020 (Dollars in Thousands) Derivatives designated as hedges: Gain in OCI on derivatives $ — $ 43,556 Gain reclassified from OCI into interest income (effective portion) $ 8,274 $ 3,112 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 $ 4,851 $ (6,280) Gain (loss) recognized in interest rate swap income for risk participation agreements 369 (301) Gain (loss) recognized in other income for foreign currency exchange contracts: Matched commercial customer book 6 (26) Foreign currency loan 73 397 Total gain (loss) for derivatives not designated as hedges $ 5,299 $ (6,210) 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 derivative 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 March 31, 2021 and 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 $0, and less than $0.1 million, respectively. In addition, at March 31, 2021 and December 31, 2020, the Company had posted initial-margin collateral in the form of a U.S. Treasury note amounting to $49.3 million and $60.4 million, respectively, to CME for these derivatives. The cash and U.S. Treasury note were considered restricted assets and were included in cash and due from banks and in available for sale securities, respectively. At March 31, 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 non-performance risk, totaled $28.3 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 March 31, 2021 and December 31, 2020, the Company had posted collateral in the form of cash amounting to $35.9 million and $49.2 million, respectively, which was considered to be a restricted asset and was included in short-term investments. If the Company had breached any of these provisions at March 31, 2021 or December 31, 2020, it would have been required to settle its obligations under the agreements at the termination value. In addition, the Company had cross-default provisions with its commercial customer loan agreements which provide cross-collateralization with the customer loan collateral.

Balance Sheet Offsetting

Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 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 March 31, 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 financial position, as of the dates indicated: As of March 31, 2021 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Interest rate swaps $ — $ — $ — $ — $ — $ — Customer-related positions: Interest rate swaps 90,748 — 90,748 1,426 — 89,322 Risk participation agreements 391 — 391 — — 391 Foreign currency exchange contracts – matched customer book 81 — 81 — — 81 Foreign currency exchange contracts – foreign currency loan 18 — 18 — — 18 $ 91,238 $ — $ 91,238 $ 1,426 $ — $ 89,812 Derivative Liabilities Interest rate swaps $ — $ — $ — $ — $ — $ — Customer-related positions: Interest rate swaps 33,620 — 33,620 1,426 32,194 — Risk participation agreements 530 — 530 — — 530 Foreign currency exchange contracts – matched customer book 61 — 61 — — 61 Foreign currency exchange contracts – foreign currency loan 5 — 5 — — 5 $ 34,216 $ — $ 34,216 $ 1,426 $ 32,194 $ 596 As of December 31, 2020 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Interest rate swaps $ — $ — $ — $ — $ — $ — 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 Interest rate swaps $ — $ — $ — $ — $ — $ — 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	3 Months Ended
	Mar. 31, 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 equity securities, mutual funds and exchange-traded funds are traded in an active market and therefore were categorized as Level 1. Mutual funds at net asset value amounted to $52.0 million at March 31, 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 March 31, 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 March 31, 2021 and December 31, 2020: Fair Value Measurements at Reporting Date Using Balance as of March 31, 2021 Quoted Prices in Significant Significant Description (Dollars in thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 2,691,702 $ — $ 2,691,702 $ — Government-sponsored commercial mortgage-backed securities 116,271 — 116,271 — U.S. Agency bonds 831,672 — 831,672 — U.S. Treasury securities 69,090 69,090 — — State and municipal bonds and obligations 277,518 — 277,518 — Rabbi trust investments 94,005 85,720 8,285 — Loans held for sale 2,022 — 2,022 — Interest rate swap contracts Customer-related positions 90,748 — 90,748 — Risk participation agreements 391 — 391 — Foreign currency forward contracts Matched customer book 81 — 81 — Foreign currency loan 18 — 18 — Total $ 4,173,518 $ 154,810 $ 4,018,708 $ — Liabilities Interest rate swap contracts Customer-related positions $ 33,620 $ — $ 33,620 $ — Risk participation agreements 530 — 530 — Foreign currency forward contracts Matched customer book 61 — 61 — Foreign currency loan 5 — 5 — Total $ 34,216 $ — $ 34,216 $ — 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 three months ended March 31, 2021 and year ended December 31, 2020. For the fair value measurements which are classified as Level 3 within the fair value hierarchy, the Company’s Treasury and Finance groups determine the valuation policies and procedures. For the valuation of the qualified zone academy bond, the Company uses third-party valuation information. Management determined that no changes to the quantitative unobservable inputs were necessary. Management employs various techniques to analyze the valuation it receives from third parties, such as analyzing changes in market yields. Management reviews changes in fair value from period to period to ensure that values received from the third parties are consistent with their expectation of the market. The Company held no assets or liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) as of March 31, 2021. The table below presents a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the three months ended March 31, 2020: Securities Qualified Zone Academy Bond (In thousands) Balance at January 1, 2020: $ 6,310 Gains and losses (realized/unrealized): Included in net income 27 Included in other comprehensive income (88) Balance at March 31, 2020 $ 6,249 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 March 31, 2021 and December 31, 2020. Fair Value Measurements at Reporting Date Using Description Balance as of March 31, 2021 Quoted Prices Significant Significant (Dollars in thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 11,685 $ — $ — $ 11,685 Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices Significant Significant (Dollars 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 Carrying Value as of March 31, 2021 Fair Value as of March 31, 2021 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,772,722 $ 9,870,710 $ — $ — $ 9,870,710 FHLB stock 8,805 8,805 — 8,805 — Bank-owned life insurance 79,110 79,110 — 79,110 — Liabilities Deposits $ 12,980,875 $ 12,980,753 $ — $ 12,980,753 $ — FHLB advances 14,473 14,299 — 14,299 — Escrow deposits from borrowers 14,878 14,878 — 14,878 — Fair Value Measurements at Reporting Date Using 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	3 Months Ended
	Mar. 31, 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, 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 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. For the Three Months Ended March 31, 2021 2020 (Dollars In Thousands) Insurance commissions $ 28,147 $ 27,477 Service charges on deposit accounts 5,367 6,098 Trust and investment advisory fees 5,663 5,095 Debit card processing fees 2,749 2,470 Other non-interest income 1,792 2,052 Total noninterest income in-scope of ASC 606 43,718 43,192 Total noninterest income out-of-scope of ASC 606 11,494 (9,823) Total noninterest income $ 55,212 $ 33,369 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 $12.9 million as of March 31, 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 charges 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 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 March 31, 2021 and December 31, 2020, respectively, 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 and are settled within each network. Debit card processing fees earned but not yet received amounted to $0.3 million as of both March 31, 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	3 Months Ended
	Mar. 31, 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 income (loss) for the dates indicated including the amount of income tax (expense) benefit allocated to each component of other comprehensive income (loss): Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Pre-Tax Tax After Tax Pre-Tax Tax After Tax (Dollars In Thousands) Unrealized (losses) gains on securities available for sale: Change in fair value of securities available for sale $ (94,979) $ 20,982 $ (73,997) $ 33,802 $ (7,515) $ 26,287 Less: reclassification adjustment for gains included in net income 1,164 (257) 907 122 (27) 95 Net change in fair value of securities available for sale (96,143) 21,239 (74,904) 33,680 (7,488) 26,192 Unrealized gains (losses) on cash flow hedges: Change in fair value of cash flow hedges — — — 43,556 (12,244) 31,312 Less: net cash flow hedge losses reclassified into interest income (1) 8,274 (2,326) 5,948 3,112 (875) 2,237 Net change in fair value of cash flow hedges (8,274) 2,326 (5,948) 40,444 (11,369) 29,075 Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (3,537) 994 (2,543) — — — Less: net accretion of prior service cost 2,945 (828) 2,117 — — — Net change in other comprehensive income for defined benefit postretirement plans 592 (166) 426 — — — Total other comprehensive income $ (103,825) $ 23,399 $ (80,426) $ 74,124 $ (18,857) $ 55,267 (1) Represents amortization of realized gains on terminated cash flow hedges for the three months ended March 31, 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 $23.9 million, net of tax, at March 31, 2021. 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) income before reclassifications (73,997) — — (73,997) Less: Amounts reclassified from accumulated other comprehensive income 907 5,948 (426) 6,429 Net current-period other comprehensive income (74,904) (5,948) 426 (80,426) Ending Balance: March 31, 2021 $ (29,232) $ 23,867 $ (20,827) $ (26,192) Beginning Balance: January 1, 2020 $ 21,798 $ 15,624 $ (81,269) $ (43,847) Other comprehensive income (loss) before reclassifications 26,287 31,312 — 57,599 Less: Amounts reclassified from accumulated other comprehensive income 95 2,237 — 2,332 Net current-period other comprehensive income 26,192 29,075 — 55,267 Ending Balance: March 31, 2020 $ 47,990 $ 44,699 $ (81,269) $ 11,420

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 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 March 31, 2021 and 2020, was as follows: As of and for the Three Months Ended March 31, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 100,091 $ — $ — $ 100,091 $ 100,146 $ — $ — $ 100,146 (Release of) provision for allowance for loan losses (580) — — (580) 28,600 — — 28,600 Net interest income after provision for loan losses 100,671 — — 100,671 71,546 — — 71,546 Noninterest income 26,960 28,284 (32) 55,212 6,868 26,523 (22) 33,369 Noninterest expense 75,274 19,811 (1,036) 94,049 78,465 17,642 (935) 95,172 Income before provision for income taxes 52,357 8,473 1,004 61,834 (51) 8,881 913 9,743 Income tax provision 11,793 2,378 — 14,171 (1,214) 2,512 — 1,298 Net income $ 40,564 $ 6,095 $ 1,004 $ 47,663 $ 1,163 $ 6,369 $ 913 $ 8,445 Total assets $ 16,595,311 $ 194,664 $ (63,180) $ 16,726,795 $ 12,221,799 $ 182,564 $ (60,609) $ 12,343,754 Total liabilities $ 13,359,075 $ 43,855 $ (63,180) $ 13,339,750 $ 10,696,509 $ 45,120 $ (60,609) $ 10,681,020

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 7, 2021, the Company entered into a definitive merger agreement with Century Bancorp, Inc. (“Century”) under which the Company will acquire Century for $641.9 million in cash (the “Merger Agreement”). Century is the stock holding company of Century Bank and Trust Company, a Massachusetts-chartered stock bank headquartered in Medford, Massachusetts with $6.4 billion in assets, $5.4 billion in deposits and 27 full-service branches in Massachusetts as of December 31, 2020. Pursuant to the terms of the Merger Agreement, Century Bank and Trust Company will merge with and into the Bank upon completion of the transaction. The transaction is subject to customary closing conditions, including the receipt of regulatory approval and Century shareholder approval. The Company currently expects the merger to be completed during the fourth quarter of 2021. The Merger Agreement has been unanimously approved by the Boards of Directors of each of the Company and Century. Under the terms of the Merger Agreement, at the effective time of the merger, each holder of Century Class A and Class B common stock will receive a cash payment of $115.28 per share. Additional information about the Merger Agreement and the merger can be found in the Company's Current Report on Form 8-K filed with the SEC on April 8, 2021. The merger is subject to certain risks and uncertainties, and there can be no assurance that the Company will be able to complete the merger on the expected timeline or at all. See “Risk Factors” included in Part II, Item 1A of this Quarterly Report on Form 10-Q.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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 Update (“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 year's presentation. The accompanying consolidated balance sheet as of March 31, 2021, the consolidated statements of income and comprehensive income and of changes in shareholders’ equity for the three months ended March 31, 2021 and 2020 and statement of cash flows for the three months ended March 31, 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 months ended March 31, 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 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	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 March 31, 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. The Company anticipates deferring adoption of this standard to January 1, 2022. To address the impact of ASU 2016-13, the Company has formed a committee, including 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 evaluated portfolio segmentation, methodologies and economic forecasting inputs to the process and continues to design the control environment under the new standard. A third party has been engaged to assist the Company in project management, documentation, model governance and related internal controls implementation. The Company is currently assessing the impact of the new standard on its consolidated financial statements. 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. Relevant standards that were adopted during the period ended March 31, 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 Board’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)	3 Months Ended
	Mar. 31, 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 March 31, 2021 and December 31, 2020 were as follows: As of March 31, 2021 Amortized Unrealized Unrealized Fair (In Thousands) Debt securities: Government-sponsored residential mortgage-backed securities $ 2,713,898 $ 23,199 $ (45,395) $ 2,691,702 Government-sponsored commercial mortgage-backed securities 119,064 — (2,793) 116,271 U.S. Agency bonds 860,554 — (28,882) 831,672 U.S. Treasury securities 69,385 30 (325) 69,090 State and municipal bonds and obligations 260,818 16,700 — 277,518 $ 4,023,719 $ 39,929 $ (77,395) $ 3,986,253 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 March 31, 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 March 31, 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 $ — $ — $ 20,503 $ 21,777 $ 87,383 $ 91,340 $ 2,606,012 $ 2,578,585 $ 2,713,898 $ 2,691,702 Government-sponsored commercial mortgage-backed securities — — 24,090 23,771 94,974 92,500 — — 119,064 116,271 U.S. Agency bonds — — 99,784 98,111 760,770 733,561 — — 860,554 831,672 U.S. Treasury securities 10,065 10,095 59,320 58,995 — — — — 69,385 69,090 State and municipal bonds and obligations 405 406 25,244 26,220 72,587 76,077 162,582 174,815 260,818 277,518 Total $ 10,470 $ 10,501 $ 228,941 $ 228,874 $ 1,015,714 $ 993,478 $ 2,768,594 $ 2,753,400 $ 4,023,719 $ 3,986,253 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 March 31, 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 March 31, 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 18 $ 45,395 $ 2,004,883 $ — $ — $ 45,395 $ 2,004,883 Government-sponsored commercial mortgage-backed securities 7 2,793 116,271 — — 2,793 116,271 U.S. Agency bonds 13 28,882 831,672 — — 28,882 831,672 U.S. Treasury securities 2 325 58,995 — — 325 58,995 40 $ 77,395 $ 3,011,821 $ — $ — $ 77,395 $ 3,011,821 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)	3 Months Ended
	Mar. 31, 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: As of March 31, As of December 31, 2021 2020 (In thousands) Commercial and industrial $ 1,986,366 $ 1,995,016 Commercial real estate 3,676,941 3,573,630 Commercial construction 249,416 305,708 Business banking 1,513,051 1,339,164 Residential real estate 1,406,510 1,370,957 Consumer home equity 832,466 868,270 Other consumer 251,725 277,780 Gross loans before unamortized premiums, unearned discounts and deferred fees 9,916,475 9,730,525 Allowance for credit losses (111,080) (113,031) Unamortized premiums, net of unearned discounts and deferred fees (32,673) (23,536) Loans after the allowance for credit losses, unamortized premiums, unearned discounts and deferred fees $ 9,772,722 $ 9,593,958
Summary of the changes in the allowance for loan losses	The following table summarizes the changes in the allowance for loan losses for the periods indicated: For the Three Months Ended March 31, 2021 2020 (In thousands) Balance at the beginning of period $ 113,031 $ 82,297 Loans charged off (1,982) (2,343) Recoveries 611 584 (Release of) provision for loan losses (580) 28,600 Balance at end of period $ 111,080 $ 109,138
Summary of allowance for credit losses on financing receivables by loan category	The following tables summarize changes in the allowance for loan losses by loan category and bifurcates the amount of allowance allocated to each loan category based on collective impairment analysis and loans evaluated individually for impairment: For the Three Months Ended March 31, 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 — (234) — (1,384) — — (364) — (1,982) Recoveries 9 — — 365 10 71 156 — 611 (Release of) provision (1,220) 803 (1,203) 1,371 (210) (239) 239 (121) (580) Ending balance $ 25,406 $ 55,138 $ 3,350 $ 13,504 $ 6,235 $ 3,576 $ 3,498 $ 373 $ 111,080 Ending balance: individually evaluated for impairment $ 4,761 $ 210 $ — $ 1,387 $ 1,516 $ 263 $ — $ — $ 8,137 Ending balance: acquired with deteriorated credit quality $ 1,283 $ 822 $ — $ — $ 327 $ — $ — $ — $ 2,432 Ending balance: collectively evaluated for impairment $ 19,362 $ 54,106 $ 3,350 $ 12,117 $ 4,392 $ 3,313 $ 3,498 $ 373 $ 100,511 Loans ending balance: Individually evaluated for impairment $ 17,907 $ 4,536 $ — $ 21,001 $ 26,459 $ 4,461 $ 26 $ — $ 74,390 Acquired with deteriorated credit quality 2,944 1,554 — — 3,119 — — — 7,617 Collectively evaluated for impairment 1,965,515 3,670,851 249,416 1,492,050 1,376,932 828,005 251,699 — 9,834,468 Total loans by group $ 1,986,366 $ 3,676,941 $ 249,416 $ 1,513,051 $ 1,406,510 $ 832,466 $ 251,725 $ — $ 9,916,475 For the Three Months Ended March 31, 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 — — — (1,337) — (473) (533) — (2,343) Recoveries 322 1 — 127 60 14 60 — 584 Provision (release of) 9,290 14,496 1,288 3,131 (212) 345 319 (57) 28,600 Ending balance $ 30,531 $ 49,227 $ 4,712 $ 10,181 $ 6,228 $ 3,913 $ 4,019 $ 327 $ 109,138 Ending balance: individually evaluated for impairment $ 4,037 $ 270 $ — $ 453 $ 1,275 $ 221 $ — $ — $ 6,256 Ending balance: acquired with deteriorated credit quality $ — $ 936 $ — $ — $ 256 $ — $ — $ — $ 1,192 Ending balance: collectively evaluated for impairment $ 26,494 $ 48,021 $ 4,712 $ 9,728 $ 4,697 $ 3,692 $ 4,019 $ 327 $ 101,690 Loans ending balance: Individually evaluated for impairment $ 32,423 $ 8,054 $ — $ 10,258 $ 29,393 $ 6,280 $ 23 $ — $ 86,431 Acquired with deteriorated credit quality 3,939 5,780 — — 3,424 — — — 13,143 Collectively evaluated for impairment 1,734,760 3,509,887 293,135 769,658 1,387,186 923,274 369,629 — 8,987,529 Total loans by group $ 1,771,122 $ 3,523,721 $ 293,135 $ 779,916 $ 1,420,003 $ 929,554 $ 369,652 $ — $ 9,087,103
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 March 31, 2021 Category Commercial and Commercial Commercial Business Total (In thousands) Unrated $ 684,938 $ 6,318 $ — $ 1,079,605 $ 1,770,861 Pass 1,171,994 3,353,758 232,981 347,867 5,106,600 Special mention 68,826 127,751 10,345 57,387 264,309 Substandard 45,573 186,707 6,090 26,492 264,862 Doubtful 15,035 2,407 — 1,700 19,142 Loss — — — — — Total $ 1,986,366 $ 3,676,941 $ 249,416 $ 1,513,051 $ 7,425,774 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 March 31, As of December 31, 2021 2020 (In Thousands) Commercial and industrial $ 12,266 $ 11,714 Commercial real estate 1,016 915 Business banking 16,993 17,430 Residential real estate 8,127 6,815 Consumer home equity 3,524 3,602 Other consumer 349 529 Total non-accrual loans $ 42,275 $ 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 March 31, 2021 30-59 60-89 90 or More Total Past Current Total Recorded (In thousands) Commercial and industrial $ 9,460 $ 3 $ 1,174 $ 10,637 $ 1,975,729 $ 1,986,366 $ 252 Commercial real estate 3,225 — 1,403 4,628 3,672,313 3,676,941 1,138 Commercial construction — — — — 249,416 249,416 — Business banking 13,299 1,404 8,513 23,216 1,489,835 1,513,051 — Residential real estate 5,738 857 6,271 12,866 1,393,644 1,406,510 280 Consumer home equity 1,416 496 3,006 4,918 827,548 832,466 9 Other consumer 975 419 349 1,743 249,982 251,725 — Total $ 34,113 $ 3,179 $ 20,716 $ 58,008 $ 9,858,467 $ 9,916,475 $ 1,679 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 table shows the TDR loans on accrual and nonaccrual status as of the dates indicated: As of March 31, 2021 TDRs on Accrual Status TDRs on Nonaccrual Status Total TDRs Number of Loans Balance of Number of Balance of Number of Balance of (Dollars in thousands) Commercial and industrial 1 $ 5,641 6 $ 7,583 7 $ 13,224 Commercial real estate 1 3,520 1 468 2 3,988 Business banking 5 4,008 6 1,075 11 5,083 Residential real estate 140 22,565 30 3,557 170 26,122 Consumer home equity 79 3,607 14 854 93 4,461 Other consumer 3 26 — — 3 26 Total 229 $ 39,367 57 $ 13,537 286 $ 52,904 As of December 31, 2020 TDRs on Accrual Status TDRs on Nonaccrual Status Total TDRs Number of Loans Balance of Number of Loans Balance 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 March 31, 2021 For the Three Months Ended March 31, 2020 Number Pre- Post- Number Pre- Post- (Dollars in thousands) Business banking — $ — $ — 1 $ 244 $ 244 Residential real estate 1 295 295 8 414 419 Consumer home equity — — — 1 24 24 Total 1 $ 295 $ 295 10 $ 682 $ 687 (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 March 31, 2021 2020 (In thousands) Extended maturity and interest only/principal deferred $ — $ 46 Court-ordered concession 295 — Other — 641 Total $ 295 $ 687
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 loans 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 nonaccrual: For the Three Months Ended March 31, 2021 2020 Number of Recorded Number of Recorded (Dollars in thousands) Troubled debt restructurings that subsequently defaulted (1): Commercial and industrial — $ — 2 $ 4,613 Business banking 1 419 — — Consumer home equity 1 59 1 1,335 Total 2 $ 478 3 $ 5,948 (1) This table does not reflect any TDRs which were fully charged off, paid off, or otherwise settled during the period.
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 March 31, 2021 As of December 31, 2020 Recorded Unpaid Related Recorded Unpaid Related (In thousands) With no related allowance recorded: Commercial and industrial $ 10,071 $ 11,312 $ — $ 9,182 $ 11,212 $ — Commercial real estate 4,068 4,113 — 3,955 3,974 — Business banking 4,961 7,260 — 5,250 7,659 — Residential real estate 14,408 16,714 — 14,730 17,010 — Consumer home equity 2,370 2,370 — 2,571 2,571 — Other consumer 26 26 — 29 29 — Sub-total 35,904 41,795 — 35,717 42,455 — With an allowance recorded: Commercial and industrial 7,836 8,147 4,761 8,161 8,432 4,555 Commercial real estate 468 489 210 480 497 210 Business banking 16,040 20,925 1,387 16,651 21,146 1,435 Residential real estate 12,051 12,051 1,516 12,326 12,326 1,565 Consumer home equity 2,091 2,091 263 2,274 2,274 289 Sub-total 38,486 43,703 8,137 39,892 44,675 8,054 Total $ 74,390 $ 85,498 $ 8,137 $ 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 March 31, 2021 2020 Average Total Average Total (In thousands) With no related allowance recorded: Commercial and industrial $ 9,899 $ 46 $ 20,880 $ 70 Commercial real estate 4,176 44 7,491 44 Business banking 5,024 26 2,286 17 Residential real estate 14,648 144 14,801 173 Consumer home equity 2,438 20 3,606 40 Other consumer 27 — 23 — Sub-total 36,212 280 49,087 344 With an allowance recorded: Commercial and industrial 7,965 — 11,730 — Commercial real estate 657 — 348 — Business banking 16,325 14 8,782 15 Residential real estate 12,248 127 11,727 137 Consumer home equity 2,150 18 2,857 31 Sub-total 39,345 159 35,444 183 Total $ 75,557 $ 439 $ 84,531 $ 527
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: As of March 31, 2021 As of December 31, 2020 (In Thousands) Outstanding balance $ 8,662 $ 9,982 Carrying amount 7,617 $ 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 March 31, 2021 2020 (In thousands) Balance at beginning of period $ 2,495 $ 3,923 Accretion (216) (422) Other change in expected cash flows (248) (155) Balance at end of period $ 2,031 $ 3,346
Summary of the Company's loan participations	The following table summarizes the Company’s loan participations: As of and for the three months ended March 31, 2021 As of and for the year ended December 31, 2020 Balance Nonperforming Impaired Gross Balance Nonperforming Impaired Gross (Dollars in thousands) Commercial and industrial $ 579,812 1.31 % 1.31 % $ — $ 598,873 1.11 % 1.11 % $ — Commercial real estate 345,261 0.00 % 0.00 % — 306,202 0.00 % 0.00 % — Commercial construction 86,447 0.00 % 0.00 % — 119,600 0.00 % 0.00 % — Business banking 31 0.00 % 0.00 % — 34 0.00 % 0.00 % — Total loan participations $ 1,011,551 0.75 % 0.75 % $ — $ 1,024,709 0.65 % 0.65 % $ —

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2021 Banking Insurance Net (In Thousands) Balances not subject to amortization Goodwill $ 298,611 $ 70,866 $ 369,477 Balances subject to amortization Insurance agency — 6,398 6,398 Core deposits 127 — 127 Total other intangible assets 127 6,398 6,525 Total goodwill and other intangible assets $ 298,738 $ 77,264 $ 376,002 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 — 6,899 6,899 Core deposits 158 — 158 Total other intangible assets 158 6,899 7,057 Total goodwill and other intangible assets $ 298,769 $ 77,765 $ 376,534

Earnings Per Share ("EPS") (Tab

Earnings Per Share ("EPS") (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	For the Three Months Ended March 31, 2021 (Dollars in thousands, except per share data) Net income applicable to common shares $ 47,663 Average number of common shares outstanding 186,758,154 Less: Average unallocated ESOP shares (14,709,110) Average number of common shares outstanding used to calculate basic earnings per common share 172,049,044 Common stock equivalents — Average number of common shares outstanding used to calculate diluted earnings per common share 172,049,044 Earnings per common share Basic and diluted $ 0.28

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Summary of Lease Cost	As of the dates indicated, the Company had the following related to operating leases: As of March 31, 2021 As of December 31, 2020 (In thousands) Right-of-use assets $ 79,163 $ 81,596 Lease liabilities 82,910 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 sheet. The following table is a summary of the Company’s components of net lease cost for the periods indicated: For the Three Months Ended March 31, 2021 2020 (In thousands) Operating lease cost $ 3,561 $ 3,613 Finance lease cost 31 2 Variable lease cost 490 522 Total lease cost $ 4,082 $ 4,137
Summary of Other Information Related to Leases	Supplemental balance sheet information related to operating leases are as follows: As of March 31, 2021 As of As of December 31, 2020 Weighted-average remaining lease term (in years) 8.33 8.50 Weighted-average discount rate 2.63 % 2.65 %

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Summary of Company's Tax Provision and Applicable Tax Rates	The following table sets forth information regarding the Company’s tax provision and applicable tax rates for the periods indicated: For the Three Months Ended March 31, 2021 2020 (Dollars in thousands) Combined federal and state income tax provisions $ 14,171 $ 1,298 Effective income tax rates 22.9 % 13.3 %

Low Income Housing Tax Credit_2

Low Income Housing Tax Credits and Other Tax Credit Investments (Tables)	3 Months Ended
	Mar. 31, 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 LIHTC projects using the proportional amortization method for the periods indicated: Three Months Ended Year Ended December 31, 2020 (In thousands) Current recorded investment included in other assets $ 62,904 $ 58,504 Commitments to fund qualified affordable housing projects included in recorded investment noted above 34,430 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 March 31, 2021 2020 (In thousands) Tax credits and benefits recognized $ 1,464 $ 1,519 Amortization expense included in income tax expense 1,264 1,191

Employee Benefits (Tables)

Employee Benefits (Tables)	3 Months Ended
	Mar. 31, 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: For the Three Months Ended March 31, 2021 2020 (In Thousands) Components of net periodic benefit cost: Service cost $ 7,896 $ 6,232 Interest cost 1,269 2,616 Expected return on plan assets (8,141) (7,425) Prior service (credit) cost (2,946) 6 Recognized net actuarial loss 3,538 2,361 Net periodic benefit cost $ 1,616 $ 3,790
Schedule of Assets Held in Rabbi Trust	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 March 31, 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 $ 5,230 $ — $ 5,230 $ 5,157 $ — $ 5,157 Equities 61,662 18,828 80,490 59,235 19,492 78,727 Fixed income 8,110 175 8,285 7,441 358 7,799 Total assets $ 75,002 $ 19,003 $ 94,005 $ 71,833 $ 19,850 $ 91,683

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2021 As of December 31, 2020 (In Thousands) Commitments to extend credit $ 3,959,011 $ 3,818,952 Standby letters of credit 63,986 60,221 Forward commitments to sell loans 35,564 41,160

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2021: For the Three Months Ended (In thousands) Unrealized gains on terminated hedges included in AOCI - January 1 $ 41,473 Unrealized gains on terminated hedges arising during the period — Reclassification adjustments for amortization of unrealized (gains) into net income (8,274) Unrealized gains on terminated hedges included in AOCI - March 31 $ 33,199
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: As of March 31, 2021 Number of Positions Total Notional (Dollars in Thousands) Interest rate swaps 562 $ 3,571,918 Risk participation agreements 70 288,803 Foreign exchange contracts: Matched commercial customer book 74 8,428 Foreign currency loan 3 7,988 As of 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 balance sheet for the periods indicated. There were no derivatives designated as hedging instruments at March 31, 2021 or December 31, 2020. Asset Derivatives Liability Derivatives Balance Fair Value at March 31, Fair Value at December 31, 2020 Balance Sheet Fair Value at March 31, Fair Value at December 31, 2020 (Dollars in thousands) Derivatives not designated as hedging instruments Customer-related positions: Interest rate swaps Other assets $ 90,748 $ 141,822 Other liabilities $ 33,620 $ 42,600 Risk participation agreements Other assets 391 722 Other liabilities 530 1,230 Foreign currency exchange contracts - matched customer book Other assets 81 90 Other liabilities 61 77 Foreign currency exchange contracts - foreign currency loan Other assets 18 9 Other liabilities 5 69 Total $ 91,238 $ 142,643 $ 34,216 $ 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: For the Three Months Ended March 31, 2021 2020 (Dollars in Thousands) Derivatives designated as hedges: Gain in OCI on derivatives $ — $ 43,556 Gain reclassified from OCI into interest income (effective portion) $ 8,274 $ 3,112 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 $ 4,851 $ (6,280) Gain (loss) recognized in interest rate swap income for risk participation agreements 369 (301) Gain (loss) recognized in other income for foreign currency exchange contracts: Matched commercial customer book 6 (26) Foreign currency loan 73 397 Total gain (loss) for derivatives not designated as hedges $ 5,299 $ (6,210)

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	3 Months Ended
	Mar. 31, 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 financial position, as of the dates indicated: As of March 31, 2021 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Interest rate swaps $ — $ — $ — $ — $ — $ — Customer-related positions: Interest rate swaps 90,748 — 90,748 1,426 — 89,322 Risk participation agreements 391 — 391 — — 391 Foreign currency exchange contracts – matched customer book 81 — 81 — — 81 Foreign currency exchange contracts – foreign currency loan 18 — 18 — — 18 $ 91,238 $ — $ 91,238 $ 1,426 $ — $ 89,812 Derivative Liabilities Interest rate swaps $ — $ — $ — $ — $ — $ — Customer-related positions: Interest rate swaps 33,620 — 33,620 1,426 32,194 — Risk participation agreements 530 — 530 — — 530 Foreign currency exchange contracts – matched customer book 61 — 61 — — 61 Foreign currency exchange contracts – foreign currency loan 5 — 5 — — 5 $ 34,216 $ — $ 34,216 $ 1,426 $ 32,194 $ 596 As of December 31, 2020 Gross Gross Net Gross Amounts Not Offset Net Description Financial Collateral (In thousands) Derivative Assets Interest rate swaps $ — $ — $ — $ — $ — $ — 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 Interest rate swaps $ — $ — $ — $ — $ — $ — 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)	3 Months Ended
	Mar. 31, 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 March 31, 2021 and December 31, 2020: Fair Value Measurements at Reporting Date Using Balance as of March 31, 2021 Quoted Prices in Significant Significant Description (Dollars in thousands) Assets Securities available for sale Government-sponsored residential mortgage-backed securities $ 2,691,702 $ — $ 2,691,702 $ — Government-sponsored commercial mortgage-backed securities 116,271 — 116,271 — U.S. Agency bonds 831,672 — 831,672 — U.S. Treasury securities 69,090 69,090 — — State and municipal bonds and obligations 277,518 — 277,518 — Rabbi trust investments 94,005 85,720 8,285 — Loans held for sale 2,022 — 2,022 — Interest rate swap contracts Customer-related positions 90,748 — 90,748 — Risk participation agreements 391 — 391 — Foreign currency forward contracts Matched customer book 81 — 81 — Foreign currency loan 18 — 18 — Total $ 4,173,518 $ 154,810 $ 4,018,708 $ — Liabilities Interest rate swap contracts Customer-related positions $ 33,620 $ — $ 33,620 $ — Risk participation agreements 530 — 530 — Foreign currency forward contracts Matched customer book 61 — 61 — Foreign currency loan 5 — 5 — Total $ 34,216 $ — $ 34,216 $ — 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 Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs Level (3)	The table below presents a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the three months ended March 31, 2020: Securities Qualified Zone Academy Bond (In thousands) Balance at January 1, 2020: $ 6,310 Gains and losses (realized/unrealized): Included in net income 27 Included in other comprehensive income (88) Balance at March 31, 2020 $ 6,249
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 March 31, 2021 and December 31, 2020. Fair Value Measurements at Reporting Date Using Description Balance as of March 31, 2021 Quoted Prices Significant Significant (Dollars in thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 11,685 $ — $ — $ 11,685 Fair Value Measurements at Reporting Date Using Description Balance as of December 31, 2020 Quoted Prices Significant Significant (Dollars in thousands) Assets Collateral-dependent impaired loans whose fair value is based upon appraisals $ 11,036 $ — $ — 11,036
Schedule of 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 Carrying Value as of March 31, 2021 Fair Value as of March 31, 2021 Quoted Prices Significant Significant (In thousands) Assets Loans, net of allowance for loan losses $ 9,772,722 $ 9,870,710 $ — $ — $ 9,870,710 FHLB stock 8,805 8,805 — 8,805 — Bank-owned life insurance 79,110 79,110 — 79,110 — Liabilities Deposits $ 12,980,875 $ 12,980,753 $ — $ 12,980,753 $ — FHLB advances 14,473 14,299 — 14,299 — Escrow deposits from borrowers 14,878 14,878 — 14,878 — Fair Value Measurements at Reporting Date Using 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)	3 Months Ended
	Mar. 31, 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. For the Three Months Ended March 31, 2021 2020 (Dollars In Thousands) Insurance commissions $ 28,147 $ 27,477 Service charges on deposit accounts 5,367 6,098 Trust and investment advisory fees 5,663 5,095 Debit card processing fees 2,749 2,470 Other non-interest income 1,792 2,052 Total noninterest income in-scope of ASC 606 43,718 43,192 Total noninterest income out-of-scope of ASC 606 11,494 (9,823) Total noninterest income $ 55,212 $ 33,369

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 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 income (loss) for the dates indicated including the amount of income tax (expense) benefit allocated to each component of other comprehensive income (loss): Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Pre-Tax Tax After Tax Pre-Tax Tax After Tax (Dollars In Thousands) Unrealized (losses) gains on securities available for sale: Change in fair value of securities available for sale $ (94,979) $ 20,982 $ (73,997) $ 33,802 $ (7,515) $ 26,287 Less: reclassification adjustment for gains included in net income 1,164 (257) 907 122 (27) 95 Net change in fair value of securities available for sale (96,143) 21,239 (74,904) 33,680 (7,488) 26,192 Unrealized gains (losses) on cash flow hedges: Change in fair value of cash flow hedges — — — 43,556 (12,244) 31,312 Less: net cash flow hedge losses reclassified into interest income (1) 8,274 (2,326) 5,948 3,112 (875) 2,237 Net change in fair value of cash flow hedges (8,274) 2,326 (5,948) 40,444 (11,369) 29,075 Defined benefit pension plans: Change in actuarial net loss — — — — — — Less: amortization of actuarial net loss (3,537) 994 (2,543) — — — Less: net accretion of prior service cost 2,945 (828) 2,117 — — — Net change in other comprehensive income for defined benefit postretirement plans 592 (166) 426 — — — Total other comprehensive income $ (103,825) $ 23,399 $ (80,426) $ 74,124 $ (18,857) $ 55,267 (1) Represents amortization of realized gains on terminated cash flow hedges for the three months ended March 31, 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 $23.9 million, net of tax, at March 31, 2021.
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) income before reclassifications (73,997) — — (73,997) Less: Amounts reclassified from accumulated other comprehensive income 907 5,948 (426) 6,429 Net current-period other comprehensive income (74,904) (5,948) 426 (80,426) Ending Balance: March 31, 2021 $ (29,232) $ 23,867 $ (20,827) $ (26,192) Beginning Balance: January 1, 2020 $ 21,798 $ 15,624 $ (81,269) $ (43,847) Other comprehensive income (loss) before reclassifications 26,287 31,312 — 57,599 Less: Amounts reclassified from accumulated other comprehensive income 95 2,237 — 2,332 Net current-period other comprehensive income 26,192 29,075 — 55,267 Ending Balance: March 31, 2020 $ 47,990 $ 44,699 $ (81,269) $ 11,420

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2021 and 2020, was as follows: As of and for the Three Months Ended March 31, 2021 2020 Banking Insurance Other / Total Banking Insurance Other / Total (In thousands) Net interest income $ 100,091 $ — $ — $ 100,091 $ 100,146 $ — $ — $ 100,146 (Release of) provision for allowance for loan losses (580) — — (580) 28,600 — — 28,600 Net interest income after provision for loan losses 100,671 — — 100,671 71,546 — — 71,546 Noninterest income 26,960 28,284 (32) 55,212 6,868 26,523 (22) 33,369 Noninterest expense 75,274 19,811 (1,036) 94,049 78,465 17,642 (935) 95,172 Income before provision for income taxes 52,357 8,473 1,004 61,834 (51) 8,881 913 9,743 Income tax provision 11,793 2,378 — 14,171 (1,214) 2,512 — 1,298 Net income $ 40,564 $ 6,095 $ 1,004 $ 47,663 $ 1,163 $ 6,369 $ 913 $ 8,445 Total assets $ 16,595,311 $ 194,664 $ (63,180) $ 16,726,795 $ 12,221,799 $ 182,564 $ (60,609) $ 12,343,754 Total liabilities $ 13,359,075 $ 43,855 $ (63,180) $ 13,339,750 $ 10,696,509 $ 45,120 $ (60,609) $ 10,681,020

Securities - Narrative (Detail)

Securities - Narrative (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Securities [Abstract]
Gross realized gains from sales of available for sale securities	$ 1,200,000	$ 100,000
Gross realized losses from sales of available for sale securities	0	0
Other-than-temporary impairment was recorded	$ 0	$ 0

Securities - Summary Of Debt Se

Securities - Summary Of Debt Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,023,719	$ 3,125,184
Unrealized Gains	39,929	62,549
Unrealized Losses	(77,395)	(3,872)
Fair Value	3,986,253	3,183,861
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,713,898	2,106,658
Unrealized Gains	23,199	42,142
Unrealized Losses	(45,395)	0
Fair Value	2,691,702	2,148,800
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,064	17,054
Unrealized Gains	0	27
Unrealized Losses	(2,793)	0
Fair Value	116,271	17,081
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	860,554	670,468
Unrealized Gains	0	113
Unrealized Losses	(28,882)	(3,872)
Fair Value	831,672	666,709
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	69,385	70,106
Unrealized Gains	30	263
Unrealized Losses	(325)	0
Fair Value	69,090	70,369
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	260,818	260,898
Unrealized Gains	16,700	20,004
Unrealized Losses	0	0
Fair Value	$ 277,518	$ 280,902

Securities - Summary Of Fair Va

Securities - Summary Of Fair Value Of Available For Sale Securities By Contractual Maturities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	$ 10,470	$ 50,429
Due in one year or less, Fair value	10,501	50,659
Due after one year to five years, Amortized Cost	228,941	186,659
Due after one year to five years, Fair value	228,874	190,308
Due after five to ten years, Amortized Cost	1,015,714	759,068
Due after five to ten years, Fair value	993,478	763,869
Due after ten years, Amortized Cost	2,768,594	2,129,028
Due after ten years, Fair value	2,753,400	2,179,025
Total Amortized Cost	4,023,719	3,125,184
Available for sale securities	3,986,253	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	20,503	46,293
Due after one year to five years, Fair value	21,777	48,925
Due after five to ten years, Amortized Cost	87,383	96,338
Due after five to ten years, Fair value	91,340	100,278
Due after ten years, Amortized Cost	2,606,012	1,964,027
Due after ten years, Fair value	2,578,585	1,999,597
Total Amortized Cost	2,713,898	2,106,658
Available for sale securities	2,691,702	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	24,090	0
Due after one year to five years, Fair value	23,771	0
Due after five to ten years, Amortized Cost	94,974	17,054
Due after five to ten years, Fair value	92,500	17,081
Due after ten years, Amortized Cost	0	0
Due after ten years, Fair value	0	0
Total Amortized Cost	119,064	17,054
Available for sale securities	116,271	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	99,784	99,772
Due after one year to five years, Fair value	98,111	99,834
Due after five to ten years, Amortized Cost	760,770	570,696
Due after five to ten years, Fair value	733,561	566,875
Due after ten years, Amortized Cost	0	0
Due after ten years, Fair value	0	0
Total Amortized Cost	860,554	670,468
Available for sale securities	831,672	666,709
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	10,065	50,023
Due in one year or less, Fair value	10,095	50,251
Due after one year to five years, Amortized Cost	59,320	20,083
Due after one year to five years, Fair value	58,995	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
Total Amortized Cost	69,385	70,106
Available for sale securities	69,090	70,369
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	405	406
Due in one year or less, Fair value	406	408
Due after one year to five years, Amortized Cost	25,244	20,511
Due after one year to five years, Fair value	26,220	21,431
Due after five to ten years, Amortized Cost	72,587	74,980
Due after five to ten years, Fair value	76,077	79,635
Due after ten years, Amortized Cost	162,582	165,001
Due after ten years, Fair value	174,815	179,428
Total Amortized Cost	260,818	260,898
Available for sale securities	$ 277,518	$ 280,902

Securities - Summary Of Governm

Securities - Summary Of Government-Sponsored Residential Mortgage-Backed Securities With Gross Unrealized Losses (Detail) $ in Thousands	Mar. 31, 2021USD ($)loans	Dec. 31, 2020USD ($)
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings	40	6
Less than 12 Months, Gross Unrealized Loss	$ 77,395	$ 3,872
Less than 12 Months, Fair Value	3,011,821	416,824
12 Months or Longer, Gross Unrealized Loss	0	0
12 Months or Longer, Fair Value	0	0
Gross Unrealized Losses	77,395	3,872
Fair Value	$ 3,011,821	$ 416,824
Government-sponsored residential mortgage-backed securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings	18
Less than 12 Months, Gross Unrealized Loss	$ 45,395
Less than 12 Months, Fair Value	2,004,883
12 Months or Longer, Gross Unrealized Loss	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	45,395
Fair Value	$ 2,004,883
Government-sponsored commercial mortgage-backed securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings	7
Less than 12 Months, Gross Unrealized Loss	$ 2,793
Less than 12 Months, Fair Value	116,271
12 Months or Longer, Gross Unrealized Loss	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	2,793
Fair Value	$ 116,271
U.S. Agency bonds
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings	13	6
Less than 12 Months, Gross Unrealized Loss	$ 28,882	$ 3,872
Less than 12 Months, Fair Value	831,672	416,824
12 Months or Longer, Gross Unrealized Loss	0	0
12 Months or Longer, Fair Value	0	0
Gross Unrealized Losses	28,882	3,872
Fair Value	$ 831,672	$ 416,824
U.S. Treasury securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Number of holdings | loans	2
Less than 12 Months, Gross Unrealized Loss	$ 325
Less than 12 Months, Fair Value	58,995
12 Months or Longer, Gross Unrealized Loss	0
12 Months or Longer, Fair Value	0
Gross Unrealized Losses	325
Fair Value	$ 58,995

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	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 9,916,475	$ 9,730,525	$ 9,087,103
Allowance for credit losses	(111,080)	(113,031)	(109,138)	$ (82,297)
Unamortized premiums, net of unearned discounts and deferred fees	(32,673)	(23,536)
Recorded investment	9,772,722	9,593,958
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,986,366	1,995,016	1,771,122
Allowance for credit losses	(25,406)	(26,617)	(30,531)	(20,919)
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,676,941	3,573,630	3,523,721
Allowance for credit losses	(55,138)	(54,569)	(49,227)	(34,730)
Commercial construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	249,416	305,708	293,135
Allowance for credit losses	(3,350)	(4,553)	(4,712)	(3,424)
Business banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,513,051	1,339,164	779,916
Allowance for credit losses	(13,504)	(13,152)	(10,181)	(8,260)
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,406,510	1,370,957	1,420,003
Allowance for credit losses	(6,235)	(6,435)	(6,228)	(6,380)
Consumer home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	832,466	868,270	929,554
Allowance for credit losses	(3,576)	(3,744)	(3,913)	(4,027)
Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	251,725	277,780	369,652
Allowance for credit losses	$ (3,498)	$ (3,467)	$ (4,019)	$ (4,173)

Loans and Allowance for Loan _4

Loans and Allowance for Loan Losses - Narrative (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Changes in lines of credit,resrticted to commercial exposure
Loan syndications, amount	$ 100,000,000
Mortgage loans partially or wholly-owned by others and serviced by the company	12,900,000		$ 13,500,000
Recorded investment	9,772,722,000		9,593,958,000
Total loans	$ 9,916,475,000	$ 9,087,103,000	9,730,525,000
Maximum number of days required for special mention	90 days
Amount of specific reserve associated with the TDR	$ 4,100,000		3,500,000
Amount of additional commitments to lend to borrowers who have been a party to a TDR	0		0
Outstanding recorded investment of loans that were new to troubled debt restructuring	300,000		3,900,000
Amounts charged-off on TDRs	0	400,000
Loan participation interest held	1,000,000,000		1,000,000,000
Payment Deferral | CARES Act
Changes in lines of credit,resrticted to commercial exposure
Loan modifications	178,400,000		332,700,000
Commercial and industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,986,366,000	1,771,122,000	1,995,016,000
Business banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,513,051,000	$ 779,916,000	1,339,164,000
Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	7,425,774,000		7,213,518,000
Nonperforming Loans | Commercial and industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,986,366,000		1,995,016,000
Nonperforming Loans | Business banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,513,051,000		1,339,164,000
Unrated
Changes in lines of credit,resrticted to commercial exposure
Lines of credit, exposure	100,000
Unrated | Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,770,861,000		1,580,852,000
Unrated | Nonperforming Loans | Commercial and industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	684,938,000		655,346,000
Unrated | Nonperforming Loans | Business banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	1,079,605,000		918,921,000
Unrated | Nonperforming Loans | Paycheck Protection Program | Commercial and industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	609,900,000		568,800,000
Unrated | Nonperforming Loans | Paycheck Protection Program | Business banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	628,200,000		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
Loss
Changes in lines of credit,resrticted to commercial exposure
Recorded investment	0
Loss | Nonperforming Loans
Changes in lines of credit,resrticted to commercial exposure
Total loans	0		0
Loss | Nonperforming Loans | Commercial and industrial
Changes in lines of credit,resrticted to commercial exposure
Total loans	0		0
Loss | Nonperforming Loans | Business banking
Changes in lines of credit,resrticted to commercial exposure
Total loans	0		0
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
Funds borrowed from federal banks	14,500,000		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	832,400,000		884,100,000
Funds borrowed from federal banks	$ 0		$ 0

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Summarizes the Changes in the Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	$ 113,031	$ 82,297
Loans charged off	(1,982)	(2,343)
Recoveries	611	584
(Release of) provision for loan losses	(580)	28,600
Balance at end of period	$ 111,080	$ 109,138

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Summary of Changes in Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	$ 113,031	$ 82,297	$ 82,297
Allowance for loan losses, Charge-offs	(1,982)	(2,343)
Allowance for loan losses, Recoveries	611	584
Allowance for loan losses, Provision (benefit)	(580)	28,600
Balance at end of period	111,080	109,138	113,031
Ending balance: individually evaluated for impairment	8,137	6,256
Ending balance: acquired with deteriorated credit quality	2,432	1,192
Ending balance: collectively evaluated for impairment	100,511	101,690
Loans ending balance:
Individually evaluated for impairment	74,390	86,431
Acquired with deteriorated credit quality	7,617	13,143
Collectively evaluated for impairment	9,834,468	8,987,529
Total loans	9,916,475	9,087,103	9,730,525
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	26,617	20,919	20,919
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	9	322
Allowance for loan losses, Provision (benefit)	(1,220)	9,290
Balance at end of period	25,406	30,531	26,617
Ending balance: individually evaluated for impairment	4,761	4,037
Ending balance: acquired with deteriorated credit quality	1,283	0
Ending balance: collectively evaluated for impairment	19,362	26,494
Loans ending balance:
Individually evaluated for impairment	17,907	32,423
Acquired with deteriorated credit quality	2,944	3,939
Collectively evaluated for impairment	1,965,515	1,734,760
Total loans	1,986,366	1,771,122	1,995,016
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	54,569	34,730	34,730
Allowance for loan losses, Charge-offs	(234)	0
Allowance for loan losses, Recoveries	0	1
Allowance for loan losses, Provision (benefit)	803	14,496
Balance at end of period	55,138	49,227	54,569
Ending balance: individually evaluated for impairment	210	270
Ending balance: acquired with deteriorated credit quality	822	936
Ending balance: collectively evaluated for impairment	54,106	48,021
Loans ending balance:
Individually evaluated for impairment	4,536	8,054
Acquired with deteriorated credit quality	1,554	5,780
Collectively evaluated for impairment	3,670,851	3,509,887
Total loans	3,676,941	3,523,721	3,573,630
Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	4,553	3,424	3,424
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	0	0
Allowance for loan losses, Provision (benefit)	(1,203)	1,288
Balance at end of period	3,350	4,712	4,553
Ending balance: individually evaluated for impairment	0	0
Ending balance: acquired with deteriorated credit quality	0	0
Ending balance: collectively evaluated for impairment	3,350	4,712
Loans ending balance:
Individually evaluated for impairment	0	0
Acquired with deteriorated credit quality	0	0
Collectively evaluated for impairment	249,416	293,135
Total loans	249,416	293,135	305,708
Business banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	13,152	8,260	8,260
Allowance for loan losses, Charge-offs	(1,384)	(1,337)
Allowance for loan losses, Recoveries	365	127
Allowance for loan losses, Provision (benefit)	1,371	3,131
Balance at end of period	13,504	10,181	13,152
Ending balance: individually evaluated for impairment	1,387	453
Ending balance: acquired with deteriorated credit quality	0	0
Ending balance: collectively evaluated for impairment	12,117	9,728
Loans ending balance:
Individually evaluated for impairment	21,001	10,258
Acquired with deteriorated credit quality	0	0
Collectively evaluated for impairment	1,492,050	769,658
Total loans	1,513,051	779,916	1,339,164
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	6,435	6,380	6,380
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	10	60
Allowance for loan losses, Provision (benefit)	(210)	(212)
Balance at end of period	6,235	6,228	6,435
Ending balance: individually evaluated for impairment	1,516	1,275
Ending balance: acquired with deteriorated credit quality	327	256
Ending balance: collectively evaluated for impairment	4,392	4,697
Loans ending balance:
Individually evaluated for impairment	26,459	29,393
Acquired with deteriorated credit quality	3,119	3,424
Collectively evaluated for impairment	1,376,932	1,387,186
Total loans	1,406,510	1,420,003	1,370,957
Consumer home equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	3,744	4,027	4,027
Allowance for loan losses, Charge-offs	0	(473)
Allowance for loan losses, Recoveries	71	14
Allowance for loan losses, Provision (benefit)	(239)	345
Balance at end of period	3,576	3,913	3,744
Ending balance: individually evaluated for impairment	263	221
Ending balance: acquired with deteriorated credit quality	0	0
Ending balance: collectively evaluated for impairment	3,313	3,692
Loans ending balance:
Individually evaluated for impairment	4,461	6,280
Acquired with deteriorated credit quality	0	0
Collectively evaluated for impairment	828,005	923,274
Total loans	832,466	929,554	868,270
Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	3,467	4,173	4,173
Allowance for loan losses, Charge-offs	(364)	(533)
Allowance for loan losses, Recoveries	156	60
Allowance for loan losses, Provision (benefit)	239	319
Balance at end of period	3,498	4,019	3,467
Ending balance: individually evaluated for impairment	0	0
Ending balance: acquired with deteriorated credit quality	0	0
Ending balance: collectively evaluated for impairment	3,498	4,019
Loans ending balance:
Individually evaluated for impairment	26	23
Acquired with deteriorated credit quality	0	0
Collectively evaluated for impairment	251,699	369,629
Total loans	251,725	369,652	277,780
Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of period	494	384	384
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	0	0
Allowance for loan losses, Provision (benefit)	(121)	(57)
Balance at end of period	373	327	$ 494
Ending balance: individually evaluated for impairment	0	0
Ending balance: acquired with deteriorated credit quality	0	0
Ending balance: collectively evaluated for impairment	373	327
Loans ending balance:
Individually evaluated for impairment	0	0
Acquired with deteriorated credit quality	0	0
Collectively evaluated for impairment	0	0
Total loans	$ 0	$ 0

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Summary of Internal Risk-rating Categories (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 9,916,475	$ 9,730,525	$ 9,087,103
Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	7,425,774	7,213,518
Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,770,861	1,580,852
Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	5,106,600	5,073,668
Special mention | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	264,309	280,101
Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	264,862	260,207
Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	19,142	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	1,986,366	1,995,016	1,771,122
Commercial and industrial | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,986,366	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	684,938	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	1,171,994	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	68,826	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	45,573	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	15,035	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	3,676,941	3,573,630	3,523,721
Commercial real estate | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,676,941	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	6,318	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	3,353,758	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	127,751	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	186,707	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	2,407	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	249,416	305,708	293,135
Commercial construction | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	249,416	305,708
Commercial construction | Unrated | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	0	0
Commercial construction | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	232,981	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	10,345	10,330
Commercial construction | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	6,090	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	1,513,051	1,339,164	$ 779,916
Business banking | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,513,051	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	1,079,605	918,921
Business banking | Pass | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	347,867	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	57,387	57,092
Business banking | Substandard | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	26,492	24,788
Business banking | Doubtful | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,700	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 _8

Loans and Allowance for Loan Losses - Summary Pertaining to the Breakdown of the Company's Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	$ 42,275	$ 41,005
Commercial and industrial
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	12,266	11,714
Commercial real estate
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	1,016	915
Business banking
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	16,993	17,430
Residential real estate
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	8,127	6,815
Consumer home equity
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	3,524	3,602
Other consumer
Disclosure Detail Of Non Accrual Loans [Line Items]
Total non-accrual loans	$ 349	$ 529

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Summary of Shows the Age Analysis of Past Due Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 58,008	$ 47,622
Current	9,858,467	9,682,903
Total loans	9,916,475	9,730,525	$ 9,087,103
Recorded Investment > 90 Days and Accruing	1,679	2,247
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	34,113	18,251
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,179	7,250
90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	20,716	22,121
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	10,637	2,196
Current	1,975,729	1,992,820
Total loans	1,986,366	1,995,016	1,771,122
Recorded Investment > 90 Days and Accruing	252	848
Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	9,460	4
Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3	268
Commercial and industrial | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,174	1,924
Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	4,628	2,101
Current	3,672,313	3,571,529
Total loans	3,676,941	3,573,630	3,523,721
Recorded Investment > 90 Days and Accruing	1,138	1,111
Commercial real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,225	0
Commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	556
Commercial real estate | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,403	1,545
Commercial construction
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Current	249,416	305,708
Total loans	249,416	305,708	293,135
Recorded Investment > 90 Days and Accruing	0	0
Commercial construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial construction | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Business banking
Financing Receivable, Past Due [Line Items]
Total Past Due	23,216	18,786
Current	1,489,835	1,320,378
Total loans	1,513,051	1,339,164
Recorded Investment > 90 Days and Accruing	0	0
Business banking | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	13,299	5,279
Business banking | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,404	3,311
Business banking | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,513	10,196
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	12,866	16,605
Current	1,393,644	1,354,352
Total loans	1,406,510	1,370,957
Recorded Investment > 90 Days and Accruing	280	279
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,738	9,184
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	857	2,517
Residential real estate | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	6,271	4,904
Consumer home equity
Financing Receivable, Past Due [Line Items]
Total Past Due	4,918	5,205
Current	827,548	863,065
Total loans	832,466	868,270
Recorded Investment > 90 Days and Accruing	9	9
Consumer home equity | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,416	1,806
Consumer home equity | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	496	364
Consumer home equity | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,006	3,035
Other consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	1,743	2,729
Current	249,982	275,051
Total loans	251,725	277,780	$ 369,652
Recorded Investment > 90 Days and Accruing	0	0
Other consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	975	1,978
Other consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	419	234
Other consumer | 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 349	$ 517

Loans and Allowance for Loan_10

Loans and Allowance for Loan Losses - Summary of TDR Loans on Accrual and Nonaccrual (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2021USD ($)loans	Mar. 31, 2021USD ($)contract	Mar. 31, 2020contract	Dec. 31, 2020USD ($)loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	286	1	10	301
Balance of Loans	$ 52,904	$ 52,904		$ 53,204
Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	229			248
Balance of Loans	$ 39,367	39,367		$ 41,095
Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	57			53
Balance of Loans	$ 13,537	13,537		$ 12,109
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	7			8
Balance of Loans	$ 13,224	13,224		$ 12,447
Commercial and industrial | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	1			1
Balance of Loans	$ 5,641	5,641		$ 5,628
Commercial and industrial | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	6			7
Balance of Loans	$ 7,583	7,583		$ 6,819
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	2			2
Balance of Loans	$ 3,988	3,988		$ 4,001
Commercial real estate | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	1			1
Balance of Loans	$ 3,520	3,520		$ 3,521
Commercial real estate | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	1			1
Balance of Loans	$ 468	$ 468		$ 480
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	11	0	1	12
Balance of Loans	$ 5,083	$ 5,083		$ 5,193
Business banking | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	5			6
Balance of Loans	$ 4,008	4,008		$ 4,471
Business banking | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	6			6
Balance of Loans	$ 1,075	$ 1,075		$ 722
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	170	1	8	173
Balance of Loans	$ 26,122	$ 26,122		$ 26,689
Residential real estate | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	140			146
Balance of Loans	$ 22,565	22,565		$ 23,416
Residential real estate | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	30			27
Balance of Loans	$ 3,557	$ 3,557		$ 3,273
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	93	0	1	103
Balance of Loans	$ 4,461	$ 4,461		$ 4,845
Consumer home equity | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	79			91
Balance of Loans	$ 3,607	3,607		$ 4,030
Consumer home equity | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	14			12
Balance of Loans	$ 854	854		$ 815
Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	3			3
Balance of Loans	$ 26	26		$ 29
Other consumer | Special Mention | Contractual Obligation Modification | TDRs on Accrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	3			3
Balance of Loans	$ 26	26		$ 29
Other consumer | Special Mention | Contractual Obligation Modification | TDRs on Nonaccrual Status
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loans	0			0
Balance of Loans	$ 0	$ 0		$ 0

Loans and Allowance for Loan_11

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				12 Months Ended
	Mar. 31, 2021loans	Mar. 31, 2021contract	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)contract	Dec. 31, 2020loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	286	1		10	301
Pre- Modification Outstanding Recorded Investment			$ 295	$ 682
Post-Modification Modification Outstanding Recorded Investment			295	$ 687
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	11	0		1	12
Pre- Modification Outstanding Recorded Investment			0	$ 244
Post-Modification Modification Outstanding Recorded Investment			0	$ 244
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	170	1		8	173
Pre- Modification Outstanding Recorded Investment			295	$ 414
Post-Modification Modification Outstanding Recorded Investment			295	$ 419
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts	93	0		1	103
Pre- Modification Outstanding Recorded Investment			0	$ 24
Post-Modification Modification Outstanding Recorded Investment			$ 0	$ 24

Loans and Allowance for Loan_12

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
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	$ 295	$ 687
Extended maturity and interest only/principal deferred
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	0	46
Court-ordered concession
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	295	0
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post modification balance of TDRs	$ 0	$ 641

Loans and Allowance for Loan_13

Loans and Allowance for Loan Losses - Summary of Company considers a loan to have defaulted when it reaches 90 days past due or is transferred to nonaccrual (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)contract	Mar. 31, 2020USD ($)contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	2	3
Recorded Investment | $	$ 478	$ 5,948
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	0	2
Recorded Investment | $	$ 0	$ 4,613
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	1	0
Recorded Investment | $	$ 419	$ 0
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	1	1
Recorded Investment | $	$ 59	$ 1,335

Loans and Allowance for Loan_14

Loans and Allowance for Loan Losses - Summary of Company's Impaired Loans by Loan Portfolio (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	$ 35,904	$ 35,717
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	41,795	42,455
Impaired financing receivable, with no related allowance, Recorded Investment	38,486	39,892
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	43,703	44,675
Impaired financing receivable, Related Allowance	8,137	8,054
Impaired financing receivable, Recorded Investment	74,390	75,609
Impaired financing receivable, Unpaid Principal Balance	85,498	87,130
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	10,071	9,182
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	11,312	11,212
Impaired financing receivable, with no related allowance, Recorded Investment	7,836	8,161
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	8,147	8,432
Impaired financing receivable, Related Allowance	4,761	4,555
Commercial real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	4,068	3,955
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	4,113	3,974
Impaired financing receivable, with no related allowance, Recorded Investment	468	480
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	489	497
Impaired financing receivable, Related Allowance	210	210
Business banking
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	4,961	5,250
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	7,260	7,659
Impaired financing receivable, with no related allowance, Recorded Investment	16,040	16,651
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	20,925	21,146
Impaired financing receivable, Related Allowance	1,387	1,435
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	14,408	14,730
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	16,714	17,010
Impaired financing receivable, with no related allowance, Recorded Investment	12,051	12,326
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	12,051	12,326
Impaired financing receivable, Related Allowance	1,516	1,565
Consumer home equity
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	2,370	2,571
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	2,370	2,571
Impaired financing receivable, with no related allowance, Recorded Investment	2,091	2,274
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	2,091	2,274
Impaired financing receivable, Related Allowance	263	289
Other consumer
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Recorded Investment	26	29
Impaired financing receivable, with no related allowance, Unpaid Principal Balance	$ 26	$ 29

Loans and Allowance for Loan_15

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
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	$ 36,212	$ 49,087
Impaired financing receivable, with no related allowance, Total Interest Recognized	280	344
Impaired financing receivable, with related allowance, Average Recorded Investment	39,345	35,444
Impaired financing receivable, with related allowance, Total Interest Recognized	159	183
Impaired financing receivable, Average Recorded Investment	75,557	84,531
Impaired financing receivable, Total Interest Recognized	439	527
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	9,899	20,880
Impaired financing receivable, with no related allowance, Total Interest Recognized	46	70
Impaired financing receivable, with related allowance, Average Recorded Investment	7,965	11,730
Impaired financing receivable, with related allowance, Total Interest Recognized	0	0
Commercial real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	4,176	7,491
Impaired financing receivable, with no related allowance, Total Interest Recognized	44	44
Impaired financing receivable, with related allowance, Average Recorded Investment	657	348
Impaired financing receivable, with related allowance, Total Interest Recognized	0	0
Business banking
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	5,024	2,286
Impaired financing receivable, with no related allowance, Total Interest Recognized	26	17
Impaired financing receivable, with related allowance, Average Recorded Investment	16,325	8,782
Impaired financing receivable, with related allowance, Total Interest Recognized	14	15
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	14,648	14,801
Impaired financing receivable, with no related allowance, Total Interest Recognized	144	173
Impaired financing receivable, with related allowance, Average Recorded Investment	12,248	11,727
Impaired financing receivable, with related allowance, Total Interest Recognized	127	137
Consumer home equity
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	2,438	3,606
Impaired financing receivable, with no related allowance, Total Interest Recognized	20	40
Impaired financing receivable, with related allowance, Average Recorded Investment	2,150	2,857
Impaired financing receivable, with related allowance, Total Interest Recognized	18	31
Other consumer
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, with no related allowance, Average Recorded Investment	27	23
Impaired financing receivable, with no related allowance, Total Interest Recognized	$ 0	$ 0

Loans and Allowance for Loan_16

Loans and Allowance for Loan Losses - Summary of Outstanding and Carrying Amounts of PCI Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	$ 74,390	$ 86,431
Outstanding balance
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	8,662		$ 9,982
Carrying amount
Financing Receivable, Impaired [Line Items]
Financing receivable, purchased with credit deterioration, amount at purchase price	$ 7,617		$ 9,297

Loans and Allowance for Loan_17

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
	Mar. 31, 2021	Mar. 31, 2020
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 2,495	$ 3,923
Accretion	(216)	(422)
Other change in expected cash flows	(248)	(155)
Balance at end of period	$ 2,031	$ 3,346

Loans and Allowance for Loan_18

Loans and Allowance for Loan Losses - Summary of the Company's Loan participations (Detail) - Loan Participations and Assignments - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 1,011,551		$ 1,024,709
Nonperforming Loan Rate (%)	0.75%		0.65%
Impaired (%)	0.75%		0.65%
Gross Charge-offs	$ 0	$ 0
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 579,812		$ 598,873
Nonperforming Loan Rate (%)	1.31%		1.11%
Impaired (%)	1.31%		1.11%
Gross Charge-offs	$ 0	0
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance	$ 345,261		$ 306,202
Nonperforming 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	$ 86,447		$ 119,600
Nonperforming 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	$ 31		$ 34
Nonperforming Loan Rate (%)	0.00%		0.00%
Impaired (%)	0.00%		0.00%
Gross Charge-offs	$ 0	$ 0

Goodwill and Other Intangible_2

Goodwill and Other Intangibles - Summary of Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balances not subject to amortization
Goodwill	$ 369,477	$ 369,477
Balances subject to amortization
Total other intangible assets	6,525	7,057
Total goodwill and other intangible assets	376,002	376,534
Insurance agency
Balances subject to amortization
Balances subject to amortization	6,398	6,899
Core deposits
Balances subject to amortization
Balances subject to amortization	127	158
Banking Business
Balances not subject to amortization
Goodwill	298,611	298,611
Balances subject to amortization
Total other intangible assets	127	158
Total goodwill and other intangible assets	298,738	298,769
Banking Business | Insurance agency
Balances subject to amortization
Balances subject to amortization	0	0
Banking Business | Core deposits
Balances subject to amortization
Balances subject to amortization	127	158
Insurance Agency Business
Balances not subject to amortization
Goodwill	70,866	70,866
Balances subject to amortization
Total other intangible assets	6,398	6,899
Total goodwill and other intangible assets	77,264	77,765
Insurance Agency Business | Insurance agency
Balances subject to amortization
Balances subject to amortization	6,398	6,899
Insurance Agency Business | Core deposits
Balances subject to amortization
Balances subject to amortization	$ 0	$ 0

Earnings Per Share ("EPS") (Det

Earnings Per Share ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income applicable to common shares	$ 47,663
Average number of common shares outstanding used to calculated basic earnings per common share (in shares)	186,758,154
Less: Average unallocated ESOP shares (in shares)	(14,709,110)
Average number of common shares outstanding used to calculated basic earnings per common share (in shares)	172,049,044	0
Common stock equivalents (in shares)	0
Average number of common shares outstanding used to calculate diluted earnings per common share (in shares)	172,049,044
Earnings per common share
Basic and diluted (in dollars per share)	$ 0.28

Leases - Narrative (Detail)

Leases - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disclosure of Leases [Line Items]
Payment of lease payments	$ 3.6	$ 3.5
Minimum
Disclosure of Leases [Line Items]
Operating lease remaining lease term	1 year
Maximum
Disclosure of Leases [Line Items]
Operating lease remaining lease term	25 years

Leases - Summary of Information

Leases - Summary of Information Relating to Operating Leases (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Right-of-use assets	$ 79,163	$ 81,596
Lease liabilities	$ 82,910	$ 85,330

Leases - Summary of Net Lease C

Leases - Summary of Net Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease cost	$ 3,561	$ 3,613
Finance lease cost	31	2
Variable lease cost	490	522
Total lease cost	$ 4,082	$ 4,137

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information Related to Operating Leases (Detail)	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted-average remaining lease term (in years)	8 years 3 months 29 days	8 years 6 months
Weighted-average discount rate	2.63%	2.65%

Income Taxes - Summary of Compa

Income Taxes - Summary of Company's Tax Provision and Applicable Tax Rates (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax provision	$ 14,171	$ 1,298
Effective income tax rates	22.90%	13.30%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax provision	$ 14,171,000	$ 1,298,000
Deferred tax asset valuation allowance	12,000,000
Issuance of stock for charitable contributions	91,300,000
Charitable cash contribution	$ 3,700,000

Low Income Housing Tax Credit_3

Low Income Housing Tax Credits and Other Tax Credit Investments - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Investments In Affordable Housing Projects [Line Items]
Tax credit investments	$ 64.1	$ 59.8
Renewable Energy Program
Investments In Affordable Housing Projects [Line Items]
Equity investments	1.2
Outstanding investment commitments	$ 1.7	$ 1.7
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

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
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Investments in Affordable Housing Projects [Abstract]
Current recorded investment included in other assets	$ 62,904		$ 58,504
Commitments to fund qualified affordable housing projects included in recorded investment noted above	34,430		$ 31,487
Tax credits and benefits recognized	1,464	$ 1,519
Amortization expense included in income tax expense	$ 1,264	$ 1,191

Employee Benefits - Narrative (

Employee Benefits - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Nov. 01, 2020	Oct. 31, 2020
Primary Beneficiary
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments	$ 94,005	$ 91,683
Primary Beneficiary | Equities
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments	80,490	$ 78,727
Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Decrease in non-service cost expense	3,800
Discretionary employer contributions to defined benefit plans	$ 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 (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Components of net periodic benefit cost:
Service cost	$ 7,896	$ 6,232
Interest cost	1,269	2,616
Expected return on plan assets	(8,141)	(7,425)
Prior service (credit) cost	(2,946)	6
Recognized net actuarial loss	3,538	2,361
Net periodic benefit cost	$ 1,616	$ 3,790

Employee Benefits - Asset Held

Employee Benefits - Asset Held In Rabbi Trust By Plan Type (Details) - Primary Beneficiary - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Book Value	$ 75,002	$ 71,833
Mark-to-Market	19,003	19,850
Fair Value	94,005	91,683
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Book Value	5,230	5,157
Fair Value	5,230	5,157
Equities
Defined Benefit Plan Disclosure [Line Items]
Book Value	61,662	59,235
Mark-to-Market	18,828	19,492
Fair Value	80,490	78,727
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Book Value	8,110	7,441
Mark-to-Market	175	358
Fair Value	$ 8,285	$ 7,799

Commitments and Contingencies -

Commitments and Contingencies - Summary of Financial Instruments as of the Dates Indicated (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Commitments to extend credit
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	$ 3,959,011	$ 3,818,952
Standby letters of credit
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	63,986	60,221
Forward commitments to sell loans
Disclosure Of Financial Instruments Indicated [Line Items]
Contractual obligation	$ 35,564	$ 41,160

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Detail) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
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) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning Balance	$ 3,428,052
Unrealized gains on terminated hedges arising during the period	0
Reclassification adjustments for amortization of unrealized (gains) into net interest income	(8,274)
Ending balance	3,387,045
Accumulated Gain (Loss), Net, Terminated Cash Flow Hedge, Parent
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning Balance	41,473
Ending balance	$ 33,199

Derivative Financial Instrume_4

Derivative Financial Instruments - Narrative (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Credit exposure to settled variation margin in excess of customer related interest rate swap	$ 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	28.3	42.6
Non Cleared Derivative Transactions | Cash and cash equivalents | Customer Related Interest Rate Swap Derivatives
Derivative [Line Items]
Additional collateral posted	35.9
Non Cleared Derivative Transactions | Available-for-sale Securities | Customer Related Interest Rate Swap Derivatives
Derivative [Line Items]
Additional collateral posted		49.2
Restricted Assets
Derivative [Line Items]
Initial margin collateral posted cash	49.3
Initial margin collateral posted treasury note		$ 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	$ 28.3

Derivative Financial Instrume_5

Derivative Financial Instruments - Customer-related derivative positions (Detail) - Not Designated as Hedging Instrument $ in Thousands	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Interest rate swaps
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions	562	576
Total Notional	$ 3,571,918	$ 3,652,385
Risk participation agreements
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions	70	70
Total Notional	$ 288,803	$ 287,732
Matched commercial customer book
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions	74	40
Total Notional	$ 8,428	$ 4,242
Foreign currency loan
Disclosure Of Customer Related Derivatives Not Designated As Hedging [Line Items]
Number of Positions	3	3
Total Notional	$ 7,988	$ 10,798

Derivative Financial Instrume_6

Derivative Financial Instruments - Classification on the balance sheet for the periods indicated (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Foreign currency exchange contracts - foreign currency loan
Asset Derivatives
Total, Asset Derivatives	$ 18
Asset Derivatives
Asset Derivatives
Derivatives not designated as hedging instruments, Interest rate swaps, Other assets	90,748	$ 141,822
Total, Asset Derivatives	91,238	142,643
Asset Derivatives | Risk participation agreements
Asset Derivatives
Derivatives not designated as hedging instruments, Other assets	391	722
Asset Derivatives | Foreign currency exchange contracts - matched customer book
Asset Derivatives
Derivatives not designated as hedging instruments, Other assets	81	90
Asset Derivatives | Foreign currency exchange contracts - foreign currency loan
Asset Derivatives
Derivatives not designated as hedging instruments, Other assets	18	9
Liability Derivatives
Liability Derivatives
Derivative not designated as hedging instruments, Interest rate swaps, Other liabilities	33,620	42,600
Total, Liability Derivatives	34,216	43,976
Liability Derivatives | Risk participation agreements
Liability Derivatives
Derivatives not designated as hedging instruments, Other liabilities	530	1,230
Liability Derivatives | Foreign currency exchange contracts - matched customer book
Liability Derivatives
Derivatives not designated as hedging instruments, Other liabilities	61	77
Liability Derivatives | Foreign currency exchange contracts - foreign currency loan
Liability Derivatives
Derivatives not designated as hedging instruments, Other liabilities	$ 5	$ 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
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gain in OCI on derivatives	$ 0	$ 43,556
Gain reclassified from OCI into interest income (effective portion)	8,274	3,112
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0
Gain (loss) recognized in other income for foreign currency exchange contracts:	5,299	(6,210)
Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain reclassified from OCI into interest income (effective portion)	8,274	3,112
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
Interest Income | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) recognized in interest rate swap income	4,851	(6,280)
Interest Income | Risk participation agreements
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) recognized in interest rate swap income	369	(301)
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	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:	6	(26)
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:	$ 73	$ 397

Balance Sheet Offsetting - Disc

Balance Sheet Offsetting - Disclosure Detail Of Balance Sheet Offsetting Of Financial Assets And Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Customer-related positions
Derivative Assets
Gross Amounts Recognized	$ 91,238	$ 142,643
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	91,238	142,643
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	1,426	48
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	(1)
Net Amount	89,812	142,594
Derivative Liabilities
Gross Amounts Recognized	34,216	43,976
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	34,216	43,976
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	1,426	48
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	32,194	42,552
Net Amount	596	1,376
Interest rate swaps
Derivative Assets
Gross Amounts Recognized	0	0
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	0	0
Derivative Liabilities
Gross Amounts Recognized	0	0
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	0	0
Interest rate swaps | Customer-related positions
Derivative Assets
Gross Amounts Recognized	90,748	141,822
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	90,748	141,822
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	1,426	48
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	89,322	141,774
Derivative Liabilities
Gross Amounts Recognized	33,620	42,600
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	33,620	42,600
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	1,426	48
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	32,194	42,552
Net Amount	0	0
Risk participation agreements | Customer-related positions
Derivative Assets
Gross Amounts Recognized	391	722
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	391	722
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	391	722
Derivative Liabilities
Gross Amounts Recognized	530	1,230
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	530	1,230
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	530	1,230
Foreign currency exchange contracts - matched customer book | Customer-related positions
Derivative Assets
Gross Amounts Recognized	81	90
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	81	90
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	(1)
Net Amount	81	89
Derivative Liabilities
Gross Amounts Recognized	61	77
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	61	77
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	61	77
Foreign currency exchange contracts - foreign currency loan
Derivative Assets
Gross Amounts Recognized	18
Gross Amounts Offset in the Statement of Financial Position	0
Net Amounts Presented in the Statement of Financial Position	18
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0
Net Amount	18
Foreign currency exchange contracts - foreign currency loan | Customer-related positions
Derivative Assets
Gross Amounts Recognized		9
Gross Amounts Offset in the Statement of Financial Position		0
Net Amounts Presented in the Statement of Financial Position		9
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments		0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)		0
Net Amount		9
Derivative Liabilities
Gross Amounts Recognized	5	69
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts Presented in the Statement of Financial Position	5	69
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Pledged (Received)	0	0
Net Amount	$ 5	$ 69

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Narrative (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 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
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	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
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	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	52,000,000	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
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	$ 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	Mar. 31, 2021	Dec. 31, 2020
Assets
Available for sale securities	$ 3,986,253	$ 3,183,861
Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	2,691,702	2,148,800
Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	116,271	17,081
U.S. Agency bonds
Assets
Available for sale securities	831,672	666,709
U.S. Treasury securities
Assets
Available for sale securities	69,090	70,369
Fair Value, Recurring
Assets
Rabbi trust investments	94,005	91,683
Loans held for sale	2,022	1,140
Customer-related positions	90,748	141,822
Risk participation agreements	391	722
Matched customer book	81	90
Foreign currency loan	18	9
Total	4,173,518	3,419,327
Liabilities
Customer-related positions	33,620	42,600
Risk participation agreements	530	1,230
Matched customer book	61	77
Foreign currency loan	5	69
Total	34,216	43,976
Fair Value, Recurring | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	2,691,702	2,148,800
Fair Value, Recurring | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	116,271	17,081
Fair Value, Recurring | U.S. Agency bonds
Assets
Available for sale securities	831,672	666,709
Fair Value, Recurring | U.S. Treasury securities
Assets
Available for sale securities	69,090	70,369
Fair Value, Recurring | State and municipal bonds and obligations
Assets
Available for sale securities		280,902
Fair Value, Recurring | State and municipal bonds and obligations | State and municipal bonds and obligations
Assets
Available for sale securities	277,518
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Rabbi trust investments	85,720	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	154,810	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) | State and municipal bonds and obligations
Assets
Available for sale securities	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	69,090	70,369
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal bonds and obligations | State and municipal bonds and obligations
Assets
Available for sale securities		0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Assets
Rabbi trust investments	8,285	7,799
Loans held for sale	2,022	1,140
Customer-related positions	90,748	141,822
Risk participation agreements	391	722
Matched customer book	81	90
Foreign currency loan	18	9
Total	4,018,708	3,265,074
Liabilities
Customer-related positions	33,620	42,600
Risk participation agreements	530	1,230
Matched customer book	61	77
Foreign currency loan	5	69
Total	34,216	43,976
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored residential mortgage-backed securities
Assets
Available for sale securities	2,691,702	2,148,800
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored commercial mortgage-backed securities
Assets
Available for sale securities	116,271	17,081
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Agency bonds
Assets
Available for sale securities	831,672	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 | State and municipal bonds and obligations
Assets
Available for sale securities	277,518	280,902
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Assets
Rabbi trust investments	0
Loans held for sale	0	0
Customer-related positions	0	0
Risk participation agreements	0	0
Matched customer book	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) | State and municipal bonds and obligations
Assets
Available for sale securities	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 | State and municipal bonds and obligations
Assets
Available for sale securities		$ 0

Fair Value of Assets and Liab_5

Fair Value of Assets and Liabilities - Summary Of The Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs Level (3) (Detail) - Available-for-sale Securities $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 6,310
Gains and losses (realized/unrealized):
Included in net income	27
Included in other comprehensive income	(88)
Ending balance	$ 6,249

Fair Value of Assets and Liab_6

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	Mar. 31, 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	$ 11,685	$ 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	$ 11,685	$ 11,036

Fair Value of Assets and Liab_7

Fair Value of Assets and Liabilities - Schedule of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for credit losses	$ 9,772,722	$ 9,593,958
FHLB stock	8,805	8,805
Bank-owned life insurance	79,110	78,561
Deposits	12,980,875	12,155,784
FHLB advances	14,473	14,624
Escrow deposits from borrowers	14,878	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 credit losses	0	0
FHLB stock	0	0
Bank-owned life insurance	0	0
Deposits	0	0
FHLB advances	0	0
Escrow deposits from 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 credit losses	0	0
FHLB stock	8,805	8,805
Bank-owned life insurance	79,110	78,561
Deposits	12,980,753	12,155,843
FHLB advances	14,299	14,434
Escrow deposits from borrowers	14,878	13,425
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for credit losses	9,870,710	9,779,195
FHLB stock	0	0
Bank-owned life insurance	0	0
Deposits	0	0
FHLB advances	0	0
Escrow deposits from borrowers	0	0
Carrying Value
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for credit losses	9,772,722	9,593,958
FHLB stock	8,805	8,805
Bank-owned life insurance	79,110	78,561
Deposits	12,980,875	12,155,784
FHLB advances	14,473	14,624
Escrow deposits from borrowers	14,878	13,425
Fair Value
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Loans, net of allowance for credit losses	9,870,710	9,779,195
FHLB stock	8,805	8,805
Bank-owned life insurance	79,110	78,561
Deposits	12,980,753	12,155,843
FHLB advances	14,299	14,434
Escrow deposits from borrowers	$ 14,878	$ 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
	Mar. 31, 2021	Mar. 31, 2020
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	$ 43,718	$ 43,192
Total noninterest income out-of-scope of ASC 606	11,494	(9,823)
Total noninterest income	55,212	33,369
Insurance commissions
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	28,147	27,477
Service charges on deposit accounts
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	5,367	6,098
Trust and investment advisory fees
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	5,663	5,095
Debit card processing fees
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	2,749	2,470
Other non-interest income
Revenue from External Customer [Line Items]
Total noninterest income in-scope of ASC 606	$ 1,792	$ 2,052

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Narrative (Detail) - Other Assets - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Insurance commission earned but not yet received	$ 12.9	$ 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
	Mar. 31, 2021	Mar. 31, 2020
Unrealized gains (losses) on securities available for sale:
Change in fair value of securities available for sale, Pre Tax Amount	$ (94,979)	$ 33,802
Less: reclassification adjustments for gains included in net income, Pre-Tax Amount	1,164	122
Net change in fair value of securities available for sale, Pre Tax Amount	(96,143)	33,680
Unrealized gains (losses) on cash flow hedges:
Change in fair value of cash flow hedges, Pre Tax Amount	0	43,556
Less: net cash flow hedge losses reclassified into interest income, Pre Tax Amount	8,274	3,112
Net change in fair value of cash flow hedges, Pre Tax Amount	(8,274)	40,444
Defined benefit pension plans:
Change in actuarial net loss, Pre Tax Amount	0	0
Less: amortization of actuarial net loss, Pre-Tax Amount	(3,537)	0
Net change in other comprehensive income for defined benefit postretirement plans, Pre Tax Amount	592	0
Total other comprehensive income, Pre Tax Amount	(103,825)	74,124
Unrealized gains (losses) on securities available for sale:
Change in fair value of securities available for sale, Tax (Expense) Benefit	20,982	(7,515)
Less: reclassification adjustments for gains included in net income, Tax (Expense) Benefit	(257)	(27)
Less: net accretion of prior service cost, Pre-Tax Amount	2,945	0
Net change in fair value of securities available for sale, Tax (Expense) Benefit	21,239	(7,488)
Unrealized gains (losses) on cash flow hedges:
Change in fair value of cash flow hedges, Tax (Expense) Benefit	0	(12,244)
Less: net cash flow hedge losses reclassified into interest income, Tax (Expense) Benefit	(2,326)	(875)
Net change in fair value of cash flow hedges, Tax (Expense) Benefit	2,326	(11,369)
Defined benefit pension plans:
Change in actuarial net loss, Tax (Expense) Benefit	0	0
Less: amortization of actuarial net loss, Tax (Expense) Benefit	994	0
Less: net accretion of prior service cost, After Tax Amount	(828)	0
Net change in other comprehensive income for defined benefit postretirement plans, Tax (Expense) Benefit	(166)	0
Total other comprehensive income, Tax (Expense) Benefit	23,399	(18,857)
Unrealized gains (losses) on securities available for sale:
Change in fair value of securities available for sale, After Tax Amount	(73,997)	26,287
Less: reclassification adjustment for gains included in net income, After Tax Amount	907	95
Net change in fair value of securities available for sale, After Tax Amount	(74,904)	26,192
Unrealized gains (losses) on cash flow hedges:
Change in fair value of cash flow hedges, After Tax Amount	0	31,312
Less: net cash flow hedge losses reclassified into interest income, Amount After Tax	5,948	2,237
Net change in fair value of cash flow hedges, Amount After Tax	(5,948)	29,075
Defined benefit pension plans:
Amortization of actuarial net loss, Amount After Tax	0	0
Less: amortization of actuarial net loss, After Tax Amount	(2,543)	0
Less: net accretion of prior service cost, After Tax Amount	2,117	0
Net change in other comprehensive income for defined benefit postretirement plans, Amount After Tax	426	0
Net current-period other comprehensive income	(80,426)	$ 55,267
Total realized gain, net of tax	41,200
Balance of gain after amortization, net of tax	$ 23,900

Other Comprehensive Income - Sc

Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 3,428,052	$ 1,600,153
Other comprehensive (loss) income before reclassifications	(73,997)	57,599
Less: Amounts reclassified from accumulated other comprehensive income	6,429	2,332
Net current-period other comprehensive income	(80,426)	55,267
Ending balance	3,387,045	1,662,734
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	54,234	(43,847)
Ending balance	(26,192)	11,420
Defined Benefit Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(21,253)	(81,269)
Other comprehensive (loss) income before reclassifications	0	0
Less: Amounts reclassified from accumulated other comprehensive income	(426)	0
Net current-period other comprehensive income	426	0
Ending balance	(20,827)	(81,269)
Unrealized Gains and (Losses) on Cash Flow Hedges | 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) income before reclassifications	0	31,312
Less: Amounts reclassified from accumulated other comprehensive income	5,948	2,237
Net current-period other comprehensive income	(5,948)	29,075
Ending balance	23,867	44,699
Unrealized Gains and (Losses) on Available for Sale Securities | 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) income before reclassifications	(73,997)	26,287
Less: Amounts reclassified from accumulated other comprehensive income	907	95
Net current-period other comprehensive income	(74,904)	26,192
Ending balance	$ (29,232)	$ 47,990

Segment Reporting - Schedule Of

Segment Reporting - Schedule Of Segment Reporting Information, By Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income	$ 100,091	$ 100,146
Allowance for loan losses, Provision (benefit)	(580)	28,600
Net interest income after provision for loan losses	100,671	71,546
Noninterest income	55,212	33,369
Noninterest expense	94,049	95,172
Income before income tax expense	61,834	9,743
Income tax provision	14,171	1,298
Net income	47,663	8,445
Total assets	16,726,795	12,343,754	$ 15,964,190
Total liabilities	13,339,750	10,681,020	$ 12,536,138
Other/Eliminations
Segment Reporting Information [Line Items]
Net interest income	0	0
Allowance for loan losses, Provision (benefit)	0	0
Net interest income after provision for loan losses	0	0
Noninterest income	(32)	(22)
Noninterest expense	(1,036)	(935)
Income before income tax expense	1,004	913
Income tax provision	0	0
Net income	1,004	913
Total assets	(63,180)	(60,609)
Total liabilities	(63,180)	(60,609)
Banking Business | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	100,091	100,146
Allowance for loan losses, Provision (benefit)	(580)	28,600
Net interest income after provision for loan losses	100,671	71,546
Noninterest income	26,960	6,868
Noninterest expense	75,274	78,465
Income before income tax expense	52,357	(51)
Income tax provision	11,793	(1,214)
Net income	40,564	1,163
Total assets	16,595,311	12,221,799
Total liabilities	13,359,075	10,696,509
Insurance Agency Business | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	0	0
Allowance for loan losses, Provision (benefit)	0	0
Net interest income after provision for loan losses	0	0
Noninterest income	28,284	26,523
Noninterest expense	19,811	17,642
Income before income tax expense	8,473	8,881
Income tax provision	2,378	2,512
Net income	6,095	6,369
Total assets	194,664	182,564
Total liabilities	$ 43,855	$ 45,120

Subsequent Events (Detail)

Subsequent Events (Detail) - Subsequent Event - Century Merger Agreement $ / shares in Units, $ in Millions	Apr. 07, 2021USD ($)bank$ / shares
Subsequent Event [Line Items]
Cash payment	$ 641.9
Assets acquired	6,400
Deposits acquired	$ 5,400
Number of full-service branches acquired | bank	27
Common Class A
Subsequent Event [Line Items]
Share price (in dollars per share) | $ / shares	$ 115.28
Common Class B
Subsequent Event [Line Items]
Share price (in dollars per share) | $ / shares	$ 115.28

Uncategorized Items - ebc-20210

Label	Element	Value
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201602Member