Randolph Bancorp (RNDB) 10-K 11 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 28, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	RNDB
Entity Registrant Name	Randolph Bancorp, Inc.
Entity Central Index Key	0001667161
Current Fiscal Year End Date	--12-31
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, par value $.01 per share
Entity Incorporation, State or Country Code	MA
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		5,414,738
Entity Shell Company	false
Entity File Number	001-37780
Entity Tax Identification Number	81-1844402
Entity Address, Address Line One	10 Cabot Place
Entity Address, City or Town	Stoughton
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02072
City Area Code	781
Local Phone Number	963-2100
Document Annual Report	true
Document Transition Report	false
Entity Public Float			$ 46,925,380
ICFR Auditor Attestation Flag	false
Documents Incorporated by Reference	Portions of the Registrant’s Proxy Statement for its 2021 Annual Meeting of Shareholders are incorporated by reference into Part III of this Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks	$ 4,206	$ 4,371
Interest-bearing deposits	9,568	3,881
Total cash and cash equivalents	13,774	8,252
Certificates of deposit		490
Securities available for sale, at fair value	55,366	57,503
Loans held for sale, at fair value	119,112	62,792
Loans, net of allowance for loan losses of $6,784 in 2020 and $4,280 in 2019	483,644	469,131
Federal Home Loan Bank of Boston stock, at cost	3,576	2,417
Accrued interest receivable	1,562	1,393
Mortgage servicing rights, net	12,377	8,556
Premises and equipment, net	4,781	5,748
Bank-owned life insurance	8,622	8,441
Foreclosed real estate, net	132
Other assets	18,126	6,281
Total assets	721,072	631,004
Deposits:
Noninterest-bearing	96,731	61,603
Interest bearing	399,847	344,581
Brokered	31,729	90,858
Total deposits	528,307	497,042
Federal Reserve Bank advances	11,431
Federal Home Loan Bank of Boston advances	61,895	44,403
Mortgagors' escrow accounts	2,338	2,052
Post-employment benefit obligations	2,382	2,464
Other liabilities	14,900	6,581
Total liabilities	621,253	552,542
Commitments and contingencies (Note 16)
Stockholders' Equity:
Preferred stock, no par value; authorized: 1,000,000 shares; issued: none
Common stock, $.01 par value; authorized: 15,000,000 shares; issued and outstanding: 5,495,514 shares at December 31, 2020 and 5,576,855 shares at December 31, 2019	54	56
Additional paid-in capital	50,937	51,127
Retained earnings	51,689	31,757
ESOP-Unearned compensation	(3,756)	(3,944)
Accumulated other comprehensive income (loss), net of tax	895	(534)
Total stockholders' equity	99,819	78,462
Total liabilities and stockholders' equity	$ 721,072	$ 631,004

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Loans, allowance for loan losses	$ 6,784	$ 4,280
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	5,495,514	5,576,855
Common stock, shares outstanding	5,495,514	5,576,855

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Interest and dividend income:
Loans	$ 22,212	$ 23,631
Securities-taxable	1,273	1,467
Securities-tax exempt	28	43
Interest-bearing deposits and certificates of deposit	75	90
Total interest and dividend income	23,588	25,231
Interest expense:
Deposits	3,778	5,328
Federal Reserve Bank and Federal Home Loan Bank of Boston advances	943	2,070
Total interest expense	4,721	7,398
Net interest income	18,867	17,833
Provision for loan losses	2,553
Net interest income after provision for loan losses	16,314	17,833
Non-interest income:
Customer service fees	1,283	1,407
Gain on loan origination and sale activities, net	54,236	18,900
Mortgage servicing fees, net	(1,153)	394
Gain on sales/calls of securities and impairment write-down, net		16
Increase in cash surrender value of life insurance	181	185
Other	864	761
Total non-interest income	55,411	21,663
Non-interest expenses:
Salaries and employee benefits	33,161	24,896
Occupancy and equipment	3,545	2,783
Data processing	943	810
Professional fees	1,277	1,185
Marketing	689	967
FDIC insurance	187	168
Other	6,514	5,141
Total non-interest expenses	46,316	35,950
Income before income taxes	25,409	3,546
Income tax expense	5,477	118
Net income	$ 19,932	$ 3,428
Earnings per common share:
Basic	$ 3.89	$ 0.64
Diluted	$ 3.86	$ 0.64
Weighted average shares outstanding
Basic	5,126,561	5,383,617
Diluted	5,163,042	5,383,617

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Net income		$ 19,932	$ 3,428
Securities available for sale:
Unrealized holding gains (losses)		1,546	1,517
Reclassification adjustment for net (gains) losses and impairment write-down realized in income	[1]		(16)
Net unrealized gain (loss)		1,546	1,501
Net-of-tax amount		1,546	1,501
Net-of-tax amount		(117)	(131)
Total other comprehensive income		1,429	1,370
Comprehensive income		21,361	4,798
Supplemental Retirement Plan [Member]
Securities available for sale:
Actuarial losses	[2]	45	36
Prior service credits recognized	[2]	(57)	(84)
Actuarial gains (losses) arising during the year		(105)	(83)
Net change in supplemental retirement plan		$ (117)	$ (131)
[1]	Amounts are included in gain (loss) on sales/calls of securities and impairment write-down, net in the consolidated statements of operations.
[2]	Amounts are included in other non-interest expenses in the consolidated statements of operations.

Consolidated Statements Changes

Consolidated Statements Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Unearned Compensation ESOP [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2018	$ 77,961	$ 60	$ 55,608	$ 28,329	$ (4,132)	$ (1,904)
Beginning balance, shares at Dec. 31, 2018		5,903,793
Net income	3,428			3,428
Other comprehensive income	1,370					1,370
Stock repurchased	(5,438)	$ (4)	(5,434)
Stock repurchased, shares		(353,572)
Restricted stock awards granted, shares		33,335
Restricted stock awards forfeited, shares		(2,500)
Share redemption for tax withholdings for restricted stock vesting	(61)		(61)
Share redemption for tax with holdings for restricted stock vesting, shares		(4,201)
Stock-based compensation	919		919
ESOP shares committed to be released	283		95		188
Ending balance at Dec. 31, 2019	78,462	$ 56	51,127	31,757	(3,944)	(534)
Ending balance, shares at Dec. 31, 2019		5,576,855
Net income	19,932			19,932
Other comprehensive income	1,429					1,429
Stock repurchased	(1,749)	$ (2)	(1,747)
Stock repurchased, shares		(131,388)
Restricted stock awards granted, shares		65,630
Restricted stock awards forfeited, shares		(9,251)
Share redemption for tax withholdings for restricted stock vesting	(75)		(75)
Share redemption for tax with holdings for restricted stock vesting, shares		(6,332)
Stock-based compensation	1,564		1,564
ESOP shares committed to be released	256		68		188
Ending balance at Dec. 31, 2020	$ 99,819	$ 54	$ 50,937	$ 51,689	$ (3,756)	$ 895
Ending balance, shares at Dec. 31, 2020		5,495,514

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 19,932,000	$ 3,428,000
Adjustments to reconcile net income to net cash used in operating activities:
Provision for loan losses	2,553,000
Loans originated for sale	(1,564,552,000)	(913,656,000)
Net gain on sales of mortgage loans	(54,236,000)	(18,900,000)
Proceeds from sales of mortgage loans	1,560,043,000	913,548,000
Net amortization of securities	307,000	187,000
Net change in deferred loan costs and fees, and purchase premiums	284,000	102,000
Gain on sales/calls of securities and impairment write-down		(16,000)
Depreciation and amortization	1,508,000	857,000
Stock-based compensation	1,564,000	919,000
ESOP expense	256,000	283,000
Increase in cash surrender value of life insurance	(182,000)	(185,000)
Net increase in mortgage servicing rights	(3,822,000)	(770,000)
Loss on disposal of assets	49,000
Other, net	(6,997,000)	(2,272,000)
Net cash used in operating activities	(43,293,000)	(16,475,000)
Cash flows from investing activities:
Redemptions of certificates of deposit	490,000	1,715,000
Securities available for sale:
Sales	0	534,000
Calls/maturities	4,650,000	500,000
Purchases	(15,493,000)	(12,395,000)
Principal payments on mortgage-backed securities	14,218,000	5,760,000
Loan originations, net of principal repayments	(10,224,000)	(8,583,000)
Proceeds from sale of portfolio loans		23,689,000
Loan purchases and participations	(1,803,000)	(5,412,000)
Redemptions (purchases) of Federal Home Loan Bank of Boston stock, net	(1,159,000)	2,283,000
Proceeds from sale of foreclosed real estate		61,000
Purchases of premises and equipment	(589,000)	(237,000)
Net cash provided by (used in) investing activities	(9,910,000)	7,915,000
Cash flows from financing activities:
Net increase in non-brokered deposits	90,394,000	29,634,000
Net increase (decrease) in brokered deposits	(59,129,000)	30,278,000
Net increase in Federal Reserve Bank borrowings	11,431,000
Net increase (decrease) in short-term Federal Home Loan Bank of Boston borrowings	(19,822,000)	(62,862,000)
Issuance of long-term Federal Home Loan Bank of Boston advances	40,000,000	20,000,000
Repayments of long-term Federal Home Loan Bank of Boston advances	(2,686,000)	(1,771,000)
Net increase (decrease) in mortgagors' escrow accounts	286,000	(77,000)
Repurchases of common stock	(1,749,000)	(5,438,000)
Stock repurchase payable		(70,000)
Net cash provided by financing activities	58,725,000	9,694,000
Net change in cash and cash equivalents	5,522,000	1,134,000
Cash and cash equivalents at beginning of year	8,252,000	7,118,000
Cash and cash equivalents at end of year	13,774,000	8,252,000
Supplemental cash flow information:
Interest paid on deposits and borrowed funds	5,018,000	7,057,000
Income taxes paid (refunded), net	4,225,000	(266,000)
Non-cash items:
Donation of land, net		73,000
Transfer of held for sale loans to portfolio	3,262,000
Transfer of portfolio loans to held for sale		$ 28,608,000
Transfer of portfolio loans to foreclosed real estate	$ 132,000

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	1. BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations Randolph Bancorp, Inc. (the “Company”) is a bank holding company whose principal subsidiary is Envision Bank (the “Bank”). Envision Bank provides a variety of financial services to individuals and small businesses through its five branch offices in Massachusetts and seven loan production offices and lending centers located throughout Massachusetts and Southern New Hampshire. The Bank’s primary deposit products are checking, savings and term certificate accounts and its primary lending products are residential and commercial mortgage loans. The Bank is also actively involved in the sale and servicing of residential mortgage loans in the secondary market. The Federal Deposit Insurance Corporation (“FDIC”) provides insurance coverage on all deposits up to $250,000 per depositor. As an FDIC insured institution, the Bank is subject to supervision, examination and regulation by the FDIC. Additionally, as a Massachusetts chartered savings bank, the Bank’s depositors are also insured by the Depositors Insurance Fund (“DIF”), a private industry-sponsored insurance company. The DIF insures bank deposits in excess of the FDIC insurance limits. Basis of Presentation The consolidated financial statements include the accounts of Randolph Bancorp, Inc. (a Massachusetts corporation) and its wholly-owned subsidiary, Envision Bank (together, the “Company”). The Bank has subsidiaries involved in owning investment securities and foreclosed real estate and a subsidiary which provides loan closing services. All intercompany accounts and transactions have been eliminated in consolidation. The following significant accounting and reporting policies of the Company conform to U.S. generally accepted accounting principles (“GAAP”) and are used in preparing and presenting these consolidated financial statements. Use of estimates In preparing 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 consolidated balance sheet and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Cash and cash equivalents Cash equivalents include amounts due from banks, federal funds sold on a daily basis and interest-bearing deposits with original maturities of ninety days or less. Certificates of deposit Certificates of deposit have original maturities ranging from one to five years and are carried at cost. Fair value hierarchy The Company groups its assets and liabilities that are measured at fair value in three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1 – Valuation is based on quoted prices in active markets for identical assets and liabilities. Valuations are obtained from readily available pricing sources. Level 2 – Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets and liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets and liabilities. Level 3 – Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. Level 3 assets and liabilities include those for which the value is determined using unobservable inputs to pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. Transfers between levels are recognized at the end of a reporting period, if applicable. Securities All securities are classified as available for sale and are recorded at fair value, with unrealized gains and losses excluded from earnings and reported in other comprehensive income/loss. Purchase premiums and discounts are recognized in interest income using the level yield method over the terms of the securities. Anticipated prepayments on mortgage-backed securities are used in applying this method. Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method. On a quarterly basis, the Company evaluates all securities with a decline in fair value below the amortized cost of the investment to determine whether or not the impairment is deemed to be other than temporary (“OTTI”). OTTI is required to be recognized: (1) if the Company intends to sell the security; (2) if it is “more likely than not” that the Company will be required to sell the security before recovery of its amortized cost basis; or (3) for debt securities, if the present value of expected cash flows is not sufficient to recover the entire amortized cost basis. For all impaired debt securities that the Company intends to sell, or more likely than not will be required to sell, the full amount of the decline in fair value is recognized as OTTI through earnings. For all other impaired debt securities, credit-related OTTI is recognized through earnings and non-credit related OTTI is recognized in other comprehensive income/loss, net of applicable taxes. Because the Company’s assessments are based on available factual information as well as subjective information, the determination as to whether an OTTI exists and, if so, the amount of impairment, is subjective and, therefore, the timing and amount of OTTI constitute material estimates that are subject to significant change. Federal Home Loan Bank of Boston stock The Bank, as a member of the Federal Home Loan Bank of Boston (“FHLBB”), is required to maintain an investment in capital stock of the FHLBB. Based on redemption provisions of the FHLBB, the stock has no quoted market value and is carried at cost. The Company periodically evaluates for impairment based on ultimate recovery of its cost basis in the FHLBB stock. Loans held for sale and related derivatives The origination of residential mortgage loans is an integral part of the Company’s business. The Company generally sells its originations of such loans in the secondary market to either government-sponsored enterprises (“GSEs”) or other financial institutions. The servicing of loans sold to GSEs is generally retained while loans sold to other financial institutions are generally done on a servicing released basis. The Bank utilizes the fair value option pursuant to Accounting Standards Codification (“ASC”) 825, “Financial Instruments” for its residential mortgage loans being held for sale. Fair value is determined based on either commitments in effect from investors or prevailing market price and include the value of mortgage servicing rights. Gains and losses on the sales of loans are determined using the specific identification method. In determining the amount of the gain or loss the Company takes into consideration the direct costs of originating the loan. Also included in the net gain on loan origination and sale activities presented in the accompanying statements of operations are fair value adjustments for mortgage banking derivatives (interest rate lock commitments with borrowers, and forward loan sale commitments with investors for the delivery of mortgage loans to third party investors including To Be Announced securities (“TBAs”)) and loans held for sale. Loans The Company grants residential real estate, commercial real estate, construction, commercial and consumer loans to customers. A substantial portion of the loan portfolio is represented by mortgage loans in Massachusetts and Rhode Island. The ability of the Company’s borrowers to honor their contracts is affected by real estate values and general economic conditions in these markets. Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding unpaid principal balances adjusted for charge-offs, the allowance for loan losses, and net deferred loan origination fees and costs and purchase premiums. Interest income is accrued on the unpaid principal balance. Certain direct loan origination costs and purchase premiums, net of origination fees, are deferred and recognized in interest income using the level yield method without anticipating prepayments. Interest is not accrued on loans which are ninety days or more past due, or when, in the judgment of management, the collectability of the principal or interest becomes doubtful. Past due status is based on contractual terms of the loan. Interest income previously accrued on such loans is reversed against current period earnings. Loans are returned to accrual status when all principal and interest amounts contractually due are brought current and future payments are reasonably assured. The Company periodically may agree to modify the contractual terms of loans. When a loan is modified and a concession is made to a borrower experiencing financial difficulty, the modification is considered a troubled debt restructuring (“TDR”). All TDRs are initially classified as impaired and placed on nonaccrual status. Generally, a nonaccrual loan that is restructured remains on nonaccrual for a period of six months to demonstrate that the borrower can meet the restructured terms. If the borrower’s ability to meet the revised terms is not reasonably assured, the loan remains on nonaccrual status. Allowance for loan losses The allowance for loan losses is a valuation allowance for probable incurred credit losses. Loan losses are charged against the allowance when management believes the uncollectibility of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The allowance for loan losses is evaluated on a regular basis and is based upon management’s periodic review of the collectibility of the loans in light of historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, estimated value of any underlying collateral and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as either additional information becomes available or circumstances change. The allowance for loan losses is allocated to loan types using both a formula-based approach applied to groups of loans (general component) and an analysis of certain individual loans for impairment (allocated component). General component The general component of the allowance for loan losses covers loans that are collectively evaluated for impairment and is based on historical loss experience adjusted for qualitative factors stratified by loan segments. Management uses a rolling average of historical losses based on a trailing 48 month time frame appropriate to capture relevant loss data for each loan segment. This historical loss factor is supplemented by the following qualitative factors: changes in the volume and severity of past due loans and adversely classified or graded loans, the volume of nonaccrual loans and trends in charge-offs and recoveries; changes in the nature and volume of the portfolio and in the terms of loans; changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses; changes in the experience, ability, and depth of lending management and other relevant staff; changes in international, national, regional and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; changes in the quality of the institution’s review system; the effect of other external factors such as competition and legal and regulatory requirements on the level of estimated credit losses in the institution’s existing portfolio; changes in the value of underlying collateral-dependent loans; and the existence of concentrations of credit, and changes in the level of such concentrations. The qualitative factors are determined based on the various risk characteristics of each loan segment. Risk characteristics relevant to each portfolio segment are as follows: Residential one-to four-family real estate – The Company generally does not originate loans with a loan-to-value ratio greater than 80 percent. All loans in this segment are collateralized by one-to four-family owner, and non-owner-occupied, residential real estate and repayment is dependent on the credit quality of the individual borrower. The overall health of the economy, including unemployment rates and housing prices, will have an effect on the credit quality in this segment. Second mortgages and home equity lines of credit (HELOC) – Loans in this segment are primarily secured by second-position liens, and the Company may or may not also have a first-position lien. Regardless of which creditor is in first position, the Company does not originate loans with a combined loan-to-value ratio greater than 80 percent. All loans in this segment are collateralized by owner-occupied residential real estate and repayment is dependent on the credit quality of the individual borrower. The overall health of the economy, including unemployment rates and housing prices, will have an effect on the credit quality in this segment. Commercial real estate – Loans in this segment consist of owner-occupied and non-owner-occupied property primarily located in Massachusetts and Rhode Island. The underlying cash flows generated by the operating entities of owner-occupied real estate support the associated debt. Rental cash flows, for which management obtains periodic rent rolls, support the debt associated with non-owner-occupied real estate and can be negatively impacted by increased vacancy rates. Construction – Loans in this segment primarily include residential real estate development loans for which payment is derived from sale of the property. Credit risk is affected by cost overruns, time to sell at an adequate price, and market conditions. Commercial and Industrial – Loans in this segment are made to businesses and are generally secured by assets of the business. Repayment is expected from the cash flows of the business. A weakened economy, and resultant decreased consumer spending, would have an effect on the credit quality in this segment. During 2020, the Company funded 197 PPP loans totaling $15.4 million. The Company had $10.9 million of Paycheck Protection Program (“PPP”) loans outstanding at December 31, 2020. These loans are fully guaranteed by the SBA and the Company does not reserve for these loans. Consumer – Loans in this segment primarily include personal unsecured loans, refinanced student loans and auto loans purchased from third party lenders. Repayment is dependent on the credit quality of the individual borrower. Allocated component The allocated component of the allowance for loan losses relates to loans that are individually classified as impaired. Residential real estate, commercial and industrial, commercial real estate and construction loans are evaluated for impairment on a loan-by-loan basis. Impairment is measured by either the present value of expected future cash flows discounted at the loan’s effective interest rate, or the fair value of the collateral if the loan is collateral dependent. An allowance is established when the discounted cash flows (or collateral value) of the impaired loan are lower than the carrying value of that loan. Large groups of smaller balance homogeneous loans are collectively evaluated for impairment. Accordingly, the Company does not generally identify individual consumer loans or second mortgages and HELOCs for impairment disclosures unless such loans are 90 days past due or are classified as a troubled debt restructuring. A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed. Bank-owned life insurance Bank-owned life insurance policies are reflected on the consolidated balance sheets at their cash surrender value net of charges or other amounts that are probable at settlement. Changes in the net cash surrender value of the policies, as well as insurance proceeds received, are reflected in non-interest income in the consolidated statements of operations and are not subject to income taxes, unless such policies are surrendered prior to the death of the insured individuals. Mortgage servicing rights The Company services mortgage loans for others. Mortgage servicing rights are recognized as separate assets at fair value when rights are acquired through purchase or through sale of financial assets (“MSRs”). Capitalized servicing rights are amortized into mortgage servicing income in proportion to, and over the period of, the estimated future net servicing income of the underlying financial assets. MSRs are evaluated for impairment based upon the fair value of the rights as compared to amortized cost. Impairment is determined by stratifying rights by predominant risk characteristics, such as interest rates and terms. Fair value is based on a valuation model that calculates the present value of estimated future net servicing income, using market-based assumptions. Impairment is recognized through a valuation allowance for an individual stratum, to the extent that fair value is less than the capitalized amount for the stratum. Changes in the valuation allowance, if any, are reported in mortgage servicing income. Premises and equipment Land is carried at cost. Buildings, equipment and leasehold improvements are stated at cost, less accumulated depreciation and amortization computed predominantly on the straight-line method over the estimated useful lives of the assets or the expected terms of the leases, if shorter. Expected terms include lease option periods to the extent that the exercise of such options is reasonably assured. Premises and equipment held for sale are stated at the lower of amortized cost or fair value less costs to sell. Transfers of financial assets Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Company, (2) the transferee obtains the right to pledge or exchange the transferred assets, and (3) the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity. During the normal course of business, the Company may transfer a portion of a financial asset, for example, a participation loan. In order to be eligible for sales treatment, all cash flows from the loan must be divided proportionately, the rights of each loan holder must have the same priority, the loan holders must have no recourse to the transferor other than standard representations and warranties, and no loan holder can have the right to pledge or exchange the entire loan. In certain cases, the Company may have an obligation to repurchase mortgage loans sold to third parties and to refund fees to the purchaser if a payment default or prepayment occurs, in each case within a prescribed time period not exceeding four months after the sale date, or in the case of a violation of its representations and warranties under the provisions of its loan sale agreements. The Company evaluates its obligations under these provisions and recognizes a liability for the fair value of its recourse obligations. At December 31, 2020 and 2019, the Company determined that its obligations in connection with the recourse provisions of its loan sale agreements were insignificant. Foreclosed real estate Real estate acquired through, or in lieu of, loan foreclosure are held for sale and are initially recorded at fair value, less costs to sell, at the date of foreclosure, establishing a new cost basis. Subsequent to foreclosure, valuations are periodically performed by management and the assets are carried at the lower of carrying amount or fair value less costs to sell. Revenue and expenses from operations, changes in the valuation allowance and any direct write-downs are included in foreclosed real estate expense. Supplemental retirement plan The Company accounts for its supplemental retirement plan using an actuarial model that allocates cost over the service period of participants in the plan. The Company accounts for the over-funded or under-funded status of the plan as an asset or liability in its consolidated balance sheets and recognizes changes in the funded status in the year in which the changes occur through other comprehensive income/loss. Employee Stock Ownership Plan Compensation expense for the Employee Stock Ownership Plan (“ESOP”) is computed based on the number of shares allocated to participants during the period multiplied by the average fair market value of the Company’s shares. This expense is recognized ratably throughout the year based on the expected allocation of shares for the year. Unearned compensation applicable to the ESOP is reflected as a reduction of stockholders’ equity. The difference between the average fair market value and cost of the shares allocated by the ESOP is recorded as an adjustment to additional paid-in capital. Stock-based compensation The fair value of restricted stock and stock options is determined on the date of grant and amortized to compensation expense with a corresponding increase to additional paid-in capital over the required service period, but in no event beyond the date of an employee’s or director’s date of termination. Forfeitures of unvested awards and grants are recorded as incurred. Advertising costs Advertising costs are expensed as incurred. Income taxes Deferred income tax assets and liabilities are determined using the liability (or balance sheet) method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax basis of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. A valuation allowance is established against deferred tax assets when, based upon available evidence including historical and projected taxable income, that some or all of the deferred tax assets will not be realized. A tax position is recognized as a benefit if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded. The Company does not have any uncertain tax positions at December 31, 2020 and 2019 which require accrual or disclosure. The Company records interest and penalties as part of income tax expense. No interest or penalties were recorded for the years ended December 31, 2020 and 2019. Comprehensive income (loss) Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net income (loss). Although certain changes in assets and liabilities are reported as a separate component of equity, such items, along with net income (loss), are components of comprehensive income (loss). The components of accumulated other comprehensive loss (“AOCI”), included in stockholders’ equity, are as follows: December 31, December 31, 2020 2019 (In thousands) Securities available for sale: Net unrealized gain (loss) $ 1,713 $ 167 Tax effect (313 ) (313 ) Net-of-tax amount 1,400 (146 ) Supplemental retirement plan Unrecognized net actuarial loss (712 ) (652 ) Unrecognized net prior service credit 254 311 (458 ) (341 ) Tax effect (47 ) (47 ) Net-of-tax amount (505 ) (388 ) Accumulated other comprehensive income (loss) $ 895 $ (534 ) In 2021, the Company expects to recognize $45,000 in prior service credits and $62,000 in net actuarial losses as components of cost for the supplemental retirement plan. These amounts are included in accumulated other comprehensive loss at December 31, 2020. Prior service credits and net actuarial gains and losses are amortized to periodic pension cost over varying periods based on the plan participants to whom they relate. Segment reporting An operating segment is defined as a component of a business for which separate financial information is available that is evaluated regularly by the chief operating decision-maker in determining how to allocate resources and evaluate performance. The Company has two reporting business segments, namely, “Envision Bank” and “Envision Mortgage”. Management allocates indirect costs, such as IT, Marketing, Accounting and Administration, to each business segment in order to fully measure each segment’s results of operations. See Note 18 for disclosure of the Company’s segment information. Earnings per share Basic earnings per share represents income available to common stockholders divided by the weighted average of common shares outstanding during the period. Unvested restricted shares of common stock having dividend rights are treated as “participating securities” and, accordingly, are considered outstanding in computing basic earnings per share. Unallocated ESOP shares are not considered outstanding in computing earnings per share. Diluted earnings per share reflects additional common shares that would have been outstanding if dilutive potential shares had been issued. Stock options represent potential dilutive shares with the number of such shares computed using the treasury stock method. Business combinations We account for business combinations under the acquisition method of accounting. The application of this method of accounting requires the use of significant estimates and assumptions in the determination of the fair value of tangible and identified intangible assets acquired and liabilities assumed in order to properly allocate purchase price consideration between assets from those that are recorded as goodwill. Our estimates of the fair values of assets acquired and liabilities assumed are based upon assumptions that we believe to be reasonable, and whenever necessary, include assistance from independent third-party appraisal and valuation firms. Costs incurred to consummate a business combination are expensed as incurred. Recent accounting pronouncements On January 1, 2019, the Company early adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. In January 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-01, Financial Instruments In February 2016, FASB issued ASU 2016-02, Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses In April 2017, the FASB issued ASU 2017-08 Receivables – Non-refundable Fees and Other Costs In August 2018, the FASB issued ASU 2018-13 Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement, In December 2019, FASB issued ASU 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes the tax effect of items that are not included in continuing operations such as items included in other comprehensive income (loss). This ASU is effective for emerging growth companies for annual periods beginning after December 15 , 20 21 , and interim periods beginning after December 15 , 20 22 . The impact of adoption of this ASU is limited and not expected to be material .

Securities Available for Sale

Securities Available for Sale	12 Months Ended
	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Securities Available for Sale	2 . SECURITIES AVAILABLE FOR SALE The amortized cost and fair value of securities available for sale, including gross unrealized gains and losses, are as follows: Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (In thousands) December 31, 2020 U.S. Government-sponsored enterprises $ 1,993 $ 3 $ — $ 1,996 Corporate 4,300 56 — 4,356 Municipal 595 5 — 600 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 32,538 919 — 33,457 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 8,857 525 — 9,382 U.S. Government-guaranteed 977 24 — 1,001 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 996 52 — 1,048 U.S. Government-guaranteed 3,398 128 — 3,526 Total securities available for sale $ 53,654 $ 1,712 $ — $ 55,366 December 31, 2019 U.S. Government-sponsored enterprises $ 4,000 $ 13 $ (1 ) $ 4,012 Corporate 1,513 15 — 1,528 Municipal 744 9 — 753 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 35,238 458 (286 ) 35,410 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 8,977 — (53 ) 8,924 U.S. Government-guaranteed 1,363 7 — 1,370 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,395 23 — 1,418 U.S. Government-guaranteed 4,106 10 (28 ) 4,088 Total securities available for sale $ 57,336 $ 535 $ (368 ) $ 57,503 The amortized cost and fair value of debt securities by contractual maturity at December 31, 2020 are presented below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Amortized Fair Cost Value (In thousands) Within 1 year $ 503 $ 507 After 1 year through 5 years 5,315 5,347 After 5 years through 10 years 1,070 1,098 6,888 6,952 Mortgage-backed securities and collateralized mortgage obligations 46,766 48,414 $ 53,654 $ 55,366 Obligations of U.S. Government-sponsored enterprises consist primarily of securities issued by the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association. At December 31, 2020 and 2019, investment securities having a fair value of $1,958,000 and $2,013,000, respectively, were pledged as collateral for a line of credit with the Federal Reserve Bank of Boston (the “FRB”). There were no individual holdings of investment securities at December 31, 2020 and 2019, other than holdings of the U.S. Government and its agencies, which exceeded 10% of the Company’s stockholders’ equity as of such dates. The Company had no securities in a loss position at December 31, 2020. Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position follows at December 31, 2019: Less Over Twelve Months Gross Gross Unrealized Fair Unrealized Fair Losses Value Losses Value December 31, 2019 Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (1 ) $ 1,999 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (123 ) 11,256 (163 ) 9,632 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (53 ) 8,924 — — Collateralized mortgage obligations: U.S. Government-guaranteed (15 ) 1,891 (13 ) 883 Total debt securities $ (191 ) $ 22,071 $ (177 ) $ 12,514 At December 31, 2020, no debt securities had unrealized losses. The Company currently does not believe it is probable that it will be unable to collect all amounts due according to the contractual terms of its investments. Therefore, it is expected that the securities would not be settled at a price less than the par value of the investment. Because the Company does not intend to sell any debt securities and it is more likely than not that the Company will not be required to sell any debt securities before recovery of its amortized cost basis, it does not consider its investments to be other-than-temporarily impaired at December 31, 2020. There were no security sales for the year ended December 31, 2020. For the year ended December 31, 2019, proceeds from the sale of a security amounted to $534,000 which resulted in a realized gain of $16,000.

Loans

Loans	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Loans	3 . LOANS A summary of the loan portfolio is as follows: December 31, 2020 2019 (In thousands) Mortgage loans on real estate: Residential: One-to four-family $ 235,648 $ 244,711 Home equity loans and lines of credit 48,166 41,669 Commercial 143,893 125,405 Construction 31,050 35,485 458,757 447,270 Commercial and industrial 20,259 9,093 Consumer 10,289 15,641 Total loans 489,305 472,004 Allowance for loan losses (6,784 ) (4,280 ) Net deferred loan costs and fees, and purchase premiums 1,123 1,407 $ 483,644 $ 469,131 The Company periodically transfers a portion of its originated commercial real estate loans to participating lenders. The amounts transferred have been accounted for as sales and are therefore not included in the Company’s accompanying consolidated balance sheets. The Company continues to service the loans on behalf of the participating lenders and, as such, collects cash payments from the borrowers, remits payments to participating lenders and disburses required escrow funds to relevant parties. At December 31, 2020 and 2019, the Company was servicing loans for participants aggregating $2,410,000 and $5,283,000, respectively. See Note 4 for information relating to the Company’s servicing of residential mortgage loans for others. The following tables present activity in the allowance for loan losses, by loan category, for the years ended December 31, 2020 and 2019 and allocation of the allowance to each category as of such dates: Second Residential Mortgages Commercial Commercial 1-4 Family and HELOC Real Estate Construction and Industrial Consumer Total (In thousands) Allowance for loan losses Balance at December 31, 2018 $ 1,092 $ 292 $ 1,648 $ 765 $ 265 $ 375 $ 4,437 Provision (credit) for loan losses (21 ) (3 ) 192 (73 ) (30 ) (65 ) — Loans charged-off — — — — — (192 ) (192 ) Recoveries 25 — — — — 10 35 Balance at December 31, 2019 1,096 289 1,840 692 235 128 4,280 Provision for loan losses 543 156 1,562 59 179 54 2,553 Loans charged-off — (3 ) — — — (68 ) (71 ) Recoveries 7 — — — 2 13 22 Balance at December 31, 2020 $ 1,646 $ 442 $ 3,402 $ 751 $ 416 $ 127 $ 6,784 Second Residential Mortgages Commercial Commercial 1-4 Family and HELOC Real Estate Construction and Industrial (1) Consumer Total December 31, 2020 Allowance for impaired loans $ 133 $ — $ — $ — $ — $ — $ 133 Allowance for non-impaired loans 1,513 442 3,402 751 416 127 6,651 Total allowance for loan losses $ 1,646 $ 442 $ 3,402 $ 751 $ 416 $ 127 $ 6,784 Impaired loans $ 3,575 $ 623 $ 4,751 $ — $ — $ — $ 8,949 Non-impaired loans 232,073 47,543 139,142 31,050 20,259 10,289 480,356 Total loans $ 235,648 $ 48,166 $ 143,893 $ 31,050 $ 20,259 $ 10,289 $ 489,305 December 31, 2019 Allowance for impaired loans $ 116 $ — $ — $ — $ — $ — $ 116 Allowance for non-impaired loans 980 289 1,840 692 235 128 4,164 Total allowance for loan losses $ 1,096 $ 289 $ 1,840 $ 692 $ 235 $ 128 $ 4,280 Impaired loans $ 5,640 $ 407 $ 46 $ — $ — $ — $ 6,093 Non-impaired loans 239,071 41,262 125,359 35,485 9,093 15,641 465,911 Total loans $ 244,711 $ 41,669 $ 125,405 $ 35,485 $ 9,093 $ 15,641 $ 472,004 (1) Non-impaired loan balance includes $10.9 million of PPP loans, for which no allowance is provided due to the full guarantee from the SBA. The following table presents past due and non-accrual loans, by loan category, at December 31, 2020 and 2019: 30 - 59 Days Past Due 60 - 89 Days Past Due 90 Days or More Past Due Total Past Due (1) Non-accrual Loans (In thousands) December 31, 2020 Residential one-to four-family $ — $ — $ — $ — $ 1,876 Home equity loans and lines of credit 95 — 317 412 584 Commercial real estate — — 26 26 4,713 Construction — — — — — Commercial and industrial — — — — — Consumer 38 64 — 102 — Total $ 133 $ 64 $ 343 $ 540 $ 7,173 December 31, 2019 Residential one-to four-family $ 215 $ 587 $ — $ 802 $ 2,922 Home equity loans and lines of credit 188 244 — 432 336 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer 76 11 — 87 — Total $ 479 $ 842 $ — $ 1,321 $ 3,258 (1) Excludes non-accrual loans which are separately presented. Further information pertaining to impaired loans, which includes both non-accrual loans and troubled debt restructurings, follows: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) December 31, 2020 Impaired loans without a valuation allowance: Residential one-to four-family $ 2,160 $ 2,181 $ — Home equity loans and lines of credit 626 623 — Commercial real estate 4,753 4,751 — Total 7,539 7,555 — Impaired loans with a valuation allowance: Residential one-to four-family 1,382 1,394 133 Total impaired loans $ 8,921 $ 8,949 $ 133 December 31, 2019 Impaired loans without a valuation allowance: Residential one-to four-family $ 3,322 $ 3,322 $ — Home equity loans and lines of credit 407 407 — Commercial real estate 46 46 — Total 3,775 3,775 — Impaired loans with a valuation allowance: Residential one-to four-family 2,318 2,318 116 Total 2,318 2,318 116 Total impaired loans $ 6,093 $ 6,093 $ 116 Information related to the average balances of impaired loans and the interest income recognized on such loans, follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Year Ended December 31, 2020 Residential one-to four-family $ 3,550 $ 399 $ 159 Home equity loans and lines of credit 588 60 — Commercial real estate 2,838 8 — Total $ 6,976 $ 467 $ 159 Year Ended December 31, 2019 Residential one-to four-family $ 5,594 $ 236 $ 87 Home equity loans and lines of credit 424 11 10 Commercial real estate 132 4 — Consumer 35 1 — Total $ 6,185 $ 252 $ 97 No additional funds are committed to be advanced in connection with impaired loans. Troubled Debt Restructurings The Company periodically grants concessions to borrowers experiencing financial difficulties. The Company’s troubled debt restructurings consist primarily of interest rate concessions for periods of three months to thirty years for residential real estate loans and home equity loans, and for periods up to one year for commercial real estate loans. At December 31, 2020, the Company had sixteen residential real estate loans, one home equity loan and one commercial real estate loan aggregating $2,833,000, $42,000 and $40,000, respectively, which were subject to troubled debt restructuring agreements. At December 31, 2019, the Company had eighteen residential real estate loans, one consumer loan and one commercial real estate loan aggregating $3,616,000, $44,000 and $46,000, respectively, which were subject to troubled debt restructuring agreements. As of December 31, 2020 and 2019, $1,749,000 and $3,706,000, respectively, in troubled debt restructurings were performing in accordance with the terms of the modified loan agreements. For the year ended December 31, 2020 the Company entered into one loan modifications meeting the criteria of a troubled debt restructuring in which a loan term concession was granted to a borrower. For the year ended December 31, 2019, the Company entered into six loan modification meeting the criteria of a troubled debt restructuring. Management performs a discounted cash flow calculation to determine the amount of impairment reserve required on each of the troubled debt restructurings. Any reserve required is recorded as part of the allowance for loan losses. At December 31, 2020 and 2019 allowances of $133,000 and $116,000, respectively, related to troubled debt restructurings. During the years ended December 31, 2020 and 2019, there were no troubled debt restructurings that defaulted (over 30 days past due) within twelve months of the restructure date. No additional funds are committed to be advanced on loans being accounted for as troubled debt restructurings. At December 31, 2020, there were two residential real estate troubled debt restructurings that were granted payment deferral plans. One loan, totaling $298,000, was performing in accordance with its modified terms and is currently in repayment, and one loan, for $196,000 was not performing in accordance with its modified terms and is currently still in payment suspense. Credit Quality Information The Company utilizes an eight-grade internal loan rating system for commercial real estate, construction and commercial loans, as follows: Loans rated 1 – 3A are considered “pass” rated loans with low to average risk. Loans rated 4 are considered “special mention.” These loans are starting to show signs of potential weakness and are being closely monitored by management. Loans rated 5 are considered “substandard” and are inadequately protected by the current net worth and paying capacity of the obligors and/or the collateral pledged. There is a distinct possibility that the Company will sustain some loss if the weakness is not corrected. Loans rated 6 are considered “doubtful” and have all the weaknesses inherent in those classified substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently existing facts, highly questionable and improbable. Loans rated 7 are considered uncollectible (“loss”) and of such little value that their continuance as loans is not warranted. On an annual basis, or more often if needed, the Company formally reviews the ratings on all commercial real estate, construction and commercial loans. Annually, the Company engages an independent third party to review a significant portion of loans within these segments. Management uses the results of these reviews as part of its annual review process. The following table presents the Company’s loans by risk rating at December 31, 2020 and 2019: December 31, 2020 December 31, 2019 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3A $ 129,925 $ 31,050 $ 19,828 $ 121,703 $ 35,485 $ 8,134 Loans rated 4 9,257 — 431 3,702 — 206 Loans rated 5 4,711 — — — — 753 $ 143,893 $ 31,050 $ 20,259 $ 125,405 $ 35,485 $ 9,093 Residential mortgages, home equity loans and lines of credit, and consumer loans are monitored for credit quality based primarily on their payment status. When one of these loans becomes more than 90 days delinquent it is assigned an internal loan rating. At December 31, 2020, $1,072,000 in residential mortgages were rated as substandard and $803,000 in residential mortgages and $584,000 in home equity loans and lines of credit were rated as special mention. At December 31, 2019, $2,925,000 was rated as substandard and $1,239,000 in residential mortgages and $336,000 in home equity loans were rated as special mention.

Loan Servicing

Loan Servicing	12 Months Ended
	Dec. 31, 2020
Transfers And Servicing [Abstract]
Loan Servicing	4 . LOAN SERVICING Mortgage loans serviced for others are not included in the accompanying consolidated balance sheets. The unpaid principal balances of mortgage loans serviced for others were $1,760,306,000 and $1,049,807,000 at December 31, 2020 and 2019, respectively. In connection with these serviced loans, we maintained $14.2 million and $8.9 million of custodial escrow balances at December 31, 2020 and 2019, respectively. The following table summarizes the activity in the Company’s MSRs for the indicated periods: For the Years Ended December 31, 2020 2019 Mortgage servicing rights: (In thousands) Balance at beginning of year $ 9,484 $ 7,786 Additions through originations 8,432 2,979 Amortization (2,544 ) (1,281 ) Balance at end of year $ 15,372 $ 9,484 Valuation allowance: Balance at beginning of year $ 928 $ 8 Provision (credit) 2,067 920 Balance at end of year $ 2,995 $ 928 Mortgage servicing rights, amortized cost $ 12,377 $ 8,556 Mortgage servicing rights, fair value $ 12,490 $ 8,817 At December 31, 2020 and 2019, the fair value of MSRs was determined using a discount rate of 12% and projected annual prepayment speeds ranging from 19% to 27% for 2020 and 9% to 14% for 2019. During the years ended December 31, 2020 and 2019, the Company increased the valuation allowance for its MSRs by $2,067,000 and $920,000, respectively. Such adjustments were due to changes in fair value caused by the impact of interest rate movements on actual and expected loan prepayments. Contractually specified servicing fees for the years ended December 31, 2020 and 2019 amounted to $3,458,000 and $2,585,000, respectively, and are included in mortgage servicing fees, net.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Premises and Equipment	5 . PREMISES AND EQUIPMENT A summary of the cost and accumulated depreciation and amortization of premises and equipment is as follows: December 31, Estimated 2020 2019 Useful Life (In thousands) (In years) Land and improvements $ 953 $ 953 Buildings and improvements 3,343 3,305 5 to 50 Leasehold improvements 2,236 2,231 3 to 10 Furniture and equipment 5,558 5,170 3 to 10 Construction-in-progress 145 82 12,235 11,741 Less accumulated depreciation and amortization (7,454 ) (5,993 ) $ 4,781 $ 5,748 Total depreciation and amortization expense for the years ended December 31, 2020 and 2019 amounted to $1,508,000 and $857,000, respectively. During 2017, the Company amended the lease for its Andover loan operations center relocating offices within an office complex. As part of this lease amendment, the landlord funded the cost of leasehold improvements which amounted to $646,000. These costs have been capitalized as part of premises and equipment and a tenant improvement allowance has been recorded as part of other liabilities in the accompanying consolidated balance sheet. Both the leasehold improvements and tenant improvement allowance are being amortized over the initial lease term of approximately five years. In July 2018, the Company entered into a sublease agreement for 27% of the space in its Andover location. This sublease commenced on October 1, 2018 and runs co-terminus with the Company’s lease which expires in March 2023 In October 2018, the Board of Directors approved a plan to consolidate mortgage banking operations in the Company’s North Attleboro loan operations center (see Note 20 for additional information). As part of this decision, certain mortgage banking employees not directly involved in the loan origination process remained at the Andover location. Based on an analysis of space needs for the remaining employees, the area not currently under sublease was subdivided resulting in approximately half of the total leased space in Andover becoming available for sublease. In connection with these actions, the Company recognized a fair value “cease use” liability of $565,000 based on estimated future cash flows which is included in the restructuring charge recorded in the fourth quarter of 2018. This space remained unoccupied and the Company adjusted the cease use liability at December 31, 2019 on the assumption that this space will continue to be unoccupied through the lease term which ends in March 2023. In December of 2020, the Board of Directors approved a plan to consolidated mortgage banking operations to its Salem, New Hampshire location. As part of this decision, all mortgage banking employees located in the Andover, Massachusetts location were relocated to Salem or will work remotely. In connection with these actions, the Company recognized a fair value “cease use” liability of $294,000 based on estimated future cash flows for the Andover lease and sublease agreements. The space allocated to the Company remains unoccupied and the Company adjusted the cease use liability on the assumption that this space will continue to be unoccupied through the lease term which ends in March 2023. The Company will continue to collect income on its sublease agreement until that agreement expires in March 2023.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Deposits	6 . DEPOSITS A summary of deposit balances, by type, is as follows: December 31, 2020 2019 (In thousands) Demand deposits $ 96,731 $ 61,603 NOW accounts 53,530 39,043 Money market deposits 77,393 71,530 Regular and other savings accounts 185,481 126,876 Brokered deposits 10,056 10,167 Total non-certificate accounts 423,191 309,219 Term certificates less than $250,000 60,026 85,425 Term certificates of $250,000 or more 23,418 21,707 Term certificates - brokered 21,672 80,691 Total certificate accounts 105,116 187,823 $ 528,307 $ 497,042 A summary of term certificates, including brokered deposits, by maturity is as follows: December 31, 2020 December 31, 2019 Weighted Weighted Average Average Maturing during: Amount Rate Amount Rate (Dollars in thousands) 2020 $ — — % 140,987 1.92 % 2021 81,320 0.95 18,840 1.88 2022 20,122 1.46 25,610 2.12 2023 2,269 1.06 1,743 1.28 2024 781 1.15 643 1.32 2025 624 0.64 — — $ 105,116 1.05 % $ 187,823 1.94 %

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Borrowings	7 . BORROWINGS A summary of borrowings from the FHLBB at December 31, 2020 and 2019 is as follows: 2020 2019 Weighted Weighted Average Average Amount Rate Amount Rate (Dollars in thousands) Fixed-rate advances maturing: 2020* $ — — % $ 22,476 1.80 % 2021* 21,895 1.27 11,927 1.86 2022 10,000 2.20 10,000 2.20 2023 - - — — 2024 - - — 2025 30,000 1.35 — $ 61,895 1.46 % $ 44,403 1.91 % * Includes amortizing advances which require monthly principal and interest payments. There were no overnight advances or advances having a one-month maturity at December 31, 2020. Included in FHLBB borrowings at December 31, 2019 are overnight advances and advances having a one-month maturity of $19.8 million. Selected information for such short-term borrowings for the years presented is as follows (in 000’s): 2020 2019 Average daily balance $ 2,265 $ 73,551 Maximum outstanding at any month end 16,181 128,283 Advances from the FHLBB are secured by a blanket pledge agreement on the Bank’s qualified collateral, defined principally as 75% of the carrying value of pledged first mortgage loans on owner-occupied residential property and 65% on pledged commercial real estate loans. Available borrowing capacity at December 31, 2020 was $93.9 million. At December 31, 2020, the Bank was in compliance with the FHLBB collateral requirements. The Bank also has a $4,195,000 available line of credit with the FHLBB at an interest rate that adjusts daily. Borrowings under the line are limited to 2% of the Bank’s total assets. At December 31, 2020 and 2019, there were no advances outstanding. The Bank also has a $2,000,000 available line of credit with the FRB and a $7,500,000 available line of credit with a correspondent bank. No advances were outstanding under either of these lines at December 31, 2020 and 2019. As a participating lender in the PPP, the Company also has access to additional borrowing capacity through the Federal Reserve’s Paycheck Protection Program Lending Facility (the “PPPLF”). Only loans issued through the PPP may be pledged as collateral. At December 31, 2020, the bank had $11.4 million in outstanding advances. $11.2 million of the advances are scheduled to mature in 2022 and the remaining $225,000 are scheduled to mature in 2025. All advances have an interest rate of 0.35%. As loans are forgiven as part of the PPP, the funding received as part of the Federal Reserve’s PPPLF is repaid in full.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	8 . INCOME TAXES Allocation of federal and state income taxes between current and deferred portions is as follows (in thousands): Years Ended December 31, 2020 2019 Current tax expense: Federal $ 789 $ — State 1,393 118 Total current tax expense 2,182 118 Deferred tax expense (benefit): Federal 4,174 723 State 887 226 5,061 949 Change in valuation allowance (1,766 ) (949 ) Total deferred tax expense (benefit) 3,295 — Total tax expense $ 5,477 $ 118 The reasons for the differences between the statutory federal income tax expense (benefit) and the actual tax expense are summarized as follows (in thousands): Years Ended December 31, 2020 2019 Statutory federal tax rate of 21% $ 5,341 $ 745 Increase (decrease) resulting from: State taxes, net of federal tax effect 1,801 272 Bank-owned life insurance (38 ) (39 ) Tax-exempt income (6 ) (9 ) Change in valuation allowance (1,766 ) (949 ) Other, net 145 98 Total tax expense $ 5,477 $ 118 The Tax Cuts and Jobs Act of 2017 repealed the alternative minimum tax (“AMT”) and also provided that existing AMT credit carryforwards be refunded over a four-year The components of the net deferred tax asset are as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Federal $ 2,962 $ 4,809 State 1,286 1,066 4,248 5,875 Valuation allowance (531 ) (2,297 ) 3,717 3,578 Deferred tax liabilities: Federal (4,837 ) (2,547 ) State (2,175 ) (1,031 ) (7,012 ) (3,578 ) Net deferred tax liability $ (3,295 ) $ — The tax effects of items giving rise to deferred tax assets (liabilities) are as follows (in thousands): December 31, 2020 2019 Employee benefit plans $ 785 $ 714 Allowance for loan losses 2,071 1,203 Funded status of post-retirement benefits (47 ) (47 ) Securities available for sale (313 ) (313 ) Depreciation and amortization 144 279 Net deferred loan origination costs (281 ) (350 ) Mortgage servicing rights (3,479 ) (2,366 ) Net operating loss carryforward - 2,517 Charitable contribution carryforward 531 619 Derivatives (2,722 ) (377 ) Stock-based compensation 290 185 Other, net 257 233 (2,764 ) 2,297 Valuation allowance on net deferred tax assets (531 ) (2,297 ) Net deferred tax liability $ (3,295 ) $ — From 2014 to June 30, 2020, the Company has maintained a valuation allowance on its net deferred tax asset based on a determination that it was more likely than not that such assets would not be realized. This determination was based on the Company's net operating loss carryforward position, its current period operating results exclusive of non-recurring items and its expectations for the upcoming year. As a result, the 100% valuation allowance for deferred tax assets relating to the net operating loss carryforwards was maintained. Due to the level of income earned during the year ended 2020 and the Company being in a net deferred tax liability position at December 31, 2020, the full amount of the Company’s net operating loss carryforwards was absorbed and the previously held valuation allowance was reversed. The Company continues to maintain a valuation allowance for its charitable contribution carryforward as management concluded that improvements to operating earnings, while significant, would need to be sustained for an additional period to provide sufficient evidence that realizability of the deferred tax asset was more likely than not to occur. At December 31, 2020, the Company has a charitable contribution carryforward of $531,000 of which all but $77,000 expires on December 31, 2021. The federal income tax reserve for loan losses at the Company’s base year amounted to $2,033,000. If any portion of the reserve is used for purposes other than to absorb the losses for which it was established, approximately 150% of the amount actually used (limited to the amount of the reserve) would be subject to taxation in the fiscal year in which used. As the Company intends to use the reserve only to absorb loan losses, a deferred income tax liability of $571,000 has not been provided. The Company’s income tax returns are subject to review and examination by federal and state taxing authorities. The Company is currently open to audit under the applicable statutes of limitations by the Internal Revenue Service for the years ended December 31, 2016 through 2020. The years open to examination by state taxing authorities vary by jurisdiction; no years prior to 2016 are open.

On-Balance Sheet Derivative Ins

On-Balance Sheet Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2020
Derivative Instruments And Hedging Activities Disclosure [Abstract]
On-Balance Sheet Derivative Instruments and Hedging Activities	9 . ON-BALANCE SHEET DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Derivative Loan Commitments Mortgage loan interest rate lock commitments qualify as derivative loan commitments if the loan that will result from exercise of the commitment will be held for sale upon funding. The Company enters into commitments to fund residential mortgage loans at specified rates and times in the future, with the intention that these loans will subsequently be sold in the secondary market or to other financial institutions. Outstanding derivative loan commitments expose the Company to the risk that the price of the loans arising from exercise of the loan commitment might decline from inception of the rate lock to funding of the loan due to an increase in mortgage interest rates. If interest rates increase, the value of these loan commitments decreases. Conversely, if interest rates decrease, the value of these loan commitments increases. The notional amount of derivative loan commitments was $396,551,000 and $89,925,000 at December 31, 2020 and 2019, respectively. The fair value of such commitments at December 31, 2020 and 2019 was an asset of $11,821,000 and $1,472,000, respectively, and is included in other assets in the accompanying consolidated balance sheets. During the years ended December 31, 2020 and 2019, the increase in aggregate fair value of $10,349,000 and $845,000, respectively, related to interest rate lock commitments was recognized and included in the net gain on loan origination and sales activities in the accompanying consolidated statements of operations. Forward Loan Sale Commitments The Company utilizes both “mandatory delivery” and “best efforts” forward loan sale commitments and, effective in the fourth quarter of 2018, TBA securities to hedge the financial impact of changes in interest rates on the value of loans that would result from the exercise of the derivative loan commitments. With a “mandatory delivery” contract, the Company commits to deliver a certain principal amount of mortgage loans to an investor at a specified price on or before a specified date. If the Company fails to deliver the amount of mortgages necessary to fulfill the commitment by the specified date, it may be obligated to pay a “pair-off” fee, based on then-current market prices, to the investor to compensate the investor in the event of a loss in value. With a “best efforts” contract, the Company commits to deliver an individual mortgage loan of a specified principal amount and quality to an investor if the loan to the underlying borrower closes. Generally, the price the investor will pay the seller for an individual loan is specified prior to the loan being funded (e.g., on the same day the lender commits to lend funds to a potential borrower). The Company expects that these forward loan sale commitments and TBA securities will experience changes in fair value that serve to substantially offset the change in fair value of derivative loan commitments the degree to which depends on the notional amount of such sale commitments. The aggregate notional amount of forward loan sale commitments and TBA securities was $390,248,000 and $85,401,000 at December 31, 2020 and 2019, respectively. The fair value of such commitments at December 31, 2020 and 2019 consisted of liabilities of $2,180,000 and $140,000, respectively, included in other liabilities in the consolidated balance sheets and assets of $44,000 and $11,000, respectively, included in other assets in the consolidated balance sheets. During the years ended December 31, 2020 and 2019, net increases (reductions) in the aggregate fair value liability of $2,007,000 and ($124,000), respectively, related to forward loan sale commitments and TBA securities were recognized and included in net gain on loan originations and sales activities in the accompanying consolidated statements of operations.

Minimum Regulatory Capital Requ

Minimum Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2020
Banking And Thrifts [Abstract]
Minimum Regulatory Capital Requirements	1 0 . MINIMUM REGULATORY CAPITAL REQUIREMENTS The Bank is subject to various regulatory capital requirements administered by federal banking agencies. Capital adequacy guidelines and prompt corrective actions regulations involve qualitative measures of assets, liabilities, and certain off-balance sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgement by regulators. Failure to meet capital requirements can initiate regulatory action. The final rules implementing Basel Committee on Banking Supervision’s capital guidelines for U.S. banks (Basel III rules) became effective for the Bank on January 1, 2015. Under BASEL III, community banking institutions must maintain a capital conservation buffer of common equity tier 1 capital in an amount greater than 2.5% of total risk-weighted assets to avoid being subject to limitations on capital distributions and discretionary bonuses. Quantitative measures established by regulation to ensure capital adequacy require the Bank to maintain minimum amounts and ratios (set forth in the following tables) of total, Tier 1 capital and common equity Tier 1 capital to risk weighted assets, and Tier 1 capital to average assets (all as defined). Management believes, as of December 31, 2020 and 2019, that the Bank met all capital adequacy requirements to which it is subject. As of December 31, 2020, the most recent notification from the FDIC categorized the Bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized, the Bank must maintain minimum total risk-based, Tier 1 risk-based, common equity Tier 1 and Tier 1 leverage ratios as set forth in the following tables. There are no conditions or events since the notification that management believes have changed the Bank’s category. The Bank’s actual and minimum capital amounts and ratios, exclusive of the capital conservation buffer, are presented in the following table: Minimum To Be Well For Minimum Capitalized Under Capital Prompt Corrective Actual Adequacy Purposes Action Provisions Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) December 31, 2020 Total capital (to risk weighted assets) $ 97,406 15.7 % $ 49,682 8.0 % $ 62,102 10.0 % Tier 1 capital (to risk weighted assets) 90,037 14.5 37,261 6.0 49,682 8.0 Common equity Tier 1 capital (to risk weighted assets) 90,037 14.5 27,946 4.5 40,366 6.5 Tier 1 capital (to average assets) 90,037 12.7 28,466 4.0 35,582 5.0 December 31, 2019 Total capital (to risk weighted assets) 76,652 16.7 36,637 8.0 45,796 10.0 Tier 1 capital (to risk weighted assets) 72,372 15.8 27,478 6.0 36,637 8.0 Common equity Tier 1 capital (to risk weighted assets) 72,372 15.8 20,608 4.5 29,768 6.5 Tier 1 capital (to average assets) 72,372 11.3 25,627 4.0 32,033 5.0

Post-retirement Plans

Post-retirement Plans	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Post-retirement Plans	1 1 . POST-RETIREMENT PLANS Supplemental retirement agreements The Company maintains supplemental retirement agreements with certain officers and directors (none of whom currently provide services to the Company) that provide for supplemental benefits commencing with retirement. The present value of future benefits payable is accrued over the terms of employment or anticipated term of each participating director’s position, as applicable, taking into consideration the vesting provisions in the agreements. At December 31, 2020 and 2019, the accrued benefits related to the agreements amounted to $453,000 and $507,000, respectively. Total expense, included in other non-interest expenses, related to these supplemental agreements amounted to $65,000 and $51,000 for the years ended December 31, 2020 and 2019, respectively. Supplemental retirement plan The Company has a master supplemental retirement plan (“Plan”) which covers certain officers and directors of the Company. In 2020 and 2019, the only active participants in the Plan were certain directors, as the Plan is frozen to new participants. Information pertaining to activity in the Plan follows: Years Ended December 31, 2020 2019 (In thousands) Change in plan assets: Fair value of plan assets at beginning of year $ — $ — Employer contributions 201 201 Benefits paid (201 ) (201 ) Fair value of plan assets at end of year — — Change in benefit obligation: Benefit obligation at beginning of year 1,506 1,561 Service cost 11 10 Interest cost 36 53 Actuarial (gain) loss 105 83 Benefits paid (201 ) (201 ) Benefit obligation at end of year 1,457 1,506 Unfunded status and accrued supplemental pension cost at year end $ (1,457 ) $ (1,506 ) Accumulated benefit obligation at year end $ 1,457 $ 1,506 The assumptions used to determine the benefit obligation are as follows: December 31, 2020 2019 Discount rate 1.25 % 2.50 % Annual inflation factor 1.00 % 1.00 % Net periodic benefit cost, included in other non-interest expenses, attributable to the Plan for the years ended December 31, 2020 and 2019, consists of the following: 2020 2019 (In thousands) Service cost $ 11 $ 10 Interest cost 36 53 Amortization of net actuarial loss 45 36 Amortization of prior service credit (57 ) (84 ) $ 35 $ 15 The following assumptions were used to determine the net periodic benefit cost for the years ended December 31, 2020 and 2019: 2020 2019 Discount rate 2.50 % 3.60 % Annual inflation factor 1.00 % 1.00 % Estimated future benefit payments, which reflect expected future services, as appropriate, are as follows: Years Ending December 31, Amount (In thousands) 2021 $ 199 2022 207 2023 358 2024 201 2025 197 2026-2030 239 Endorsement split-dollar life insurance arrangements The Company is the sole owner of life insurance policies pertaining to certain of the Company’s current and former directors and executives. The Company has entered into agreements with these directors and executives whereby the Company will pay to the directors’ and executives’ estates or beneficiaries a portion of the death benefit that the Company will receive as beneficiary of such policies. Expense associated with this post-retirement benefit for the years ended December 31, 2020 and 2019 amounted to $20,000 and $19,000, respectively. At December 31, 2020 and 2019, the accrued benefits related to the split-dollar arrangements amounted to $472,000 and $451,000, respectively. 401(k) Plan The Company maintains a 401(k) Plan whereby each employee reaching the age of 21 automatically becomes a participant in the plan. Employees may contribute up to 15% of their compensation subject to certain limits based on federal tax laws. All employees who have worked for one year or 1,000 hours are eligible for an automatic employer contribution of 3% of employees’ compensation, which requires no vesting period. The Company also matches 50% of the first 2% of an eligible employee’s contributions, allowing for a total employer contribution of 4% of employees’ compensation. Matching contributions vest over a four year service period. In addition, a profit-sharing provision allows for an additional discretionary contribution by the Company upon approval of the Board of Directors. For the years ended December 31, 2020 and 2019, expense attributable to the 401(k) Plan amounted to $852,000 and $753,000, respectively, with no additional discretionary contribution made.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	1 2 . STOCK-BASED COMPENSATION Under the Randolph Bancorp, Inc. 2017 Stock Option and Incentive Plan (the “2017 Equity Plan”), the Company may grant options, restricted stock, restricted units or performance awards to its directors, officers and employees. Both incentive stock options and non-qualified stock options may be granted under the Equity Plan with 586,872 shares reserved for options. The exercise price of each option equals the market price of the Company’s stock on the date of the grant and the maximum term of each options is 10 years. The total number of shares reserved for restricted stock is 234,749. Options and awards generally vest ratably over three to five years. In addition, the Company granted 15,000 shares of restricted stock and 44,118 options in 2020 as an inducement for senior executives to accept employment (the “2020 Inducement Plan”). The inducement awards and options vest ratably over five years. The fair value of shares awarded is based on the market price at the date of grant. Stock Options The fair value of each option grant is estimated on the date of the grant using the Black-Scholes option-pricing model with the following assumptions: • Volatility incorporates peer group volatility because the Company does not have a sufficient trading history. • Expected life represents the period of time that the option is expected to be outstanding, taking into account the contractual term, and the vesting period. • Expected dividend yield is based on the Company's history and expectation of dividend payouts. • The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for a period equivalent to the expected life of the option. The Company made the following grants of options to purchase shares of common stock during the years ended December 31, 2020 and 2019: 2020 2019 Options granted 333,118 57,252 Vesting period (years) 3 - 5 3 - 5 Expiration period (years) 10 10 Expected volatility 24.94% - 29.87% 26.14% - 29.09% Expected life (years) 6 - 6.5 6 - 6.5 Expected dividend yield — — Risk free interest rate 0.44%-1.47% 2.37% - 2.61% Option fair value $2.69 - $4.87 $2.99 - $5.83 The following table presents the activity and certain other information related to stock option grants under the 2017 Equity Plan and the 2020 Inducement Plan for the year ended December 31, 2020: Options Stock Option Grants Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Balance at January 1, 2020 360,207 $ 14.82 7.01 $ — Granted 333,118 12.15 Forfeited (14,543 ) 15.34 Expired (91,614 ) 14.67 Balance at December 31, 2020 587,168 $ 13.32 8.40 $ 5,132,675 Exercisable at December 31, 2020 139,448 $ 14.85 6.95 $ 1,005,646 Unrecognized compensation cost (inclusive of directors' options) $ 1,456,227 Weighted average remaining recognition period (years) 2.96 For the years ended December 31, 2020 and 2019, stock-based compensation expense applicable to stock options was $703,000 and $366,000, respectively. Restricted Stock Shares issued upon vesting may be either authorized but unissued shares or reacquired shares held by the Company. Any shares not issued because vesting requirements are not met will again be available for issuance under the plan. The fair market value of shares awarded, based on the market price at the date of grant, is recorded as unearned compensation and amortized over the applicable vesting period. The following table presents the activity and certain other information related to restricted stock awards under the Equity Plan for the year ended December 31, 2020: Restricted Stock Awards Weighted Average Grant Price Restricted stock awards at January 1, 2020 125,861 $ 14.76 Granted 65,630 10.93 Vested (60,228 ) 14.70 Forfeited (9,251 ) 14.88 Non-vested stock awards at December 31, 2020 122,012 $ 12.72 Unrecognized compensation cost $ 1,344,170 Weighted average remaining recognition period (years) 3.42 Total expense for the restricted stock awards was $891,000 and $553,000 for the years ended December 31, 2020 and 2019, respectively.

Employee Stock Ownership Plan

Employee Stock Ownership Plan	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Employee Stock Ownership Plan	1 3 . EMPLOYEE STOCK OWNERSHIP PLAN The Company maintains an Employee Stock Ownership Plan (“ESOP”), which is a tax-qualified retirement plan providing eligible employees the opportunity to own Company stock. The Company granted a loan to the ESOP for the purchase of 469,498 shares of its common stock at $10.00 per share. The loan is payable annually over 25 years with interest at the prime rate to be reset each January 1 st Shares are committed to be released on a monthly basis and allocated as of December 31 st

Share Repurchase Program

Share Repurchase Program	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Share Repurchase Program	1 4 . SHARE REPURCHASE PROGRAM In September 2017, the Company’s Board of Directors adopted a share repurchase program under which the Company may repurchase up to 10%, or 586,854 shares of its then outstanding common shares. Repurchases under the program may be made in open market or in privately negotiated transactions and pursuant to any trading plan that may be adopted in accordance with Rule 10b5-1 of the Securities and Exchange Commission. Any repurchased shares will be held by the Company as authorized but unissued shares. The repurchase program expired on September 14, 2020, at which time, the Company had repurchased 568,403 shares at a cost of $8,452,000 in connection with this program. In October 2020, the Company’s Board of Directors adopted a share repurchase program under which the Company may repurchase up to 10%, or 552,000 shares of its then outstanding common shares. Repurchases under the program may be made in open market or in privately negotiated transactions and pursuant to any trading plan that may be adopted in accordance with Rule 10b5-1 of the Securities and Exchange Commission. Any repurchased shares will be held by the Company as authorized but unissued shares. The repurchase program may be suspended or terminated at any time without prior notice and is currently set to expire on October 29, 2021. As of December 31, 2020, the company had repurchased 29,345 shares at a cost of $520,000 in connection with this program.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	15. EARNINGS PER SHARE Basic earnings per share represents net income divided by the weighted average of common shares outstanding during the period. Unvested restricted shares of common stock having dividend rights are treated as “participating securities” and, accordingly, are considered outstanding in computing basic earnings per share. Unallocated ESOP shares are not considered to be outstanding for purposes of computing earnings per share. The following table sets forth the calculation of the average number of shares outstanding used to calculate the basic and diluted earnings per share for the periods indicated: 2020 2019 Average number of common shares outstanding 5,511,524 5,787,385 Less: Average unallocated ESOP shares (384,963 ) (403,768 ) Average number of common shares outstanding used to calculate basic earnings per share 5,126,561 5,383,617 Effect of dilutive stock options 36,481 — Average number of common shares outstanding used to calculate dilutive earnings per share 5,163,042 5,383,617

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 6 . COMMITMENTS AND CONTINGENCIES In the normal course of business, there are outstanding commitments and contingencies which are not reflected in the accompanying consolidated financial statements. Lease commitments Pursuant to the terms of non-cancelable lease and sublease agreements in effect at December 31, 2020, future minimum rent commitments are as follows: Years Ending December 31, Leases Sub-lease Net (In thousands) 2021 $ 651 (91 ) $ 560 2022 334 (94 ) 240 2023 145 (16 ) 129 2024 91 — 91 2025 23 — 23 Thereafter — — — $ 1,244 $ (201 ) $ 1,043 The leases contain options to extend for periods of two to ten years. The cost of unexercised options periods is not included above. Total rent expense, net of sublease income, for the years ended December 31, 2020 and 2019 amounted to $904,000 and $887,000, respectively. Loan commitments The Company is a party to financial instruments with off-balance-sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit. These instruments involve, to varying degrees, elements of market, credit and interest rate risk which are not recognized in the consolidated financial statements. The Company’s exposure to credit loss is represented by the contractual amount of these commitments. The Company uses the same credit policies in making commitments and conditional obligations as it does for on-balance-sheet instruments. At December 31, 2020 and 2019, the following financial instruments were outstanding whose contract amounts represent credit risk: 2020 2019 (In thousands) Commitments to originate loans $ 411,401 $ 117,086 Unused lines and letters of credit 71,458 52,721 Unadvanced funds on construction loans 9,110 11,029 Overdraft lines of credit 7,969 8,178 Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The commitments for lines of credit may expire without being drawn upon. Therefore, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The majority of these financial instruments are collateralized by real estate. Employment Arrangement and Change in Control Agreements The Company has entered into an employment arrangement with its President and Chief Executive Officer that provides for three years of salary continuation in the event his employment is terminated without cause or he resigns for good reason, subject to his providing a release of claims and complying with a non-solicitation and non-disclosure agreement. The Company has also entered into change in control agreements with five members of senior management which provide that if, within two years of a change of control of the Company or the Bank, the executive is involuntarily terminated other than for cause, disability or death, or voluntarily resigns for good reason, the executive will be entitled to a lump-sum payment equal to two times salary plus bonus. The Company has also entered into change in control agreements with four members of senior management which provide that if, within one year of a change of control of the Company or the Bank, the executive is involuntarily terminated other than for cause, disability or death, or voluntarily resigns for good reason, the executive will be entitled to a lump-sum payment equal to one times salary plus bonus. Other contingencies The Company is not currently a party to any pending legal proceedings that it believes would have a material adverse effect on its financial condition, results of operations or cash flows.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	1 7 . FAIR VALUE OF ASSETS AND LIABILITIES Determination of fair value The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. Fair value 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 assets and liabilities. 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 asset or liability. The following methods and assumptions were used by the Company in estimating fair value disclosures: Cash and cash equivalents Certificates of deposit Securities Federal Home Loan Bank of Boston stock Loans held for sale Loans Mortgage servicing rights Deposit liabilities FHLBB advances - The fair values of the Company’s FHLBB advances are estimated using discounted cash flow analyses based on the current borrowing rates in the market for similar types of borrowing arrangements. Accrued interest On-balance-sheet derivatives Off-balance sheet credit-related instruments Assets and liabilities measured at fair value on a recurring basis Assets and liabilities measured at fair value on a recurring basis are summarized below. . Total Level 1 Level 2 Level 3 Fair December 31, 2020 (In thousands) Assets: Securities available for sale $ — $ 55,366 $ — $ 55,366 Portfolio loans (fair value option) 13,780 — 13,780 Loans held for sale (fair value option) — 119,112 — 119,112 Derivative loan commitments — 11,821 — 11,821 Forward loan sale commitments — 44 — 44 Liabilities: Forward loan sale commitments, including TBAs — 2,180 — 2,180 December 31, 2019 Assets: Securities available for sale: Debt securities $ — $ 57,503 $ — $ 57,503 Portfolio loans (fair value option) — 9,826 — 9,826 Loans held for sale (fair value option) — 62,792 — 62,792 Derivative loan commitments — 1,472 — 1,472 Forward loan sale commitments — 11 — 11 Liabilities: Forward loan sale commitments, including TBAs — 140 — 140 There were no transfers between levels for assets and liabilities recorded at fair value on a recurring basis during 2020 or 2019. Assets and liabilities measured at fair value on a non-recurring basis The Company may also be required, from time to time, to measure certain other assets on a non-recurring basis in accordance with U.S. generally accepted accounting principles. These adjustments to fair value usually result from application of lower-of-cost-or-market accounting or write-downs of individual assets and liabilities. The following table summarizes the fair value hierarchy used to determine each adjustment and the carrying value of the related assets and liabilities as of December 31, 2020 and 2019. The gains and losses represent the amounts recorded during 2020 and 2019 on the assets and liabilities held at year-end. There no liabilities recorded at fair value on a non-recurring basis as of December 31, 2020 and 2019. Year Ended December 31, 2020 December 31, 2020 Level 1 Level 2 Level 3 Total Assets: (In thousands) Collateral dependent impaired loans $ — $ — $ 6,318 $ — Mortgage servicing rights — 12,377 — (2,067 ) Foreclosed real estate — — 132 — $ — $ 12,377 $ 6,450 $ (2,067 ) Year Ended December 31, 2019 December 31, 2019 Level 1 Level 2 Level 3 Total Gains (Losses) (In thousands) Collateral dependent impaired loans $ — $ — $ 2,250 $ — Mortgage servicing rights — 8,556 — (920 ) $ — $ 8,556 $ 2,250 $ (920 ) Gains or losses applicable to impaired loans are based on the appraised value of the underlying collateral, discounted as necessary due to management’s estimates of changes in market conditions, less estimated selling costs, and are not recorded directly to current earnings but rather as a component in determining the allowance for loan losses. The Company utilizes an independent valuation from a third party which uses a discounted cash flow model to estimate the fair value of mortgage servicing rights. The model utilizes loan prepayment assumptions based on current market conditions and applies a discount rate based on indicated rates of return required by market participants. During the years ended December 31, 2020 and 2019, the valuation allowance increased due to faster actual and projected loan prepayment speeds attributable to the decrease in interest rates on residential mortgage loans during the periods. Summary of fair values of financial instruments The estimated fair values, and related carrying amounts, of the Company’s financial instruments are presented below. Certain financial instruments and all non-financial instruments are exempt from disclosure requirements. Accordingly, the aggregate fair value amounts presented herein do not represent the underlying fair value of the Company. This table excludes financial instruments for which the carrying amount approximates fair value. Financial assets for which the fair value approximates carrying value include cash and cash equivalents and accrued interest receivable. Financial liabilities for which the fair value approximates carrying value include mortgagor’s escrow accounts and accrued interest payable. December 31, 2020 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Securities available for sale 55,366 55,366 — 55,366 — Loans held for sale 119,112 119,112 — 119,112 — Loans, net 483,644 490,914 — — 490,914 Derivative assets 11,865 11,865 — 11,865 — Financial liabilities: Deposits $ 528,307 $ 528,786 $ — $ 528,786 $ — FRB advances 11,431 11,431 — 11,431 — FHLBB advances 61,895 63,071 — 63,071 — Derivative liabilities 2,180 2,180 — 2,180 — December 31, 2019 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 490 $ 492 $ — $ 492 $ — Securities available for sale 57,503 57,503 — 57,503 — Loans held for sale 62,792 62,792 — 62,792 — Loans, net 469,131 469,416 — — 469,416 Derivative assets 1,483 1,483 — 1,483 — Financial liabilities: Deposits $ 497,042 $ 496,979 $ — $ 496,979 $ — FHLBB advances 44,403 44,433 — 44,433 — Derivative liabilities 140 140 — 140 —

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment Information	18. SEGMENT INFORMATION The Company reports its activities in one of two business segments, namely Envision Bank (“EB”) and Envision Mortgage (“EM”). EB operations primarily consist of accepting deposits from customers within the communities surrounding the Bank’s five full service branch offices, through the internet, and investing those funds in residential and commercial real estate loans, home equity lines of credit, construction loans, commercial and industrial loans, and consumer loans. EM’s operations primarily consist of the origination and sale of residential mortgage loans and the servicing of loans sold to government-sponsored entities. A portion of the loans originated by EM are held in the loan portfolio of EB. Segment information as of and for the year ended December 31, 2020, follows: For the Year Ended December 31, 2020 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 16,235 $ 2,632 $ 18,867 Provision for loan losses 2,553 — 2,553 Net interest income after provision for loan losses 13,682 2,632 16,314 Non-interest income: Customer service fees 1,180 103 1,283 Gain on loan origination and sale activities, net (1) — 55,729 55,729 Mortgage servicing fees, net (381 ) (772 ) (1,153 ) Other 465 580 1,045 Total non-interest income 1,264 55,640 56,904 Non-interest expenses: Salaries and employee benefits 9,161 24,000 33,161 Occupancy and equipment 1,770 1,775 3,545 Other non-interest expenses 5,228 4,382 9,610 Total non-interest expenses 16,159 30,157 46,316 Income (loss) before income taxes and elimination of inter-segment profit $ (1,213 ) $ 28,115 26,902 Elimination of inter-segment profit (1,493 ) Income before income taxes 25,409 Income tax expense 5,477 Net income $ 19,932 Total assets, December 31, 2020 $ 537,722 $ 183,350 $ 721,072 (1) Before elimination of inter-segment profit The information above was derived from the internal management reporting system used by management to measure performance of the segments. The Company’s internal transfer pricing arrangements determined by management primarily consist of the following: 1. EM’s cost of funds is based on the weighted average rate of overnight advances from the FHLBB for the period. 2. EM is credited with service released premiums and a sales premium totaling 1.50% for new loans transferred to EB’s loans held for investment, and a 1.00% fee for HELOC originations. This income for the year ended December 31, 2020 totaled $1,493,000. 3. Loan servicing fees are charged to EB by EM based on the balance of residential mortgage loans held in portfolio at a rate of 0.14% per annum and amounted to $381,000 for the year ended December 31, 2020. 4. Certain cost centers provide services to both business segments. The cost centers include Accounting, Marketing, IT and Administration. Costs which are common to both business segments are referred to as “indirect costs” and are allocated using relevant benchmarks, e.g. headcount, number of accounts, etc. Segment information as of and for the year ended December 31, 2019 follows: For the Year Ended December 31, 2019 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 15,985 $ 1,848 $ 17,833 Provision for loan losses — — — Net interest income after provision for loan losses 15,985 1,848 17,833 Non-interest income: Customer service fees 1,268 139 1,407 Gain on loan origination and sale activities, net (1) — 19,851 19,851 Mortgage servicing fees, net (363 ) 757 394 Other 596 366 962 Total non-interest income 1,501 21,113 22,614 Non-interest expenses: Salaries and employee benefits 7,065 17,831 24,896 Occupancy and equipment 1,527 1,256 2,783 Other non-interest expenses 4,789 3,482 8,271 Total non-interest expenses 13,381 22,569 35,950 Income before income taxes and elimination of inter-segment profit $ 4,105 $ 392 4,497 Elimination of inter-segment profit (951 ) Income before income taxes 3,546 Income tax expense 118 Net income $ 3,428 Total assets, December 31, 2019 $ 521,144 $ 109,860 $ 631,004 (1) Before elimination of inter-segment profit The information above was derived from the internal management reporting system used by management to measure performance of the segments. The Company’s internal transfer pricing arrangements determined by management primarily consist of the following: 1. EM’s cost of funds is based on the weighted average rate of overnight advances from the FHLBB for the period. 2. EM is credited with service released premiums and a sales premium totaling 1.50% for new loans transferred to EB’s loans held for investment, and a 1.00% fee for HELOC originations. This income for the year ended December 31, 2019 totaled $951,000. 3. Loan servicing fees are charged to EB by EM based on the balance of residential mortgage loans held in portfolio at a rate of 0.14% per annum and amounted to $363,000 for the year ended December 31, 2019. 4. Certain cost centers provide services to both business segments. The cost centers include Accounting, Marketing, IT and Administration. Costs which are common to both business segments are referred to as “indirect costs” and are allocated using relevant benchmarks, e.g. headcount, number of accounts, etc.

Other Non-Interest Expenses

Other Non-Interest Expenses	12 Months Ended
	Dec. 31, 2020
Other Income And Expenses [Abstract]
Other Non-Interest Expenses	1 9 . OTHER NON-INTEREST EXPENSES Included in other non-interest expenses in 2020 and 2019 are certain items exceeding 1% of the Company’s total interest and non-interest income as follows: 2020 2019 (In thousands) Software amortization, licenses and maintenance $ 1,303 $ 1,017 Card related expenses 429 459 Data communication and telephone 391 418 Directors fees, including stock-based compensation 579 586

Global Pandemic Affecting Rando

Global Pandemic Affecting Randolph Bancorp, Inc.	12 Months Ended
	Dec. 31, 2020
Risks And Uncertainties [Abstract]
Global Pandemic Affecting Randolph Bancorp, Inc. In 2020	20 . GLOBAL PANDEMIC AFFECTING RANDOLPH BANCORP, INC. On March 13, 2020, the United States Government declared a national emergency in response to the coronavirus (“COVID-19”) outbreak. This outbreak has caused, among other things, widespread shutdowns of businesses and volatile markets and has severely disrupted normal economic activity in the region the Company serves as well as across the nation. The following summarizes the more significant financial repercussions of this national emergency for the Company. Credit Quality and Allowance for Loan Losses The Company increased the allowance for loan losses during 2020 directly related to its estimate, based on available information, of probable incurred losses resulting from the impact of the COVID-19 pandemic. As the Company acquires additional information on overall economic prospects together with further assessments of the impact on individual borrowers, the loss estimated will be revised as needed, and these revisions could be material. The Company’s approach to estimating the impact of this pandemic on credit quality is presented in Note 3 – “Loans and Allowance for Loan Losses.” Disaster Response Plan Costs The Company implemented its disaster response plans when the national emergency was declared and a stay-at-home order was issued in the Commonwealth of Massachusetts. To operate in this mode the Company incurred expenses for, among other things, compensation for front-line and quarantined employees, buying equipment for a remote workforce, cleaning of office and branch buildings, and communications with customers regarding the status of the Company’s operations. These plan costs amounted to $229,000 for the year ended December 31, 2020. Loan Payment Deferral and Paycheck Protection Program In response to the pandemic’s effect on our customers, the Company implemented a series of measures through the date of this report, including participation in the PPP and granting payment deferrals for residential mortgage, home equity and certain commercial borrowers who were current in their payments. As of December 31, 2020, the Company had a balance of $10.9 million loans as part of the PPP. These loans are included with commercial and industrial loans, are pledged to the PPPLF and have no direct effect on the Company’s capital ratios. T In accordance with interagency guidance issued in March 2020 and/or the CARES Act enacted in March 2020, these short-term deferrals are not considered troubled debt restructurings, provided the loan was current as of the date the deferral program was implemented, or December 31, 2019 for deferrals made under the CARES Act. The Company has agreed to loan payment deferrals on commercial loans totaling $38.4 million, residential real estate loans in portfolio totaling $18.8 million and residential real estate loans serviced for others totaling $68.5 million as of December 31, 2020. The commercial loan payment deferrals are concentrated in the hotel and hospitality, restaurant and retail service industries. The qualifying residential real estate and commercial loan borrowers were required to contact the Company to receive loan payment deferrals. The table below summarizes the status of the bank’s loan deferral activity at December 31, 2020: Deferrals Suspended/ Resumed Full Granted Reduced Payment Payment Payoff (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 15,514 $ 12,974 $ 2,109 $ 431 Home equity loans and lines of credit 3,179 626 1,287 1,266 Construction 350 350 - - Commercial 34,754 6,544 25,406 2,804 Total real estate loans 53,797 20,494 28,802 4,501 Commercial and industrial 3,645 - 1,635 2,010 Consumer 68 68 - - Total $ 57,510 $ 20,562 $ 30,437 $ 6,511 The payment deferral programs were applied prospectively from the respective dates of the events and did not change the delinquency status of the loans as of such dates. Accordingly, if all payments were current at the date of the event, the loan will not be reported as past due during the deferral period. Furthermore, for loans subject to the deferral programs on which payments were past due prior to the event, the delinquency status of such loans was frozen to the status that existed at the date of the event until the end of the deferral period. Accordingly, the table below summarizes the risk rating and for all loans that were granted deferral, and any loans that were listed in nonaccrual status at December 31, 2020: Pass Rated / Special Sub- Non- Not Rated Mention standard accrual (1) (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 14,887 $ 196 $ - $ 196 Home equity loans and lines of credit 1,913 - - - Construction 350 - - Commercial 19,020 8,748 4,182 4,182 Total real estate loans 36,170 8,944 4,182 4,378 Commercial and industrial 1,204 431 - - Consumer 68 - - - Total $ 37,442 $ 9,375 $ 4,182 $ 4,378 (1) Nonaccrual loans are risk rated as either special mention or substandard and are included as a balance in those columns.

Parent Company Condensed Financ

Parent Company Condensed Financial Statements	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Parent Company Condensed Financial Statements	21 . PARENT COMPANY CONDENSED FINANCIAL STATEMENTS Financial information as of December 31, 2020 and 2019 and for the years then ended pertaining to Randolph Bancorp, Inc. is as follows: BALANCE SHEETS December 31, December 31, 2020 2019 Assets Cash and due from bank $ 4,829 $ 1,445 Investment in Envision Bank 90,959 72,872 ESOP loan 4,042 4,162 Total assets $ 99,830 $ 78,479 Liabilities Income taxes payable $ 8 $ — Due to Envision Bank 3 17 Total liabilities 11 17 Stockholders' Equity Common stock 54 56 Additional paid-in capital 50,937 51,127 Retained earnings 51,689 31,757 ESOP-Unearned compensation (3,756 ) (3,944 ) Accumulated other comprehensive loss, net of tax 895 (534 ) Total stockholders' equity 99,819 78,462 Total liabilities and stockholders' equity $ 99,830 $ 78,479 STATEMENTS OF OPERATIONS Years Ended December 31, 2020 2019 Interest income $ 198 $ 235 Dividend income 5,000 - Operating expenses 171 194 Income before incomes taxes and equity in undistributed net income of Envision Bank 5,027 41 Applicable income taxes 7 3 Income before equity in undistributed net income of Envision Bank 5,020 38 Equity in undistributed net income of Envision Bank 14,912 3,390 Net income $ 19,932 $ 3,428 STATEMENTS OF CASH FLOWS Years Ended December 31, 2020 2019 Cash flows from operating activities: Net income $ 19,932 $ 3,428 Adjustments to reconcile net income to net cash provided by (used in) operating activities: Equity in undistributed net income of Envision Bank (14,912 ) (3,390 ) Dividends received from Envision Bank (5,000 ) — Change in income taxes payable 8 — Change in intercompany receivable/payable (15 ) (39 ) Net cash provided by (used in) operating activities 13 (1 ) Cash flows from investing activities: Principal payments received on ESOP loan 120 104 Dividends received from Envision Bank 5,000 — Net cash provided by investing activities 5,120 104 Cash flows from financing activities: Stock repurchases (1,749 ) (5,438 ) Stock repurchase payable — (70 ) Net cash used in financing activities (1,749 ) (5,508 ) Net change in cash and due from bank 3,384 (5,405 ) Cash and due from bank at the beginning of year 1,445 6,850 Cash and due from bank at end of year $ 4,829 $ 1,445

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	22. SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) First Quarter Second Quarter Third Quarter Fourth Quarter 2020 2019 2020 2019 2020 2019 2020 2019 (Dollars in thousands, except per share data) Interest and dividend income $ 6,053 $ 6,016 $ 6,059 $ 6,454 $ 5,648 $ 6,541 $ 5,828 $ 6,220 Interest expense 1,628 1,638 1,326 1,965 979 1,968 788 1,827 Net interest and dividend income 4,425 4,378 4,733 4,489 4,669 4,573 5,040 4,393 Provision (credit) for loan losses 724 — 1,068 (144 ) 546 — 215 144 Customer service fees 306 329 266 362 330 363 381 353 Gain on loan origination and sale activities, net 7,144 2,588 14,370 5,068 18,102 5,782 14,620 5,462 Mortgage servicing fees, net (1,254 ) 319 (1,354 ) 224 1,180 (181 ) 275 32 Gain on sales/calls of securities and impairment write-down, net — — — — — — — 16 Increase in cash surrender value of life insurance 45 45 45 48 46 45 45 47 Other 210 132 172 153 216 294 266 182 Total non-interest income 6,451 3,413 13,499 5,855 19,874 6,303 15,587 6,092 Total non-interest expense 10,959 7,878 11,379 8,863 11,051 9,718 12,927 9,491 Provision (benefit) for income taxes 11 (36 ) 594 119 2,661 14 2,211 21 Net income (loss) $ (818 ) $ (51 ) $ 5,191 $ 1,506 $ 10,285 $ 1,144 $ 5,274 $ 829 Basic earnings (loss) per share $ (0.16 ) $ (0.01 ) $ 1.02 $ 0.28 $ 2.01 $ 0.21 $ 1.03 $ 0.16 Diluted earnings (loss) per share $ (0.16 ) $ (0.01 ) $ 1.02 $ 0.28 $ 2.01 $ 0.21 $ 1.01 $ 0.16 Weighted average common shares (basic) 5,158,294 5,478,544 5,092,490 5,465,205 5,120,367 5,345,786 5,135,069 5,248,021 Weighted average common shares (diluted) 5,158,294 5,478,544 5,092,490 5,465,205 5,120,367 5,345,786 5,244,414 5,248,021

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Randolph Bancorp, Inc. (the “Company”) is a bank holding company whose principal subsidiary is Envision Bank (the “Bank”). Envision Bank provides a variety of financial services to individuals and small businesses through its five branch offices in Massachusetts and seven loan production offices and lending centers located throughout Massachusetts and Southern New Hampshire. The Bank’s primary deposit products are checking, savings and term certificate accounts and its primary lending products are residential and commercial mortgage loans. The Bank is also actively involved in the sale and servicing of residential mortgage loans in the secondary market. The Federal Deposit Insurance Corporation (“FDIC”) provides insurance coverage on all deposits up to $250,000 per depositor. As an FDIC insured institution, the Bank is subject to supervision, examination and regulation by the FDIC. Additionally, as a Massachusetts chartered savings bank, the Bank’s depositors are also insured by the Depositors Insurance Fund (“DIF”), a private industry-sponsored insurance company. The DIF insures bank deposits in excess of the FDIC insurance limits.
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of Randolph Bancorp, Inc. (a Massachusetts corporation) and its wholly-owned subsidiary, Envision Bank (together, the “Company”). The Bank has subsidiaries involved in owning investment securities and foreclosed real estate and a subsidiary which provides loan closing services. All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of estimates In preparing 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 consolidated balance sheet and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and cash equivalents Cash equivalents include amounts due from banks, federal funds sold on a daily basis and interest-bearing deposits with original maturities of ninety days or less.
Certificates of Deposit	Certificates of deposit Certificates of deposit have original maturities ranging from one to five years and are carried at cost.
Fair Value Hierarchy	Fair value hierarchy The Company groups its assets and liabilities that are measured at fair value in three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1 – Valuation is based on quoted prices in active markets for identical assets and liabilities. Valuations are obtained from readily available pricing sources. Level 2 – Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets and liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets and liabilities. Level 3 – Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. Level 3 assets and liabilities include those for which the value is determined using unobservable inputs to pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. Transfers between levels are recognized at the end of a reporting period, if applicable.
Securities	Securities All securities are classified as available for sale and are recorded at fair value, with unrealized gains and losses excluded from earnings and reported in other comprehensive income/loss. Purchase premiums and discounts are recognized in interest income using the level yield method over the terms of the securities. Anticipated prepayments on mortgage-backed securities are used in applying this method. Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method. On a quarterly basis, the Company evaluates all securities with a decline in fair value below the amortized cost of the investment to determine whether or not the impairment is deemed to be other than temporary (“OTTI”). OTTI is required to be recognized: (1) if the Company intends to sell the security; (2) if it is “more likely than not” that the Company will be required to sell the security before recovery of its amortized cost basis; or (3) for debt securities, if the present value of expected cash flows is not sufficient to recover the entire amortized cost basis. For all impaired debt securities that the Company intends to sell, or more likely than not will be required to sell, the full amount of the decline in fair value is recognized as OTTI through earnings. For all other impaired debt securities, credit-related OTTI is recognized through earnings and non-credit related OTTI is recognized in other comprehensive income/loss, net of applicable taxes. Because the Company’s assessments are based on available factual information as well as subjective information, the determination as to whether an OTTI exists and, if so, the amount of impairment, is subjective and, therefore, the timing and amount of OTTI constitute material estimates that are subject to significant change.
Federal Home Loan Bank of Boston Stock	Federal Home Loan Bank of Boston stock The Bank, as a member of the Federal Home Loan Bank of Boston (“FHLBB”), is required to maintain an investment in capital stock of the FHLBB. Based on redemption provisions of the FHLBB, the stock has no quoted market value and is carried at cost. The Company periodically evaluates for impairment based on ultimate recovery of its cost basis in the FHLBB stock.
Loans Held for Sale and related derivatives	Loans held for sale and related derivatives The origination of residential mortgage loans is an integral part of the Company’s business. The Company generally sells its originations of such loans in the secondary market to either government-sponsored enterprises (“GSEs”) or other financial institutions. The servicing of loans sold to GSEs is generally retained while loans sold to other financial institutions are generally done on a servicing released basis. The Bank utilizes the fair value option pursuant to Accounting Standards Codification (“ASC”) 825, “Financial Instruments” for its residential mortgage loans being held for sale. Fair value is determined based on either commitments in effect from investors or prevailing market price and include the value of mortgage servicing rights. Gains and losses on the sales of loans are determined using the specific identification method. In determining the amount of the gain or loss the Company takes into consideration the direct costs of originating the loan. Also included in the net gain on loan origination and sale activities presented in the accompanying statements of operations are fair value adjustments for mortgage banking derivatives (interest rate lock commitments with borrowers, and forward loan sale commitments with investors for the delivery of mortgage loans to third party investors including To Be Announced securities (“TBAs”)) and loans held for sale.
Loans	Loans The Company grants residential real estate, commercial real estate, construction, commercial and consumer loans to customers. A substantial portion of the loan portfolio is represented by mortgage loans in Massachusetts and Rhode Island. The ability of the Company’s borrowers to honor their contracts is affected by real estate values and general economic conditions in these markets. Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding unpaid principal balances adjusted for charge-offs, the allowance for loan losses, and net deferred loan origination fees and costs and purchase premiums. Interest income is accrued on the unpaid principal balance. Certain direct loan origination costs and purchase premiums, net of origination fees, are deferred and recognized in interest income using the level yield method without anticipating prepayments. Interest is not accrued on loans which are ninety days or more past due, or when, in the judgment of management, the collectability of the principal or interest becomes doubtful. Past due status is based on contractual terms of the loan. Interest income previously accrued on such loans is reversed against current period earnings. Loans are returned to accrual status when all principal and interest amounts contractually due are brought current and future payments are reasonably assured. The Company periodically may agree to modify the contractual terms of loans. When a loan is modified and a concession is made to a borrower experiencing financial difficulty, the modification is considered a troubled debt restructuring (“TDR”). All TDRs are initially classified as impaired and placed on nonaccrual status. Generally, a nonaccrual loan that is restructured remains on nonaccrual for a period of six months to demonstrate that the borrower can meet the restructured terms. If the borrower’s ability to meet the revised terms is not reasonably assured, the loan remains on nonaccrual status.
Allowance for Loan Losses	Allowance for loan losses The allowance for loan losses is a valuation allowance for probable incurred credit losses. Loan losses are charged against the allowance when management believes the uncollectibility of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The allowance for loan losses is evaluated on a regular basis and is based upon management’s periodic review of the collectibility of the loans in light of historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, estimated value of any underlying collateral and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as either additional information becomes available or circumstances change. The allowance for loan losses is allocated to loan types using both a formula-based approach applied to groups of loans (general component) and an analysis of certain individual loans for impairment (allocated component). General component The general component of the allowance for loan losses covers loans that are collectively evaluated for impairment and is based on historical loss experience adjusted for qualitative factors stratified by loan segments. Management uses a rolling average of historical losses based on a trailing 48 month time frame appropriate to capture relevant loss data for each loan segment. This historical loss factor is supplemented by the following qualitative factors: changes in the volume and severity of past due loans and adversely classified or graded loans, the volume of nonaccrual loans and trends in charge-offs and recoveries; changes in the nature and volume of the portfolio and in the terms of loans; changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses; changes in the experience, ability, and depth of lending management and other relevant staff; changes in international, national, regional and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; changes in the quality of the institution’s review system; the effect of other external factors such as competition and legal and regulatory requirements on the level of estimated credit losses in the institution’s existing portfolio; changes in the value of underlying collateral-dependent loans; and the existence of concentrations of credit, and changes in the level of such concentrations. The qualitative factors are determined based on the various risk characteristics of each loan segment. Risk characteristics relevant to each portfolio segment are as follows: Residential one-to four-family real estate – The Company generally does not originate loans with a loan-to-value ratio greater than 80 percent. All loans in this segment are collateralized by one-to four-family owner, and non-owner-occupied, residential real estate and repayment is dependent on the credit quality of the individual borrower. The overall health of the economy, including unemployment rates and housing prices, will have an effect on the credit quality in this segment. Second mortgages and home equity lines of credit (HELOC) – Loans in this segment are primarily secured by second-position liens, and the Company may or may not also have a first-position lien. Regardless of which creditor is in first position, the Company does not originate loans with a combined loan-to-value ratio greater than 80 percent. All loans in this segment are collateralized by owner-occupied residential real estate and repayment is dependent on the credit quality of the individual borrower. The overall health of the economy, including unemployment rates and housing prices, will have an effect on the credit quality in this segment. Commercial real estate – Loans in this segment consist of owner-occupied and non-owner-occupied property primarily located in Massachusetts and Rhode Island. The underlying cash flows generated by the operating entities of owner-occupied real estate support the associated debt. Rental cash flows, for which management obtains periodic rent rolls, support the debt associated with non-owner-occupied real estate and can be negatively impacted by increased vacancy rates. Construction – Loans in this segment primarily include residential real estate development loans for which payment is derived from sale of the property. Credit risk is affected by cost overruns, time to sell at an adequate price, and market conditions. Commercial and Industrial – Loans in this segment are made to businesses and are generally secured by assets of the business. Repayment is expected from the cash flows of the business. A weakened economy, and resultant decreased consumer spending, would have an effect on the credit quality in this segment. During 2020, the Company funded 197 PPP loans totaling $15.4 million. The Company had $10.9 million of Paycheck Protection Program (“PPP”) loans outstanding at December 31, 2020. These loans are fully guaranteed by the SBA and the Company does not reserve for these loans. Consumer – Loans in this segment primarily include personal unsecured loans, refinanced student loans and auto loans purchased from third party lenders. Repayment is dependent on the credit quality of the individual borrower. Allocated component The allocated component of the allowance for loan losses relates to loans that are individually classified as impaired. Residential real estate, commercial and industrial, commercial real estate and construction loans are evaluated for impairment on a loan-by-loan basis. Impairment is measured by either the present value of expected future cash flows discounted at the loan’s effective interest rate, or the fair value of the collateral if the loan is collateral dependent. An allowance is established when the discounted cash flows (or collateral value) of the impaired loan are lower than the carrying value of that loan. Large groups of smaller balance homogeneous loans are collectively evaluated for impairment. Accordingly, the Company does not generally identify individual consumer loans or second mortgages and HELOCs for impairment disclosures unless such loans are 90 days past due or are classified as a troubled debt restructuring. A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed.
Bank-owned Life Insurance	Bank-owned life insurance Bank-owned life insurance policies are reflected on the consolidated balance sheets at their cash surrender value net of charges or other amounts that are probable at settlement. Changes in the net cash surrender value of the policies, as well as insurance proceeds received, are reflected in non-interest income in the consolidated statements of operations and are not subject to income taxes, unless such policies are surrendered prior to the death of the insured individuals.
Mortgage Servicing Rights	Mortgage servicing rights The Company services mortgage loans for others. Mortgage servicing rights are recognized as separate assets at fair value when rights are acquired through purchase or through sale of financial assets (“MSRs”). Capitalized servicing rights are amortized into mortgage servicing income in proportion to, and over the period of, the estimated future net servicing income of the underlying financial assets. MSRs are evaluated for impairment based upon the fair value of the rights as compared to amortized cost. Impairment is determined by stratifying rights by predominant risk characteristics, such as interest rates and terms. Fair value is based on a valuation model that calculates the present value of estimated future net servicing income, using market-based assumptions. Impairment is recognized through a valuation allowance for an individual stratum, to the extent that fair value is less than the capitalized amount for the stratum. Changes in the valuation allowance, if any, are reported in mortgage servicing income.
Premises and Equipment	Premises and equipment Land is carried at cost. Buildings, equipment and leasehold improvements are stated at cost, less accumulated depreciation and amortization computed predominantly on the straight-line method over the estimated useful lives of the assets or the expected terms of the leases, if shorter. Expected terms include lease option periods to the extent that the exercise of such options is reasonably assured. Premises and equipment held for sale are stated at the lower of amortized cost or fair value less costs to sell.
Transfers of Financial Assets	Transfers of financial assets Transfers of financial assets are accounted for as sales when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Company, (2) the transferee obtains the right to pledge or exchange the transferred assets, and (3) the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity. During the normal course of business, the Company may transfer a portion of a financial asset, for example, a participation loan. In order to be eligible for sales treatment, all cash flows from the loan must be divided proportionately, the rights of each loan holder must have the same priority, the loan holders must have no recourse to the transferor other than standard representations and warranties, and no loan holder can have the right to pledge or exchange the entire loan. In certain cases, the Company may have an obligation to repurchase mortgage loans sold to third parties and to refund fees to the purchaser if a payment default or prepayment occurs, in each case within a prescribed time period not exceeding four months after the sale date, or in the case of a violation of its representations and warranties under the provisions of its loan sale agreements. The Company evaluates its obligations under these provisions and recognizes a liability for the fair value of its recourse obligations. At December 31, 2020 and 2019, the Company determined that its obligations in connection with the recourse provisions of its loan sale agreements were insignificant.
Foreclosed Real Estate	Foreclosed real estate Real estate acquired through, or in lieu of, loan foreclosure are held for sale and are initially recorded at fair value, less costs to sell, at the date of foreclosure, establishing a new cost basis. Subsequent to foreclosure, valuations are periodically performed by management and the assets are carried at the lower of carrying amount or fair value less costs to sell. Revenue and expenses from operations, changes in the valuation allowance and any direct write-downs are included in foreclosed real estate expense.
Supplemental Retirement Plans	Supplemental retirement plan The Company accounts for its supplemental retirement plan using an actuarial model that allocates cost over the service period of participants in the plan. The Company accounts for the over-funded or under-funded status of the plan as an asset or liability in its consolidated balance sheets and recognizes changes in the funded status in the year in which the changes occur through other comprehensive income/loss.
Employee Stock Ownership Plan	Employee Stock Ownership Plan Compensation expense for the Employee Stock Ownership Plan (“ESOP”) is computed based on the number of shares allocated to participants during the period multiplied by the average fair market value of the Company’s shares. This expense is recognized ratably throughout the year based on the expected allocation of shares for the year. Unearned compensation applicable to the ESOP is reflected as a reduction of stockholders’ equity. The difference between the average fair market value and cost of the shares allocated by the ESOP is recorded as an adjustment to additional paid-in capital.
Stock-Based Compensation	Stock-based compensation The fair value of restricted stock and stock options is determined on the date of grant and amortized to compensation expense with a corresponding increase to additional paid-in capital over the required service period, but in no event beyond the date of an employee’s or director’s date of termination. Forfeitures of unvested awards and grants are recorded as incurred.
Advertising Cost	Advertising costs Advertising costs are expensed as incurred.
Income Taxes	Income taxes Deferred income tax assets and liabilities are determined using the liability (or balance sheet) method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax basis of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. A valuation allowance is established against deferred tax assets when, based upon available evidence including historical and projected taxable income, that some or all of the deferred tax assets will not be realized. A tax position is recognized as a benefit if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded. The Company does not have any uncertain tax positions at December 31, 2020 and 2019 which require accrual or disclosure. The Company records interest and penalties as part of income tax expense. No interest or penalties were recorded for the years ended December 31, 2020 and 2019.
Comprehensive Income (Loss)	Comprehensive income (loss) Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net income (loss). Although certain changes in assets and liabilities are reported as a separate component of equity, such items, along with net income (loss), are components of comprehensive income (loss). The components of accumulated other comprehensive loss (“AOCI”), included in stockholders’ equity, are as follows: December 31, December 31, 2020 2019 (In thousands) Securities available for sale: Net unrealized gain (loss) $ 1,713 $ 167 Tax effect (313 ) (313 ) Net-of-tax amount 1,400 (146 ) Supplemental retirement plan Unrecognized net actuarial loss (712 ) (652 ) Unrecognized net prior service credit 254 311 (458 ) (341 ) Tax effect (47 ) (47 ) Net-of-tax amount (505 ) (388 ) Accumulated other comprehensive income (loss) $ 895 $ (534 ) In 2021, the Company expects to recognize $45,000 in prior service credits and $62,000 in net actuarial losses as components of cost for the supplemental retirement plan. These amounts are included in accumulated other comprehensive loss at December 31, 2020. Prior service credits and net actuarial gains and losses are amortized to periodic pension cost over varying periods based on the plan participants to whom they relate.
Segment Reporting	Segment reporting An operating segment is defined as a component of a business for which separate financial information is available that is evaluated regularly by the chief operating decision-maker in determining how to allocate resources and evaluate performance. The Company has two reporting business segments, namely, “Envision Bank” and “Envision Mortgage”. Management allocates indirect costs, such as IT, Marketing, Accounting and Administration, to each business segment in order to fully measure each segment’s results of operations. See Note 18 for disclosure of the Company’s segment information.
Earnings (Loss) Per Share	Earnings per share Basic earnings per share represents income available to common stockholders divided by the weighted average of common shares outstanding during the period. Unvested restricted shares of common stock having dividend rights are treated as “participating securities” and, accordingly, are considered outstanding in computing basic earnings per share. Unallocated ESOP shares are not considered outstanding in computing earnings per share. Diluted earnings per share reflects additional common shares that would have been outstanding if dilutive potential shares had been issued. Stock options represent potential dilutive shares with the number of such shares computed using the treasury stock method.
Business Combinations	Business combinations We account for business combinations under the acquisition method of accounting. The application of this method of accounting requires the use of significant estimates and assumptions in the determination of the fair value of tangible and identified intangible assets acquired and liabilities assumed in order to properly allocate purchase price consideration between assets from those that are recorded as goodwill. Our estimates of the fair values of assets acquired and liabilities assumed are based upon assumptions that we believe to be reasonable, and whenever necessary, include assistance from independent third-party appraisal and valuation firms. Costs incurred to consummate a business combination are expensed as incurred.
Recent Accounting Pronouncements	Recent accounting pronouncements On January 1, 2019, the Company early adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. In January 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-01, Financial Instruments In February 2016, FASB issued ASU 2016-02, Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses In April 2017, the FASB issued ASU 2017-08 Receivables – Non-refundable Fees and Other Costs In August 2018, the FASB issued ASU 2018-13 Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement, In December 2019, FASB issued ASU 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes the tax effect of items that are not included in continuing operations such as items included in other comprehensive income (loss). This ASU is effective for emerging growth companies for annual periods beginning after December 15 , 20 21 , and interim periods beginning after December 15 , 20 22 . The impact of adoption of this ASU is limited and not expected to be material .

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Components of Accumulated Other Comprehensive Loss (AOCI) and Related Tax Effects	The components of accumulated other comprehensive loss (“AOCI”), included in stockholders’ equity, are as follows: December 31, December 31, 2020 2019 (In thousands) Securities available for sale: Net unrealized gain (loss) $ 1,713 $ 167 Tax effect (313 ) (313 ) Net-of-tax amount 1,400 (146 ) Supplemental retirement plan Unrecognized net actuarial loss (712 ) (652 ) Unrecognized net prior service credit 254 311 (458 ) (341 ) Tax effect (47 ) (47 ) Net-of-tax amount (505 ) (388 ) Accumulated other comprehensive income (loss) $ 895 $ (534 )

Securities Available for Sale (

Securities Available for Sale (Tables)	12 Months Ended
	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Schedule of Amortized Cost and Fair Value of Securities	The amortized cost and fair value of securities available for sale, including gross unrealized gains and losses, are as follows: Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (In thousands) December 31, 2020 U.S. Government-sponsored enterprises $ 1,993 $ 3 $ — $ 1,996 Corporate 4,300 56 — 4,356 Municipal 595 5 — 600 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 32,538 919 — 33,457 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 8,857 525 — 9,382 U.S. Government-guaranteed 977 24 — 1,001 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 996 52 — 1,048 U.S. Government-guaranteed 3,398 128 — 3,526 Total securities available for sale $ 53,654 $ 1,712 $ — $ 55,366 December 31, 2019 U.S. Government-sponsored enterprises $ 4,000 $ 13 $ (1 ) $ 4,012 Corporate 1,513 15 — 1,528 Municipal 744 9 — 753 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 35,238 458 (286 ) 35,410 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 8,977 — (53 ) 8,924 U.S. Government-guaranteed 1,363 7 — 1,370 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,395 23 — 1,418 U.S. Government-guaranteed 4,106 10 (28 ) 4,088 Total securities available for sale $ 57,336 $ 535 $ (368 ) $ 57,503
Investments Classified by Contractual Maturity Date	The amortized cost and fair value of debt securities by contractual maturity at December 31, 2020 are presented below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Amortized Fair Cost Value (In thousands) Within 1 year $ 503 $ 507 After 1 year through 5 years 5,315 5,347 After 5 years through 10 years 1,070 1,098 6,888 6,952 Mortgage-backed securities and collateralized mortgage obligations 46,766 48,414 $ 53,654 $ 55,366
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	The Company had no securities in a loss position at December 31, 2020. Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position follows at December 31, 2019: Less Over Twelve Months Gross Gross Unrealized Fair Unrealized Fair Losses Value Losses Value December 31, 2019 Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (1 ) $ 1,999 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (123 ) 11,256 (163 ) 9,632 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (53 ) 8,924 — — Collateralized mortgage obligations: U.S. Government-guaranteed (15 ) 1,891 (13 ) 883 Total debt securities $ (191 ) $ 22,071 $ (177 ) $ 12,514

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Summary of Loan Portfolio	A summary of the loan portfolio is as follows: December 31, 2020 2019 (In thousands) Mortgage loans on real estate: Residential: One-to four-family $ 235,648 $ 244,711 Home equity loans and lines of credit 48,166 41,669 Commercial 143,893 125,405 Construction 31,050 35,485 458,757 447,270 Commercial and industrial 20,259 9,093 Consumer 10,289 15,641 Total loans 489,305 472,004 Allowance for loan losses (6,784 ) (4,280 ) Net deferred loan costs and fees, and purchase premiums 1,123 1,407 $ 483,644 $ 469,131 The table below summarizes the status of the bank’s loan deferral activity at December 31, 2020: Deferrals Suspended/ Resumed Full Granted Reduced Payment Payment Payoff (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 15,514 $ 12,974 $ 2,109 $ 431 Home equity loans and lines of credit 3,179 626 1,287 1,266 Construction 350 350 - - Commercial 34,754 6,544 25,406 2,804 Total real estate loans 53,797 20,494 28,802 4,501 Commercial and industrial 3,645 - 1,635 2,010 Consumer 68 68 - - Total $ 57,510 $ 20,562 $ 30,437 $ 6,511
Summary of Activity in the Allowance for Loan Losses by Loan Category	The following tables present activity in the allowance for loan losses, by loan category, for the years ended December 31, 2020 and 2019 and allocation of the allowance to each category as of such dates: Second Residential Mortgages Commercial Commercial 1-4 Family and HELOC Real Estate Construction and Industrial Consumer Total (In thousands) Allowance for loan losses Balance at December 31, 2018 $ 1,092 $ 292 $ 1,648 $ 765 $ 265 $ 375 $ 4,437 Provision (credit) for loan losses (21 ) (3 ) 192 (73 ) (30 ) (65 ) — Loans charged-off — — — — — (192 ) (192 ) Recoveries 25 — — — — 10 35 Balance at December 31, 2019 1,096 289 1,840 692 235 128 4,280 Provision for loan losses 543 156 1,562 59 179 54 2,553 Loans charged-off — (3 ) — — — (68 ) (71 ) Recoveries 7 — — — 2 13 22 Balance at December 31, 2020 $ 1,646 $ 442 $ 3,402 $ 751 $ 416 $ 127 $ 6,784
Summary of Additional Information Pertaining to the Allowance for Loan Losses	Second Residential Mortgages Commercial Commercial 1-4 Family and HELOC Real Estate Construction and Industrial (1) Consumer Total December 31, 2020 Allowance for impaired loans $ 133 $ — $ — $ — $ — $ — $ 133 Allowance for non-impaired loans 1,513 442 3,402 751 416 127 6,651 Total allowance for loan losses $ 1,646 $ 442 $ 3,402 $ 751 $ 416 $ 127 $ 6,784 Impaired loans $ 3,575 $ 623 $ 4,751 $ — $ — $ — $ 8,949 Non-impaired loans 232,073 47,543 139,142 31,050 20,259 10,289 480,356 Total loans $ 235,648 $ 48,166 $ 143,893 $ 31,050 $ 20,259 $ 10,289 $ 489,305 December 31, 2019 Allowance for impaired loans $ 116 $ — $ — $ — $ — $ — $ 116 Allowance for non-impaired loans 980 289 1,840 692 235 128 4,164 Total allowance for loan losses $ 1,096 $ 289 $ 1,840 $ 692 $ 235 $ 128 $ 4,280 Impaired loans $ 5,640 $ 407 $ 46 $ — $ — $ — $ 6,093 Non-impaired loans 239,071 41,262 125,359 35,485 9,093 15,641 465,911 Total loans $ 244,711 $ 41,669 $ 125,405 $ 35,485 $ 9,093 $ 15,641 $ 472,004 (1) Non-impaired loan balance includes $10.9 million of PPP loans, for which no allowance is provided due to the full guarantee from the SBA.
Schedule of Past Due and Non-Accrual Loans by Loan Category	The following table presents past due and non-accrual loans, by loan category, at December 31, 2020 and 2019: 30 - 59 Days Past Due 60 - 89 Days Past Due 90 Days or More Past Due Total Past Due (1) Non-accrual Loans (In thousands) December 31, 2020 Residential one-to four-family $ — $ — $ — $ — $ 1,876 Home equity loans and lines of credit 95 — 317 412 584 Commercial real estate — — 26 26 4,713 Construction — — — — — Commercial and industrial — — — — — Consumer 38 64 — 102 — Total $ 133 $ 64 $ 343 $ 540 $ 7,173 December 31, 2019 Residential one-to four-family $ 215 $ 587 $ — $ 802 $ 2,922 Home equity loans and lines of credit 188 244 — 432 336 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer 76 11 — 87 — Total $ 479 $ 842 $ — $ 1,321 $ 3,258 (1) Excludes non-accrual loans which are separately presented. Accordingly, the table below summarizes the risk rating and for all loans that were granted deferral, and any loans that were listed in nonaccrual status at December 31, 2020: Pass Rated / Special Sub- Non- Not Rated Mention standard accrual (1) (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 14,887 $ 196 $ - $ 196 Home equity loans and lines of credit 1,913 - - - Construction 350 - - Commercial 19,020 8,748 4,182 4,182 Total real estate loans 36,170 8,944 4,182 4,378 Commercial and industrial 1,204 431 - - Consumer 68 - - - Total $ 37,442 $ 9,375 $ 4,182 $ 4,378 (1) Nonaccrual loans are risk rated as either special mention or substandard and are included as a balance in those columns.
Summary of Impaired Loans and Information Related to Average Balances of Impaired Loans and Interest Income Recognized	Further information pertaining to impaired loans, which includes both non-accrual loans and troubled debt restructurings, follows: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) December 31, 2020 Impaired loans without a valuation allowance: Residential one-to four-family $ 2,160 $ 2,181 $ — Home equity loans and lines of credit 626 623 — Commercial real estate 4,753 4,751 — Total 7,539 7,555 — Impaired loans with a valuation allowance: Residential one-to four-family 1,382 1,394 133 Total impaired loans $ 8,921 $ 8,949 $ 133 December 31, 2019 Impaired loans without a valuation allowance: Residential one-to four-family $ 3,322 $ 3,322 $ — Home equity loans and lines of credit 407 407 — Commercial real estate 46 46 — Total 3,775 3,775 — Impaired loans with a valuation allowance: Residential one-to four-family 2,318 2,318 116 Total 2,318 2,318 116 Total impaired loans $ 6,093 $ 6,093 $ 116 Information related to the average balances of impaired loans and the interest income recognized on such loans, follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Year Ended December 31, 2020 Residential one-to four-family $ 3,550 $ 399 $ 159 Home equity loans and lines of credit 588 60 — Commercial real estate 2,838 8 — Total $ 6,976 $ 467 $ 159 Year Ended December 31, 2019 Residential one-to four-family $ 5,594 $ 236 $ 87 Home equity loans and lines of credit 424 11 10 Commercial real estate 132 4 — Consumer 35 1 — Total $ 6,185 $ 252 $ 97
Summary of Company's Loans by Risk Rating	The following table presents the Company’s loans by risk rating at December 31, 2020 and 2019: December 31, 2020 December 31, 2019 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3A $ 129,925 $ 31,050 $ 19,828 $ 121,703 $ 35,485 $ 8,134 Loans rated 4 9,257 — 431 3,702 — 206 Loans rated 5 4,711 — — — — 753 $ 143,893 $ 31,050 $ 20,259 $ 125,405 $ 35,485 $ 9,093

Loan Servicing (Tables)

Loan Servicing (Tables)	12 Months Ended
	Dec. 31, 2020
Transfers And Servicing [Abstract]
Summary of Activity Relating to Mortgage Servicing Rights	The following table summarizes the activity in the Company’s MSRs for the indicated periods: For the Years Ended December 31, 2020 2019 Mortgage servicing rights: (In thousands) Balance at beginning of year $ 9,484 $ 7,786 Additions through originations 8,432 2,979 Amortization (2,544 ) (1,281 ) Balance at end of year $ 15,372 $ 9,484 Valuation allowance: Balance at beginning of year $ 928 $ 8 Provision (credit) 2,067 920 Balance at end of year $ 2,995 $ 928 Mortgage servicing rights, amortized cost $ 12,377 $ 8,556 Mortgage servicing rights, fair value $ 12,490 $ 8,817

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Summary of Cost and Accumulated Depreciation and Amortization of Premises and Equipment	A summary of the cost and accumulated depreciation and amortization of premises and equipment is as follows: December 31, Estimated 2020 2019 Useful Life (In thousands) (In years) Land and improvements $ 953 $ 953 Buildings and improvements 3,343 3,305 5 to 50 Leasehold improvements 2,236 2,231 3 to 10 Furniture and equipment 5,558 5,170 3 to 10 Construction-in-progress 145 82 12,235 11,741 Less accumulated depreciation and amortization (7,454 ) (5,993 ) $ 4,781 $ 5,748

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Summary of Deposit Balances by Type	A summary of deposit balances, by type, is as follows: December 31, 2020 2019 (In thousands) Demand deposits $ 96,731 $ 61,603 NOW accounts 53,530 39,043 Money market deposits 77,393 71,530 Regular and other savings accounts 185,481 126,876 Brokered deposits 10,056 10,167 Total non-certificate accounts 423,191 309,219 Term certificates less than $250,000 60,026 85,425 Term certificates of $250,000 or more 23,418 21,707 Term certificates - brokered 21,672 80,691 Total certificate accounts 105,116 187,823 $ 528,307 $ 497,042
Summary of Term Certificates, Including Brokered Deposits, by Maturity	A summary of term certificates, including brokered deposits, by maturity is as follows: December 31, 2020 December 31, 2019 Weighted Weighted Average Average Maturing during: Amount Rate Amount Rate (Dollars in thousands) 2020 $ — — % 140,987 1.92 % 2021 81,320 0.95 18,840 1.88 2022 20,122 1.46 25,610 2.12 2023 2,269 1.06 1,743 1.28 2024 781 1.15 643 1.32 2025 624 0.64 — — $ 105,116 1.05 % $ 187,823 1.94 %

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of Borrowings from FHLBB	A summary of borrowings from the FHLBB at December 31, 2020 and 2019 is as follows: 2020 2019 Weighted Weighted Average Average Amount Rate Amount Rate (Dollars in thousands) Fixed-rate advances maturing: 2020* $ — — % $ 22,476 1.80 % 2021* 21,895 1.27 11,927 1.86 2022 10,000 2.20 10,000 2.20 2023 - - — — 2024 - - — 2025 30,000 1.35 — $ 61,895 1.46 % $ 44,403 1.91 % * Includes amortizing advances which require monthly principal and interest payments.
Summary of Outstanding Balances of Short Term Borrowings from FHLBB	There were no overnight advances or advances having a one-month maturity at December 31, 2020. Included in FHLBB borrowings at December 31, 2019 are overnight advances and advances having a one-month maturity of $19.8 million. Selected information for such short-term borrowings for the years presented is as follows (in 000’s): 2020 2019 Average daily balance $ 2,265 $ 73,551 Maximum outstanding at any month end 16,181 128,283

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Allocation of Federal and State Income Taxes Between Current and Deferred Portions	Allocation of federal and state income taxes between current and deferred portions is as follows (in thousands): Years Ended December 31, 2020 2019 Current tax expense: Federal $ 789 $ — State 1,393 118 Total current tax expense 2,182 118 Deferred tax expense (benefit): Federal 4,174 723 State 887 226 5,061 949 Change in valuation allowance (1,766 ) (949 ) Total deferred tax expense (benefit) 3,295 — Total tax expense $ 5,477 $ 118
Summary of Differences Between Statutory Federal Income Tax Expense (Benefit) and Actual Tax Expense	The reasons for the differences between the statutory federal income tax expense (benefit) and the actual tax expense are summarized as follows (in thousands): Years Ended December 31, 2020 2019 Statutory federal tax rate of 21% $ 5,341 $ 745 Increase (decrease) resulting from: State taxes, net of federal tax effect 1,801 272 Bank-owned life insurance (38 ) (39 ) Tax-exempt income (6 ) (9 ) Change in valuation allowance (1,766 ) (949 ) Other, net 145 98 Total tax expense $ 5,477 $ 118
Summary of Components of Net Deferred Tax Asset	The components of the net deferred tax asset are as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Federal $ 2,962 $ 4,809 State 1,286 1,066 4,248 5,875 Valuation allowance (531 ) (2,297 ) 3,717 3,578 Deferred tax liabilities: Federal (4,837 ) (2,547 ) State (2,175 ) (1,031 ) (7,012 ) (3,578 ) Net deferred tax liability $ (3,295 ) $ —
Summary of Deferred Tax Assets (Liabilities)	The tax effects of items giving rise to deferred tax assets (liabilities) are as follows (in thousands): December 31, 2020 2019 Employee benefit plans $ 785 $ 714 Allowance for loan losses 2,071 1,203 Funded status of post-retirement benefits (47 ) (47 ) Securities available for sale (313 ) (313 ) Depreciation and amortization 144 279 Net deferred loan origination costs (281 ) (350 ) Mortgage servicing rights (3,479 ) (2,366 ) Net operating loss carryforward - 2,517 Charitable contribution carryforward 531 619 Derivatives (2,722 ) (377 ) Stock-based compensation 290 185 Other, net 257 233 (2,764 ) 2,297 Valuation allowance on net deferred tax assets (531 ) (2,297 ) Net deferred tax liability $ (3,295 ) $ —

Minimum Regulatory Capital Re_2

Minimum Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2020
Banking And Thrifts [Abstract]
Summary of Actual and Minimum Capital Amounts and Ratios Exclusive of Capital Conservation Buffer	The Bank’s actual and minimum capital amounts and ratios, exclusive of the capital conservation buffer, are presented in the following table: Minimum To Be Well For Minimum Capitalized Under Capital Prompt Corrective Actual Adequacy Purposes Action Provisions Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) December 31, 2020 Total capital (to risk weighted assets) $ 97,406 15.7 % $ 49,682 8.0 % $ 62,102 10.0 % Tier 1 capital (to risk weighted assets) 90,037 14.5 37,261 6.0 49,682 8.0 Common equity Tier 1 capital (to risk weighted assets) 90,037 14.5 27,946 4.5 40,366 6.5 Tier 1 capital (to average assets) 90,037 12.7 28,466 4.0 35,582 5.0 December 31, 2019 Total capital (to risk weighted assets) 76,652 16.7 36,637 8.0 45,796 10.0 Tier 1 capital (to risk weighted assets) 72,372 15.8 27,478 6.0 36,637 8.0 Common equity Tier 1 capital (to risk weighted assets) 72,372 15.8 20,608 4.5 29,768 6.5 Tier 1 capital (to average assets) 72,372 11.3 25,627 4.0 32,033 5.0

Post-retirement Plans (Tables)

Post-retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Summary of Information Pertaining to Activity in Plan	The Company has a master supplemental retirement plan (“Plan”) which covers certain officers and directors of the Company. In 2020 and 2019, the only active participants in the Plan were certain directors, as the Plan is frozen to new participants. Information pertaining to activity in the Plan follows: Years Ended December 31, 2020 2019 (In thousands) Change in plan assets: Fair value of plan assets at beginning of year $ — $ — Employer contributions 201 201 Benefits paid (201 ) (201 ) Fair value of plan assets at end of year — — Change in benefit obligation: Benefit obligation at beginning of year 1,506 1,561 Service cost 11 10 Interest cost 36 53 Actuarial (gain) loss 105 83 Benefits paid (201 ) (201 ) Benefit obligation at end of year 1,457 1,506 Unfunded status and accrued supplemental pension cost at year end $ (1,457 ) $ (1,506 ) Accumulated benefit obligation at year end $ 1,457 $ 1,506
Summary of Assumptions Used to Determine Benefit Obligation	The assumptions used to determine the benefit obligation are as follows: December 31, 2020 2019 Discount rate 1.25 % 2.50 % Annual inflation factor 1.00 % 1.00 % The following assumptions were used to determine the net periodic benefit cost for the years ended December 31, 2020 and 2019: 2020 2019 Discount rate 2.50 % 3.60 % Annual inflation factor 1.00 % 1.00 %
Summary of Net Periodic Benefit Cost Included in Salaries and Employee Benefits Expense	Net periodic benefit cost, included in other non-interest expenses, attributable to the Plan for the years ended December 31, 2020 and 2019, consists of the following: 2020 2019 (In thousands) Service cost $ 11 $ 10 Interest cost 36 53 Amortization of net actuarial loss 45 36 Amortization of prior service credit (57 ) (84 ) $ 35 $ 15
Summary of Estimated Future Benefit Payments Expected Future Services	Estimated future benefit payments, which reflect expected future services, as appropriate, are as follows: Years Ending December 31, Amount (In thousands) 2021 $ 199 2022 207 2023 358 2024 201 2025 197 2026-2030 239

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Grants of Options to Purchase Shares of Common Stock	The Company made the following grants of options to purchase shares of common stock during the years ended December 31, 2020 and 2019: 2020 2019 Options granted 333,118 57,252 Vesting period (years) 3 - 5 3 - 5 Expiration period (years) 10 10 Expected volatility 24.94% - 29.87% 26.14% - 29.09% Expected life (years) 6 - 6.5 6 - 6.5 Expected dividend yield — — Risk free interest rate 0.44%-1.47% 2.37% - 2.61% Option fair value $2.69 - $4.87 $2.99 - $5.83
Summary of Activity and Certain Other Information Related to Stock Options Grants Under 2017 Equity Plan and 2020 Inducement Plan	The following table presents the activity and certain other information related to stock option grants under the 2017 Equity Plan and the 2020 Inducement Plan for the year ended December 31, 2020: Options Stock Option Grants Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Balance at January 1, 2020 360,207 $ 14.82 7.01 $ — Granted 333,118 12.15 Forfeited (14,543 ) 15.34 Expired (91,614 ) 14.67 Balance at December 31, 2020 587,168 $ 13.32 8.40 $ 5,132,675 Exercisable at December 31, 2020 139,448 $ 14.85 6.95 $ 1,005,646 Unrecognized compensation cost (inclusive of directors' options) $ 1,456,227 Weighted average remaining recognition period (years) 2.96
Summary of Activity and Certain Other Information Related to Restricted Stock Awards Under Equity Plan	The following table presents the activity and certain other information related to restricted stock awards under the Equity Plan for the year ended December 31, 2020: Restricted Stock Awards Weighted Average Grant Price Restricted stock awards at January 1, 2020 125,861 $ 14.76 Granted 65,630 10.93 Vested (60,228 ) 14.70 Forfeited (9,251 ) 14.88 Non-vested stock awards at December 31, 2020 122,012 $ 12.72 Unrecognized compensation cost $ 1,344,170 Weighted average remaining recognition period (years) 3.42

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Calculation of Average Number of Shares Outstanding Used to Calculate Basic and Diluted Earnings Per Share	The following table sets forth the calculation of the average number of shares outstanding used to calculate the basic and diluted earnings per share for the periods indicated: 2020 2019 Average number of common shares outstanding 5,511,524 5,787,385 Less: Average unallocated ESOP shares (384,963 ) (403,768 ) Average number of common shares outstanding used to calculate basic earnings per share 5,126,561 5,383,617 Effect of dilutive stock options 36,481 — Average number of common shares outstanding used to calculate dilutive earnings per share 5,163,042 5,383,617

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rent Commitments	Pursuant to the terms of non-cancelable lease and sublease agreements in effect at December 31, 2020, future minimum rent commitments are as follows: Years Ending December 31, Leases Sub-lease Net (In thousands) 2021 $ 651 (91 ) $ 560 2022 334 (94 ) 240 2023 145 (16 ) 129 2024 91 — 91 2025 23 — 23 Thereafter — — — $ 1,244 $ (201 ) $ 1,043
Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk	At December 31, 2020 and 2019, the following financial instruments were outstanding whose contract amounts represent credit risk: 2020 2019 (In thousands) Commitments to originate loans $ 411,401 $ 117,086 Unused lines and letters of credit 71,458 52,721 Unadvanced funds on construction loans 9,110 11,029 Overdraft lines of credit 7,969 8,178

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	Assets and liabilities measured at fair value on a recurring basis are summarized below. . Total Level 1 Level 2 Level 3 Fair December 31, 2020 (In thousands) Assets: Securities available for sale $ — $ 55,366 $ — $ 55,366 Portfolio loans (fair value option) 13,780 — 13,780 Loans held for sale (fair value option) — 119,112 — 119,112 Derivative loan commitments — 11,821 — 11,821 Forward loan sale commitments — 44 — 44 Liabilities: Forward loan sale commitments, including TBAs — 2,180 — 2,180 December 31, 2019 Assets: Securities available for sale: Debt securities $ — $ 57,503 $ — $ 57,503 Portfolio loans (fair value option) — 9,826 — 9,826 Loans held for sale (fair value option) — 62,792 — 62,792 Derivative loan commitments — 1,472 — 1,472 Forward loan sale commitments — 11 — 11 Liabilities: Forward loan sale commitments, including TBAs — 140 — 140
Schedule of Assets Measured at Fair Value on a Non-Recurring Basis	The following table summarizes the fair value hierarchy used to determine each adjustment and the carrying value of the related assets and liabilities as of December 31, 2020 and 2019. The gains and losses represent the amounts recorded during 2020 and 2019 on the assets and liabilities held at year-end. There no liabilities recorded at fair value on a non-recurring basis as of December 31, 2020 and 2019. Year Ended December 31, 2020 December 31, 2020 Level 1 Level 2 Level 3 Total Assets: (In thousands) Collateral dependent impaired loans $ — $ — $ 6,318 $ — Mortgage servicing rights — 12,377 — (2,067 ) Foreclosed real estate — — 132 — $ — $ 12,377 $ 6,450 $ (2,067 ) Year Ended December 31, 2019 December 31, 2019 Level 1 Level 2 Level 3 Total Gains (Losses) (In thousands) Collateral dependent impaired loans $ — $ — $ 2,250 $ — Mortgage servicing rights — 8,556 — (920 ) $ — $ 8,556 $ 2,250 $ (920 )
Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments	The estimated fair values, and related carrying amounts, of the Company’s financial instruments are presented below. Certain financial instruments and all non-financial instruments are exempt from disclosure requirements. Accordingly, the aggregate fair value amounts presented herein do not represent the underlying fair value of the Company. This table excludes financial instruments for which the carrying amount approximates fair value. Financial assets for which the fair value approximates carrying value include cash and cash equivalents and accrued interest receivable. Financial liabilities for which the fair value approximates carrying value include mortgagor’s escrow accounts and accrued interest payable. December 31, 2020 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Securities available for sale 55,366 55,366 — 55,366 — Loans held for sale 119,112 119,112 — 119,112 — Loans, net 483,644 490,914 — — 490,914 Derivative assets 11,865 11,865 — 11,865 — Financial liabilities: Deposits $ 528,307 $ 528,786 $ — $ 528,786 $ — FRB advances 11,431 11,431 — 11,431 — FHLBB advances 61,895 63,071 — 63,071 — Derivative liabilities 2,180 2,180 — 2,180 — December 31, 2019 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 490 $ 492 $ — $ 492 $ — Securities available for sale 57,503 57,503 — 57,503 — Loans held for sale 62,792 62,792 — 62,792 — Loans, net 469,131 469,416 — — 469,416 Derivative assets 1,483 1,483 — 1,483 — Financial liabilities: Deposits $ 497,042 $ 496,979 $ — $ 496,979 $ — FHLBB advances 44,403 44,433 — 44,433 — Derivative liabilities 140 140 — 140 —

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Summary of Segment Information	Segment information as of and for the year ended December 31, 2020, follows: For the Year Ended December 31, 2020 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 16,235 $ 2,632 $ 18,867 Provision for loan losses 2,553 — 2,553 Net interest income after provision for loan losses 13,682 2,632 16,314 Non-interest income: Customer service fees 1,180 103 1,283 Gain on loan origination and sale activities, net (1) — 55,729 55,729 Mortgage servicing fees, net (381 ) (772 ) (1,153 ) Other 465 580 1,045 Total non-interest income 1,264 55,640 56,904 Non-interest expenses: Salaries and employee benefits 9,161 24,000 33,161 Occupancy and equipment 1,770 1,775 3,545 Other non-interest expenses 5,228 4,382 9,610 Total non-interest expenses 16,159 30,157 46,316 Income (loss) before income taxes and elimination of inter-segment profit $ (1,213 ) $ 28,115 26,902 Elimination of inter-segment profit (1,493 ) Income before income taxes 25,409 Income tax expense 5,477 Net income $ 19,932 Total assets, December 31, 2020 $ 537,722 $ 183,350 $ 721,072 (1) Before elimination of inter-segment profit Segment information as of and for the year ended December 31, 2019 follows: For the Year Ended December 31, 2019 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 15,985 $ 1,848 $ 17,833 Provision for loan losses — — — Net interest income after provision for loan losses 15,985 1,848 17,833 Non-interest income: Customer service fees 1,268 139 1,407 Gain on loan origination and sale activities, net (1) — 19,851 19,851 Mortgage servicing fees, net (363 ) 757 394 Other 596 366 962 Total non-interest income 1,501 21,113 22,614 Non-interest expenses: Salaries and employee benefits 7,065 17,831 24,896 Occupancy and equipment 1,527 1,256 2,783 Other non-interest expenses 4,789 3,482 8,271 Total non-interest expenses 13,381 22,569 35,950 Income before income taxes and elimination of inter-segment profit $ 4,105 $ 392 4,497 Elimination of inter-segment profit (951 ) Income before income taxes 3,546 Income tax expense 118 Net income $ 3,428 Total assets, December 31, 2019 $ 521,144 $ 109,860 $ 631,004 (1) Before elimination of inter-segment profit

Other Non-Interest Expenses (Ta

Other Non-Interest Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Other Income And Expenses [Abstract]
Schedule of Company's Total Interest and Non-Interest Income Included in Other Non-Interest Expenses	Included in other non-interest expenses in 2020 and 2019 are certain items exceeding 1% of the Company’s total interest and non-interest income as follows: 2020 2019 (In thousands) Software amortization, licenses and maintenance $ 1,303 $ 1,017 Card related expenses 429 459 Data communication and telephone 391 418 Directors fees, including stock-based compensation 579 586

Global Pandemic Affecting Ran_2

Global Pandemic Affecting Randolph Bancorp, Inc. (Tables)	12 Months Ended
	Dec. 31, 2020
Risks And Uncertainties [Abstract]
Summary of Loan Portfolio	A summary of the loan portfolio is as follows: December 31, 2020 2019 (In thousands) Mortgage loans on real estate: Residential: One-to four-family $ 235,648 $ 244,711 Home equity loans and lines of credit 48,166 41,669 Commercial 143,893 125,405 Construction 31,050 35,485 458,757 447,270 Commercial and industrial 20,259 9,093 Consumer 10,289 15,641 Total loans 489,305 472,004 Allowance for loan losses (6,784 ) (4,280 ) Net deferred loan costs and fees, and purchase premiums 1,123 1,407 $ 483,644 $ 469,131 The table below summarizes the status of the bank’s loan deferral activity at December 31, 2020: Deferrals Suspended/ Resumed Full Granted Reduced Payment Payment Payoff (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 15,514 $ 12,974 $ 2,109 $ 431 Home equity loans and lines of credit 3,179 626 1,287 1,266 Construction 350 350 - - Commercial 34,754 6,544 25,406 2,804 Total real estate loans 53,797 20,494 28,802 4,501 Commercial and industrial 3,645 - 1,635 2,010 Consumer 68 68 - - Total $ 57,510 $ 20,562 $ 30,437 $ 6,511
Schedule of Past Due and Non-Accrual Loans by Loan Category	The following table presents past due and non-accrual loans, by loan category, at December 31, 2020 and 2019: 30 - 59 Days Past Due 60 - 89 Days Past Due 90 Days or More Past Due Total Past Due (1) Non-accrual Loans (In thousands) December 31, 2020 Residential one-to four-family $ — $ — $ — $ — $ 1,876 Home equity loans and lines of credit 95 — 317 412 584 Commercial real estate — — 26 26 4,713 Construction — — — — — Commercial and industrial — — — — — Consumer 38 64 — 102 — Total $ 133 $ 64 $ 343 $ 540 $ 7,173 December 31, 2019 Residential one-to four-family $ 215 $ 587 $ — $ 802 $ 2,922 Home equity loans and lines of credit 188 244 — 432 336 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer 76 11 — 87 — Total $ 479 $ 842 $ — $ 1,321 $ 3,258 (1) Excludes non-accrual loans which are separately presented. Accordingly, the table below summarizes the risk rating and for all loans that were granted deferral, and any loans that were listed in nonaccrual status at December 31, 2020: Pass Rated / Special Sub- Non- Not Rated Mention standard accrual (1) (In thousands) December 31, 2020 Real estate loans: Residential: One-to-four family $ 14,887 $ 196 $ - $ 196 Home equity loans and lines of credit 1,913 - - - Construction 350 - - Commercial 19,020 8,748 4,182 4,182 Total real estate loans 36,170 8,944 4,182 4,378 Commercial and industrial 1,204 431 - - Consumer 68 - - - Total $ 37,442 $ 9,375 $ 4,182 $ 4,378 (1) Nonaccrual loans are risk rated as either special mention or substandard and are included as a balance in those columns.

Parent Company Condensed Fina_2

Parent Company Condensed Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Balance Sheets	Financial information as of December 31, 2020 and 2019 and for the years then ended pertaining to Randolph Bancorp, Inc. is as follows: BALANCE SHEETS December 31, December 31, 2020 2019 Assets Cash and due from bank $ 4,829 $ 1,445 Investment in Envision Bank 90,959 72,872 ESOP loan 4,042 4,162 Total assets $ 99,830 $ 78,479 Liabilities Income taxes payable $ 8 $ — Due to Envision Bank 3 17 Total liabilities 11 17 Stockholders' Equity Common stock 54 56 Additional paid-in capital 50,937 51,127 Retained earnings 51,689 31,757 ESOP-Unearned compensation (3,756 ) (3,944 ) Accumulated other comprehensive loss, net of tax 895 (534 ) Total stockholders' equity 99,819 78,462 Total liabilities and stockholders' equity $ 99,830 $ 78,479
Statements of Operations	STATEMENTS OF OPERATIONS Years Ended December 31, 2020 2019 Interest income $ 198 $ 235 Dividend income 5,000 - Operating expenses 171 194 Income before incomes taxes and equity in undistributed net income of Envision Bank 5,027 41 Applicable income taxes 7 3 Income before equity in undistributed net income of Envision Bank 5,020 38 Equity in undistributed net income of Envision Bank 14,912 3,390 Net income $ 19,932 $ 3,428
Statements of Cash Flows	STATEMENTS OF CASH FLOWS Years Ended December 31, 2020 2019 Cash flows from operating activities: Net income $ 19,932 $ 3,428 Adjustments to reconcile net income to net cash provided by (used in) operating activities: Equity in undistributed net income of Envision Bank (14,912 ) (3,390 ) Dividends received from Envision Bank (5,000 ) — Change in income taxes payable 8 — Change in intercompany receivable/payable (15 ) (39 ) Net cash provided by (used in) operating activities 13 (1 ) Cash flows from investing activities: Principal payments received on ESOP loan 120 104 Dividends received from Envision Bank 5,000 — Net cash provided by investing activities 5,120 104 Cash flows from financing activities: Stock repurchases (1,749 ) (5,438 ) Stock repurchase payable — (70 ) Net cash used in financing activities (1,749 ) (5,508 ) Net change in cash and due from bank 3,384 (5,405 ) Cash and due from bank at the beginning of year 1,445 6,850 Cash and due from bank at end of year $ 4,829 $ 1,445

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Quarterly Financial Data	First Quarter Second Quarter Third Quarter Fourth Quarter 2020 2019 2020 2019 2020 2019 2020 2019 (Dollars in thousands, except per share data) Interest and dividend income $ 6,053 $ 6,016 $ 6,059 $ 6,454 $ 5,648 $ 6,541 $ 5,828 $ 6,220 Interest expense 1,628 1,638 1,326 1,965 979 1,968 788 1,827 Net interest and dividend income 4,425 4,378 4,733 4,489 4,669 4,573 5,040 4,393 Provision (credit) for loan losses 724 — 1,068 (144 ) 546 — 215 144 Customer service fees 306 329 266 362 330 363 381 353 Gain on loan origination and sale activities, net 7,144 2,588 14,370 5,068 18,102 5,782 14,620 5,462 Mortgage servicing fees, net (1,254 ) 319 (1,354 ) 224 1,180 (181 ) 275 32 Gain on sales/calls of securities and impairment write-down, net — — — — — — — 16 Increase in cash surrender value of life insurance 45 45 45 48 46 45 45 47 Other 210 132 172 153 216 294 266 182 Total non-interest income 6,451 3,413 13,499 5,855 19,874 6,303 15,587 6,092 Total non-interest expense 10,959 7,878 11,379 8,863 11,051 9,718 12,927 9,491 Provision (benefit) for income taxes 11 (36 ) 594 119 2,661 14 2,211 21 Net income (loss) $ (818 ) $ (51 ) $ 5,191 $ 1,506 $ 10,285 $ 1,144 $ 5,274 $ 829 Basic earnings (loss) per share $ (0.16 ) $ (0.01 ) $ 1.02 $ 0.28 $ 2.01 $ 0.21 $ 1.03 $ 0.16 Diluted earnings (loss) per share $ (0.16 ) $ (0.01 ) $ 1.02 $ 0.28 $ 2.01 $ 0.21 $ 1.01 $ 0.16 Weighted average common shares (basic) 5,158,294 5,478,544 5,092,490 5,465,205 5,120,367 5,345,786 5,135,069 5,248,021 Weighted average common shares (diluted) 5,158,294 5,478,544 5,092,490 5,465,205 5,120,367 5,345,786 5,244,414 5,248,021

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)LoanSegment	Dec. 31, 2019USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents maturity period	90 days
Time period to capture relevant loan loss data	48 months
Number of PPP Loan Funded | Loan	197
Total PPP Loan Funded	$ 15,400,000
Outstanding PPP Loan	$ 10,900,000
Obligation to repurchase mortgage loans prescribed time period	4 months
Description of tax benefit	A tax position is recognized as a benefit if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded.
Uncertain tax positions	$ 0	$ 0
Interest or penalties	$ 0	$ 0
Number of business segments | Segment	2
Supplemental Retirement Plan [Member]
Summary Of Significant Accounting Policies [Line Items]
Prior service credits	$ 45,000
Net actuarial losses	$ 62,000
Consumer Loans or Second Mortgages and HELOCs [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment disclosure requirement	Unless such loans are 90 days past due or are classified as a troubled debt restructuring.
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
FDIC insurance coverage limit	$ 250,000
Certificates of deposit maturity period	5 years
Maximum [Member] | Residential One-to-Four Family Real Estate Portfolio Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Loan-to-value ratio	80.00%
Maximum [Member] | Second Mortgages and Home Equity Lines of Credit Property Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Loan-to-value ratio	80.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Certificates of deposit maturity period	1 year
Percentage of tax benefit that likely of being realized on examination with taxing authority	50.00%

Basis of Presentation and Sum_5

Basis of Presentation and Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Loss (AOCI) and Related Tax Effects (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Total other comprehensive income	$ 1,429	$ 1,370
Accumulated other comprehensive income (loss), net of tax	895	(534)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	1,713	167
Other comprehensive Loss, Tax effect	(313)	(313)
Total other comprehensive income	1,400	(146)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	(712)	(652)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	254	311
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	(458)	(341)
Other comprehensive Loss, Tax effect	(47)	(47)
Total other comprehensive income	$ (505)	$ (388)

Securities Available for Sale -

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 53,654	$ 57,336
Gross Unrealized Gains	1,712	535
Gross Unrealized Losses		(368)
Fair Value	55,366	57,503
Debt Securities [Member] | US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,993	4,000
Gross Unrealized Gains	3	13
Gross Unrealized Losses		(1)
Fair Value	1,996	4,012
Debt Securities [Member] | Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,300	1,513
Gross Unrealized Gains	56	15
Fair Value	4,356	1,528
Debt Securities [Member] | Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	595	744
Gross Unrealized Gains	5	9
Fair Value	600	753
Debt Securities [Member] | Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,538	35,238
Gross Unrealized Gains	919	458
Gross Unrealized Losses		(286)
Fair Value	33,457	35,410
Debt Securities [Member] | Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,857	8,977
Gross Unrealized Gains	525
Gross Unrealized Losses		(53)
Fair Value	9,382	8,924
Debt Securities [Member] | Commercial Mortgage Backed Securities, U.S. Government-guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	977	1,363
Gross Unrealized Gains	24	7
Fair Value	1,001	1,370
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	996	1,395
Gross Unrealized Gains	52	23
Fair Value	1,048	1,418
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,398	4,106
Gross Unrealized Gains	128	10
Gross Unrealized Losses		(28)
Fair Value	$ 3,526	$ 4,088

Securities Available for Sale_2

Securities Available for Sale - Investments Classified by Contractual Maturity Date (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Available-for-sale Securities, Debt Maturities, Amortized Cost
Within 1 year	$ 503
After 1 year through 5 years	5,315
After 5 years through 10 years	1,070
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total	6,888
Mortgage-backed securities and collateralized mortgage obligations	46,766
Available-for-sale Debt Securities, Amortized Cost Basis, Total	53,654
Available-for-sale Securities, Debt Maturities, Fair Value
Within 1 year	507
After 1 year through 5 years	5,347
After 5 years through 10 years	1,098
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Fair Value Total	6,952
Mortgage-backed securities and collateralized mortgage obligations	48,414
Available-for-sale Securities, Debt Securities, Fair Value Total	$ 55,366

Securities Available for Sale_3

Securities Available for Sale - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)Debt_Security	Dec. 31, 2019USD ($)
Schedule of Available-for-sale Securities [Line Items]
Fair value of investment securities pledged as collateral	$ 1,958,000	$ 2,013,000
Securities in loss position	$ 0
Number of debt securities with unrealized losses | Debt_Security	0
Proceeds from sales of available-for-sale securities	$ 0	534,000
Available-for-sale securities, gross realized gains		16,000
Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities on equity	$ 0	$ 0

Securities Available for Sale_4

Securities Available for Sale - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Detail) - Debt Securities [Member] $ in Thousands	Dec. 31, 2019USD ($)
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	$ (191)
Less Than Twelve Months, Fair Value	22,071
Over Twelve Months, Gross Unrealized Losses	(177)
Over Twelve Months, Fair Value	12,514
US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Over Twelve Months, Gross Unrealized Losses	(1)
Over Twelve Months, Fair Value	1,999
Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(123)
Less Than Twelve Months, Fair Value	11,256
Over Twelve Months, Gross Unrealized Losses	(163)
Over Twelve Months, Fair Value	9,632
Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(53)
Less Than Twelve Months, Fair Value	8,924
Collateralized Mortgage Obligations, US Government Guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(15)
Less Than Twelve Months, Fair Value	1,891
Over Twelve Months, Gross Unrealized Losses	(13)
Over Twelve Months, Fair Value	$ 883

Loans - Summary of Loan Portfol

Loans - Summary of Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 489,305	$ 472,004
Allowance for loan losses	(6,784)	(4,280)
Net deferred loan costs and fees, and purchase premiums	1,123	1,407
Loans, net	483,644	469,131
Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	458,757	447,270
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	143,893	125,405
Commercial Real Estate Loans [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	143,893	125,405
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,259	9,093
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,289	15,641
One-to-Four Family [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	235,648	244,711
One-to-Four Family [Member] | Residential Real Estate [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	235,648	244,711
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	48,166	41,669
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	31,050	35,485
Construction [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 31,050	$ 35,485

Loans - Additional Information

Loans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)TDR	Dec. 31, 2019USD ($)TDR
Accounts, Notes, Loans and Financing Receivable [Line Items]
Servicing loans for participants	$ 2,410,000	$ 5,283,000
Impaired loans, additional funds committed	$ 0
Loans subject to troubled debt restructurings | TDR	1	6
Troubled debt restructuring amount	$ 1,749,000	$ 3,706,000
Allowances related to troubled debt restructurings	$ 133,000	116,000
Minimum past due days for loan rating	90 days
Total loans	$ 489,305,000	472,004,000
Consumer Loans [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		2,925,000
Consumer Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		336,000
Residential Mortgage [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,072,000	1,239,000
Residential Mortgage [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	803,000
30 - 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans, additional funds committed	0
Troubled debt restructurings defaulted over 30 days past due	$ 0	$ 0
Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR	1
Loans subject to troubled debt restructurings, amount	$ 42,000
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR	16	18
Loans subject to troubled debt restructurings, amount	$ 2,833,000	$ 3,616,000
Residential Real Estate [Member] | Payment Deferral [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt restructurings that were granted payment deferral plans | TDR	2
Residential Real Estate [Member] | Performing Financial Instruments [Member] | Payment Deferral [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings, amount	$ 298,000
Residential Real Estate [Member] | Nonperforming Financial Instruments [Member] | Payment Deferral [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings, amount	$ 196,000
Residential Real Estate [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, interest rate concession period	3 months
Residential Real Estate [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, interest rate concession period	30 years
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR	1	1
Loans subject to troubled debt restructurings, amount	$ 40,000	$ 44,000
Total loans	143,893,000	125,405,000
Commercial Real Estate Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,711,000
Commercial Real Estate Loans [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,257,000	$ 3,702,000
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR		1
Loans subject to troubled debt restructurings, amount		$ 46,000
Total loans	$ 10,289,000	$ 15,641,000

Loans - Summary of Activity in

Loans - Summary of Activity in the Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				$ 4,280			$ 4,280	$ 4,437
Provision (credit) for loan losses	$ 215	$ 546	$ 1,068	724	$ 144	$ (144)	2,553
Loans charged-off							(71)	(192)
Recoveries							22	35
Ending balance	6,784				4,280		6,784	4,280
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				1,840			1,840	1,648
Provision (credit) for loan losses							1,562	192
Ending balance	3,402				1,840		3,402	1,840
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				235			235	265
Provision (credit) for loan losses							179	(30)
Recoveries							2
Ending balance	416				235		416	235
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				128			128	375
Provision (credit) for loan losses							54	(65)
Loans charged-off							(68)	(192)
Recoveries							13	10
Ending balance	127				128		127	128
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				1,096			1,096	1,092
Provision (credit) for loan losses							543	(21)
Recoveries							7	25
Ending balance	1,646				1,096		1,646	1,096
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				289			289	292
Provision (credit) for loan losses							156	(3)
Loans charged-off							(3)
Ending balance	442				289		442	289
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				$ 692			692	765
Provision (credit) for loan losses							59	(73)
Ending balance	$ 751				$ 692		$ 751	$ 692

Loans - Summary of Additional I

Loans - Summary of Additional Information Pertaining to the Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	$ 133	$ 116
Allowance for non-impaired loans	6,651	4,164
Total allowance for loan losses	6,784	4,280	$ 4,437
Impaired loans	8,949	6,093
Non-impaired loans	480,356	465,911
Total loans	489,305	472,004
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	3,402	1,840
Total allowance for loan losses	3,402	1,840	1,648
Impaired loans	4,751	46
Non-impaired loans	139,142	125,359
Total loans	143,893	125,405
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	416	235
Total allowance for loan losses	416	235	265
Non-impaired loans	20,259	9,093
Total loans	20,259	9,093
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	127	128
Total allowance for loan losses	127	128	375
Non-impaired loans	10,289	15,641
Total loans	10,289	15,641
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	133	116
Allowance for non-impaired loans	1,513	980
Total allowance for loan losses	1,646	1,096	1,092
Impaired loans	3,575	5,640
Non-impaired loans	232,073	239,071
Total loans	235,648	244,711
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	442	289
Total allowance for loan losses	442	289	292
Impaired loans	623	407
Non-impaired loans	47,543	41,262
Total loans	48,166	41,669
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	751	692
Total allowance for loan losses	751	692	$ 765
Non-impaired loans	31,050	35,485
Total loans	$ 31,050	$ 35,485

Loans - Summary of Additional_2

Loans - Summary of Additional Information Pertaining to the Allowance for Loan Losses (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-impaired loans	$ 480,356	$ 465,911
PPP Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-impaired loans	$ 10,900	$ 10,900

Loans - Schedule of Past Due an

Loans - Schedule of Past Due and Non-Accrual Loans by Loan Category (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 540	$ 1,321
Non-accrual Loans	7,173	3,258
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	102	87
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		802
Non-accrual Loans	1,876	2,922
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	412	432
Non-accrual Loans	584	336
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	26
Non-accrual Loans	4,713
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	133	479
30 - 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38	76
30 - 59 Days Past Due [Member] | One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		215
30 - 59 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	95	188
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	64	842
60 - 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	64	11
60 - 89 Days Past Due [Member] | One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		587
60 - 89 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 244
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	343
90 Days or More Past Due [Member] | Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	317
90 Days or More Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 26

Loans - Summary of Impaired Loa

Loans - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	$ 7,539	$ 3,775
Unpaid Principal Balance without a valuation allowance	7,555	3,775
Recorded Investment with a valuation allowance		2,318
Unpaid Principal Balance with a valuation allowance		2,318
Related Allowance, Total impaired loans	133	116
Recorded Investment, Total impaired loans	8,921	6,093
Unpaid Principal Balance, Total impaired loans	8,949	6,093
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	4,753	46
Unpaid Principal Balance without a valuation allowance	4,751	46
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	2,160	3,322
Unpaid Principal Balance without a valuation allowance	2,181	3,322
Recorded Investment with a valuation allowance	1,382	2,318
Unpaid Principal Balance with a valuation allowance	1,394	2,318
Related Allowance, Total impaired loans	133	116
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	626	407
Unpaid Principal Balance without a valuation allowance	$ 623	$ 407

Loans - Summary of Information

Loans - Summary of Information Related to Average Balances of Impaired Loans and Interest Income Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 6,976	$ 6,185
Interest Income Recognized	467	252
Cash Basis Interest Recognized	159	97
Residential Real Estate [Member] | One-to-Four Family [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,550	5,594
Interest Income Recognized	399	236
Cash Basis Interest Recognized	159	87
Residential Real Estate [Member] | Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	588	424
Interest Income Recognized	60	11
Cash Basis Interest Recognized		10
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,838	132
Interest Income Recognized	$ 8	4
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		35
Interest Income Recognized		$ 1

Loans - Summary of Company's Lo

Loans - Summary of Company's Loans by Risk Rating (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 489,305	$ 472,004
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	31,050	35,485
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	143,893	125,405
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	20,259	9,093
Pass [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	31,050	35,485
Pass [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	129,925	121,703
Pass [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	19,828	8,134
Special Mention [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,257	3,702
Special Mention [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	431	206
Substandard [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 4,711
Substandard [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans		$ 753

Loan Servicing - Additional Inf

Loan Servicing - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Servicing Assets At Amortized Value [Line Items]
Unpaid principal balances of residential mortgage loans serviced for others	$ 1,760,306,000	$ 1,049,807,000
Custodial Escrow balances	14,200,000	8,900,000
Increase (reduced) the valuation allowance of mortgage servicing rights	2,067,000	920,000
Contractually specified servicing fees, net	$ 3,458,000	$ 2,585,000
Measurement Input, Discount Rate [Member]
Servicing Assets At Amortized Value [Line Items]
Discount rate	0.12	0.12
Measurement Input, Constant Prepayment Rate [Member] | Minimum [Member]
Servicing Assets At Amortized Value [Line Items]
Discount rate	0.19	0.09
Measurement Input, Constant Prepayment Rate [Member] | Maximum [Member]
Servicing Assets At Amortized Value [Line Items]
Discount rate	0.27	0.14

Loan Servicing - Summary of Act

Loan Servicing - Summary of Activity Relating to Mortgage Servicing Rights (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Mortgage servicing rights:
Balance at beginning of year	$ 9,484	$ 7,786
Additions through originations	8,432	2,979
Amortization	(2,544)	(1,281)
Balance at end of year	15,372	9,484
Valuation allowance:
Balance at beginning of year	928	8
Provision (credit)	2,067	920
Balance at end of year	2,995	928
Mortgage servicing rights, amortized cost	12,377	8,556
Mortgage servicing rights, fair value	$ 12,490	$ 8,817

Premises and Equipment - Summar

Premises and Equipment - Summary of Cost and Accumulated Depreciation and Amortization of Premises and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Land and improvements	$ 953	$ 953
Buildings and improvements	3,343	3,305
Leasehold improvements	2,236	2,231
Furniture and equipment	5,558	5,170
Construction-in-progress	145	82
Property plant and equipment, gross	12,235	11,741
Less accumulated depreciation and amortization	(7,454)	(5,993)
Property plant and equipment, net	$ 4,781	$ 5,748
Buildings and Improvements [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	5 years
Buildings and Improvements [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	50 years
Leasehold Improvements [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Leasehold Improvements [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	10 years
Furniture and Equipment [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Furniture and Equipment [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	10 years

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) - USD ($)	Jul. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Depreciation and amortization expense		$ 1,508,000	$ 857,000
Leasehold improvements funded by landlord				$ 646,000
Leasehold improvements allowance amortized period				5 years
Tenant improvement allowance amortized period				5 years
Percentage of land occupied under sublease agreement	27.00%
Termination of lease	2023
Consolidation of Mortgage Banking Operations [Member] | Andover [Member]
Property Plant And Equipment [Line Items]
Fair value, Cease use liability					$ 565,000
Consolidation of Mortgage Banking Operations [Member] | Salem, New Hampshire [Member]
Property Plant And Equipment [Line Items]
Fair value, Cease use liability		$ 294,000

Deposits - Summary of Deposit B

Deposits - Summary of Deposit Balances by Type (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Demand deposits	$ 96,731	$ 61,603
NOW accounts	53,530	39,043
Money market deposits	77,393	71,530
Regular and other savings accounts	185,481	126,876
Brokered deposits	10,056	10,167
Total non-certificate accounts	423,191	309,219
Term certificates less than $250,000	60,026	85,425
Term certificates of $250,000 or more	23,418	21,707
Term certificates - brokered	21,672	80,691
Total certificate accounts	105,116	187,823
Total deposits	$ 528,307	$ 497,042

Deposits - Summary of Term Cert

Deposits - Summary of Term Certificates, Including Brokered Deposits, by Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amount
2020		$ 140,987
2021	$ 81,320	18,840
2022	20,122	25,610
2023	2,269	1,743
2024	781	643
2025	624
Total certificate accounts	$ 105,116	$ 187,823
Weighted Average Rate
2020		1.92%
2021	0.95%	1.88%
2022	1.46%	2.12%
2023	1.06%	1.28%
2024	1.15%	1.32%
2025	0.64%
Total	1.05%	1.94%

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings from FHLBB (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fixed-rate advances maturing:
2020*		$ 22,476
2021	$ 21,895	11,927
2022	10,000	10,000
2025	30,000
Advances From Federal Home Loan Banks	$ 61,895	$ 44,403
Weighted Average Rate
2020*		1.80%
2021	1.27%	1.86%
2022	2.20%	2.20%
2025	1.35%
Advances from FHLBB, Weighted Average Rate	1.46%	1.91%

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Overnight advances of FHLBB borrowings	$ 0	$ 19,800,000
Federal Home Loan Bank advances	$ 61,895,000	44,403,000
Interest Rate at Period End	0.35%
Paycheck Protection Program [Member]
Debt Instrument [Line Items]
outstanding advances	$ 11,400,000
Correspondent Bank [Member]
Debt Instrument [Line Items]
Available borrowing capacity		7,500,000
Federal Home Loan Bank advances	$ 0	0
FHLBB [Member]
Debt Instrument [Line Items]
Percentage on carrying value of first mortgage loans pledged as collateral	75.00%
Available borrowing capacity	$ 93,900,000
FHLBB [Member] | Commercial Real Estate Loans [Member]
Debt Instrument [Line Items]
Percentage on carrying value of first mortgage loans pledged as collateral	65.00%
FHLBB With Interest Rate Adjusts Daily [Member]
Debt Instrument [Line Items]
Available borrowing capacity	$ 4,195,000
Federal Home Loan Bank advances	$ 0	0
FHLBB With Interest Rate Adjusts Daily [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage on total assets for borrowings under line of credit	2.00%
Federal Reserve Bank of Boston [Member]
Debt Instrument [Line Items]
Available borrowing capacity	$ 2,000,000
Federal Home Loan Bank advances	0	$ 0
Two Thousand And Twenty Two Maturity [Member] | Paycheck Protection Program [Member]
Debt Instrument [Line Items]
outstanding advances	11,200,000
Two Thousand And Twenty Five Maturity [Member] | Paycheck Protection Program [Member]
Debt Instrument [Line Items]
outstanding advances	$ 225,000

Borrowings - Summary of Outstan

Borrowings - Summary of Outstanding Balances of Short Term Borrowings from FHLBB (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank Advances Activity For Year [Abstract]
Average daily balance	$ 2,265,000	$ 73,551,000
Maximum outstanding at any month end	$ 16,181,000	$ 128,283,000

Income Taxes - Allocation of Fe

Income Taxes - Allocation of Federal and State Income Taxes Between Current and Deferred Portions (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Current tax expense:
Federal									$ 789
State									1,393	$ 118
Total current tax expense									2,182	118
Deferred tax expense (benefit):
Federal									4,174	723
State									887	226
Total deferred federal and state tax expense (benefit)									5,061	949
Change in valuation allowance									(1,766)	(949)
Total deferred tax expense (benefit)									3,295
Total tax expense	$ 2,211	$ 2,661	$ 594	$ 11	$ 21	$ 14	$ 119	$ (36)	$ 5,477	$ 118

Income Taxes - Summary of Diffe

Income Taxes - Summary of Differences Between Statutory Federal Income Tax Expense (Benefit) and Actual Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Statutory federal tax rate of 21%									$ 5,341	$ 745
Increase (decrease) resulting from:
State taxes, net of federal tax effect									1,801	272
Bank-owned life insurance									(38)	(39)
Tax-exempt income									(6)	(9)
Change in valuation allowance									(1,766)	(949)
Other, net									145	98
Total tax expense	$ 2,211	$ 2,661	$ 594	$ 11	$ 21	$ 14	$ 119	$ (36)	$ 5,477	$ 118

Income Taxes - Summary of Dif_2

Income Taxes - Summary of Differences Between Statutory Federal Income Tax Expense (Benefit) and Actual Tax Expense (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory federal tax rate	21.00%	21.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax [Line Items]
Alternative minimum tax refundable period	4 years
Income tax refund received		$ 231,000
Valuation allowance for deferred tax assets	100.00%
Charitable contribution carryforward	$ 531,000
Federal income tax reserve for loan losses	$ 2,033,000
Percentage of tax reserve for loan losses used for purpose other than to absorb losses subject to taxation	150.00%
Deferred income tax liability not been provided	$ 571,000
Deferred Tax Assets Charitable Contribution Carryforward Expires on December 31, 2021 [Member]
Income Tax [Line Items]
Charitable contribution carryforward	$ 77,000
Charitable contributions carryforward expiration years	Dec. 31, 2021
Other Assets [Member]
Income Tax [Line Items]
Income tax refund received	$ 231,000

Income Taxes - Summary of Compo

Income Taxes - Summary of Components of Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Deferred tax assets, gross	$ 4,248	$ 5,875
Valuation allowance	(531)	(2,297)
Deferred tax assets, net	3,717	3,578
Deferred tax liabilities:
Deferred tax liabilities, gross	(7,012)	(3,578)
Net deferred tax liability	(3,295)
Federal [Member]
Deferred tax assets:
Deferred tax assets, gross	2,962	4,809
Deferred tax liabilities:
Deferred tax liabilities, gross	(4,837)	(2,547)
State [Member]
Deferred tax assets:
Deferred tax assets, gross	1,286	1,066
Deferred tax liabilities:
Deferred tax liabilities, gross	$ (2,175)	$ (1,031)

Income Taxes - Summary of Defer

Income Taxes - Summary of Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Employee benefit plans	$ 785	$ 714
Allowance for loan losses	2,071	1,203
Funded status of post-retirement benefits	(47)	(47)
Securities available for sale	(313)	(313)
Depreciation and amortization	144	279
Net deferred loan origination costs	(281)	(350)
Mortgage servicing rights	(3,479)	(2,366)
Net operating loss carryforward		2,517
Charitable contribution carryforward	531	619
Derivatives	(2,722)	(377)
Stock-based compensation	290	185
Other, net	257	233
Deferred tax assets (liabilities) before valuation allowances	(2,764)	2,297
Valuation allowance on net deferred tax assets	(531)	$ (2,297)
Net deferred tax liability	$ (3,295)

On-Balance Sheet Derivative I_2

On-Balance Sheet Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative, Notional amount	$ 396,551,000	$ 89,925,000
Derivative Loan Commitments [Member] | Net Gain on Sales of Mortgage Loans [Member]
Derivative [Line Items]
Increase (reductions) in aggregate fair value on derivatives, interest rate lock commitments	10,349,000	845,000
Undesignated Forward Loan Sale Commitments and TBA Securities [Member]
Derivative [Line Items]
Derivative, Notional amount	390,248,000	85,401,000
Undesignated Forward Loan Sale Commitments and TBA Securities [Member] | Net Gain on Sales of Mortgage Loans [Member]
Derivative [Line Items]
Increase (reductions) in aggregate fair value on derivatives, interest rate lock commitments	2,007,000	(124,000)
Other Assets [Member] | Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative fair value, Asset	11,821,000	1,472,000
Other Assets [Member] | Undesignated Forward Loan Sale Commitments and TBA Securities [Member]
Derivative [Line Items]
Derivative fair value, Asset	44,000	11,000
Other Liabilities [Member] | Undesignated Forward Loan Sale Commitments and TBA Securities [Member]
Derivative [Line Items]
Derivative fair value, Liability	$ 2,180,000	$ 140,000

Minimum Regulatory Capital Re_3

Minimum Regulatory Capital Requirements - Additional Information (Detail)	Dec. 31, 2020
Minimum [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Capital conservation buffer of common equity tier 1 capital to risk weighted assets ratio (as a percent)	0.025

Minimum Regulatory Capital Re_4

Minimum Regulatory Capital Requirements - Summary of Actual and Minimum Capital Amounts and Ratios Exclusive of Capital Conservation Buffer (Detail) - Bank [Member] $ in Thousands	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk weighted assets), actual amount	$ 97,406	$ 76,652
Tier 1 capital (to risk weighted assets), actual amount	90,037	72,372
Common equity Tier 1 capital (to risk weighted assets), actual amount	90,037	72,372
Tier 1 capital (to average assets), actual amount	$ 90,037	$ 72,372
Total capital (to risk weighted assets), actual ratio	0.157	0.167
Tier 1 capital (to risk weighted assets), actual ratio	0.145	0.158
Common equity Tier 1 capital (to risk weighted assets), actual ratio	14.50%	15.80%
Tier 1 capital (to average assets), actual ratio	0.127	0.113
Total capital (to risk weighted assets), for minimum capital adequacy purposes amount	$ 49,682	$ 36,637
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes amount	37,261	27,478
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	27,946	20,608
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	$ 28,466	$ 25,627
Total capital (to risk weighted assets), for minimum capital adequacy purposes ratio	0.080	0.080
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	0.060	0.060
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	4.50%	4.50%
Tier 1 capital (to average assets), for minimum capital adequacy purposes ratio	0.040	0.040
Total capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	$ 62,102	$ 45,796
Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	49,682	36,637
Common equity Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	40,366	29,768
Tier 1 capital (to average assets), minimum to be well capitalized under prompt corrective action provisions amount	$ 35,582	$ 32,033
Total capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	0.100	0.100
Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	0.080	0.080
Common equity Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	6.50%	6.50%
Tier 1 capital (to average assets), minimum to be well capitalized under prompt corrective action provisions ratio	0.050	0.050

Post-Retirement Plans - Additio

Post-Retirement Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Other non-interest expense	$ 6,514,000	$ 5,141,000
Supplemental Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefits	453,000	507,000
Other non-interest expense	65,000	51,000
Endorsement Split-Dollar Life Insurance Arrangements [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefits	472,000	451,000
Post-retirement benefit expense	$ 20,000	19,000
401(k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Description of employees eligibility	The Company maintains a 401(k) Plan whereby each employee reaching the age of 21 automatically becomes a participant in the plan.  Employees may contribute up to 15% of their compensation subject to certain limits based on federal tax laws. All employees who have worked for one year or 1,000 hours are eligible for an automatic employer contribution of 3% of employees’ compensation, which requires no vesting period.
Minimum age of employee to become participant	21 years
Maximum annual contributions per employee, percent	15.00%
Minimum number of year worked by employees	1 year
Minimum number of hours worked by employees	1000 hours
Employer contribution percentage on employees compensation	3.00%
Automatic employer matching contributions vesting period	0 years
Employer matching contribution, percent	50.00%
Employer match of eligible employees contributions percentage	2.00%
Employer matching contributions vesting period	4 years
Contribution expense	$ 852,000	$ 753,000
401(k) Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage on employees compensation	4.00%

Post-Retirement Plans - Summary

Post-Retirement Plans - Summary of Information Pertaining to Activity in Plan (Details) - Supplemental Retirement Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in plan assets:
Employer contributions	$ 201	$ 201
Benefits paid	(201)	(201)
Change in benefit obligation:
Benefit obligation at beginning of year	1,506	1,561
Service cost	11	10
Interest cost	36	53
Actuarial (gain) loss	105	83
Benefits paid	(201)	(201)
Benefit obligation at end of year	1,457	1,506
Unfunded status and accrued supplemental pension cost at year end	(1,457)	(1,506)
Accumulated benefit obligation at year end	$ 1,457	$ 1,506

Post-Retirement Plans - Summa_2

Post-Retirement Plans - Summary of Assumptions Used to Determine Benefit Obligation (Details) - Supplemental Retirement Plan [Member]	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.25%	2.50%
Annual inflation factor	1.00%	1.00%

Post-Retirement Plans - Summa_3

Post-Retirement Plans - Summary of Net Periodic Benefit Cost Included in Other Non-Interest Expenses Attributable to Plan (Details) - Supplemental Retirement Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 11	$ 10
Interest cost	36	53
Amortization of net actuarial loss	45	36
Amortization of prior service credit	(57)	(84)
Net periodic benefit cost	$ 35	$ 15

Post-Retirement Plans - Summa_4

Post-Retirement Plans - Summary of Assumptions Used to Determine Net Periodic Benefit Cost (Details) - Supplemental Retirement Plan [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.50%	3.60%
Annual inflation factor	1.00%	1.00%

Post-Retirement Plans - Summa_5

Post-Retirement Plans - Summary of Estimated Future Benefit Payments Expected Future Services (Details) - Supplemental Retirement Plan [Member] $ in Thousands	Dec. 31, 2020USD ($)
Defined Benefit Plan Disclosure [Line Items]
2021	$ 199
2022	207
2023	358
2024	201
2025	197
2026-2030	$ 239

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock awards granted	65,630
Options granted	333,118	57,252
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option term	10 years	10 years
Stock-based compensation expense	$ 703,000	$ 366,000
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 891,000	$ 553,000
Minimum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period	3 years	3 years
Maximum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period	5 years	5 years
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	586,872
Stock option term	10 years
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	234,749
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period	3 years
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period	5 years
2020 Inducement Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period	5 years
2020 Inducement Plan [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted	44,118
2020 Inducement Plan [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock awards granted	15,000

Stock Based Compensation - Summ

Stock Based Compensation - Summary of Grants of Options to Purchase Shares of Common Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted	333,118	57,252
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period (years)	10 years	10 years
Expected volatility, minimum	24.94%	26.14%
Expected volatility, maximum	29.87%	29.09%
Risk free interest rate, minimum	0.44%	2.37%
Risk free interest rate, maximum	1.47%	2.61%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option fair value	$ 2.69	$ 2.99
Minimum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (years)	3 years	3 years
Expected life (years)	6 years	6 years
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option fair value	$ 4.87	$ 5.83
Maximum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (years)	5 years	5 years
Expected life (years)	6 years 6 months	6 years 6 months

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity and Certain Other Information Related to Stock Options Grants Under 2017 Equity Plan and 2020 Inducement Plan (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock Option Grants
Beginning Balance	360,207
Granted	333,118	57,252
Forfeited	(14,543)
Expired	(91,614)
Ending Balance	587,168	360,207
Exercisable at December 31, 2020	139,448
Unrecognized compensation cost (inclusive of directors' options)	$ 1,456,227
Weighted Average Exercise Price
Beginning Balance	$ 14.82
Granted	12.15
Forfeited	15.34
Expired	14.67
Ending Balance	13.32	$ 14.82
Exercisable at December 31, 2020	$ 14.85
Weighted Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term	8 years 4 months 24 days	7 years 3 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 11 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 0
Aggregate Intrinsic Value, Outstanding	5,132,675	$ 0
Aggregate Intrinsic Value, Exercisable	$ 1,005,646
Stock Options [Member]
Stock Option Grants
Weighted average remaining recognition period (years)	2 years 11 months 15 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Activity and Certain Other Information Related to Restricted Stock Awards Under Equity Plan (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Restricted Stock Awards
Beginning Balance | shares	125,861
Granted | shares	65,630
Vested | shares	(60,228)
Forfeited | shares	(9,251)
Ending Balance | shares	122,012
Unrecognized compensation cost | $	$ 1,344,170
Weighted Average Grant Price
Beginning Balance | $ / shares	$ 14.76
Granted | $ / shares	10.93
Vested | $ / shares	14.70
Forfeited | $ / shares	14.88
Ending Balance | $ / shares	$ 12.72
Restricted Stock [Member]
Restricted Stock Awards
Weighted average remaining recognition period (years)	3 years 5 months 1 day

Employee Stock Ownership Plan -

Employee Stock Ownership Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Loan repaid term	25 years
Interest rate	4.75%	5.50%
Number of allocated shares	18,780
Annual allocation of shares, expiration year	2040
ESOP expense	$ 256,000	$ 283,000
Unallocated shares	375,598
Unallocated shares, value	$ 8,286,000
Common Stock [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of stock, price per share	$ 10
The Randolph Savings Charitable Foundation, Inc. [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of share in employee stock ownership plan	469,498

Share Repurchase Program - Addi

Share Repurchase Program - Additional Information (Detail) - USD ($)	Sep. 14, 2020	Oct. 31, 2020	Sep. 30, 2017	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Cost of shares repurchased				$ 1,749,000	$ 5,438,000
September 2017 Share Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program percentage of outstanding shares repurchased			10.00%
Number of shares authorized to repurchase			586,854
Number of shares repurchased	568,403
Cost of shares repurchased	$ 8,452,000
October 2020 Share Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program percentage of outstanding shares repurchased		10.00%
Number of shares authorized to repurchase		552,000
Number of shares repurchased				29,345
Cost of shares repurchased				$ 520,000

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Calculation of Average Number of Shares Outstanding Used to Calculate Basic and Diluted Earnings Per Share (Detail) - shares	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Average number of common shares outstanding									5,511,524	5,787,385
Less: Average unallocated ESOP shares									(384,963)	(403,768)
Average number of common shares outstanding used to calculate basic earnings per share	5,135,069	5,120,367	5,092,490	5,158,294	5,248,021	5,345,786	5,465,205	5,478,544	5,126,561	5,383,617
Effect of dilutive stock options									36,481
Average number of common shares outstanding used to calculate dilutive earnings per share	5,244,414	5,120,367	5,092,490	5,158,294	5,248,021	5,345,786	5,465,205	5,478,544	5,163,042	5,383,617

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Minimum Rent Commitments (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021	$ 651
2022	334
2023	145
2024	91
2025	23
Future minimum rent commitments, Leases	1,244
2021	(91)
2022	(94)
2023	(16)
Future minimum rent commitments, Sub-leases	(201)
2021	560
2022	240
2023	129
2024	91
2025	23
Future minimum rent commitments, Net	$ 1,043

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)Member	Dec. 31, 2019USD ($)
Commitments And Contingencies [Line Items]
Rent expense | $	$ 904,000	$ 887,000
Salary continuation term of employment arrangement	3 years
Five Members of Senior Management [Member]
Commitments And Contingencies [Line Items]
Number of members with change in control agreements	5
Change in control agreement description of terms	The company provide that if, within two years of a change of control of the Company or the Bank, the executive in involuntarily terminated other than for cause, disability or death, or voluntarily resigns for good reason, the executive will be entitled to a lump-sum payment equal to two times salary plus bonus, except for one executive where the payment is equal to one times salary plus bonus.
Four Members of Senior Management [Member]
Commitments And Contingencies [Line Items]
Number of members with change in control agreements	4
Change in control agreement description of terms	The company provide that if, within one year of a change of control of the Company or the Bank, the executive is involuntarily terminated other than for cause, disability or death, or voluntarily resigns for good reason, the executive will be entitled to a lump-sum payment equal to one times salary plus bonus.
Minimum [Member]
Commitments And Contingencies [Line Items]
Lease options to extend the period	2 years
Maximum [Member]
Commitments And Contingencies [Line Items]
Lease options to extend the period	10 years

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments to Originate Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 411,401	$ 117,086
Unused Lines and Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	71,458	52,721
Unadvanced Funds on Construction Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	9,110	11,029
Overdraft Lines of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 7,969	$ 8,178

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Recorded at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 55,366	$ 57,503
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	55,366	57,503
Fair value, Loans held for sale	119,112	62,792
Derivative assets	11,865	1,483
Derivative liabilities	2,180	140
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	55,366
Fair value, Portfolio loans	13,780	9,826
Fair value, Loans held for sale	119,112	62,792
Fair Value, Measurements, Recurring [Member] | Derivative Loan Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	11,821	1,472
Fair Value, Measurements, Recurring [Member] | Forward Loan Sale Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	44	11
Fair Value, Measurements, Recurring [Member] | Forward Loan Sale Commitments, including TBAs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	2,180	140
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value		57,503
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	55,366
Fair value, Portfolio loans	13,780	9,826
Fair value, Loans held for sale	119,112	62,792
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Derivative Loan Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	11,821	1,472
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Forward Loan Sale Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	44	11
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Forward Loan Sale Commitments, including TBAs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 2,180	140
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value		$ 57,503

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Additional information (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, assets, level 1 to level 2 transfers, amount	$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers, amount	0	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
Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on nonrecurring basis	$ 0	$ 0

Fair Value of Assets and Liab_5

Fair Value of Assets and Liabilities - Schedule of Assets Recorded at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, fair value	$ 12,490	$ 8,817
Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (losses) on assets held, mortgage servicing rights	(2,067)	(920)
Gains (Losses) on assets held	(2,067)
Gains (Losses) on assets held		(920)
Fair Value, Nonrecurring | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, fair value	12,377	8,556
Assets, Fair Value Disclosure	12,377	8,556
Fair Value, Nonrecurring | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Collateral dependent impaired loans	6,318	2,250
Fair value, Foreclosed real estate	132
Assets, Fair Value Disclosure	$ 6,450	$ 2,250

Fair Value of Assets and Liab_6

Fair Value of Assets and Liabilities - Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets:
Securities available for sale	$ 55,366	$ 57,503
Level 2 [Member]
Financial assets:
Certificates of deposit		492
Securities available for sale	55,366	57,503
Loans held for sale	119,112	62,792
Derivative assets	11,865	1,483
Financial liabilities:
Deposits	528,786	496,979
FRB advances	11,431
FHLBB advances	63,071	44,433
Derivative liabilities	2,180	140
Level 3 [Member]
Financial assets:
Loans, net	490,914	469,416
Carrying Amount [Member]
Financial assets:
Certificates of deposit		490
Securities available for sale	55,366	57,503
Loans held for sale	119,112	62,792
Loans, net	483,644	469,131
Derivative assets	11,865	1,483
Financial liabilities:
Deposits	528,307	497,042
FRB advances	11,431
FHLBB advances	61,895	44,403
Derivative liabilities	2,180	140
Fair Value [Member]
Financial assets:
Certificates of deposit		492
Securities available for sale	55,366	57,503
Loans held for sale	119,112	62,792
Loans, net	490,914	469,416
Derivative assets	11,865	1,483
Financial liabilities:
Deposits	528,786	496,979
FRB advances	11,431
FHLBB advances	63,071	44,433
Derivative liabilities	$ 2,180	$ 140

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)SegmentOffice	Dec. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Number of business segments | Segment									2
Number of branch offices | Office									5
Servicing fees amount	$ (275,000)	$ (1,180,000)	$ 1,354,000	$ 1,254,000	$ (32,000)	$ 181,000	$ (224,000)	$ (319,000)	$ 1,153,000	$ (394,000)
Envision Mortgage [Member]
Segment Reporting Information [Line Items]
Premium percentage for new loans									1.50%	1.50%
Premium income									$ 1,493,000	$ 951,000
Percentage of fees for HELOC									1.00%	1.00%
Servicing fees amount									$ 772,000	$ (757,000)
Envision Bank [Member]
Segment Reporting Information [Line Items]
Percentage of loan servicing fees									0.14%	0.14%
Servicing fees amount									$ 381,000	$ 363,000

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail) - USD ($)		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income		$ 5,040,000	$ 4,669,000	$ 4,733,000	$ 4,425,000	$ 4,393,000	$ 4,573,000	$ 4,489,000	$ 4,378,000	$ 18,867,000	$ 17,833,000
Provision for loan losses		215,000	546,000	1,068,000	724,000	144,000		(144,000)		2,553,000
Net interest income after provision for loan losses										16,314,000	17,833,000
Non-interest income:
Customer service fees		381,000	330,000	266,000	306,000	353,000	363,000	362,000	329,000	1,283,000	1,407,000
Gain on loan origination and sale activities, net	[1]									55,729,000	19,851,000
Mortgage servicing fees, net		275,000	1,180,000	(1,354,000)	(1,254,000)	32,000	(181,000)	224,000	319,000	(1,153,000)	394,000
Other										1,045,000	962,000
Total non-interest income										56,904,000	22,614,000
Non-interest expenses:
Salaries and employee benefits										33,161,000	24,896,000
Occupancy and equipment										3,545,000	2,783,000
Other non-interest expenses										9,610,000	8,271,000
Total non-interest expenses		12,927,000	11,051,000	11,379,000	10,959,000	9,491,000	9,718,000	8,863,000	7,878,000	46,316,000	35,950,000
Income (loss) before income taxes and elimination of inter-segment profit										26,902,000	4,497,000
Elimination of inter-segment profit										(1,493,000)	(951,000)
Income before income taxes										25,409,000	3,546,000
Income tax expense		2,211,000	2,661,000	594,000	11,000	21,000	14,000	119,000	(36,000)	5,477,000	118,000
Net income		5,274,000	$ 10,285,000	$ 5,191,000	$ (818,000)	829,000	$ 1,144,000	$ 1,506,000	$ (51,000)	19,932,000	3,428,000
Total assets		721,072,000				631,004,000				721,072,000	631,004,000
Envision Bank [Member]
Segment Reporting Information [Line Items]
Net interest income										16,235,000	15,985,000
Provision for loan losses										2,553,000
Net interest income after provision for loan losses										13,682,000	15,985,000
Non-interest income:
Customer service fees										1,180,000	1,268,000
Mortgage servicing fees, net										(381,000)	(363,000)
Other										465,000	596,000
Total non-interest income										1,264,000	1,501,000
Non-interest expenses:
Salaries and employee benefits										9,161,000	7,065,000
Occupancy and equipment										1,770,000	1,527,000
Other non-interest expenses										5,228,000	4,789,000
Total non-interest expenses										16,159,000	13,381,000
Income (loss) before income taxes and elimination of inter-segment profit										(1,213,000)	4,105,000
Total assets		537,722,000				521,144,000				537,722,000	521,144,000
Envision Mortgage [Member]
Segment Reporting Information [Line Items]
Net interest income										2,632,000	1,848,000
Net interest income after provision for loan losses										2,632,000	1,848,000
Non-interest income:
Customer service fees										103,000	139,000
Gain on loan origination and sale activities, net	[1]									55,729,000	19,851,000
Mortgage servicing fees, net										(772,000)	757,000
Other										580,000	366,000
Total non-interest income										55,640,000	21,113,000
Non-interest expenses:
Salaries and employee benefits										24,000,000	17,831,000
Occupancy and equipment										1,775,000	1,256,000
Other non-interest expenses										4,382,000	3,482,000
Total non-interest expenses										30,157,000	22,569,000
Income (loss) before income taxes and elimination of inter-segment profit										28,115,000	392,000
Total assets		$ 183,350,000				$ 109,860,000				$ 183,350,000	$ 109,860,000
[1]	Before elimination of inter-segment profit

Other Non-Interest Expenses - A

Other Non-Interest Expenses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other Income And Expenses [Abstract]
Percentage of certain items exceeding interest and non interest income	1.00%	1.00%

Other Non-Interest Expenses - S

Other Non-Interest Expenses - Schedule of Company's Total Interest and Non-Interest Income Included in Other Non-Interest Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other Income And Expenses [Abstract]
Software amortization, licenses and maintenance	$ 1,303	$ 1,017
Card related expenses	429	459
Data communication and telephone	391	418
Directors fees, including stock-based compensation	$ 579	$ 586

Global Pandemic Affecting Ran_3

Global Pandemic Affecting Randolph Bancorp, Inc.- Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)
Unusual Risk Or Uncertainty [Line Items]
Disaster Response Plan Costs	$ 229,000
Commercial Loan [Member] | Payment Deferral [Member]
Unusual Risk Or Uncertainty [Line Items]
Loan, amount	38,400,000
Residential Real Estate Loans In Portfolio [Member] | Payment Deferral [Member]
Unusual Risk Or Uncertainty [Line Items]
Loan, amount	18,800,000
Residential Real Estate Loan Serviced For Other [Member] | Payment Deferral [Member]
Unusual Risk Or Uncertainty [Line Items]
Loan, amount	68,500,000
Paycheck Protection Program [Member]
Unusual Risk Or Uncertainty [Line Items]
Loan, amount	$ 10,900,000

Global Pandemic Affecting Ran_4

Global Pandemic Affecting Randolph Bancorp, Inc. - Summary of Loan Portfolio (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	$ 57,510
Suspended/Reduction Payment	20,562
Resumed Payment	30,437
Full Payoff	6,511
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	53,797
Suspended/Reduction Payment	20,494
Resumed Payment	28,802
Full Payoff	4,501
Residential Real Estate [Member] | One-to-Four Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	15,514
Suspended/Reduction Payment	12,974
Resumed Payment	2,109
Full Payoff	431
Residential Real Estate [Member] | Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	3,179
Suspended/Reduction Payment	626
Resumed Payment	1,287
Full Payoff	1,266
Residential Real Estate [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	350
Suspended/Reduction Payment	350
Residential Real Estate [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	34,754
Suspended/Reduction Payment	6,544
Resumed Payment	25,406
Full Payoff	2,804
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	3,645
Resumed Payment	1,635
Full Payoff	2,010
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferrals Granted	68
Suspended/Reduction Payment	$ 68

Global Pandemic Affecting Ran_5

Global Pandemic Affecting Randolph Bancorp, Inc. - Summary of Loan PortfolioSchedule of Past Due and Non-Accrual Loans (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	$ 37,442
Special Mention	9,375
Sub-standard	4,182
Non-accrual	4,378	[1]
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	36,170
Special Mention	8,944
Sub-standard	4,182
Non-accrual	4,378	[1]
Residential Real Estate [Member] | One-to-Four Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	14,887
Special Mention	196
Non-accrual	196	[1]
Residential Real Estate [Member] | Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	1,913
Residential Real Estate [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	350
Residential Real Estate [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	19,020
Special Mention	8,748
Sub-standard	4,182
Non-accrual	4,182	[1]
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	1,204
Special Mention	431
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Pass Rated / Not Rated	$ 68
[1]	(1) Nonaccrual loans are risk rated as either special mention or substandard and are included as a balance in those columns.

Parent Company Condensed Fina_3

Parent Company Condensed Financial Statements - Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks	$ 4,206	$ 4,371
Total assets	721,072	631,004
Liabilities
Total liabilities	621,253	552,542
Stockholders' Equity:
Common stock	54	56
Additional paid-in capital	50,937	51,127
Retained earnings	51,689	31,757
ESOP-Unearned compensation	(3,756)	(3,944)
Accumulated other comprehensive income (loss), net of tax	895	(534)
Total stockholders' equity	99,819	78,462	$ 77,961
Total liabilities and stockholders' equity	721,072	631,004
Randolph Bancorp, Inc. and Predecessor Randolph Bancorp [Member]
Assets
Cash and due from banks	4,829	1,445
Investment in Envision Bank	90,959	72,872
ESOP loan	4,042	4,162
Total assets	99,830	78,479
Liabilities
Income taxes payable	8
Due to Envision Bank	3	17
Total liabilities	11	17
Stockholders' Equity:
Common stock	54	56
Additional paid-in capital	50,937	51,127
Retained earnings	51,689	31,757
ESOP-Unearned compensation	(3,756)	(3,944)
Accumulated other comprehensive income (loss), net of tax	895	(534)
Total stockholders' equity	99,819	78,462
Total liabilities and stockholders' equity	$ 99,830	$ 78,479

Parent Company Condensed Fina_4

Parent Company Condensed Financial Statements - Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Condensed Income Statements Captions [Line Items]
Interest income	$ 5,828	$ 5,648	$ 6,059	$ 6,053	$ 6,220	$ 6,541	$ 6,454	$ 6,016	$ 23,588	$ 25,231
Income tax expense	2,211	2,661	594	11	21	14	119	(36)	5,477	118
Net income	$ 5,274	$ 10,285	$ 5,191	$ (818)	$ 829	$ 1,144	$ 1,506	$ (51)	19,932	3,428
Randolph Bancorp, Inc. and Predecessor Randolph Bancorp [Member]
Condensed Income Statements Captions [Line Items]
Interest income									198	235
Dividend income									5,000
Operating expenses									171	194
Income before incomes taxes and equity in undistributed net income of Envision Bank									5,027	41
Income tax expense									7	3
Income before equity in undistributed net income of Envision Bank									5,020	38
Equity in undistributed net income of Envision Bank									14,912	3,390
Net income									$ 19,932	$ 3,428

Parent Company Condensed Fina_5

Parent Company Condensed Financial Statements - Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 19,932	$ 3,428
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net cash used in operating activities	(43,293)	(16,475)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	(9,910)	7,915
Cash flows from financing activities:
Stock repurchases	(1,749)	(5,438)
Net cash provided by financing activities	58,725	9,694
Net change in cash and cash equivalents	5,522	1,134
Cash and cash equivalents at beginning of year	8,252	7,118
Cash and cash equivalents at end of year	13,774	8,252
Randolph Bancorp, Inc. and Predecessor Randolph Bancorp [Member]
Cash flows from operating activities:
Net income	19,932	3,428
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed net income of Envision Bank	(14,912)	(3,390)
Dividends received from Envision Bank	(5,000)
Change in income taxes payable	8
Change in intercompany receivable/payable	(15)	(39)
Net cash used in operating activities	13	(1)
Cash flows from investing activities:
Principal payments received on ESOP loan	120	104
Dividends received from Envision Bank	5,000
Net cash provided by (used in) investing activities	5,120	104
Cash flows from financing activities:
Stock repurchases	(1,749)	(5,438)
Stock repurchase payable		(70)
Net cash provided by financing activities	(1,749)	(5,508)
Net change in cash and cash equivalents	3,384	(5,405)
Cash and cash equivalents at beginning of year	1,445	6,850
Cash and cash equivalents at end of year	$ 4,829	$ 1,445

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 5,828	$ 5,648	$ 6,059	$ 6,053	$ 6,220	$ 6,541	$ 6,454	$ 6,016	$ 23,588	$ 25,231
Interest expense	788	979	1,326	1,628	1,827	1,968	1,965	1,638	4,721	7,398
Net interest income	5,040	4,669	4,733	4,425	4,393	4,573	4,489	4,378	18,867	17,833
Provision (credit) for loan losses	215	546	1,068	724	144		(144)		2,553
Customer service fees	381	330	266	306	353	363	362	329	1,283	1,407
Gain on loan origination and sale activities, net	14,620	18,102	14,370	7,144	5,462	5,782	5,068	2,588	54,236	18,900
Mortgage servicing fees, net	275	1,180	(1,354)	(1,254)	32	(181)	224	319	(1,153)	394
Gain on sales/calls of securities and impairment write-down, net					16					16
Increase in cash surrender value of life insurance	45	46	45	45	47	45	48	45	181	185
Other	266	216	172	210	182	294	153	132	864	761
Total non-interest income	15,587	19,874	13,499	6,451	6,092	6,303	5,855	3,413	55,411	21,663
Total non-interest expense	12,927	11,051	11,379	10,959	9,491	9,718	8,863	7,878	46,316	35,950
Provision (benefit) for income taxes	2,211	2,661	594	11	21	14	119	(36)	5,477	118
Net income	$ 5,274	$ 10,285	$ 5,191	$ (818)	$ 829	$ 1,144	$ 1,506	$ (51)	$ 19,932	$ 3,428
Basic earnings (loss) per share	$ 1.03	$ 2.01	$ 1.02	$ (0.16)	$ 0.16	$ 0.21	$ 0.28	$ (0.01)	$ 3.89	$ 0.64
Diluted earnings (loss) per share	$ 1.01	$ 2.01	$ 1.02	$ (0.16)	$ 0.16	$ 0.21	$ 0.28	$ (0.01)	$ 3.86	$ 0.64
Weighted average common shares (basic)	5,135,069	5,120,367	5,092,490	5,158,294	5,248,021	5,345,786	5,465,205	5,478,544	5,126,561	5,383,617
Weighted average common shares (diluted)	5,244,414	5,120,367	5,092,490	5,158,294	5,248,021	5,345,786	5,465,205	5,478,544	5,163,042	5,383,617