Randolph Bancorp (RNDB) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 07, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	RNDB
Entity Registrant Name	Randolph Bancorp, Inc.
Entity Central Index Key	1,667,161
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		5,868,544

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 3,741	$ 4,370
Interest-bearing deposits	4,414	10,479
Total cash and cash equivalents	8,155	14,849
Certificates of deposit	2,940	3,675
Securities available for sale, at fair value	65,141	68,637
Loans held for sale, at fair value	26,541	30,452
Loans, net of allowance for loan losses of $3,545 in 2017 and $3,271 in 2016	372,777	332,991
Federal Home Loan Bank stock, at cost	2,909	2,478
Accrued interest receivable	1,307	1,163
Mortgage servicing rights, net	6,039	8,486
Premises and equipment, net	7,755	6,280
Bank-owned life insurance	7,999	7,884
Other assets	3,949	4,329
Total assets	505,512	481,224
Deposits:
Non-interest bearing	59,954	59,646
Interest bearing	298,947	291,533
Total deposits	358,901	351,179
Federal Home Loan Bank advances	56,935	38,667
Mortgagors' escrow accounts	1,311	1,572
Post-employment benefit obligations	2,723	2,886
Other liabilities	2,402	3,618
Total liabilities	422,272	397,922
Commitments and contingencies (Note 14)
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: 5,868,544 shares at September 30, 2017 and 5,868,726 shares at December 31, 2016	59	59
Additional paid-in capital	56,443	56,373
Retained earnings	32,113	32,661
ESOP-Unearned compensation	(4,366)	(4,507)
Accumulated other comprehensive loss, net of tax	(1,009)	(1,284)
Total stockholders' equity	83,240	83,302
Total liabilities and stockholders' equity	$ 505,512	$ 481,224

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Loans, allowance for loan losses	$ 3,545	$ 3,271
Preferred stock, par value
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	5,868,544	5,868,726
Common stock, shares outstanding	5,868,544	5,868,726

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest and dividend income:
Loans	$ 3,936	$ 3,434	$ 11,049	$ 8,982
Securities-taxable	339	282	1,065	908
Securities-tax exempt	87	90	264	277
Interest-bearing deposits and certificates of deposit	27	70	70	124
Total interest and dividend income	4,389	3,876	12,448	10,291
Interest expense:
Deposits	406	388	1,123	1,033
Federal Home Loan Bank advances	167	67	335	185
Total interest expense	573	455	1,458	1,218
Net interest income	3,816	3,421	10,990	9,073
Provision (credit) for loan losses		(160)	335	(98)
Net interest income after provision (credit) for loan losses	3,816	3,581	10,655	9,171
Non-interest income:
Customer service fees	359	369	1,109	1,122
Net gain on sales of mortgage loans	2,705	5,401	7,263	7,140
Mortgage servicing fees, net	199	(95)	1,149	74
Gain on sales/calls of securities		100		162
Increase in cash surrender value of life insurance	38	36	114	140
Gain on life insurance settlement				486
Bargain purchase gain		1,451		1,451
Other	270	98	780	173
Total non-interest income	3,571	7,360	10,415	10,748
Non-interest expenses:
Salaries and employee benefits	4,668	5,348	14,059	9,931
Occupancy and equipment	682	691	1,957	1,448
Data processing	179	209	540	595
Professional fees	348	393	1,019	983
Marketing	277	135	624	307
Foreclosed real estate, net		5		162
Charitable foundation contribution		2,275		2,275
Merger and integration costs	7	514	531	664
Other	1,048	1,082	3,036	2,542
Total non-interest expenses	7,209	10,652	21,766	18,907
Income (loss) before income taxes	178	289	(696)	1,012
Income tax expense (benefit)	129		(148)	3
Net income (loss)	$ 49	$ 289	$ (548)	$ 1,009
Weighted average common shares outstanding (basic and diluted)	5,429,564	5,403,923	5,427,262
Earnings (loss) per common share (basic and diluted)	$ 0.01	$ 0.05	$ (0.10)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net income (loss)	$ 49	$ 289	$ (548)	$ 1,009
Securities available for sale:
Unrealized holding gains (losses)	(334)	(257)	465	792
Reclassification adjustment for net gains realized in income	0	(100)	0	(162)
Net unrealized gains	(334)	(357)	465	630
Related tax effects	129	0	(151)	0
Net-of-tax amount	(205)	(357)	314	630
Related tax effects	0	0	0	0
Net-of-tax amount	(12)	3	(39)	8
Total other comprehensive income (loss)	(217)	(354)	275	638
Comprehensive income (loss)	(168)	(65)	(273)	1,647
Supplemental Retirement Plan [Member]
Securities available for sale:
Actuarial losses	10	7	28	25
Prior service credits recognized	(22)	(4)	(67)	(17)
Post-retirement benefit plans	$ (12)	$ 3	$ (39)	$ 8

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Randolph Savings Charitable Foundation	Initial Public Offering [Member]	Common Stock [Member]	Common Stock [Member]Randolph Savings Charitable Foundation	Common Stock [Member]Initial Public Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Randolph Savings Charitable Foundation	Additional Paid-in Capital [Member]Initial Public Offering [Member]	Retained Earnings [Member]	Unearned Compensation ESOP [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 32,459									$ 32,198		$ 261
Net income (loss)	1,009									1,009
Other comprehensive income	638											638
Issuance of common stock for initial public offering, value		$ 1,820	$ 54,501		$ 2	$ 57		$ 1,818	$ 54,444
Issuance of common stock for initial public offering, shares					181,976	5,686,750
Stock purchased by ESOP	(4,695)										$ (4,695)
ESOP shares committed to be released	120						$ 26				94
Ending balance at Sep. 30, 2016	85,852			$ 59			56,288			33,207	(4,601)	899
Ending balance, shares at Sep. 30, 2016				5,868,726
Beginning balance at Dec. 31, 2015	32,459									32,198		261
Ending balance at Dec. 31, 2016	83,302			$ 59			56,373			32,661	(4,507)	(1,284)
Ending balance, shares at Dec. 31, 2016				5,868,726
Net income (loss)	(548)									(548)
Other comprehensive income	275											275
Repurchase of common stock	$ (3)						(3)
Repurchase of common stock, shares	0			(182)
ESOP shares committed to be released	$ 214						73				141
Ending balance at Sep. 30, 2017	$ 83,240			$ 59			$ 56,443			$ 32,113	$ (4,366)	$ (1,009)
Ending balance, shares at Sep. 30, 2017				5,868,544

Consolidated Statements of Cha7

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	Sep. 30, 2016USD ($)
Initial Public Offering [Member]
Common stock issuance costs	$ 2,367

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income (loss)	$ (548,000)	$ 1,009,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Provision (credit) for loan losses	335,000	(98,000)
Bargain purchase gain		(1,451,000)
Loans originated for sale	(304,312,000)	(245,642,000)
Principal balance of loans sold	308,223,000	246,079,000
Net amortization of securities	198,000	110,000
Net change in deferred loan costs and fees	(178,000)	103,000
Gain on sales/calls of securities		(162,000)
Depreciation and amortization	457,000	353,000
Impairment write-downs on foreclosed real estate		150,000
Gain on life insurance settlement, net		(486,000)
Charitable foundation contribution		1,820,000
ESOP expense	214,000	120,000
Increase in cash surrender value of life insurance	(114,000)	(140,000)
Net (increase) decrease in mortgage servicing rights	2,447,000	(568,000)
Other, net	(1,669,000)	2,832,000
Net cash provided by operating activities	5,053,000	4,029,000
Cash flows from investing activities:
Redemptions of certificates of deposit	735,000	1,000,000
Securities available for sale:
Sales		2,521,000
Calls/maturities	841,000	6,970,000
Purchases		(21,745,000)
Principal payments on mortgage-backed securities	3,256,000	4,335,000
Loan originations, net of principal repayments	(17,874,000)	(10,554,000)
Loans purchased	(22,068,000)	(572,000)
Redemption (purchases) of Federal Home Loan Bank stock	(431,000)	1,009,000
Proceeds from sale of building		1,231,000
Proceeds from life insurance settlement		2,157,000
Acquisition of First Eastern, net of cash acquired		(10,956,000)
Purchases of premises and equipment	(1,932,000)	(674,000)
Net cash used in investing activities	(37,473,000)	(25,278,000)
Cash flows from financing activities:
Net increase in deposits	7,722,000	5,057,000
Net increase (decrease) in short-term Federal Home Loan Bank borrowings	23,191,000	(7,401,000)
Proceeds from long-term Federal Home Loan Bank advances		9,838,000
Repayments of long-term Federal Home Loan Bank advances	(4,923,000)	(13,737,000)
Net increase (decrease) in mortgagors' escrow accounts	(261,000)	33,000
Net proceeds from the issuance of common stock		54,501,000
Acquisition of common stock by ESOP		(4,695,000)
Repurchase of common stock	(3,000)
Net cash provided by financing activities	25,726,000	43,596,000
Net change in cash and cash equivalents	(6,694,000)	22,347,000
Cash and cash equivalents at beginning of period	14,849,000	4,646,000
Cash and cash equivalents at end of period	8,155,000	26,993,000
Supplemental cash flow information:
Interest paid on deposits and borrowed funds	1,462,000	1,222,000
Income taxes paid	$ 3,000	$ 7,000

Conversion and Basis of Present

Conversion and Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Conversion and Basis of Presentation	1. CONVERSION AND BASIS OF PRESENTATION Conversion Randolph Bancorp, a Massachusetts-chartered mutual holding company and the parent company of Randolph Savings Bank (the “Bank”), adopted a plan of conversion (the “Plan of Conversion”) in January 2016 which was subsequently approved by Randolph Bancorp’s Corporators in May 2016. Under the Plan of Conversion, Randolph Bancorp converted from a mutual to a stock holding company in a series of transactions in which Randolph Bancorp, Inc. (“Bancorp”), a recently formed subsidiary of Randolph Bancorp, became the surviving entity. On July 1, 2016, the mutual-to-stock transaction was completed and Bancorp sold 5,686,750 shares of its common stock, representing the adjusted maximum of the offering range, at $10.00 per share, for gross proceeds of $56,867,500, including the sale of 469,498 shares to the Bank’s newly formed employee stock ownership plan (“ESOP”). The ESOP’s shares were funded by a loan from Bancorp to be repaid over 25 years with interest at the prime rate. The direct costs of stock offering were deducted from the proceeds of the offering and amounted to $2,325,000. In connection with the Plan of Conversion, Bancorp established The Randolph Savings Charitable Foundation, Inc. (the “Foundation”). The Foundation was funded with 181,976 shares of Bancorp’s common stock and $455,000 in cash. Bancorp recognized expense of $2,274,700 in the third quarter of 2016 for this contribution. The Bancorp and the Bank are required to restrict their net worth by establishing liquidation accounts (collectively, the “liquidation account”) for the benefit of eligible account holders who continue to maintain deposit accounts at the Bank after the conversion. The liquidation account will be reduced annually to the extent eligible depositors reduce their qualifying deposits and cannot be increased thereafter with additional deposits. In the event of a complete liquidation of the Bank, each eligible account holder would be entitled to receive a distribution from the liquidation account in an amount proportionate to the adjusted qualifying account balances then held. Neither the Bancorp nor the Bank may declare or pay a cash dividend on its common stock if such dividend would cause its regulatory capital to be reduced below the amount required to maintain the liquidation account. Basis of Financial Statement Presentation The consolidated financial statements include the accounts of Randolph Bancorp, Inc. and its wholly-owned subsidiary, Randolph Savings Bank (together, the “Company”). The Bank has subsidiaries involved in owning investment securities and foreclosed real estate properties and a subsidiary which provides loan closing services. All intercompany accounts and transactions have been eliminated in consolidation. These financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the Securities and Exchange Commission (“SEC”). Accordingly, the accompanying interim financial statements do not include all information required under GAAP for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation of the financial statements, primarily consisting of normal recurring adjustments, have been included. The operating results for the nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or any other interim period. For further information, refer to the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, as filed with the SEC.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2017
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Pronouncements	1. RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board ("FASB") Accounting Standards Update (“ASU”) Revenue from Contracts with Customers 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

Acquisition

Acquisition	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Acquisition	1. ACQUISITION On July 1, 2016, the Company acquired all of the outstanding common stock of First Eastern Bankshares Corporation (“First Eastern”) for cash of $14.1 million. The results of operations of First Eastern are included in the Company’s consolidated statements of operations beginning on July 1, 2016. The following table presents selected unaudited pro forma financial information assuming the acquisition was completed on January 1, 2016. The pro forma amounts reflect adjustments related to reversal of benefit of non-recurring merger and integration costs and amortization and accretion of acquisition accounting fair value adjustments. No provision for income taxes is included in the determination of pro forma net income due to the Company’s net operating loss carryforward position. The unaudited pro forma financial information does not reflect management’s estimate of any revenue enhancement opportunities or anticipated cost savings nor any adjustments related to the stock offering completed on July 1, 2016. The unaudited pro forma financial information is presented for illustrative purposes only and is not necessarily indicative of the combined financial results of the Company and First Eastern had the acquisition transaction actually been completed at the beginning of the period presented, nor does it indicate future results for any interim or annual period. Pro forma basic and diluted earnings (loss) per share are not presented as such information is not being presented as part of our historical financial statements for the nine months ended September 30, 2016 as shares of the Company’s common stock were not outstanding for the entire period. Unaudited pro forma financial information for the nine months ended September 30, 2016 is as follows (in thousands): Net Interest Income $ 10,038 Non-interest Income 16,371 Net Income 1,598 Direct acquisition and merger integration costs associated with the First Eastern business combination are being expensed as incurred and are presented separately in the accompanying statements of operations. Costs incurred during the nine months ended September 30, 2016 consist principally of retention bonuses, systems de-conversion costs and legal and consulting fees. Costs incurred during the nine months ended September 30, 2017 consist principally of severance obligations, system conversion costs and consulting fees. As all system conversions were completed as of September 30, 2017, no additional merger integration costs associated with the First Eastern business combination are expected to be incurred.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive Loss	1. ACCUMULATED OTHER COMPREHENSIVE 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 stockholders’ equity, such items, along with net income (loss), are components of comprehensive income (loss). The components of accumulated other comprehensive loss, included in total stockholders’ equity, are as follows: September 30, December 31, 2017 2016 (In thousands) Securities available for sale: Net unrealized loss $ (233 ) $ (698 ) Tax effect (574 ) (423 ) Net-of-tax amount (807 ) (1,121 ) Supplemental retirement plan Unrecognized net actuarial loss (651 ) (679 ) Unrecognized net prior service credit 506 573 (145 ) (106 ) Tax effect (57 ) (57 ) Net-of-tax amount (202 ) (163 ) Accumulated other comprehensive loss $ (1,009 ) $ (1,284 )

Securities Available for Sale

Securities Available for Sale	9 Months Ended
	Sep. 30, 2017
Investments Debt And Equity Securities [Abstract]
Securities Available for Sale	1. 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) September 30, 2017 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 73 $ (8 ) $ 4,064 Corporate 3,013 36 (4 ) 3,045 Municipal 13,466 279 (4 ) 13,741 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 19,334 159 (417 ) 19,076 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,509 48 (369 ) 14,188 U.S. Government-guaranteed 8,264 25 (76 ) 8,213 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,931 30 — 1,961 U.S. Government-guaranteed 313 2 — 315 Total debt securities 64,829 652 (878 ) 64,603 Mutual fund 545 — (7 ) 538 Total securities available for sale $ 65,374 $ 652 $ (885 ) $ 65,141 December 31, 2016 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 92 $ (10 ) $ 4,081 Corporate 3,044 54 (18 ) 3,080 Municipal 13,857 254 (56 ) 14,055 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 21,130 172 (580 ) 20,722 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,676 56 (554 ) 14,178 U.S. Government-guaranteed 9,589 12 (144 ) 9,457 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 2,127 28 — 2,155 U.S. Government-guaranteed 368 3 — 371 Total debt securities 68,790 671 (1,362 ) 68,099 Mutual fund 545 — (7 ) 538 Total securities available for sale $ 69,335 $ 671 $ (1,369 ) $ 68,637 The amortized cost and fair value of debt securities by contractual maturity at September 30, 2017 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 $ 3,430 $ 3,440 After 1 year through 5 years 14,792 15,079 After 5 years through 10 years 2,256 2,331 20,478 20,850 Mortgage-backed securities 44,351 43,753 $ 64,829 $ 64,603 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: Less Over Twelve Months Gross Gross Unrealized Fair Unrealized Fair Losses Value Losses Value September 30, 2017 (In thousands) Debt securities: U.S. Government-sponsored enterprises $ (8 ) $ 1,992 $ — $ — Corporate (3 ) 1,027 (1 ) 472 Municipal (2 ) 1,120 (2 ) 483 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (417 ) 13,606 — — Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (369 ) 8,867 — — U.S. Government-guaranteed (76 ) 3,867 — — Total debt securities (875 ) 30,479 (3 ) 955 Mutual Fund (7 ) 537 — — $ (882 ) $ 31,016 $ (3 ) $ 955 December 31, 2016 Debt securities: U.S. Government-sponsored enterprises $ (10 ) $ 1,990 $ — $ — Corporate (14 ) 519 (4 ) 996 Municipal (46 ) 3,310 (10 ) 477 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (580 ) 16,261 — — Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (554 ) 8,766 — — U.S. Government-guaranteed (144 ) 5,927 — — Total debt securities (1,348 ) 36,773 (14 ) 1,473 Mutual Fund (7 ) 538 — — $ (1,355 ) $ 37,311 $ (14 ) $ 1,473 Management evaluates securities for other-than-temporary impairment at least on a quarterly basis, and more frequently when economic or market concerns warrant such evaluation. At September 30, 2017, 29 debt securities had unrealized losses with aggregate depreciation of approximately 2.8% of the Company’s amortized cost basis. 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 these investments. Therefore, it is expected that the bonds 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 these investments to be other-than-temporarily impaired at September 30, 2017. When possible, management actively monitors the credit rating of the underlying issuer of the debt security. As of September 30, 2017 management did not identify any securities for which the credit rating had deteriorated since purchase.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Loans and Allowance for Loan Losses	1. LOANS AND ALLOWANCE FOR LOAN LOSSES A summary of loan portfolio is as follows: September 30, 2017 December 31, 2016 (In thousands) Mortgage loans on real estate: Residential: One-to-four family $ 189,311 $ 179,025 Home equity loans and lines of credit 39,033 35,393 Commercial 96,915 88,394 Construction 23,266 23,629 348,525 326,441 Commercial and industrial 16,373 2,067 Consumer 10,068 6,578 Total loans 374,966 335,086 Allowance for loan losses (3,545 ) (3,271 ) Net deferred loan costs and fees, and purchase premiums 1,356 1,176 $ 372,777 $ 332,991 During the nine months ended September 30, 2017, the Company purchased $15.4 million in loan participations originated through a super-regional bank. These loans are to local franchisees of a major international fast food retailer and are classified with commercial and industrial loans in the accompanying table. The Company also purchased $5.0 million of refinanced student loans from an on-line lender specializing in the origination and refinancing of such loans. The following table summarizes the changes in the allowance for loan losses by portfolio segment for the three and nine months ended September 30, 2017 and 2016: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total (In thousands) Three Months Ended September 30, 2017 Allowance at June 30, 2017 $ 820 $ 338 $ 1,536 $ 389 $ 276 $ 198 $ 3,557 Provision (credit) for loan losses 15 6 42 (50 ) (15 ) 2 — Loans charged-off — — — — — (25 ) (25 ) Recoveries 7 — — — — 6 13 Balance at September 30, 2017 $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Three Months Ended September 30, 2016 Allowance at June 30, 2016 $ 1,046 $ 444 $ 1,520 $ 135 $ 36 $ 78 $ 3,259 Provision (credit) for loan losses 12 (15 ) (166 ) 9 3 (3 ) (160 ) Loans charged-off — — — — — (6 ) (6 ) Recoveries 2 — — — — 1 3 Balance at September 30, 2016 $ 1,060 $ 429 $ 1,354 $ 144 $ 39 $ 70 $ 3,096 Nine Months Ended September 30, 2017 Allowance at December 31, 2016 $ 1,018 $ 436 $ 1,410 $ 225 $ 37 $ 145 $ 3,271 Provision (credit) for loan losses (195 ) (92 ) 168 114 189 151 335 Loans charged-off — — — — — (134 ) (134 ) Recoveries 19 — — — 35 19 73 Balance at September 30, 2017 $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Nine Months Ended September 30, 2016 Allowance at December 31, 2015 $ 1,076 $ 512 $ 1,402 $ 159 $ 37 $ 53 $ 3,239 Provision (credit) for loan losses (20 ) (83 ) (48 ) (15 ) 2 66 (98 ) Loans charged-off — — — — — (66 ) (66 ) Recoveries 4 — — — — 17 21 Balance at September 30, 2016 $ 1,060 $ 429 $ 1,354 $ 144 $ 39 $ 70 $ 3,096 Additional information pertaining to the allowance for loan losses at September 30, 2017 and December 31, 2016 is as follows: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total September 30, 2017 (In thousands) Allowance for impaired loans $ 172 $ 1 $ 2 $ — $ — $ — $ 175 Allowance for non-impaired loans 670 343 1,576 339 261 181 3,370 Total allowance for loan losses $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Impaired loans $ 5,156 $ 276 $ 734 $ — $ — $ — $ 6,166 Non-impaired loans 184,155 38,757 96,181 23,266 16,373 10,068 368,800 Total loans $ 189,311 $ 39,033 $ 96,915 $ 23,266 $ 16,373 $ 10,068 $ 374,966 December 31, 2016 Allowance for impaired loans $ 190 $ 2 $ 8 $ — $ — $ — $ 200 Allowance for non-impaired loans 828 434 1,402 225 37 145 3,071 Total allowance for loan losses $ 1,018 $ 436 $ 1,410 $ 225 $ 37 $ 145 $ 3,271 Impaired loans $ 4,506 $ 276 $ 832 $ — $ — $ — $ 5,614 Non-impaired loans 174,519 35,117 87,562 23,629 2,067 6,578 329,472 Total loans $ 179,025 $ 35,393 $ 88,394 $ 23,629 $ 2,067 $ 6,578 $ 335,086 The following is a summary of past due and non-accrual loans at September 30, 2017 and December 31, 2016: 30 - 59 Days Past Due 60 - 89 Days Past Due 90 Days or More Past Due Total Past Due Non-accrual Loans (In thousands) September 30, 2017 Residential one-to-four family $ 732 $ — $ — $ 732 $ 1,906 Home equity loans and lines of credit 68 107 — 175 276 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer — — — — — Total $ 800 $ 107 $ — $ 907 $ 2,182 December 31, 2016 Residential one-to-four family $ 1,168 $ 201 $ — $ 1,369 $ 1,945 Home equity loans and lines of credit 258 — — 258 276 Commercial real estate 400 — — 400 — Construction — — — — — Commercial and industrial — — — — — Consumer 59 — — 59 — Total $ 1,885 $ 201 $ - $ 2,086 $ 2,221 At September 30, 2017 and December 31, 2016, there were no loans past due 90 days or more and still accruing interest. The following is a summary of impaired loans at September 30, 2017 and December 31, 2016: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) September 30, 2017 Impaired loans without a valuation allowance: Residential one-to-four family $ 2,631 $ 2,576 Home equity loans and lines of credit 247 247 Commercial real estate 608 608 Total 3,486 3,431 Impaired loans with a valuation allowance: Residential one-to-four family 2,600 2,580 $ 172 Home equity loans and lines of credit 30 29 1 Commercial real estate 126 126 2 Total 2,756 2,735 175 Total impaired loans $ 6,242 $ 6,166 $ 175 December 31, 2016 Impaired loans without a valuation allowance: Residential one-to-four family $ 1,922 $ 1,877 Home equity loans and lines of credit 246 246 Commercial real estate 270 270 Total 2,438 2,393 Impaired loans with a valuation allowance: Residential one-to-four family 2,648 2,629 $ 190 Home equity loans and lines of credit 31 30 2 Commercial real estate 562 562 8 Total 3,241 3,221 200 Total impaired loans $ 5,679 $ 5,614 $ 200 Additional information pertaining to impaired loans follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Nine Months Ended September 30, 2017 Residential one-to-four family $ 4,896 $ 143 $ 62 Home equity loans and lines of credit 276 1 1 Commercial real estate 732 23 — Total $ 5,904 $ 167 $ 63 Nine Months Ended September 30, 2016 Residential one-to-four family $ 5,165 $ 130 $ 49 Home equity loans and lines of credit 253 1 1 Commercial real estate 1,193 42 2 Commercial and industrial 5 1 1 Total $ 6,616 $ 174 $ 53 Three Months Ended September 30, 2017 Residential one-to-four family $ 5,124 $ 44 $ 16 Home equity loans and lines of credit 276 — — Commercial real estate 621 5 — Total $ 6,021 $ 49 $ 16 Three Months Ended September 30, 2016 Residential one-to-four family $ 5,613 $ 45 $ 23 Home equity loans and lines of credit 276 — - Commercial real estate 971 12 1 Total $ 6,860 $ 57 $ 24 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. At September 30, 2017, the Company had 20 residential real estate loans and 2 commercial real estate loans aggregating $4,382,000 and $185,000, respectively, which were subject to troubled debt restructuring agreements. At September 30, 2016, the Company had 24 residential real estate loans and 4 commercial real estate loans aggregating $5,367,000 and $683,000, respectively, which were subject to troubled debt restructuring agreements. As of September 30, 2017 and 2016, $4,567,000 and $6,050,000, respectively, in troubled debt restructurings were performing in accordance with the terms of the modified loan agreements. Included in such amounts are $1,139,000 and $1,714,000, respectively, that are being accounted for as non-accrual loans. For the nine months ended September 30, 2017 2016, Management performs a discounted cash flow calculation to determine the amount of valuation reserve required on each of the troubled debt restructurings. Any reserve required is recorded as part of the allowance for loan losses. During the three and nine months ended September 30, 2017 and 2016, there were no material changes to the allowance for loan losses as a result of loan modifications made which were considered a troubled debt restructuring. During the three and nine months ended September 30, 2017 and 2016, there were no troubled debt restructurings that defaulted (over 30 days past due) within twelve months of the restructure date. 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 – 3B 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 and industrial 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 the dates indicated: September 30, 2017 December 31, 2016 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3B (Pass rated) $ 96,713 $ 23,266 $ 16,373 $ 88,186 $ 23,286 $ 2,067 Loans rated 4 — — — — 343 — Loans rated 5 202 — — 208 — — $ 96,915 $ 23,266 $ 16,373 $ 88,394 $ 23,629 $ 2,067 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 September 30, 2017, $717,000 in residential mortgages and $29,000 in home equity loans were rated as substandard and $2,312,000 in residential mortgages and $370,000 in home equity loans were rated as special mention. At December 31, 2016, $890,000 in residential mortgages were rated as substandard and $1,471,000 in residential mortgages and $400,000 in home equity loans were rated as special mention.

Loan Servicing

Loan Servicing	9 Months Ended
	Sep. 30, 2017
Transfers And Servicing [Abstract]
Loan Servicing	1. LOAN SERVICING Mortgage loans serviced for others are not included in the accompanying consolidated balance sheets. The unpaid principal balances of residential mortgage loans serviced for others were $754,939,000 and $1,046,551,000 at September 30, 2017 and December 31, 2016, respectively. The following table summarizes the activity relating to mortgage servicing rights for the nine months ended September 30, 2017 and 2016 (in thousands): September 30, 2017 September 30, 2016 Mortgage servicing rights: Balance at beginning of year $ 8,910 $ 2,601 Additions through originations 1,486 1,676 Additions through First Eastern acquisition — 6,216 Sales (3,126 ) — Amortization (941 ) (644 ) Balance at end of period $ 6,329 $ 9,849 Valuation allowance: Balance at beginning of year $ 424 $ 34 Provision (credit) (134 ) 464 Balance at end of period $ 290 $ 498 Amortized cost, net $ 6,039 $ 9,351 Fair value $ 6,051 $ 9,360 During the three months ended September 30, 2017, the Company increased the valuation allowance for its mortgage servicing rights by $97,000. For the nine months ended September 30, 2017 On July 31, 2017, the Company sold the servicing rights to a portfolio of $379.0 million of residential mortgage loans and completed the transfer of servicing responsibilities in September 2017. A gain of $68,000 was recognized and is included in other non-interest income in the accompanying statement of operations. Under the terms of the purchase and sale agreement, the Company has received $2.7 million, or 80% of the selling price as of September 30, 2017. Included in other assets at September 30, 2017 is $595,000 due from the purchaser which is scheduled for payment prior to the close of 2017.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	1. INCOME TAXES During the nine months ended September 30, 2017 A deferred tax provision of $129,000 was recognized for the three months ended September 30, 2017, while no tax provision or benefit was recognized for the three months ended September 30, 2016. The tax provision for the current quarter resulted from a limitation in the year-to-date tax benefit included in results of operations. This tax benefit is fully offset by a tax provision attributable to other comprehensive income relating to appreciation in the fair value of available-for-sale securities. Since 2014, the Company has maintained a valuation allowance for all of its deferred tax assets 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 (“NOL”) carryforward position, its current period operating results exclusive of non-recurring items and its expectations for the upcoming year. In performing subsequent assessments, management has concluded that no significant changes in the key factors affecting the realizability of the deferred tax asset has occurred and that a valuation allowance for all deferred tax assets should be maintained.

On-Balance Sheet Derivative Ins

On-Balance Sheet Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
On-Balance Sheet Derivative Instruments and Hedging Activities	1. ON-BALANCE SHEET DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Derivative Loan Commitments Mortgage loan 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. 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 $39,959,000 and $32,904,000 at September 30, 2017 and December 31, 2016, respectively. The fair value of such commitments was an asset of $552,000 and $617,000 as of September 30, 2017 and December 31, 2016, respectively, and is included in other assets in the consolidated balance sheets. Forward Loan Sale Commitments The Company utilizes both “mandatory delivery” and “best efforts” forward loan sale commitments to mitigate the risk of potential decreases in the values 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 is obligated to pay a “pair-off” fee, based on then-current market prices, to the investor to compensate the investor for the shortfall. 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 does not account for best efforts contracts as derivative instruments, as such contracts do not require payment of a pair-off fee if the underlying mortgage loan does not close. The Company expects that these forward loan sale commitments will experience inverse changes in fair value to the change in fair value of derivative loan commitments. The notional amount of mandatory delivery forward loan sale commitments was $18,807,000 and $18,197,000 at September 30, 2017 and December 31, 2016, at September 30, 2017 and December 31, 2016, at September 30, 2017 and December 31, 2016,

Employee Stock Ownership Plan

Employee Stock Ownership Plan	9 Months Ended
	Sep. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Employee Stock Ownership Plan	1. EMPLOYEE STOCK OWNERSHIP PLAN In connection with our mutual-to-stock conversion and stock offering, the Company established an employee stock ownership plan (“ESOP) which acquired 469,498 shares of the Company’s common stock equaling 8% of the shares issued, including shares issued to the Foundation. The ESOP is a tax-qualified retirement plan providing employees the opportunity to own Company stock. Company contributions to the ESOP are allocated to eligible participants on the basis of compensation, subject to federal tax limits. The number of shares to be allocated annually is 18,780 through 2040. Shares are committed to be released on a monthly basis and allocated as of December 31 each year. During the three and nine month periods ended September 30, 2017, 4,695 shares and 14,085 shares, respectively, were committed to be released, resulting in compensation expense, based on the fair value of the Company’s stock, of $69,000 and $214,000, respectively. During the three and nine month periods ended September 30, 2016, 9,390 shares were committed to be released resulting in compensation expense of $120,200. The fair value of the 436,633 unallocated shares at September 30, 2017 was $6,684,900.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	1. EARNINGS (LOSS) PER SHARE Basic earnings (loss) per share represents net income (loss) divided by the weighted average of common shares outstanding during the period. Unallocated ESOP shares are not considered to be outstanding for purposes of computing earnings (loss) per share. There were no potentially dilutive common stock equivalents outstanding at September 30, 2017. The cost of shares issued to the ESOP, but not yet allocated or committed to be released to participants, is shown as a reduction of stockholders’ equity. During the three and nine months ended September 30, 2017, September 30, 2017

Share Repurchase Program

Share Repurchase Program	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Share Repurchase Program	1. SHARE REPURCHASE PROGRAM On September 15, 2017, the Company announced a stock repurchase program under which the Company may repurchase up to 586,854 shares, or 10% of its shares currently outstanding. Repurchases under this 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 the SEC’s Rule 10b5-1. No shares have been repurchased as part of this program as of September 30, 2017.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	1. 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. Effective July 1, 2016, the Company elected the fair value option pursuant to Accounting Standards Codification (“ASC”) 825, “Financial Instruments” for its residential mortgage loans being held for sale in the secondary market. ASC 825 allows for the irrevocable option to elect fair value accounting for the initial and subsequent measurement for certain financial assets and liabilities on a contract-by-contract basis that may otherwise not be required to be measured at fair value under other accounting standards. The Company elected the fair value option to better match changes in fair values of the loans with changes in the fair value of the forward loan sale commitments which are used to economically hedge them against changes in interest rates between the time an interest rate lock agreement is entered into with the borrower and the time the completed loan is sold. The aggregate fair value of loans held for sale, the contractual balance of loans held for sale and the gain on loans held for sale totaled $26.5 million, $25.9 million and $591,000, respectively, at September 30, 2017. The aggregate fair value of loans held for sale, the contractual balance of loans held for sale and the gain on loans held for sale totaled $30.5 million, $29.7 million and $768,000, respectively, at December 31, 2016. The change in fair value of loans held for sale reported as a component of net gains on sale of mortgage loans was $(112,000) and $911,000 for the three months ended September 30, 2017 and 2016, respectively, and $(177,000) for the nine months ended September 30, 2017. 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 (“FHLBB”) stock Loans held for sale Fair values are based on commitments in effect from investors or prevailing market prices and include the servicing value of the loans. Loans Mortgage servicing rights Deposit liabilities FHLBB advances 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 (In thousands) September 30, 2017 Assets: Securities available for sale: Debt securities $ — $ 64,603 $ — $ 64,603 Mutual fund — 538 — 538 Loans held for sale — 26,541 — 26,541 Derivative loan commitments — 552 — 552 Forward loan sale commitments — 35 — 35 Liabilities: Forward loan sale commitments — 19 — 19 December 31, 2016 Assets: Securities available for sale: Debt securities $ — $ 68,099 $ — $ 68,099 Mutual fund — 538 — 538 Loans held for sale — 30,452 — 30,452 Derivative loan commitments — 617 — 617 Forward loan sale commitments — 65 — 65 Liabilities: Forward loan sale commitments — 47 — 47 Assets measured at fair value on a non-recurring basis The Company may also be required, from time to time, to measure certain other assets at fair value 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. The following table summarizes the fair value hierarchy used to determine each adjustment and the carrying value of the related assets as of September 30, 2017 and December 31, 2016. September 30, 2017 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 1,369 Mortgage servicing rights — 6,039 — $ — $ 6,039 $ 1,369 December 31, 2016 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 518 Mortgage servicing rights — 8,486 — $ — $ 8,486 $ 518 The fair value of properties associated with collateral dependent impaired loans are based on recent appraisals for which no discounts were applied. The Company recorded a partial reversal of the valuation allowance for its mortgage servicing rights of $134,000 during the nine months ended September 30, 2017 There were no liabilities measured at fair value on a non-recurring basis at September 30, 2017 and December 31, 2016. 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 mortgagors’ escrow accounts and accrued interest payable. September 30, 2017 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,940 $ 2,949 $ — $ 2,949 $ — Securities available for sale 65,141 65,141 — 65,141 — Loans held for sale 26,541 26,541 — 26,541 — Loans, net 372,777 373,871 — — 373,871 Derivative assets 587 587 — 587 — Financial liabilities: Deposits $ 358,901 $ 358,509 $ — $ 358,509 $ — FHLBB advances 56,935 56,847 — 56,847 — Derivative liabilities 19 19 — 19 — December 31, 2016 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 3,675 $ 3,687 $ — $ 3,687 $ — Securities available for sale 68,637 68,637 — 68,637 — Loans held for sale 30,452 30,452 — 30,452 — Loans, net 332,991 331,132 — — 331,132 Derivative assets 682 682 — 682 — Financial liabilities: Deposits $ 351,179 350,979 $ — $ 350,979 $ — FHLBB advances 38,667 38,531 — 38,531 — Derivative liabilities 47 47 — 47 —

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1. COMMITMENTS AND CONTINGENCIES 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. The following financial instruments were outstanding, at the dates indicated, whose contract amounts represent credit risk: September 30, 2017 December 31, 2016 (In thousands) Commitments to originate loans $ 50,875 $ 35,682 Unused lines and letters of credit 38,430 37,045 Unadvanced funds on construction loans 7,978 9,321 Overdraft lines of credit 9,087 9,189 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. At September 30, 2017, we had $50.9 million in loan commitments outstanding, including $40.0 million related to loans to be sold in the secondary mortgage market and for which the Company had $18.8 million in forward loan sale commitments from investors. Lease commitments During the nine months ended September 30, 2017, the Company entered into a non-cancelable lease related to a new lending center in Andover, MA. This lease has an initial lease term of five years, with an option to extend for an additional period of five years. The Company expects to take occupancy of this new facility in November 2017. In addition, the Company entered into a non-cancelable lease with a five-year initial lease term and two five-year renewal options for a new branch office in Braintree, MA. This branch is expected to open in the first quarter of 2018, at which time customers of our North Randolph, MA branch will be transferred to this new branch location. The aggregate future minimum rent commitment associated with these leases was $2.5 million as of September 30, 2017. Other contingencies We are not currently a party to any pending legal proceedings that we believe would have a material adverse effect on our financial condition, results of operations or cash flows.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	1. SUBSEQUENT EVENT At the annual meeting held in August 2017, the Company’s shareholders approved the 2017 Stock Option and Incentive Plan (the “Plan”). The maximum number of shares issuable under the Plan is 821,621 consisting of up to 586,872 shares issuable pursuant to the exercise of stock options and 234,749 shares issuable as restricted stock awards or restricted stock units. In October 2017, the Governance Committee of the Board of Directors approved initial grants of stock options and restricted stock awards to both management and directors. This initial award consisted of a total of 340,387 stock options and 192,491 shares of restricted stock. The Company’s closing stock price on the date of grant was $14.66, which was used in setting the exercise price for the stock options. The restricted shares do not require any cash consideration from the awardee. Based on the closing stock price noted above, the unearned compensation associated with the restricted shares is $2.8 million. The Company has not yet determined the fair value of the grant of stock options. The fair value of stock options will be determined during the fourth quarter using the Black-Scholes model. Stock options granted become exercisable and restricted stock awarded vest at a rate of 20% annually with accelerated vesting in the event of death, disability or, in certain cases, retirement.

Conversion and Basis of Prese24

Conversion and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Financial Statement Presentation	Basis of Financial Statement Presentation The consolidated financial statements include the accounts of Randolph Bancorp, Inc. and its wholly-owned subsidiary, Randolph Savings Bank (together, the “Company”). The Bank has subsidiaries involved in owning investment securities and foreclosed real estate properties and a subsidiary which provides loan closing services. All intercompany accounts and transactions have been eliminated in consolidation. These financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the Securities and Exchange Commission (“SEC”). Accordingly, the accompanying interim financial statements do not include all information required under GAAP for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation of the financial statements, primarily consisting of normal recurring adjustments, have been included. The operating results for the nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or any other interim period. For further information, refer to the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, as filed with the SEC.
Recent Accounting Pronouncements	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

Acquisition (Tables)

Acquisition (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Summary of Unaudited Pro Forma Financial Information	Unaudited pro forma financial information for the nine months ended September 30, 2016 is as follows (in thousands): Net Interest Income $ 10,038 Non-interest Income 16,371 Net Income 1,598

Accumulated Other Comprehensi26

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Components of Accumulated Other Comprehensive Loss and Related Tax Effects	The components of accumulated other comprehensive loss, included in total stockholders’ equity, are as follows: September 30, December 31, 2017 2016 (In thousands) Securities available for sale: Net unrealized loss $ (233 ) $ (698 ) Tax effect (574 ) (423 ) Net-of-tax amount (807 ) (1,121 ) Supplemental retirement plan Unrecognized net actuarial loss (651 ) (679 ) Unrecognized net prior service credit 506 573 (145 ) (106 ) Tax effect (57 ) (57 ) Net-of-tax amount (202 ) (163 ) Accumulated other comprehensive loss $ (1,009 ) $ (1,284 )

Securities Available for Sale (

Securities Available for Sale (Tables)	9 Months Ended
	Sep. 30, 2017
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) September 30, 2017 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 73 $ (8 ) $ 4,064 Corporate 3,013 36 (4 ) 3,045 Municipal 13,466 279 (4 ) 13,741 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 19,334 159 (417 ) 19,076 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,509 48 (369 ) 14,188 U.S. Government-guaranteed 8,264 25 (76 ) 8,213 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,931 30 — 1,961 U.S. Government-guaranteed 313 2 — 315 Total debt securities 64,829 652 (878 ) 64,603 Mutual fund 545 — (7 ) 538 Total securities available for sale $ 65,374 $ 652 $ (885 ) $ 65,141 December 31, 2016 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 92 $ (10 ) $ 4,081 Corporate 3,044 54 (18 ) 3,080 Municipal 13,857 254 (56 ) 14,055 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 21,130 172 (580 ) 20,722 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,676 56 (554 ) 14,178 U.S. Government-guaranteed 9,589 12 (144 ) 9,457 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 2,127 28 — 2,155 U.S. Government-guaranteed 368 3 — 371 Total debt securities 68,790 671 (1,362 ) 68,099 Mutual fund 545 — (7 ) 538 Total securities available for sale $ 69,335 $ 671 $ (1,369 ) $ 68,637
Investments Classified by Contractual Maturity Date	The amortized cost and fair value of debt securities by contractual maturity at September 30, 2017 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 $ 3,430 $ 3,440 After 1 year through 5 years 14,792 15,079 After 5 years through 10 years 2,256 2,331 20,478 20,850 Mortgage-backed securities 44,351 43,753 $ 64,829 $ 64,603
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	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: Less Over Twelve Months Gross Gross Unrealized Fair Unrealized Fair Losses Value Losses Value September 30, 2017 (In thousands) Debt securities: U.S. Government-sponsored enterprises $ (8 ) $ 1,992 $ — $ — Corporate (3 ) 1,027 (1 ) 472 Municipal (2 ) 1,120 (2 ) 483 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (417 ) 13,606 — — Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (369 ) 8,867 — — U.S. Government-guaranteed (76 ) 3,867 — — Total debt securities (875 ) 30,479 (3 ) 955 Mutual Fund (7 ) 537 — — $ (882 ) $ 31,016 $ (3 ) $ 955 December 31, 2016 Debt securities: U.S. Government-sponsored enterprises $ (10 ) $ 1,990 $ — $ — Corporate (14 ) 519 (4 ) 996 Municipal (46 ) 3,310 (10 ) 477 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (580 ) 16,261 — — Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (554 ) 8,766 — — U.S. Government-guaranteed (144 ) 5,927 — — Total debt securities (1,348 ) 36,773 (14 ) 1,473 Mutual Fund (7 ) 538 — — $ (1,355 ) $ 37,311 $ (14 ) $ 1,473

Loans and Allowance for Loan 28

Loans and Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Summary of Loan Portfolio	A summary of loan portfolio is as follows: September 30, 2017 December 31, 2016 (In thousands) Mortgage loans on real estate: Residential: One-to-four family $ 189,311 $ 179,025 Home equity loans and lines of credit 39,033 35,393 Commercial 96,915 88,394 Construction 23,266 23,629 348,525 326,441 Commercial and industrial 16,373 2,067 Consumer 10,068 6,578 Total loans 374,966 335,086 Allowance for loan losses (3,545 ) (3,271 ) Net deferred loan costs and fees, and purchase premiums 1,356 1,176 $ 372,777 $ 332,991
Summary of Changes in the Allowance for Loan Losses by Portfolio Segment	The following table summarizes the changes in the allowance for loan losses by portfolio segment for the three and nine months ended September 30, 2017 and 2016: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total (In thousands) Three Months Ended September 30, 2017 Allowance at June 30, 2017 $ 820 $ 338 $ 1,536 $ 389 $ 276 $ 198 $ 3,557 Provision (credit) for loan losses 15 6 42 (50 ) (15 ) 2 — Loans charged-off — — — — — (25 ) (25 ) Recoveries 7 — — — — 6 13 Balance at September 30, 2017 $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Three Months Ended September 30, 2016 Allowance at June 30, 2016 $ 1,046 $ 444 $ 1,520 $ 135 $ 36 $ 78 $ 3,259 Provision (credit) for loan losses 12 (15 ) (166 ) 9 3 (3 ) (160 ) Loans charged-off — — — — — (6 ) (6 ) Recoveries 2 — — — — 1 3 Balance at September 30, 2016 $ 1,060 $ 429 $ 1,354 $ 144 $ 39 $ 70 $ 3,096 Nine Months Ended September 30, 2017 Allowance at December 31, 2016 $ 1,018 $ 436 $ 1,410 $ 225 $ 37 $ 145 $ 3,271 Provision (credit) for loan losses (195 ) (92 ) 168 114 189 151 335 Loans charged-off — — — — — (134 ) (134 ) Recoveries 19 — — — 35 19 73 Balance at September 30, 2017 $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Nine Months Ended September 30, 2016 Allowance at December 31, 2015 $ 1,076 $ 512 $ 1,402 $ 159 $ 37 $ 53 $ 3,239 Provision (credit) for loan losses (20 ) (83 ) (48 ) (15 ) 2 66 (98 ) Loans charged-off — — — — — (66 ) (66 ) Recoveries 4 — — — — 17 21 Balance at September 30, 2016 $ 1,060 $ 429 $ 1,354 $ 144 $ 39 $ 70 $ 3,096
Summary of Additional Information Pertaining to the Allowance for Loan Losses	Additional information pertaining to the allowance for loan losses at September 30, 2017 and December 31, 2016 is as follows: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total September 30, 2017 (In thousands) Allowance for impaired loans $ 172 $ 1 $ 2 $ — $ — $ — $ 175 Allowance for non-impaired loans 670 343 1,576 339 261 181 3,370 Total allowance for loan losses $ 842 $ 344 $ 1,578 $ 339 $ 261 $ 181 $ 3,545 Impaired loans $ 5,156 $ 276 $ 734 $ — $ — $ — $ 6,166 Non-impaired loans 184,155 38,757 96,181 23,266 16,373 10,068 368,800 Total loans $ 189,311 $ 39,033 $ 96,915 $ 23,266 $ 16,373 $ 10,068 $ 374,966 December 31, 2016 Allowance for impaired loans $ 190 $ 2 $ 8 $ — $ — $ — $ 200 Allowance for non-impaired loans 828 434 1,402 225 37 145 3,071 Total allowance for loan losses $ 1,018 $ 436 $ 1,410 $ 225 $ 37 $ 145 $ 3,271 Impaired loans $ 4,506 $ 276 $ 832 $ — $ — $ — $ 5,614 Non-impaired loans 174,519 35,117 87,562 23,629 2,067 6,578 329,472 Total loans $ 179,025 $ 35,393 $ 88,394 $ 23,629 $ 2,067 $ 6,578 $ 335,086
Schedule of Past Due and Non-Accrual Loans	The following is a summary of past due and non-accrual loans at September 30, 2017 and December 31, 2016: 30 - 59 Days Past Due 60 - 89 Days Past Due 90 Days or More Past Due Total Past Due Non-accrual Loans (In thousands) September 30, 2017 Residential one-to-four family $ 732 $ — $ — $ 732 $ 1,906 Home equity loans and lines of credit 68 107 — 175 276 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer — — — — — Total $ 800 $ 107 $ — $ 907 $ 2,182 December 31, 2016 Residential one-to-four family $ 1,168 $ 201 $ — $ 1,369 $ 1,945 Home equity loans and lines of credit 258 — — 258 276 Commercial real estate 400 — — 400 — Construction — — — — — Commercial and industrial — — — — — Consumer 59 — — 59 — Total $ 1,885 $ 201 $ - $ 2,086 $ 2,221
Summary of Impaired Loans and Additional Information Pertaining to Impaired Loans	The following is a summary of impaired loans at September 30, 2017 and December 31, 2016: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) September 30, 2017 Impaired loans without a valuation allowance: Residential one-to-four family $ 2,631 $ 2,576 Home equity loans and lines of credit 247 247 Commercial real estate 608 608 Total 3,486 3,431 Impaired loans with a valuation allowance: Residential one-to-four family 2,600 2,580 $ 172 Home equity loans and lines of credit 30 29 1 Commercial real estate 126 126 2 Total 2,756 2,735 175 Total impaired loans $ 6,242 $ 6,166 $ 175 December 31, 2016 Impaired loans without a valuation allowance: Residential one-to-four family $ 1,922 $ 1,877 Home equity loans and lines of credit 246 246 Commercial real estate 270 270 Total 2,438 2,393 Impaired loans with a valuation allowance: Residential one-to-four family 2,648 2,629 $ 190 Home equity loans and lines of credit 31 30 2 Commercial real estate 562 562 8 Total 3,241 3,221 200 Total impaired loans $ 5,679 $ 5,614 $ 200 Additional information pertaining to impaired loans follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Nine Months Ended September 30, 2017 Residential one-to-four family $ 4,896 $ 143 $ 62 Home equity loans and lines of credit 276 1 1 Commercial real estate 732 23 — Total $ 5,904 $ 167 $ 63 Nine Months Ended September 30, 2016 Residential one-to-four family $ 5,165 $ 130 $ 49 Home equity loans and lines of credit 253 1 1 Commercial real estate 1,193 42 2 Commercial and industrial 5 1 1 Total $ 6,616 $ 174 $ 53 Three Months Ended September 30, 2017 Residential one-to-four family $ 5,124 $ 44 $ 16 Home equity loans and lines of credit 276 — — Commercial real estate 621 5 — Total $ 6,021 $ 49 $ 16 Three Months Ended September 30, 2016 Residential one-to-four family $ 5,613 $ 45 $ 23 Home equity loans and lines of credit 276 — - Commercial real estate 971 12 1 Total $ 6,860 $ 57 $ 24
Summary of Company's Loans by Risk Rating	The following table presents the Company’s loans by risk rating at the dates indicated: September 30, 2017 December 31, 2016 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3B (Pass rated) $ 96,713 $ 23,266 $ 16,373 $ 88,186 $ 23,286 $ 2,067 Loans rated 4 — — — — 343 — Loans rated 5 202 — — 208 — — $ 96,915 $ 23,266 $ 16,373 $ 88,394 $ 23,629 $ 2,067

Loan Servicing (Tables)

Loan Servicing (Tables)	9 Months Ended
	Sep. 30, 2017
Transfers And Servicing [Abstract]
Summary of Activity Relating to Mortgage Servicing Rights	The following table summarizes the activity relating to mortgage servicing rights for the nine months ended September 30, 2017 and 2016 (in thousands): September 30, 2017 September 30, 2016 Mortgage servicing rights: Balance at beginning of year $ 8,910 $ 2,601 Additions through originations 1,486 1,676 Additions through First Eastern acquisition — 6,216 Sales (3,126 ) — Amortization (941 ) (644 ) Balance at end of period $ 6,329 $ 9,849 Valuation allowance: Balance at beginning of year $ 424 $ 34 Provision (credit) (134 ) 464 Balance at end of period $ 290 $ 498 Amortized cost, net $ 6,039 $ 9,351 Fair value $ 6,051 $ 9,360

Fair Value of Assets and Liab30

Fair Value of Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
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 (In thousands) September 30, 2017 Assets: Securities available for sale: Debt securities $ — $ 64,603 $ — $ 64,603 Mutual fund — 538 — 538 Loans held for sale — 26,541 — 26,541 Derivative loan commitments — 552 — 552 Forward loan sale commitments — 35 — 35 Liabilities: Forward loan sale commitments — 19 — 19 December 31, 2016 Assets: Securities available for sale: Debt securities $ — $ 68,099 $ — $ 68,099 Mutual fund — 538 — 538 Loans held for sale — 30,452 — 30,452 Derivative loan commitments — 617 — 617 Forward loan sale commitments — 65 — 65 Liabilities: Forward loan sale commitments — 47 — 47
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 as of September 30, 2017 and December 31, 2016. September 30, 2017 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 1,369 Mortgage servicing rights — 6,039 — $ — $ 6,039 $ 1,369 December 31, 2016 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 518 Mortgage servicing rights — 8,486 — $ — $ 8,486 $ 518
Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments	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 mortgagors’ escrow accounts and accrued interest payable. September 30, 2017 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,940 $ 2,949 $ — $ 2,949 $ — Securities available for sale 65,141 65,141 — 65,141 — Loans held for sale 26,541 26,541 — 26,541 — Loans, net 372,777 373,871 — — 373,871 Derivative assets 587 587 — 587 — Financial liabilities: Deposits $ 358,901 $ 358,509 $ — $ 358,509 $ — FHLBB advances 56,935 56,847 — 56,847 — Derivative liabilities 19 19 — 19 — December 31, 2016 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 3,675 $ 3,687 $ — $ 3,687 $ — Securities available for sale 68,637 68,637 — 68,637 — Loans held for sale 30,452 30,452 — 30,452 — Loans, net 332,991 331,132 — — 331,132 Derivative assets 682 682 — 682 — Financial liabilities: Deposits $ 351,179 350,979 $ — $ 350,979 $ — FHLBB advances 38,667 38,531 — 38,531 — Derivative liabilities 47 47 — 47 —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk	The following financial instruments were outstanding, at the dates indicated, whose contract amounts represent credit risk: September 30, 2017 December 31, 2016 (In thousands) Commitments to originate loans $ 50,875 $ 35,682 Unused lines and letters of credit 38,430 37,045 Unadvanced funds on construction loans 7,978 9,321 Overdraft lines of credit 9,087 9,189

Conversion and Basis of Prese32

Conversion and Basis of Presentation - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2016	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2016	Sep. 30, 2017	Jul. 01, 2016
Plan Of Conversion [Line Items]
Common stock, shares issued				5,868,726	5,868,544	5,686,750
Share issued, price per share						$ 10
Proceeds from issuance of common stock	$ 56,867,500		$ 54,501,000
Direct cost of stock offering				$ 2,325,000
Contribution to Randolph Charitable Foundation Inc, shares		181,976
Contribution to Randolph Charitable Foundation Inc, cash		$ 455,000
Contribution to Randolph Charitable Foundation Inc, expense recognized		$ 2,274,700
ESOP [Member]
Plan Of Conversion [Line Items]
Common stock, shares issued						469,498
Loan repayment period	25 years

Acquisition - Additional Inform

Acquisition - Additional Information (Detail) - USD ($)	Jul. 03, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Business acquisition, date				Jul. 1, 2016
Income tax expense (benefit)		$ 129,000		$ (148,000)	$ 3,000
Merger integration costs		$ 7,000	$ 514,000	531,000	$ 664,000
Pro Forma [Member]
Business Acquisition [Line Items]
Income tax expense (benefit)				0
First Eastern Bankshares Corporation [Member]
Business Acquisition [Line Items]
Cash payment to acquisition	$ 14,100,000
Merger integration costs				$ 0

Acquisition - Summary of Unaudi

Acquisition - Summary of Unaudited Pro Forma Financial Information (Detail) - First Eastern Bankshares Corporation [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Business Acquisition [Line Items]
Net Interest Income	$ 10,038
Non-interest Income	16,371
Net Income	$ 1,598

Accumulated Other Comprehensi35

Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss and Related Tax Effects (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			$ (233)		$ (698)
Total other comprehensive income (loss)	$ (217)	$ (354)	275	$ 638
Accumulated other comprehensive loss, net of tax	$ (1,009)		(1,009)		(1,284)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive Loss, Tax effect			(574)		(423)
Total other comprehensive income (loss)			(807)		(1,121)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			(651)		(679)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			506		573
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			(145)		(106)
Other comprehensive Loss, Tax effect			(57)		(57)
Total other comprehensive income (loss)			$ (202)		$ (163)

Securities Available for Sale -

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 65,374	$ 69,335
Gross Unrealized Gains	652	671
Gross Unrealized Losses	(885)	(1,369)
Fair Value	65,141	68,637
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	64,829	68,790
Gross Unrealized Gains	652	671
Gross Unrealized Losses	(878)	(1,362)
Fair Value	64,603	68,099
Debt Securities [Member] | US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,999	3,999
Gross Unrealized Gains	73	92
Gross Unrealized Losses	(8)	(10)
Fair Value	4,064	4,081
Debt Securities [Member] | Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,013	3,044
Gross Unrealized Gains	36	54
Gross Unrealized Losses	(4)	(18)
Fair Value	3,045	3,080
Debt Securities [Member] | Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,466	13,857
Gross Unrealized Gains	279	254
Gross Unrealized Losses	(4)	(56)
Fair Value	13,741	14,055
Debt Securities [Member] | Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,334	21,130
Gross Unrealized Gains	159	172
Gross Unrealized Losses	(417)	(580)
Fair Value	19,076	20,722
Debt Securities [Member] | Commercial Mortgage Backed Securities, U.S. Government-guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,264	9,589
Gross Unrealized Gains	25	12
Gross Unrealized Losses	(76)	(144)
Fair Value	8,213	9,457
Debt Securities [Member] | Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,509	14,676
Gross Unrealized Gains	48	56
Gross Unrealized Losses	(369)	(554)
Fair Value	14,188	14,178
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	313	368
Gross Unrealized Gains	2	3
Fair Value	315	371
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,931	2,127
Gross Unrealized Gains	30	28
Fair Value	1,961	2,155
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	545	545
Gross Unrealized Losses	(7)	(7)
Fair Value	$ 538	$ 538

Securities Available for Sale37

Securities Available for Sale - Investments Classified by Contractual Maturity Date (Detail) $ in Thousands	Sep. 30, 2017USD ($)
Available-for-sale Securities, Debt Maturities, Amortized Cost
Within 1 year	$ 3,430
After 1 year through 5 years	14,792
After 5 years through 10 years	2,256
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total	20,478
Mortgage-backed securities	44,351
Available-for-sale Debt Securities, Amortized Cost Basis, Total	64,829
Available-for-sale Securities, Debt Maturities, Fair Value
Within 1 year	3,440
After 1 year through 5 years	15,079
After 5 years through 10 years	2,331
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Fair Value Total	20,850
Mortgage-backed securities	43,753
Available-for-sale Securities, Debt Securities, Fair Value Total	$ 64,603

Securities Available for Sale38

Securities Available for Sale - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	$ (882)	$ (1,355)
Less Than Twelve Months, Fair Value	31,016	37,311
Over Twelve Months, Gross Unrealized Losses	(3)	(14)
Over Twelve Months, Fair Value	955	1,473
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(875)	(1,348)
Less Than Twelve Months, Fair Value	30,479	36,773
Over Twelve Months, Gross Unrealized Losses	(3)	(14)
Over Twelve Months, Fair Value	955	1,473
Debt Securities [Member] | US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(8)	(10)
Less Than Twelve Months, Fair Value	1,992	1,990
Debt Securities [Member] | Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(3)	(14)
Less Than Twelve Months, Fair Value	1,027	519
Over Twelve Months, Gross Unrealized Losses	(1)	(4)
Over Twelve Months, Fair Value	472	996
Debt Securities [Member] | Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(2)	(46)
Less Than Twelve Months, Fair Value	1,120	3,310
Over Twelve Months, Gross Unrealized Losses	(2)	(10)
Over Twelve Months, Fair Value	483	477
Debt Securities [Member] | Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(417)	(580)
Less Than Twelve Months, Fair Value	13,606	16,261
Debt Securities [Member] | Commercial Mortgage Backed Securities, U.S. Government-guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(76)	(144)
Less Than Twelve Months, Fair Value	3,867	5,927
Debt Securities [Member] | Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(369)	(554)
Less Than Twelve Months, Fair Value	8,867	8,766
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(7)	(7)
Less Than Twelve Months, Fair Value	$ 537	$ 538

Securities Available for Sale39

Securities Available for Sale - Additional Information (Detail)	Sep. 30, 2017Debt_Security
Investments Debt And Equity Securities [Abstract]
Number of debt securities with unrealized losses	29
Unrealized losses debt securities aggregate depreciation percentage	2.80%

Loans and Allowance for Loan 40

Loans and Allowance for Loan Losses - Summary of Loan Portfolio (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 374,966	$ 335,086
Allowance for loan losses	(3,545)	(3,271)
Net deferred loan costs and fees, and purchase premiums	1,356	1,176
Net loans	372,777	332,991
Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	348,525	326,441
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	96,915	88,394
Commercial Real Estate Loans [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	96,915	88,394
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	16,373	2,067
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,068	6,578
One-to-Four Family [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	189,311	179,025
One-to-Four Family [Member] | Residential Real Estate [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	189,311	179,025
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	39,033	35,393
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	23,266	23,629
Construction [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 23,266	$ 23,629

Loans and Allowance for Loan 41

Loans and Allowance for Loan Losses - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)TDR	Sep. 30, 2016USD ($)TDR	Dec. 31, 2016USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased loan participations originated through super-regional bank	$ 15,400,000		$ 15,400,000
Refinanced student loans purchased	5,000,000		5,000,000
Loans past due 90 days or more	0		0		$ 0
Impaired loans, additional funds committed	0		0
Troubled debt restructuring amount			4,567,000	$ 6,050,000
Changes to allowance for loan losses	0	$ 0	$ 0	0
Minimum past due days for loan rating			90 days
Total loans	374,966,000		$ 374,966,000		335,086,000
Residential Mortgage [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	717,000		717,000		890,000
Residential Mortgage [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,312,000		2,312,000		1,471,000
30 - 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings defaulted over 30 days past due	0	0	0	0
Non Accrual Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring amount			1,139,000	$ 1,714,000
Home Equity Loans and Lines of Credit [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	29,000		29,000
Home Equity Loans and Lines of Credit [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	370,000		$ 370,000		400,000
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR			20	24
Loans subject to troubled debt restructurings, amount	4,382,000	5,367,000	$ 4,382,000	$ 5,367,000
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR			2	4
Loans subject to troubled debt restructurings, amount	185,000	$ 683,000	$ 185,000	$ 683,000
Total loans	96,915,000		96,915,000		88,394,000
Commercial Real Estate Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 202,000		$ 202,000		$ 208,000

Loans and Allowance for Loan 42

Loans and Allowance for Loan Losses - Summary of Changes in the Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 3,557	$ 3,259	$ 3,271	$ 3,239
Provision (credit) for loan losses		(160)	335	(98)
Loans charged-off	(25)	(6)	(134)	(66)
Recoveries	13	3	73	21
Ending balance	3,545	3,096	3,545	3,096
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,536	1,520	1,410	1,402
Provision (credit) for loan losses	42	(166)	168	(48)
Ending balance	1,578	1,354	1,578	1,354
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	276	36	37	37
Provision (credit) for loan losses	(15)	3	189	2
Recoveries			35
Ending balance	261	39	261	39
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	198	78	145	53
Provision (credit) for loan losses	2	(3)	151	66
Loans charged-off	(25)	(6)	(134)	(66)
Recoveries	6	1	19	17
Ending balance	181	70	181	70
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	820	1,046	1,018	1,076
Provision (credit) for loan losses	15	12	(195)	(20)
Recoveries	7	2	19	4
Ending balance	842	1,060	842	1,060
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	338	444	436	512
Provision (credit) for loan losses	6	(15)	(92)	(83)
Ending balance	344	429	344	429
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	389	135	225	159
Provision (credit) for loan losses	(50)	9	114	(15)
Ending balance	$ 339	$ 144	$ 339	$ 144

Loans and Allowance for Loan 43

Loans and Allowance for Loan Losses - Summary of Additional Information Pertaining to the Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	$ 175		$ 200
Allowance for non-impaired loans	3,370		3,071
Total allowance for loan losses	3,545	$ 3,557	3,271	$ 3,096	$ 3,259	$ 3,239
Impaired loans	6,166		5,614
Non-impaired loans	368,800		329,472
Total loans	374,966		335,086
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	2		8
Allowance for non-impaired loans	1,576		1,402
Total allowance for loan losses	1,578	1,536	1,410	1,354	1,520	1,402
Impaired loans	734		832
Non-impaired loans	96,181		87,562
Total loans	96,915		88,394
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	261		37
Total allowance for loan losses	261	276	37	39	36	37
Non-impaired loans	16,373		2,067
Total loans	16,373		2,067
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	181		145
Total allowance for loan losses	181	198	145	70	78	53
Non-impaired loans	10,068		6,578
Total loans	10,068		6,578
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	172		190
Allowance for non-impaired loans	670		828
Total allowance for loan losses	842	820	1,018	1,060	1,046	1,076
Impaired loans	5,156		4,506
Non-impaired loans	184,155		174,519
Total loans	189,311		179,025
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	1		2
Allowance for non-impaired loans	343		434
Total allowance for loan losses	344	338	436	429	444	512
Impaired loans	276		276
Non-impaired loans	38,757		35,117
Total loans	39,033		35,393
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	339		225
Total allowance for loan losses	339	$ 389	225	$ 144	$ 135	$ 159
Non-impaired loans	23,266		23,629
Total loans	$ 23,266		$ 23,629

Loans and Allowance for Loan 44

Loans and Allowance for Loan Losses - Schedule of Past Due and Non-Accrual Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 907	$ 2,086
Non-accrual Loans	2,182	2,221
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		59
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	732	1,369
Non-accrual Loans	1,906	1,945
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	175	258
Non-accrual Loans	276	276
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		400
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	800	1,885
30 - 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		59
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	732	1,168
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	68	258
30 - 59 Days Past Due [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		400
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	107	201
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		$ 201
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	$ 107

Loans and Allowance for Loan 45

Loans and Allowance for Loan Losses - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	$ 3,486	$ 2,438
Unpaid Principal Balance without a valuation allowance	3,431	2,393
Recorded Investment with a valuation allowance	2,756	3,241
Unpaid Principal Balance with a valuation allowance	2,735	3,221
Related Allowance, Total impaired loans	175	200
Recorded Investment, Total impaired loans	6,242	5,679
Unpaid Principal Balance, Total impaired loans	6,166	5,614
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	608	270
Unpaid Principal Balance without a valuation allowance	608	270
Recorded Investment with a valuation allowance	126	562
Unpaid Principal Balance with a valuation allowance	126	562
Related Allowance, Total impaired loans	2	8
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	2,631	1,922
Unpaid Principal Balance without a valuation allowance	2,576	1,877
Recorded Investment with a valuation allowance	2,600	2,648
Unpaid Principal Balance with a valuation allowance	2,580	2,629
Related Allowance, Total impaired loans	172	190
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	247	246
Unpaid Principal Balance without a valuation allowance	247	246
Recorded Investment with a valuation allowance	30	31
Unpaid Principal Balance with a valuation allowance	29	30
Related Allowance, Total impaired loans	$ 1	$ 2

Loans and Allowance for Loan 46

Loans and Allowance for Loan Losses - Summary of Additional Information Pertaining to Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 6,021	$ 6,860	$ 5,904	$ 6,616
Interest Income Recognized	49	57	167	174
Cash Basis Interest Recognized	16	24	63	53
Residential Real Estate [Member] | One-to-Four Family [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	5,124	5,613	4,896	5,165
Interest Income Recognized	44	45	143	130
Cash Basis Interest Recognized	16	23	62	49
Residential Real Estate [Member] | Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	276	276	276	253
Interest Income Recognized			1	1
Cash Basis Interest Recognized			1	1
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	621	971	732	1,193
Interest Income Recognized	$ 5	12	$ 23	42
Cash Basis Interest Recognized		$ 1		2
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment				5
Interest Income Recognized				1
Cash Basis Interest Recognized				$ 1

Loans and Allowance for Loan 47

Loans and Allowance for Loan Losses - Summary of Company's Loans by Risk Rating (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 374,966	$ 335,086
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	96,915	88,394
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,373	2,067
Pass [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	96,713	88,186
Pass [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,373	2,067
Substandard [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	202	208
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,266	23,629
Construction [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 23,266	23,286
Construction [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans		$ 343

Loan Servicing - Additional Inf

Loan Servicing - Additional Information (Detail) - USD ($)	Jul. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Servicing Assets At Amortized Value [Line Items]
Unpaid principal balance of residential mortgage loans serviced for others		$ 754,939,000	$ 754,939,000	$ 1,046,551,000
Increased in valuation allowance of mortgage servicing rights		97,000	134,000
Mortgage servicing rights sold to third party			3,126,000
Residential Mortgage [Member]
Servicing Assets At Amortized Value [Line Items]
Mortgage servicing rights sold to third party	$ 379,000,000
Transfer of service completion date	2017-09
Gain on sale of mortgage servicing rights			68,000
Proceeds from sale of mortgage servicing rights			$ 2,700,000
Proceeds from sale of mortgage servicing rights, percentage			80.00%
Amount due from purchaser		$ 595,000	$ 595,000

Loan Servicing - Summary of Act

Loan Servicing - Summary of Activity Relating to Mortgage Servicing Rights (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Mortgage servicing rights:
Balance at beginning of year	$ 8,910	$ 2,601
Additions through originations	1,486	1,676
Sales	(3,126)
Amortization	(941)	(644)
Balance at end of period	6,329	9,849
Valuation allowance:
Balance at beginning of year	424	34
Provision (credit)	(134)	464
Balance at end of period	290	498
Amortized cost, net	6,039	9,351
Fair value	$ 6,051	9,360
First Eastern Bankshares Corporation [Member]
Mortgage servicing rights:
Additions through originations		$ 6,216

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Deferred income tax provision (benefit)	$ 129,000	$ 0	$ (151,000)	$ 0
Current state tax expense			$ 3,000	$ 3,000

On-Balance Sheet Derivative I51

On-Balance Sheet Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative, Notional amount	$ 39,959,000	$ 32,904,000
Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative, Notional amount	18,807,000	18,197,000
Other Assets [Member] | Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative fair value, Asset	552,000	617,000
Other Assets [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative fair value, Asset	35,000	65,000
Other Liabilities [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative fair value, Liability	$ 19,000	$ 47,000

Employee Stock Ownership Plan -

Employee Stock Ownership Plan - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Number of allocated shares	18,780		18,780
Annual allocation of shares, expiration year			2,040
Shares committed to be released	4,695	9,390	14,085	120,200
Fair value of shares under employee stock ownership plan	$ 69,000		$ 214,000
Unallocated shares	436,633		436,633
Unallocated shares, value	$ 6,684,900		$ 6,684,900
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
Percentage of stock issued during period shares employee stock ownership plan			8.00%

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
Earnings Per Share [Abstract]
Potentially dilutive common stock equivalents outstanding			0
Weighted average number of outstanding shares	5,868,544	5,868,726	5,868,660
Weighted Average Number of Shares, Unallocated and uncommitted ESOP shares	438,980	464,803	441,398
Weighted average common shares outstanding (basic and diluted)	5,429,564	5,403,923	5,427,262

Share Repurchase Program - Addi

Share Repurchase Program - Additional Information (Detail)	1 Months Ended	9 Months Ended
	Sep. 30, 2017shares	Sep. 30, 2017shares
Equity [Abstract]
Number of shares authorized to repurchase	586,854	586,854
Stock repurchase program percentage of outstanding shares repurchased	10.00%
Number of shares repurchased		0

Fair Value of Assets and Liab55

Fair Value of Assets and Liabilities - Additional information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain on sales of mortgage loans	$ 2,705,000	$ 5,401,000	$ 7,263,000	$ 7,140,000
Increased in valuation allowance of mortgage servicing rights	97,000		134,000
Liabilities measured at fair value on nonrecurring basis	0		0		$ 0
Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate fair value of loans held for sale	26,500,000		26,500,000		30,500,000
Contractual balance of loans held for sale	25,900,000		25,900,000		29,700,000
Net gain on sales of mortgage loans			591,000		$ 768,000
Residential Mortgage [Member] | Changes Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain on sales of mortgage loans	$ (112,000)	$ 911,000	$ (177,000)

Fair Value of Assets and Liab56

Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 65,141	$ 68,637
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	64,603	68,099
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	538	538
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	65,141	68,637
Fair value, Loans held for sale	26,541	30,452
Derivative assets	587	682
Forward loan sale commitments	19	47
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Loans held for sale	26,541	30,452
Forward loan sale commitments	19	47
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	64,603	68,099
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	538	538
Fair Value, Measurements, Recurring [Member] | Derivative Loan Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	552	617
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	35	65
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Loans held for sale	26,541	30,452
Forward loan sale commitments	19	47
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	64,603	68,099
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	538	538
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	552	617
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	$ 35	$ 65

Fair Value of Assets and Liab57

Fair Value of Assets and Liabilities - Schedule of Assets Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, fair value	$ 6,051		$ 9,360
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, fair value	6,039	$ 8,486
Assets, Fair Value Disclosure	6,039	8,486
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Collateral dependent impaired loans	1,369	518
Assets, Fair Value Disclosure	$ 1,369	$ 518

Fair Value of Assets and Liab58

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	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Securities available for sale	$ 65,141	$ 68,637
Level 2 [Member]
Financial assets:
Certificates of deposit	2,949	3,687
Securities available for sale	65,141	68,637
Loans held for sale	26,541	30,452
Derivative assets	587	682
Financial liabilities:
Deposits	358,509	350,979
FHLBB advances	56,847	38,531
Derivative liabilities	19	47
Level 3 [Member]
Financial assets:
Loans, net	373,871	331,132
Carrying Amount [Member]
Financial assets:
Certificates of deposit	2,940	3,675
Securities available for sale	65,141	68,637
Loans held for sale	26,541	30,452
Loans, net	372,777	332,991
Derivative assets	587	682
Financial liabilities:
Deposits	358,901	351,179
FHLBB advances	56,935	38,667
Derivative liabilities	19	47
Fair Value [Member]
Financial assets:
Certificates of deposit	2,949	3,687
Securities available for sale	65,141	68,637
Loans held for sale	26,541	30,452
Loans, net	373,871	331,132
Derivative assets	587	682
Financial liabilities:
Deposits	358,509	350,979
FHLBB advances	56,847	38,531
Derivative liabilities	$ 19	$ 47

Commitments and Contingencies -

Commitments and Contingencies - Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 50,900
Commitments to Originate Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	50,875	$ 35,682
Unused Lines and Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	38,430	37,045
Unadvanced Funds on Construction Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	7,978	9,321
Overdraft Lines of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 9,087	$ 9,189

Commitments and Contingencies60

Commitments and Contingencies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Commitments And Contingencies [Line Items]
Financial instruments with off-balance-sheet risk	$ 50.9
Initial lease term of non-cancelable leases	5 years
Additional period of lease term of non-cancelable leases	5 years
Aggregate future minimum rent commitment	$ 2.5
Braintree, MA [Member]
Commitments And Contingencies [Line Items]
Initial lease term of non-cancelable leases	5 years
Additional period of lease term of non-cancelable leases	5 years
Number of renewal options	2
Loans to Be Sold in the Secondary Mortgage Market
Commitments And Contingencies [Line Items]
Financial instruments with off-balance-sheet risk	$ 40
Forward Loan Sale Commitments [Member]
Commitments And Contingencies [Line Items]
Financial instruments with off-balance-sheet risk	$ 18.8

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - 2017 Stock Option and Incentive Plan [Member] - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Oct. 31, 2017	Aug. 31, 2017
Subsequent Event [Line Items]
Number of shares issuable under the plan		821,621
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock options initial award granted	340,387
Closing stock price on grant date	$ 14.66
Stock options and restricted stock award accelerated vesting rights, percentage	20.00%
Stock Option
Subsequent Event [Line Items]
Number of shares issuable under the plan		586,872
Restricted Stock Awards or Restricted Stock Units [Member]
Subsequent Event [Line Items]
Number of shares issuable under the plan		234,749
Restricted Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Restricted stock initial award granted	192,491
Unearned compensation on restricted shares	$ 2.8