Randolph Bancorp (RNDB) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
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	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		5,952,919

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 3,262	$ 3,562
Interest-bearing deposits	2,658	5,260
Total cash and cash equivalents	5,920	8,822
Certificates of deposit	2,695	2,940
Securities available for sale, at fair value	54,405	61,576
Loans held for sale, at fair value	24,120	25,390
Loans, net of allowance for loan losses of $3,890 in 2018 and $3,737 in 2017	468,938	400,373
Federal Home Loan Bank of Boston stock, at cost	3,471	3,310
Accrued interest receivable	1,521	1,432
Mortgage servicing rights, net	7,316	6,397
Premises and equipment, net	6,521	8,670
Bank-owned life insurance	8,186	8,037
Foreclosed real estate	82	193
Other assets	6,507	4,752
Total assets	589,682	531,892
Deposits:
Non-interest bearing	66,810	62,130
Interest bearing	360,363	304,706
Total deposits	427,173	366,836
Federal Home Loan Bank of Boston advances	77,411	75,954
Mortgagors' escrow accounts	1,810	907
Post-employment benefit obligations	2,588	2,750
Other liabilities	2,570	3,962
Total liabilities	511,552	450,409
Commitments and contingencies (Note 14)
Stockholders' Equity:
Preferred stock, no par value; authorized: 1,000,000 shares; issued: none
outstanding: 5,987,796 shares at September 30, 2018 and 6,034,276 at December 31, 2017	60	61
Additional paid-in capital	56,549	56,493
Retained earnings	28,556	30,415
ESOP-Unearned compensation	(4,179)	(4,319)
Accumulated other comprehensive loss, net of tax	(2,856)	(1,167)
Total stockholders' equity	78,130	81,483
Total liabilities and stockholders' equity	$ 589,682	$ 531,892

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Loans, allowance for loan losses	$ 3,890	$ 3,737
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	5,987,796	6,034,276
Common stock, shares outstanding	5,987,796	6,034,276

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest and dividend income:
Loans	$ 5,036	$ 3,936	$ 13,917	$ 11,049
Securities-taxable	386	339	1,122	1,065
Securities-tax exempt	19	87	104	264
Interest-bearing deposits and certificates of deposit	27	27	91	70
Total interest and dividend income	5,468	4,389	15,234	12,448
Interest expense:
Deposits	865	406	2,074	1,123
Federal Home Loan Bank of Boston advances	343	167	884	335
Total interest expense	1,208	573	2,958	1,458
Net interest income	4,260	3,816	12,276	10,990
Provision for loan losses	178		183	335
Net interest income after provision for loan losses	4,082	3,816	12,093	10,655
Non-interest income:
Customer service fees	357	359	1,096	1,109
Gain on loan origination and sale activities, net	1,956	2,705	5,356	7,263
Mortgage servicing fees, net	310	199	935	1,149
Gain on sale of building	230		230
Gain on sales of securities			49
Increase in cash surrender value of life insurance	73	38	148	114
Other	282	270	584	780
Total non-interest income	3,208	3,571	8,398	10,415
Non-interest expenses:
Salaries and employee benefits	4,788	4,668	14,166	14,059
Occupancy and equipment	728	682	2,157	1,957
Data processing	172	179	508	540
Professional fees	252	348	824	1,019
Marketing	205	277	867	624
FDIC insurance	48	18	131	104
Merger and integration costs		7		531
Other	1,234	1,030	3,683	2,932
Total non-interest expenses	7,427	7,209	22,336	21,766
Income (loss) before income taxes	(137)	178	(1,845)	(696)
Income tax expense (benefit)	5	129	14	(148)
Net income (loss)	$ (142)	$ 49	$ (1,859)	$ (548)
Weighted average common shares outstanding (basic and diluted)	5,567,596	5,429,564	5,585,571	5,427,262
Income (loss) per common share (basic and diluted)	$ (0.03)	$ 0.01	$ (0.33)	$ (0.10)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss)		$ (142)	$ 49	$ (1,859)	$ (548)
Securities available for sale:
Unrealized holding gains (losses)		(377)	(334)	(1,605)	465
Reclassification adjustment for net gains realized in income	[1]	0	0	(49)	0
Net unrealized gains (losses)		(377)	(334)	(1,654)	465
Related tax effects			129		(151)
Net-of-tax amount		(377)	(205)	(1,654)	314
Related tax effects		0	0	0	0
Net-of-tax amount		(12)	(12)	(35)	(39)
Total other comprehensive income (loss)		(389)	(217)	(1,689)	275
Comprehensive income (loss)		(531)	(168)	(3,548)	(273)
Supplemental Retirement Plan [Member]
Securities available for sale:
Actuarial losses	[2]	9	10	27	28
Prior service credits recognized	[2]	(21)	(22)	(62)	(67)
Post-retirement benefit plans		$ (12)	$ (12)	$ (35)	$ (39)
[1]	Amounts are included in gain on sales of securities in the consolidated statements of operations.
[2]	Amounts are included in other non-interest expenses in the consolidated statements of operations.

Consolidated Statements Changes

Consolidated Statements Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Unearned Compensation ESOP [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2016	$ 83,302	$ 59	$ 56,373	$ 32,661	$ (4,507)	$ (1,284)
Beginning balance, shares at Dec. 31, 2016		5,868,726
Net loss	(548)			(548)
Other comprehensive income (loss)	275					275
Stock repurchased	(3)		(3)
Stock repurchased, shares		(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
Beginning balance at Dec. 31, 2016	83,302	$ 59	56,373	32,661	(4,507)	(1,284)
Beginning balance, shares at Dec. 31, 2016		5,868,726
Ending balance at Dec. 31, 2017	81,483	$ 61	56,493	30,415	(4,319)	(1,167)
Ending balance, shares at Dec. 31, 2017		6,034,276
Net loss	(1,859)			(1,859)
Other comprehensive income (loss)	(1,689)					(1,689)
Stock repurchased	(631)	$ (1)	(630)
Stock repurchased, shares		(39,438)
Stock-based compensation	597		597
Restricted stock awards forfeited, shares		(7,042)
ESOP shares committed to be released	229		89		140
Ending balance at Sep. 30, 2018	$ 78,130	$ 60	$ 56,549	$ 28,556	$ (4,179)	$ (2,856)
Ending balance, shares at Sep. 30, 2018		5,987,796

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (1,859,000)	$ (548,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Provision for loan losses	183,000	335,000
Loans originated for sale	(277,474,000)	(304,312,000)
Net gain on sales of mortgage loans	(5,283,000)	(7,331,000)
Proceeds from sales of mortgage loans	284,027,000	315,554,000
Net amortization of securities	142,000	198,000
Net change in deferred loan costs and fees	(39,000)	(178,000)
Gain on sales of securities	(49,000)
Gain on sale of building	(230,000)
Depreciation and amortization	625,000	457,000
Stock-based compensation	597,000
ESOP expense	229,000	214,000
Increase in cash surrender value of life insurance	(148,000)	(114,000)
Net (increase) decrease in mortgage servicing rights	(919,000)	2,447,000
Other, net	(796,000)	(1,669,000)
Net cash provided by (used in) operating activities	(994,000)	5,053,000
Cash flows from investing activities:
Redemptions of certificates of deposit	245,000	735,000
Securities available for sale:
Calls/maturities	470,000	841,000
Purchases	(9,993,000)
Sales	8,958,000
Principal payments on mortgage-backed securities	5,940,000	3,256,000
Loan originations, net of principal repayments	(68,869,000)	(17,874,000)
Loans purchased, net of principal repayments	(3,836,000)	(22,068,000)
Proceeds from residential portfolio loan sale	3,996,000
Purchases of Federal Home Loan Bank of Boston stock	(161,000)	(431,000)
Purchases of premises and equipment	(1,373,000)	(1,932,000)
Proceeds from sale of building	649,000
Net cash used in investing activities	(63,974,000)	(37,473,000)
Cash flows from financing activities:
Net increase in non-brokered deposits	14,749,000	7,722,000
Net increase in brokered deposits	45,588,000
Net increase in short-term Federal Home Loan Bank of Boston borrowings	3,749,000	23,191,000
Repayments of long-term Federal Home Loan Bank of Boston advances	(2,292,000)	(4,923,000)
Net increase (decrease) in mortgagors' escrow accounts	903,000	(261,000)
Repurchases of common stock	(631,000)	(3,000)
Net cash provided by financing activities	62,066,000	25,726,000
Net change in cash and cash equivalents	(2,902,000)	(6,694,000)
Cash and cash equivalents at beginning of period	8,822,000	14,849,000
Cash and cash equivalents at end of period	5,920,000	8,155,000
Supplemental cash flow information:
Interest paid on deposits and borrowed funds	2,877,000	1,462,000
Income taxes paid	16,000	3,000
Transfer of premises and equipment to assets held for sale	$ 2,897,000	$ 420,000

Basis of Financial Statement Pr

Basis of Financial Statement Presentation	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Financial Statement Presentation	1. BASIS OF FINANCIAL STATEMENT PRESENTATION The consolidated financial statements include the accounts of Randolph Bancorp, Inc. (“Bancorp”) and its wholly-owned subsidiary, Envision Bank (the “Bank”, together with Bancorp, 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 three and nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or any other interim period. Prior to 2018, the Company’s operations were managed, and financial performance was evaluated, by the chief operating decision-maker on a company-wide basis. As a result, management had determined there to be a single business segment for financial reporting purposes through December 31, 2017. Due to the significance of the Company’s mortgage banking operations and the strategic focus on this business, management prepared its 2018 operating budget by breaking-out its mortgage banking activities, including residential loan origination and loan servicing. As a result, effective January 1, 2018, the Company is reporting two business segments, namely, “Envision Bank” and “Envision Mortgage”. As part of this process, management analyzed costs incurred by departments providing services to both segments (indirect costs), such as IT, Marketing, Accounting and Administration, to determine the allocation of indirect costs to each business segment in order to fully measure each segment’s results of operations. See Note 15 for disclosure of the Company’s segment information. 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, 2017, as filed with the SEC.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Pronouncements	2. RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers In January 2016, FASB issued ASU 2016-01, Financial Instruments In February 2016, FASB issued ASU 2016-02, Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses In April 2017, the FASB issued ASU 2017-08 Receivables – Non-refundable Fees and Other Costs In August 2018, the FASB issued ASU 2018-13 Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement, This ASU is effective for emerging growth companies for annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted, including adoption in an interim period. The Company is currently assessing the impact of this ASU on the consolidated financial statements.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	3 . ACCUMULATED OTHER COMPREHENSIVE LOSS Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net loss. Although certain changes in assets and liabilities are reported as a separate component of stockholders’ equity, such items, along with net loss, are components of comprehensive loss. The components of accumulated other comprehensive loss, included in total stockholders’ equity, are as follows: September 30, December 31, 2018 2017 (In thousands) Securities available for sale: Net unrealized loss $ (2,277 ) $ (624 ) Tax effect (313 ) (313 ) Net-of-tax amount (2,590 ) (937 ) Supplemental retirement plan Unrecognized net actuarial loss (640 ) (667 ) Unrecognized net prior service credit 421 484 (219 ) (183 ) Tax effect (47 ) (47 ) Net-of-tax amount (266 ) (230 ) Accumulated other comprehensive loss $ (2,856 ) $ (1,167 )

Securities Available for Sale

Securities Available for Sale	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Securities Available for Sale	4 . 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, 2018 Debt securities: U.S. Government-sponsored enterprises $ 4,000 $ 7 $ (45 ) $ 3,962 Corporate 1,527 6 (23 ) 1,510 Municipal 1,890 22 — 1,912 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 25,835 24 (1,113 ) 24,746 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,278 — (803 ) 13,475 U.S. Government-guaranteed 1,811 — (45 ) 1,766 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,689 — (46 ) 1,643 U.S. Government-guaranteed 5,107 — (229 ) 4,878 Total debt securities 56,137 59 (2,304 ) 53,892 Mutual fund 545 — (32 ) 513 Total securities available for sale $ 56,682 $ 59 $ (2,336 ) $ 54,405 December 31, 2017 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 50 $ (24 ) $ 4,025 Corporate 2,005 27 (8 ) 2,024 Municipal 12,707 179 (18 ) 12,868 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 18,729 118 (450 ) 18,397 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,451 13 (403 ) 14,061 U.S. Government-guaranteed 2,132 — (6 ) 2,126 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,871 12 (5 ) 1,878 U.S. Government-guaranteed 5,760 4 (100 ) 5,664 Total debt securities 61,654 403 (1,014 ) 61,043 Mutual fund 545 — (12 ) 533 Total securities available for sale $ 62,199 $ 403 $ (1,026 ) $ 61,576 For the nine months ended September 30, 2018, proceeds from sales of available-for-sale securities amounted to $9.0 million with gross realized gains of $49,000 and no gross realized losses. The amortized cost and fair value of debt securities by contractual maturity at September 30, 2018 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 $ 400 $ 400 After 1 year through 5 years 6,178 6,133 After 5 years through 10 years 839 851 7,417 7,384 Mortgage-backed securities 48,720 46,508 $ 56,137 $ 53,892 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, 2018 (In thousands) Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (45 ) $ 1,955 Corporate (23 ) 999 — — Residential mortgage-backed securities: U.S. Government-sponsored enterprises (433 ) 14,863 (680 ) 7,909 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (90 ) 5,066 (713 ) 8,410 U.S. Government-guaranteed (45 ) 1,766 — — Collateralized mortgage obligations: U.S. Government-sponsored enterprises (46 ) 1,643 — — U.S. Government-guaranteed (197 ) 4,331 (32 ) 547 Total debt securities (834 ) 28,668 (1,470 ) 18,821 Mutual Fund — — (32 ) 513 $ (834 ) $ 28,668 $ (1,502 ) $ 19,334 December 31, 2017 Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (24 ) $ 19,676 Corporate — — (8 ) 988 Municipal (11 ) 1,919 (7 ) 479 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (1 ) 1,623 (449 ) 13,163 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises — — (403 ) 8,805 U.S. Government-guaranteed (6 ) 2,126 — — Collateralized mortgage obligations: U.S. Government-sponsored enterprises (5 ) 678 — — U.S. Government-guaranteed (1 ) 295 (99 ) 3,756 Total debt securities (24 ) 6,641 (990 ) 46,867 Mutual Fund — — (12 ) 533 $ (24 ) $ 6,641 $ (1,002 ) $ 47,400 At September 30, 2018, 41 debt securities have unrealized losses with aggregate depreciation of 4.64% from the Company’s amortized cost basis. The unrealized losses at September 30, 2018, which related primarily to securities issued by U.S. government-sponsored enterprises, were primarily caused by interest rate increases. 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 securities would not be settled at a price less than the par value of the investment. Because the Company does not intend to sell any debt securities and it is more likely than not that the Company will not be required to sell any debt securities before recovery of its amortized cost basis, it does not consider these investments to be other-than-temporarily impaired at September 30, 2018.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans and Allowance for Loan Losses	5. LOANS AND ALLOWANCE FOR LOAN LOSSES A summary of loans held for investment at the dates indicated is as follows: September 30, 2018 December 31, 2017 (In thousands) Mortgage loans on real estate: Residential: One-to-four family $ 254,279 $ 198,475 Home equity loans and lines of credit 42,401 38,968 Commercial 108,817 101,755 Construction 28,816 25,357 434,313 364,555 Commercial and industrial 18,948 21,766 Consumer 18,075 16,337 Total loans 471,336 402,658 Allowance for loan losses (3,890 ) (3,737 ) Net deferred loan costs and fees, and purchase premiums 1,492 1,452 $ 468,938 $ 400,373 The following table summarizes the changes in the allowance for loan losses by portfolio segment for the three and nine months ended September 30, 2018 and 2017: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total (In thousands) Three Months Ended September 30, 2018 Allowance at June 30, 2018 $ 969 $ 280 $ 1,505 $ 443 $ 298 $ 247 $ 3,742 Provision (credit) for loan losses 142 11 12 17 (26 ) 22 178 Loans charged-off — — — — — (41 ) (41 ) Recoveries 7 — — — — 4 11 Balance at September 30, 2018 $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 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 Nine Months Ended September 30, 2018 Allowance at December 31, 2017 $ 854 $ 359 $ 1,620 $ 351 $ 335 $ 218 $ 3,737 Provision (credit) for loan losses 226 (68 ) (103 ) 109 (63 ) 82 183 Loans charged-off — — — — — (80 ) (80 ) Recoveries 38 — — — — 12 50 Balance at September 30, 2018 $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 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 Additional information pertaining to the allowance for loan losses at September 30, 2018 and December 31, 2017 is as follows: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total September 30, 2018 (In thousands) Allowance for impaired loans $ 97 $ — $ — $ — $ — $ — $ 97 Allowance for non-impaired loans 1,021 291 1,517 460 272 232 3,793 Total allowance for loan losses $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 Impaired loans $ 5,241 $ 243 $ 247 $ — $ — $ — $ 5,731 Non-impaired loans 249,038 42,158 108,570 28,816 18,948 18,075 465,605 Total loans $ 254,279 $ 42,401 $ 108,817 $ 28,816 $ 18,948 $ 18,075 $ 471,336 December 31, 2017 Allowance for impaired loans $ 160 $ 1 $ 1 $ — $ — $ — $ 162 Allowance for non-impaired loans 694 358 1,619 351 335 218 3,575 Total allowance for loan losses $ 854 $ 359 $ 1,620 $ 351 $ 335 $ 218 $ 3,737 Impaired loans $ 5,205 $ 276 $ 352 $ — $ — $ — $ 5,833 Non-impaired loans 193,270 38,692 101,403 25,357 21,766 16,337 396,825 Total loans $ 198,475 $ 38,968 $ 101,755 $ 25,357 $ 21,766 $ 16,337 $ 402,658 The following is a summary of past due and non-accrual loans at September 30, 2018 and December 31, 2017: 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, 2018 Residential one-to-four family $ 1,773 $ — $ 635 $ 2,408 $ 1,765 Home equity loans and lines of credit 34 96 71 201 243 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer 40 — 13 53 — Total $ 1,847 $ 96 $ 719 $ 2,662 $ 2,008 December 31, 2017 Residential one-to-four family $ 737 $ — $ — $ 737 $ 1,975 Home equity loans and lines of credit 96 — — 96 276 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer — — — — — Total $ 833 $ — $ — $ 833 $ 2,251 The following is a summary of impaired loans at September 30, 2018 and December 31, 2017: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) September 30, 2018 Impaired loans without a valuation allowance: Residential one-to-four family $ 3,004 $ 3,004 Home equity loans and lines of credit 243 243 Commercial real estate 247 247 Total 3,494 3,494 Impaired loans with a valuation allowance: Residential one-to-four family 2,237 2,237 $ 97 Total impaired loans $ 5,731 $ 5,731 $ 97 December 31, 2017 Impaired loans without a valuation allowance: Residential one-to-four family $ 2,685 $ 2,641 Home equity loans and lines of credit 247 247 Commercial real estate 257 257 Total 3,189 3,145 Impaired loans with a valuation allowance: Residential one-to-four family 2,584 2,564 $ 160 Home equity loans and lines of credit 29 29 1 Commercial real estate 95 95 1 Total 2,708 2,688 162 Total impaired loans $ 5,897 $ 5,833 $ 162 Additional information pertaining to impaired loans follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Nine Months Ended September 30, 2018 Residential one-to-four family $ 5,197 $ 168 $ 63 Home equity loans and lines of credit 256 28 28 Commercial real estate 294 12 — Total $ 5,747 $ 208 $ 91 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 Three Months Ended September 30, 2018 Residential one-to-four family $ 5,252 $ 51 $ 24 Home equity loans and lines of credit 243 3 3 Commercial real estate 259 3 — Total $ 5,754 $ 57 $ 27 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 No additional funds are committed to be advanced in connection with impaired loans. Troubled Debt Restructurings The Company periodically grants concessions to borrowers experiencing financial difficulties. The Company’s troubled debt restructurings consist primarily of interest rate concessions for periods of three months to thirty years for residential real estate loans, and for periods up to one year for commercial real estate loans. At September 30, 2018, the Company had seventeen residential real estate loans and one commercial real estate loan aggregating $3,721,000 and $54,000, respectively, which were subject to troubled debt restructuring agreements. At September 30, 2017, the Company had twenty residential real estate loans and two commercial real estate loan aggregating $4,382,000 and $185,000, respectively, which were subject to troubled debt restructuring agreements. As of September 30, 2018 and 2017, $3,530,000 and $4,567,000, respectively, in troubled debt restructurings were performing in accordance with the terms of the modified loan agreements. Included in such amounts are $369,000 and $1,139,000, respectively, that are being accounted for as non-accrual loans. For the nine months ended September 30, 2018 nine months ended 2017, 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, 2018 and 2017, 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, 2018 and 2017, 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, 2018 December 31, 2017 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3B (Pass rated) $ 108,622 $ 28,816 $ 18,948 $ 101,556 $ 25,357 $ 21,766 Loans rated 4 — — — — — — Loans rated 5 195 — — 199 — — $ 108,817 $ 28,816 $ 18,948 $ 101,755 $ 25,357 $ 21,766 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, 2018, $51,000 in consumer loans were rated as doubtful, $699,000 in residential mortgages were rated as substandard, and $2,551,000 in residential mortgages and $243,000 in home equity loans were rated as special mention. At December 31, 2017, $712,000 in residential mortgages were rated as substandard, and $2,512,000 in residential mortgages and $247,000 in home equity loans were rated as special mention.

Loan Servicing

Loan Servicing	9 Months Ended
	Sep. 30, 2018
Transfers And Servicing [Abstract]
Loan Servicing	6 . 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 $873,933,000 and $771,407,000 at September 30, 2018 and December 31, 2017, respectively. The following table summarizes the activity relating to mortgage servicing rights for the nine months ended September 30, 2018 and 2017 (in thousands): September 30, 2018 September 30, 2017 Mortgage servicing rights: Balance at beginning of year $ 6,487 $ 8,910 Additions through originations 1,726 1,486 Sales — (3,126 ) Amortization (891 ) (941 ) Balance at end of period $ 7,322 $ 6,329 Valuation allowance: Balance at beginning of year $ 90 $ 424 Provision (credit) (84 ) (134 ) Balance at end of period $ 6 $ 290 Amortized cost, net $ 7,316 $ 6,039 Fair value $ 8,028 $ 6,051 During the nine months ended September 30, 2018 and 2017, the Company decreased the valuation allowance for its mortgage servicing rights by $84,000

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	7. INCOME TAXES During the nine months ended September 30, 2018 and 2017, the Company recorded a deferred income tax benefit of $0 and $151,000, respectively, and current state tax expense of $14,000 and $3,000, respectively. The deferred income tax benefit for the 2017 period resulted from, and was limited to, an offsetting tax provision attributable to other comprehensive income, specifically, appreciation in the fair value of available-for-sale securities. A deferred tax provision of $129,000 was recognized for the three months ended September 30, 2017, while no deferred tax provision or benefit was recognized for the three months ended September 30, 2018. The tax provision for the 2017 period resulted from a limitation in the year-to-date tax benefit included in the results of operations. This provision was fully offset by a tax benefit included in other comprehensive income. Since 2014, the Company has maintained a valuation allowance for all of its net 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 its net deferred tax assets should be maintained. The Company’s NOL carryforward at September 30, 2018 was $13.4 million. The tax valuation allowance at such date totaled $3.2 million.

On-Balance Sheet Derivative Ins

On-Balance Sheet Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
On-Balance Sheet Derivative Instruments and Hedging Activities	8. 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 $34,476,000 and $24,222,000 at September 30, 2018 and December 31, 2017, respectively. The fair value of certain of these commitments was an asset of $419,000 and $363,000 as of September 30, 2018 and December 31, 2017, respectively, and is included in other assets in the consolidated balance sheets while the fair value of the other commitments was a liability of $10,000 at September 30, 2018 and is included in other liabilities in the consolidated balance sheet. 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 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 forward loan sale commitments was $34,034,000 and $29,613,000 at September 30, 2018 and December 31, 2017, at September 30, 2018 and December 31, 2017, at September 30, 2018 and December 31, 2017,

Employee Stock Ownership Plan

Employee Stock Ownership Plan	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Employee Stock Ownership Plan	9. The Company maintains an Employee Stock Ownership Plan (“ESOP”), which is a tax-qualified retirement plan providing eligible employees the opportunity to own Bancorp stock. Bancorp made a loan to the ESOP for the purchase of 469,498 shares of its common stock at $10.00 per share. The loan is payable annually over 25 years with interest at the prime rate to be reset each January 1 st Shares are committed to be released on a monthly basis and allocated as of December 31 st

Share Repurchase Program

Share Repurchase Program	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Share Repurchase Program	10. SHARE REPURCHASE PROGRAM In September 2017, the Company’s Board of Directors adopted a share repurchase program under which the Company may repurchase up to 10%, or 586,854 shares of its then outstanding common shares. Repurchases under the program may be made in open market or in privately negotiated transactions and pursuant to any trading plan that may be adopted in accordance with Rule 10b5-1 of the SEC. Any repurchased shares will be held by the Company as authorized but unissued shares. The repurchase program may be suspended or terminated at any time without prior notice, and is currently set to expire on September 14, 2019. As of September 30, 2018, the Company had repurchased 47,500 shares at a cost of $748,000 in connection with this program.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	11. 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. Unvested restricted shares of common stock having dividend rights are treated as “participating securities” and, accordingly, are considered outstanding in computing basic earnings (loss) per share. Unallocated ESOP shares are not considered to be outstanding for purposes of computing earnings per share. None of the Company’s 325,707 outstanding stock options were included in the computation of diluted earnings (loss) per share for the three and nine months ended September 30, 2018. Due to the net loss for these periods, inclusion of the stock options in the computation would have been anti-dilutive. The following table sets forth the calculation of the average number of shares outstanding used to calculate the basic and diluted earnings (loss) per share for the periods indicated: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Average number of common shares outstanding 5,987,796 5,868,545 6,010,467 5,870,938 Less: Average unallocated ESOP shares (420,200 ) (438,981 ) (424,896 ) (443,676 ) 5,567,596 5,429,564 5,585,571 5,427,262

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	12. STOCK-BASED COMPENSATION Under the Randolph Bancorp, Inc. 2017 Stock Option and Incentive Plan (the “Equity Plan”), the Company may grant options, restricted stock, restricted units or performance awards to its directors, officers and employees. Both incentive stock options and nonqualified stock options may be granted under the Equity Plan with 586,872 shares reserved for options. The exercise price of each option equals the market price of the Company’s stock on the date of the grant and the maximum term of each options is 10 years. The total number of shares reserved for restricted stock is 234,749. Options and awards generally vest ratably over five years. The fair value of shares awarded is based on the market price at the date of grant. Stock Options The fair value of each option grant is estimated on the date of the grant using the Black-Scholes option-pricing model with the following assumptions: • Volatility is based on peer group volatility because the Company does not have a sufficient trading history. • Expected life represents the period of time that the option is expected to be outstanding, taking into account the contractual term, and the vesting period. • Expected dividend yield is based on the Company's history and expectation of dividend payouts. • The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for a period equivalent to the expected life of the option. During the nine months ended September 30, 2018, the Company granted options to purchase 27,000 shares of common stock and used the following assumptions in measuring the fair value of such grants: Vesting period (years) 3-6.5 Expiration period (years) 9 Expected volatility 29.87 % Expected life (years) 3.9 Expected dividend yield — Risk free interest rate 2.68% - 2.77% Option fair value $ 3.92 A summary of stock option activity for the nine months ended September 30, 2018 is presented in the table below: Options Stock Option Grants Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Balance at December 31, 2017 316,009 $ 14.66 9.10 $ 280,423 Granted 27,000 16.15 6.50 — Forfeited (17,302 ) 14.74 — — Balance at September 30, 2018 (all non-vested) 325,707 $ 14.78 9.07 $ 570,267 Exercisable at September 30, 2018 — $ — — — Unrecognized compensation cost $ 1,218,000 Weighted average remaining recognition period (years) 3.88 For the three and nine months ended September 30, 2018, stock-based compensation expense applicable to stock options was $81,000 and $226,000, respectively. Restricted Stock Shares issued upon vesting may be either authorized but unissued shares or reacquired shares held by the Company. Any shares not issued because vesting requirements are not met will again be available for issuance under the Equity Plan. The fair market value of shares awarded, based on the market price at the date of grant, is recorded as unearned compensation and amortized over the applicable vesting period. Restricted stock awarded in 2017 was at no cost to the awardee. The following table presents the activity in restricted stock awards under the Equity Plan for the nine months ended September 30, 2018: Restricted Stock Awards Weighted Average Grant Price Restricted stock awards at December 31, 2017 176,239 $ 14.66 Granted — — Forfeited (7,042 ) 14.66 Restricted stock awards at September 30, 2018 (all non-vested) 169,197 $ 14.66 Unrecognized compensation cost $ 1,987,000 Weighted average remaining recognition period (years) 3.93 For the three and nine months ended September 30, 2018, stock-based compensation expense applicable to restricted stock was $129,000 and $371,000, respectively.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	13. Determination of fair value The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various assets and liabilities. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the asset or liability. The following methods and assumptions were used by the Company in estimating fair value disclosures: Cash and cash equivalents Certificates of deposit Securities Federal Home Loan Bank of Boston (“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, 2018 Assets: Securities available for sale: Debt securities $ — $ 53,891 $ — $ 53,891 Mutual fund — 513 — 513 Loans held for sale — 24,120 — 24,120 Loans held for investment — — 1,894 1,894 Derivative loan commitments — 419 — 419 Forward loan sale commitments — 74 — 74 Liabilities: Derivative loan commitments — 10 — 10 Forward loan sale commitments — 62 — 62 December 31, 2017 Assets: Securities available for sale: Debt securities $ — $ 61,043 $ — $ 61,043 Mutual fund — 533 — 533 Loans held for sale — 25,390 — 25,390 Loans held for investment — — 6,412 6,412 Derivative loan commitments — 363 — 363 Forward loan sale commitments — 4 — 4 Liabilities: Forward loan sale commitments — 19 — 19 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, 2018 and December 31, 2017. Period Ended September 30, 2018 September 30, 2018 Level 1 Level 2 Level 3 Total Gains (Losses) (In thousands) Collateral dependent impaired loans $ — $ — $ 1,248 $ — Mortgage servicing rights — 7,316 — 84 Assets held for sale — — 2,897 230 Foreclosed real estate — — 82 (25 ) $ — $ 7,316 $ 4,227 $ 289 December 31, 2017 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 1,630 Mortgage servicing rights — 6,397 — Assets held for sale — — 828 Foreclosed real estate — — 193 $ — $ 6,397 $ 2,651 The Company recorded a partial reversal of the valuation allowance for its mortgage servicing rights of $84,000 during the nine months ended September 30, 2018 During the nine months ended September 30, 2018, the Company sold properties which had been occupied by its former North Randolph and Stoughton branch offices and which had been classified with assets held for sale. The North Randolph sale was completed at the carrying value of this property and, accordingly, no gain or loss was recognized. The Stoughton sale was completed for above carrying value and a gain of $230,000 was recognized. During the three months ended September 30, 2018, the Company transferred its Boston branch office having a carrying value of $2,897,000 to assets held for sale. In October 2018, the Company entered into an agreement to sell this building. See Note 16 for additional information. There were no liabilities measured at fair value on a non-recurring basis at September 30, 2018 and December 31, 2017. 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, 2018 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,695 $ 2,681 $ — $ 2,681 $ — Securities available for sale 54,405 54,405 — 54,405 — Loans held for sale 24,120 24,120 — 24,120 — Loans, net 468,938 457,349 — — 457,349 Derivative assets 493 493 — 493 — Financial liabilities: Deposits $ 427,173 $ 425,481 $ — $ 425,481 $ — FHLBB advances 77,411 77,197 — 77,197 — Derivative liabilities 62 62 — 62 — December 31, 2017 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,940 $ 2,932 $ — $ 2,932 $ — Securities available for sale 61,576 61,576 — 61,576 — Loans held for sale 25,390 25,390 — 25,390 — Loans, net 400,373 398,407 — — 398,407 Derivative assets 367 367 — 367 — Financial liabilities: Deposits $ 366,836 365,997 $ — $ 365,997 $ — FHLBB advances 75,954 75,821 — 75,821 — Derivative liabilities 19 19 — 19 —

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. 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, 2018 December 31, 2017 (In thousands) Commitments to originate loans $ 48,678 $ 35,549 Unused lines and letters of credit 42,939 39,968 Unadvanced funds on construction loans 11,571 6,967 Overdraft lines of credit 8,615 8,996 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. Other contingencies The Company is not currently a party to any pending legal proceedings that it believes would have a material adverse effect on its financial condition, results of operations or cash flows.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	15. SEGMENT INFORMATION Effective January 1, 2018, management began reporting its activities in one of two business segments, namely Envision Bank (“EB”) and Envision Mortgage (“EM”). Comparative information for the 2017 period has been prepared on a basis consistent with the methodology used in 2018. Envision Bank operations primarily consist of accepting deposits from customers within the communities surrounding the Bank’s six full service branch offices and investing those funds in residential and commercial real estate loans, home equity lines of credit, construction loans, commercial and industrial loans, and consumer loans. Envision Mortgage’s operations primarily consist of the origination and sale of residential mortgage loans and the servicing of loans sold to government-sponsored entities. A portion of the loans originated by Envision Mortgage are held in the loan portfolio of Envision Bank. Segment information as of and for the three and nine months ended September 30, 2018, follows: For the Three Months Ended September 30, 2018 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 4,002 $ 258 $ 4,260 Provision for loan losses 178 — 178 Net interest income after provision for loan losses 3,824 258 4,082 Non-interest income: Customer service fees 324 33 357 Gain on loan origination and sale activities, net (1) — 2,263 2,263 Mortgage servicing fees, net (81 ) 391 310 Other 400 185 585 Total non-interest income 643 2,872 3,515 Non-interest expenses: Salaries and employee benefits 1,601 3,187 4,788 Occupancy and equipment 317 411 728 Other non-interest expenses 1,117 794 1,911 Total non-interest expenses 3,035 4,392 7,427 Income (loss) before income taxes and elimination of inter-segment profit $ 1,432 $ (1,262 ) 170 Elimination of inter-segment profit (307 ) Loss before income taxes (137 ) Income tax expense 5 Net loss $ (142 ) Total assets, September 30, 2018 $ 521,139 $ 68,543 $ 589,682 For the Nine Months Ended September 30, 2018 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 11,541 $ 735 $ 12,276 Provision for loan losses 183 — 183 Net interest income after provision for loan losses 11,358 735 12,093 Non-interest income: Customer service fees 1,035 61 1,096 Gain on loan origination and sale activities, net (1) — 6,327 6,327 Mortgage servicing fees, net (222 ) 1,157 935 Other 648 363 1,011 Total non-interest income 1,461 7,908 9,369 Non-interest expenses: Salaries and employee benefits 4,849 9,317 14,166 Occupancy and equipment 1,090 1,067 2,157 Other non-interest expenses 3,355 2,658 6,013 Total non-interest expenses 9,294 13,042 22,336 Income (loss) before income taxes and elimination of inter-segment profit $ 3,525 $ (4,399 ) (874 ) Elimination of inter-segment profit (971 ) Loss before income taxes (1,845 ) Income tax expense 14 Net loss $ (1,859 ) (1) Before elimination of inter-segment profit The information above was derived from the internal management reporting system used by management to measure performance of the segments. The Company’s internal transfer pricing arrangements determined by management primarily consist of the following: 1. EM’s cost of funds is based on the weighted average rate of overnight advances from the FHLBB for the period. 2. EM is credited with service released premiums and a sales premium totaling 1.50% for new loans transferred to EB’s loans held for investment, and a 1.00% fee for HELOC originations. This income for the three and nine months ended September 30, 2018 totaled $307,000 and $971,000, respectively. 3. Loan servicing fees are charged to EB by EM based on the number of residential mortgage loans held in portfolio at a rate of 0.14% per annum and amounted to $81,000 and $222,000 for the three and nine months ended September 30, 2018, respectively. 4. Certain cost centers provide services to both business segments. The cost centers include Finance, Marketing, IT and Administration. Costs which are common to both business segments are referred to as “indirect costs” and are allocated using relevant benchmarks, e.g. headcount, number of accounts, etc. Segment information as of and for the three and nine months ended September 30, 2017 follows: For the Three Months Ended September 30, 2017 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 3,566 $ 250 $ 3,816 Provision for loan losses — — — Net interest income after provision for loan losses 3,566 250 3,816 Non-interest income: Customer service fees 329 30 359 Gain on loan origination and sale activities, net (1) — 2,909 2,909 Mortgage servicing fees, net (67 ) 266 199 Other 34 274 308 Total non-interest income 296 3,479 3,775 Non-interest expenses: Salaries and employee benefits 1,454 3,214 4,668 Occupancy and equipment 336 346 682 Merger and integration costs — 7 7 Other non-interest expenses 1,001 851 1,852 Total non-interest expenses 2,791 4,418 7,209 Income (loss) before income taxes and elimination of inter-segment profit $ 1,071 $ (689 ) 382 Elimination of inter-segment profit (204 ) Income before income taxes 178 Income tax provision 129 Net income $ 49 Total assets, September 30, 2017 $ 444,372 $ 61,140 $ 505,512 For the Nine Months Ended September 30, 2017 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 10,215 $ 775 $ 10,990 Provision for loan losses 335 — 335 Net interest income after provision for loan losses 9,880 775 10,655 Non-interest income: Customer service fees 1,036 73 1,109 Gain on loan origination and sale activities, net (1) — 7,902 7,902 Mortgage servicing fees, net (189 ) 1,338 1,149 Other 524 369 893 Total non-interest income 1,371 9,682 11,053 Non-interest expenses: Salaries and employee benefits 4,690 9,369 14,059 Occupancy and equipment 1,008 949 1,957 Merger and integration costs 19 512 531 Other non-interest expenses 2,758 2,461 5,219 Total non-interest expenses 8,475 13,291 21,766 Income (loss) before income taxes and elimination of inter-segment profit $ 2,776 $ (2,834 ) (58 ) Elimination of inter-segment profit (638 ) Loss before income taxes (696 ) Income tax benefit (148 ) Net loss $ (548 ) (1) Before elimination of inter-segment profit The information above was derived from the internal management reporting system used by management to measure performance of the segments. The Company’s internal transfer pricing arrangements determined by management primarily consist of the following: 1. EM’s cost of funds is based on the weighted average rate of overnight advances from the FHLBB for the period. 2. EM is credited with service released premiums and a sales premium totaling 1.50% for new loans transferred to EB’s loans held for investment, and a 1.00% fee for HELOC originations. This income for the three and nine months ended September 30, 2017 totaled $204,000 and $638,000, respectively. 3. Loan servicing fees are charged to EB by EM based on the number of residential mortgage loans held in portfolio at a rate of 0.14% per annum and amounted to $67,000 and $189,000 for the three and nine months ended September 30, 2017, respectively. 4. Certain cost centers provide services to both business segments. The cost centers include Finance, Marketing, IT and Administration. Costs which are common to both business segments are referred to as “indirect costs” and are allocated using relevant benchmarks, e.g. headcount, number of accounts, etc.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	16. SUBSEQUENT EVENTS Pending Sale of Boston Branch During the third quarter of 2018, the Company began to actively market for sale its branch office in Boston and on October 23, 2018 entered into a purchase and sale agreement to sell the property for $5,000,000. Consummation of this transaction is subject to an inspection review by the buyer, removal of asbestos in accordance with an environmental engineering report and certain other customary closing conditions, including receipt of regulatory approval to close the branch. This transaction is expected to close in the fourth quarter of 2018. The Company reclassified the net book value of this property totaling $2,897,000 from premises and equipment to assets held for sale (included in other assets in the accompanying balance sheet) as of September 30, 2018. In August 2018, this property experienced significant water damage from a leaking pipe which resulted in the temporary closure of the branch. The property has undergone a clean-up of the damage, including the removal of the building contents and asbestos on the affected floors. The Company has recognized an insurance recovery of $90,000 for personal property which was damaged but has not yet reached a settlement with the insurer on its claim for real property damage. Settlement of the claim is expected to occur in the fourth quarter of 2018. While the property has undergone a clean-up from the water damage, re-construction of the affected areas is not being undertaken by the Company due to the pending sale of the property. Additional insurance proceeds received will be used to reduce the carrying value of the property. Based on a range of likely insurance settlements, management estimates that the Company would recognize a gain of from $2,000,000 to $2,150,000 on the sale of this building based on the selling price set forth in the pending purchase and sale agreement. Consolidation of Mortgage Banking Operations In October 2018, the Company’s Board of Directors approved a plan to consolidate mortgage banking operations in the Company’s North Attleboro loan operations center. As a result, the Company eliminated fifteen administrative positions supporting the origination of residential mortgages in its Andover loan operations center and will add eight similar positions in its North Attleboro location. Approximately twenty-five employees, including loan originators, remain in the Andover location. Terminated employees were given a severance package based on their length of service with the Company. In addition, retention bonuses were offered to certain employees. The estimated total cost is $235,000 and is expected to be paid in 2018. As previously disclosed, the Company entered into a sublease agreement in July 2018 for 27% of the space in its Andover location. This sublease commenced on October 1, 2018 and runs co-terminus with the Company’s lease which expires in March 2023. At September 30, 2018, the Company’s remaining minimum lease obligation, net of sublease payments, amounted to $1,223,000. The Company intends to vacate all but approximately 3,000 square feet of its remaining leased space in the Andover location in 2018 and is currently attempting to sublease this space. Management expects to complete its analysis of the expected future cash flows for this property and to record a liability at fair value once the Company ceases the use of all or a portion of its remaining leased space.

Basis of Financial Statement _2

Basis of Financial Statement Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Financial Statement Presentation	The consolidated financial statements include the accounts of Randolph Bancorp, Inc. (“Bancorp”) and its wholly-owned subsidiary, Envision Bank (the “Bank”, together with Bancorp, 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 three and nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or any other interim period. Prior to 2018, the Company’s operations were managed, and financial performance was evaluated, by the chief operating decision-maker on a company-wide basis. As a result, management had determined there to be a single business segment for financial reporting purposes through December 31, 2017. Due to the significance of the Company’s mortgage banking operations and the strategic focus on this business, management prepared its 2018 operating budget by breaking-out its mortgage banking activities, including residential loan origination and loan servicing. As a result, effective January 1, 2018, the Company is reporting two business segments, namely, “Envision Bank” and “Envision Mortgage”. As part of this process, management analyzed costs incurred by departments providing services to both segments (indirect costs), such as IT, Marketing, Accounting and Administration, to determine the allocation of indirect costs to each business segment in order to fully measure each segment’s results of operations. See Note 15 for disclosure of the Company’s segment information. 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, 2017, as filed with the SEC.

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Recent Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers In January 2016, FASB issued ASU 2016-01, Financial Instruments In February 2016, FASB issued ASU 2016-02, Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses In April 2017, the FASB issued ASU 2017-08 Receivables – Non-refundable Fees and Other Costs In August 2018, the FASB issued ASU 2018-13 Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement, This ASU is effective for emerging growth companies for annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted, including adoption in an interim period. The Company is currently assessing the impact of this ASU on the consolidated financial statements.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 2017 (In thousands) Securities available for sale: Net unrealized loss $ (2,277 ) $ (624 ) Tax effect (313 ) (313 ) Net-of-tax amount (2,590 ) (937 ) Supplemental retirement plan Unrecognized net actuarial loss (640 ) (667 ) Unrecognized net prior service credit 421 484 (219 ) (183 ) Tax effect (47 ) (47 ) Net-of-tax amount (266 ) (230 ) Accumulated other comprehensive loss $ (2,856 ) $ (1,167 )

Securities Available for Sale (

Securities Available for Sale (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 Debt securities: U.S. Government-sponsored enterprises $ 4,000 $ 7 $ (45 ) $ 3,962 Corporate 1,527 6 (23 ) 1,510 Municipal 1,890 22 — 1,912 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 25,835 24 (1,113 ) 24,746 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,278 — (803 ) 13,475 U.S. Government-guaranteed 1,811 — (45 ) 1,766 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,689 — (46 ) 1,643 U.S. Government-guaranteed 5,107 — (229 ) 4,878 Total debt securities 56,137 59 (2,304 ) 53,892 Mutual fund 545 — (32 ) 513 Total securities available for sale $ 56,682 $ 59 $ (2,336 ) $ 54,405 December 31, 2017 Debt securities: U.S. Government-sponsored enterprises $ 3,999 $ 50 $ (24 ) $ 4,025 Corporate 2,005 27 (8 ) 2,024 Municipal 12,707 179 (18 ) 12,868 Residential mortgage-backed securities: U.S. Government-sponsored enterprises 18,729 118 (450 ) 18,397 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises 14,451 13 (403 ) 14,061 U.S. Government-guaranteed 2,132 — (6 ) 2,126 Collateralized mortgage obligations: U.S. Government-sponsored enterprises 1,871 12 (5 ) 1,878 U.S. Government-guaranteed 5,760 4 (100 ) 5,664 Total debt securities 61,654 403 (1,014 ) 61,043 Mutual fund 545 — (12 ) 533 Total securities available for sale $ 62,199 $ 403 $ (1,026 ) $ 61,576
Investments Classified by Contractual Maturity Date	The amortized cost and fair value of debt securities by contractual maturity at September 30, 2018 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 $ 400 $ 400 After 1 year through 5 years 6,178 6,133 After 5 years through 10 years 839 851 7,417 7,384 Mortgage-backed securities 48,720 46,508 $ 56,137 $ 53,892
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, 2018 (In thousands) Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (45 ) $ 1,955 Corporate (23 ) 999 — — Residential mortgage-backed securities: U.S. Government-sponsored enterprises (433 ) 14,863 (680 ) 7,909 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises (90 ) 5,066 (713 ) 8,410 U.S. Government-guaranteed (45 ) 1,766 — — Collateralized mortgage obligations: U.S. Government-sponsored enterprises (46 ) 1,643 — — U.S. Government-guaranteed (197 ) 4,331 (32 ) 547 Total debt securities (834 ) 28,668 (1,470 ) 18,821 Mutual Fund — — (32 ) 513 $ (834 ) $ 28,668 $ (1,502 ) $ 19,334 December 31, 2017 Debt securities: U.S. Government-sponsored enterprises $ — $ — $ (24 ) $ 19,676 Corporate — — (8 ) 988 Municipal (11 ) 1,919 (7 ) 479 Residential mortgage-backed securities: U.S. Government-sponsored enterprises (1 ) 1,623 (449 ) 13,163 Commercial mortgage-backed securities: U.S. Government-sponsored enterprises — — (403 ) 8,805 U.S. Government-guaranteed (6 ) 2,126 — — Collateralized mortgage obligations: U.S. Government-sponsored enterprises (5 ) 678 — — U.S. Government-guaranteed (1 ) 295 (99 ) 3,756 Total debt securities (24 ) 6,641 (990 ) 46,867 Mutual Fund — — (12 ) 533 $ (24 ) $ 6,641 $ (1,002 ) $ 47,400

Loans and Allowance for Loan _2

Loans and Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Summary of Loans Held for Investment at Dates Indicated	A summary of loans held for investment at the dates indicated is as follows: September 30, 2018 December 31, 2017 (In thousands) Mortgage loans on real estate: Residential: One-to-four family $ 254,279 $ 198,475 Home equity loans and lines of credit 42,401 38,968 Commercial 108,817 101,755 Construction 28,816 25,357 434,313 364,555 Commercial and industrial 18,948 21,766 Consumer 18,075 16,337 Total loans 471,336 402,658 Allowance for loan losses (3,890 ) (3,737 ) Net deferred loan costs and fees, and purchase premiums 1,492 1,452 $ 468,938 $ 400,373
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, 2018 and 2017: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total (In thousands) Three Months Ended September 30, 2018 Allowance at June 30, 2018 $ 969 $ 280 $ 1,505 $ 443 $ 298 $ 247 $ 3,742 Provision (credit) for loan losses 142 11 12 17 (26 ) 22 178 Loans charged-off — — — — — (41 ) (41 ) Recoveries 7 — — — — 4 11 Balance at September 30, 2018 $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 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 Nine Months Ended September 30, 2018 Allowance at December 31, 2017 $ 854 $ 359 $ 1,620 $ 351 $ 335 $ 218 $ 3,737 Provision (credit) for loan losses 226 (68 ) (103 ) 109 (63 ) 82 183 Loans charged-off — — — — — (80 ) (80 ) Recoveries 38 — — — — 12 50 Balance at September 30, 2018 $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 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
Summary of Additional Information Pertaining to the Allowance for Loan Losses	Additional information pertaining to the allowance for loan losses at September 30, 2018 and December 31, 2017 is as follows: Second Residential Mortgages Commercial Commercial 1-4 Family and Real Estate Construction and Industrial Consumer Total September 30, 2018 (In thousands) Allowance for impaired loans $ 97 $ — $ — $ — $ — $ — $ 97 Allowance for non-impaired loans 1,021 291 1,517 460 272 232 3,793 Total allowance for loan losses $ 1,118 $ 291 $ 1,517 $ 460 $ 272 $ 232 $ 3,890 Impaired loans $ 5,241 $ 243 $ 247 $ — $ — $ — $ 5,731 Non-impaired loans 249,038 42,158 108,570 28,816 18,948 18,075 465,605 Total loans $ 254,279 $ 42,401 $ 108,817 $ 28,816 $ 18,948 $ 18,075 $ 471,336 December 31, 2017 Allowance for impaired loans $ 160 $ 1 $ 1 $ — $ — $ — $ 162 Allowance for non-impaired loans 694 358 1,619 351 335 218 3,575 Total allowance for loan losses $ 854 $ 359 $ 1,620 $ 351 $ 335 $ 218 $ 3,737 Impaired loans $ 5,205 $ 276 $ 352 $ — $ — $ — $ 5,833 Non-impaired loans 193,270 38,692 101,403 25,357 21,766 16,337 396,825 Total loans $ 198,475 $ 38,968 $ 101,755 $ 25,357 $ 21,766 $ 16,337 $ 402,658
Schedule of Past Due and Non-Accrual Loans	The following is a summary of past due and non-accrual loans at September 30, 2018 and December 31, 2017: 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, 2018 Residential one-to-four family $ 1,773 $ — $ 635 $ 2,408 $ 1,765 Home equity loans and lines of credit 34 96 71 201 243 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer 40 — 13 53 — Total $ 1,847 $ 96 $ 719 $ 2,662 $ 2,008 December 31, 2017 Residential one-to-four family $ 737 $ — $ — $ 737 $ 1,975 Home equity loans and lines of credit 96 — — 96 276 Commercial real estate — — — — — Construction — — — — — Commercial and industrial — — — — — Consumer — — — — — Total $ 833 $ — $ — $ 833 $ 2,251
Summary of Impaired Loans and Additional Information Pertaining to Impaired Loans	The following is a summary of impaired loans at September 30, 2018 and December 31, 2017: Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) September 30, 2018 Impaired loans without a valuation allowance: Residential one-to-four family $ 3,004 $ 3,004 Home equity loans and lines of credit 243 243 Commercial real estate 247 247 Total 3,494 3,494 Impaired loans with a valuation allowance: Residential one-to-four family 2,237 2,237 $ 97 Total impaired loans $ 5,731 $ 5,731 $ 97 December 31, 2017 Impaired loans without a valuation allowance: Residential one-to-four family $ 2,685 $ 2,641 Home equity loans and lines of credit 247 247 Commercial real estate 257 257 Total 3,189 3,145 Impaired loans with a valuation allowance: Residential one-to-four family 2,584 2,564 $ 160 Home equity loans and lines of credit 29 29 1 Commercial real estate 95 95 1 Total 2,708 2,688 162 Total impaired loans $ 5,897 $ 5,833 $ 162 Additional information pertaining to impaired loans follows: Average Interest Cash Basis Recorded Income Interest Investment Recognized Recognized (In thousands) Nine Months Ended September 30, 2018 Residential one-to-four family $ 5,197 $ 168 $ 63 Home equity loans and lines of credit 256 28 28 Commercial real estate 294 12 — Total $ 5,747 $ 208 $ 91 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 Three Months Ended September 30, 2018 Residential one-to-four family $ 5,252 $ 51 $ 24 Home equity loans and lines of credit 243 3 3 Commercial real estate 259 3 — Total $ 5,754 $ 57 $ 27 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
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, 2018 December 31, 2017 Commercial Real Construction Commercial and Industrial Commercial Real Construction Commercial and Industrial (In thousands) Loans rated 1 - 3B (Pass rated) $ 108,622 $ 28,816 $ 18,948 $ 101,556 $ 25,357 $ 21,766 Loans rated 4 — — — — — — Loans rated 5 195 — — 199 — — $ 108,817 $ 28,816 $ 18,948 $ 101,755 $ 25,357 $ 21,766

Loan Servicing (Tables)

Loan Servicing (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 and 2017 (in thousands): September 30, 2018 September 30, 2017 Mortgage servicing rights: Balance at beginning of year $ 6,487 $ 8,910 Additions through originations 1,726 1,486 Sales — (3,126 ) Amortization (891 ) (941 ) Balance at end of period $ 7,322 $ 6,329 Valuation allowance: Balance at beginning of year $ 90 $ 424 Provision (credit) (84 ) (134 ) Balance at end of period $ 6 $ 290 Amortized cost, net $ 7,316 $ 6,039 Fair value $ 8,028 $ 6,051

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Calculation of Average Number of Shares Outstanding Used to Calculate Basic and Diluted Earnings (Loss) Per Share	The following table sets forth the calculation of the average number of shares outstanding used to calculate the basic and diluted earnings (loss) per share for the periods indicated: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Average number of common shares outstanding 5,987,796 5,868,545 6,010,467 5,870,938 Less: Average unallocated ESOP shares (420,200 ) (438,981 ) (424,896 ) (443,676 ) 5,567,596 5,429,564 5,585,571 5,427,262

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Granted Options to Purchase Shares of Common Stock	During the nine months ended September 30, 2018, the Company granted options to purchase 27,000 shares of common stock and used the following assumptions in measuring the fair value of such grants: Vesting period (years) 3-6.5 Expiration period (years) 9 Expected volatility 29.87 % Expected life (years) 3.9 Expected dividend yield — Risk free interest rate 2.68% - 2.77% Option fair value $ 3.92
Summary of Stock Options Activity	A summary of stock option activity for the nine months ended September 30, 2018 is presented in the table below: Options Stock Option Grants Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Balance at December 31, 2017 316,009 $ 14.66 9.10 $ 280,423 Granted 27,000 16.15 6.50 — Forfeited (17,302 ) 14.74 — — Balance at September 30, 2018 (all non-vested) 325,707 $ 14.78 9.07 $ 570,267 Exercisable at September 30, 2018 — $ — — — Unrecognized compensation cost $ 1,218,000 Weighted average remaining recognition period (years) 3.88
Summary of Activity in Restricted Stock Awards Under Equity Plan	The following table presents the activity in restricted stock awards under the Equity Plan for the nine months ended September 30, 2018: Restricted Stock Awards Weighted Average Grant Price Restricted stock awards at December 31, 2017 176,239 $ 14.66 Granted — — Forfeited (7,042 ) 14.66 Restricted stock awards at September 30, 2018 (all non-vested) 169,197 $ 14.66 Unrecognized compensation cost $ 1,987,000 Weighted average remaining recognition period (years) 3.93

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 Assets: Securities available for sale: Debt securities $ — $ 53,891 $ — $ 53,891 Mutual fund — 513 — 513 Loans held for sale — 24,120 — 24,120 Loans held for investment — — 1,894 1,894 Derivative loan commitments — 419 — 419 Forward loan sale commitments — 74 — 74 Liabilities: Derivative loan commitments — 10 — 10 Forward loan sale commitments — 62 — 62 December 31, 2017 Assets: Securities available for sale: Debt securities $ — $ 61,043 $ — $ 61,043 Mutual fund — 533 — 533 Loans held for sale — 25,390 — 25,390 Loans held for investment — — 6,412 6,412 Derivative loan commitments — 363 — 363 Forward loan sale commitments — 4 — 4 Liabilities: Forward loan sale commitments — 19 — 19
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, 2018 and December 31, 2017. Period Ended September 30, 2018 September 30, 2018 Level 1 Level 2 Level 3 Total Gains (Losses) (In thousands) Collateral dependent impaired loans $ — $ — $ 1,248 $ — Mortgage servicing rights — 7,316 — 84 Assets held for sale — — 2,897 230 Foreclosed real estate — — 82 (25 ) $ — $ 7,316 $ 4,227 $ 289 December 31, 2017 Level 1 Level 2 Level 3 (In thousands) Collateral dependent impaired loans $ — $ — $ 1,630 Mortgage servicing rights — 6,397 — Assets held for sale — — 828 Foreclosed real estate — — 193 $ — $ 6,397 $ 2,651
Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments	The estimated fair values, and related carrying amounts, of the Company’s financial instruments are presented below. Certain financial instruments and all non-financial instruments are exempt from disclosure requirements. Accordingly, the aggregate fair value amounts presented herein do not represent the underlying fair value of the Company. This table excludes financial instruments for which the carrying amount approximates fair value. Financial assets for which the fair value approximates carrying value include cash and cash equivalents, and accrued interest receivable. Financial liabilities for which the fair value approximates carrying value include mortgagors’ escrow accounts and accrued interest payable. September 30, 2018 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,695 $ 2,681 $ — $ 2,681 $ — Securities available for sale 54,405 54,405 — 54,405 — Loans held for sale 24,120 24,120 — 24,120 — Loans, net 468,938 457,349 — — 457,349 Derivative assets 493 493 — 493 — Financial liabilities: Deposits $ 427,173 $ 425,481 $ — $ 425,481 $ — FHLBB advances 77,411 77,197 — 77,197 — Derivative liabilities 62 62 — 62 — December 31, 2017 Carrying Fair Amount Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Certificates of deposit $ 2,940 $ 2,932 $ — $ 2,932 $ — Securities available for sale 61,576 61,576 — 61,576 — Loans held for sale 25,390 25,390 — 25,390 — Loans, net 400,373 398,407 — — 398,407 Derivative assets 367 367 — 367 — Financial liabilities: Deposits $ 366,836 365,997 $ — $ 365,997 $ — FHLBB advances 75,954 75,821 — 75,821 — Derivative liabilities 19 19 — 19 —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
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, 2018 December 31, 2017 (In thousands) Commitments to originate loans $ 48,678 $ 35,549 Unused lines and letters of credit 42,939 39,968 Unadvanced funds on construction loans 11,571 6,967 Overdraft lines of credit 8,615 8,996

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Summary of Segment Information	Segment information as of and for the three and nine months ended September 30, 2018, follows: For the Three Months Ended September 30, 2018 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 4,002 $ 258 $ 4,260 Provision for loan losses 178 — 178 Net interest income after provision for loan losses 3,824 258 4,082 Non-interest income: Customer service fees 324 33 357 Gain on loan origination and sale activities, net (1) — 2,263 2,263 Mortgage servicing fees, net (81 ) 391 310 Other 400 185 585 Total non-interest income 643 2,872 3,515 Non-interest expenses: Salaries and employee benefits 1,601 3,187 4,788 Occupancy and equipment 317 411 728 Other non-interest expenses 1,117 794 1,911 Total non-interest expenses 3,035 4,392 7,427 Income (loss) before income taxes and elimination of inter-segment profit $ 1,432 $ (1,262 ) 170 Elimination of inter-segment profit (307 ) Loss before income taxes (137 ) Income tax expense 5 Net loss $ (142 ) Total assets, September 30, 2018 $ 521,139 $ 68,543 $ 589,682 For the Nine Months Ended September 30, 2018 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 11,541 $ 735 $ 12,276 Provision for loan losses 183 — 183 Net interest income after provision for loan losses 11,358 735 12,093 Non-interest income: Customer service fees 1,035 61 1,096 Gain on loan origination and sale activities, net (1) — 6,327 6,327 Mortgage servicing fees, net (222 ) 1,157 935 Other 648 363 1,011 Total non-interest income 1,461 7,908 9,369 Non-interest expenses: Salaries and employee benefits 4,849 9,317 14,166 Occupancy and equipment 1,090 1,067 2,157 Other non-interest expenses 3,355 2,658 6,013 Total non-interest expenses 9,294 13,042 22,336 Income (loss) before income taxes and elimination of inter-segment profit $ 3,525 $ (4,399 ) (874 ) Elimination of inter-segment profit (971 ) Loss before income taxes (1,845 ) Income tax expense 14 Net loss $ (1,859 ) (1) Before elimination of inter-segment profit Segment information as of and for the three and nine months ended September 30, 2017 follows: For the Three Months Ended September 30, 2017 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 3,566 $ 250 $ 3,816 Provision for loan losses — — — Net interest income after provision for loan losses 3,566 250 3,816 Non-interest income: Customer service fees 329 30 359 Gain on loan origination and sale activities, net (1) — 2,909 2,909 Mortgage servicing fees, net (67 ) 266 199 Other 34 274 308 Total non-interest income 296 3,479 3,775 Non-interest expenses: Salaries and employee benefits 1,454 3,214 4,668 Occupancy and equipment 336 346 682 Merger and integration costs — 7 7 Other non-interest expenses 1,001 851 1,852 Total non-interest expenses 2,791 4,418 7,209 Income (loss) before income taxes and elimination of inter-segment profit $ 1,071 $ (689 ) 382 Elimination of inter-segment profit (204 ) Income before income taxes 178 Income tax provision 129 Net income $ 49 Total assets, September 30, 2017 $ 444,372 $ 61,140 $ 505,512 For the Nine Months Ended September 30, 2017 Envision Bank Envision Mortgage Consolidated Total (in thousands) Net interest income $ 10,215 $ 775 $ 10,990 Provision for loan losses 335 — 335 Net interest income after provision for loan losses 9,880 775 10,655 Non-interest income: Customer service fees 1,036 73 1,109 Gain on loan origination and sale activities, net (1) — 7,902 7,902 Mortgage servicing fees, net (189 ) 1,338 1,149 Other 524 369 893 Total non-interest income 1,371 9,682 11,053 Non-interest expenses: Salaries and employee benefits 4,690 9,369 14,059 Occupancy and equipment 1,008 949 1,957 Merger and integration costs 19 512 531 Other non-interest expenses 2,758 2,461 5,219 Total non-interest expenses 8,475 13,291 21,766 Income (loss) before income taxes and elimination of inter-segment profit $ 2,776 $ (2,834 ) (58 ) Elimination of inter-segment profit (638 ) Loss before income taxes (696 ) Income tax benefit (148 ) Net loss $ (548 ) (1) Before elimination of inter-segment profit

Basis of Financial Statement _3

Basis of Financial Statement Presentation- Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018Segment
Accounting Policies [Abstract]
Number of business segments	2

Accumulated Other Comprehensi_3

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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss)	$ (389)	$ (217)	$ (1,689)	$ 275
Accumulated other comprehensive loss, net of tax	$ (2,856)		(2,856)		$ (1,167)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			(2,277)		(624)
Other comprehensive Loss, Tax effect			(313)		(313)
Total other comprehensive income (loss)			(2,590)		(937)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			(640)		(667)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			421		484
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized loss			(219)		(183)
Other comprehensive Loss, Tax effect			(47)		(47)
Total other comprehensive income (loss)			$ (266)		$ (230)

Securities Available for Sale -

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 56,682	$ 62,199
Gross Unrealized Gains	59	403
Gross Unrealized Losses	(2,336)	(1,026)
Fair Value	54,405	61,576
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	56,137	61,654
Gross Unrealized Gains	59	403
Gross Unrealized Losses	(2,304)	(1,014)
Fair Value	53,892	61,043
Debt Securities [Member] | US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,000	3,999
Gross Unrealized Gains	7	50
Gross Unrealized Losses	(45)	(24)
Fair Value	3,962	4,025
Debt Securities [Member] | Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,527	2,005
Gross Unrealized Gains	6	27
Gross Unrealized Losses	(23)	(8)
Fair Value	1,510	2,024
Debt Securities [Member] | Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,890	12,707
Gross Unrealized Gains	22	179
Gross Unrealized Losses		(18)
Fair Value	1,912	12,868
Debt Securities [Member] | Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,835	18,729
Gross Unrealized Gains	24	118
Gross Unrealized Losses	(1,113)	(450)
Fair Value	24,746	18,397
Debt Securities [Member] | Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,278	14,451
Gross Unrealized Gains		13
Gross Unrealized Losses	(803)	(403)
Fair Value	13,475	14,061
Debt Securities [Member] | Commercial Mortgage Backed Securities, U.S. Government-guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,811	2,132
Gross Unrealized Losses	(45)	(6)
Fair Value	1,766	2,126
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,689	1,871
Gross Unrealized Gains		12
Gross Unrealized Losses	(46)	(5)
Fair Value	1,643	1,878
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,107	5,760
Gross Unrealized Gains		4
Gross Unrealized Losses	(229)	(100)
Fair Value	4,878	5,664
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	545	545
Gross Unrealized Losses	(32)	(12)
Fair Value	$ 513	$ 533

Securities Available for Sale_2

Securities Available for Sale - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)Debt_Security
Investments Debt And Equity Securities [Abstract]
Proceeds from sales of available-for-sale securities	$ 8,958,000
Gross realized gains from sales of available-for-sale securities	49,000
Gross realized losses from sales of available-for-sale securities	$ 0
Number of debt securities with unrealized losses | Debt_Security	41
Unrealized losses debt securities aggregate depreciation percentage	4.64%

Securities Available for Sale_3

Securities Available for Sale - Investments Classified by Contractual Maturity Date (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Available-for-sale Securities, Debt Maturities, Amortized Cost
Within 1 year	$ 400
After 1 year through 5 years	6,178
After 5 years through 10 years	839
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total	7,417
Mortgage-backed securities	48,720
Available-for-sale Debt Securities, Amortized Cost Basis, Total	56,137
Available-for-sale Securities, Debt Maturities, Fair Value
Within 1 year	400
After 1 year through 5 years	6,133
After 5 years through 10 years	851
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Fair Value Total	7,384
Mortgage-backed securities	46,508
Available-for-sale Securities, Debt Securities, Fair Value Total	$ 53,892

Securities Available for Sale_4

Securities Available for Sale - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	$ (834)	$ (24)
Less Than Twelve Months, Fair Value	28,668	6,641
Over Twelve Months, Gross Unrealized Losses	(1,502)	(1,002)
Over Twelve Months, Fair Value	19,334	47,400
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(834)	(24)
Less Than Twelve Months, Fair Value	28,668	6,641
Over Twelve Months, Gross Unrealized Losses	(1,470)	(990)
Over Twelve Months, Fair Value	18,821	46,867
Debt Securities [Member] | US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Over Twelve Months, Gross Unrealized Losses	(45)	(24)
Over Twelve Months, Fair Value	1,955	19,676
Debt Securities [Member] | Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(23)
Less Than Twelve Months, Fair Value	999
Over Twelve Months, Gross Unrealized Losses		(8)
Over Twelve Months, Fair Value		988
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	(433)	(1)
Less Than Twelve Months, Fair Value	14,863	1,623
Over Twelve Months, Gross Unrealized Losses	(680)	(449)
Over Twelve Months, Fair Value	7,909	13,163
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	(90)
Less Than Twelve Months, Fair Value	5,066
Over Twelve Months, Gross Unrealized Losses	(713)	(403)
Over Twelve Months, Fair Value	8,410	8,805
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	(45)	(6)
Less Than Twelve Months, Fair Value	1,766	2,126
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(46)	(5)
Less Than Twelve Months, Fair Value	1,643	678
Debt Securities [Member] | Collateralized Mortgage Obligations, US Government Guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(197)	(1)
Less Than Twelve Months, Fair Value	4,331	295
Over Twelve Months, Gross Unrealized Losses	(32)	(99)
Over Twelve Months, Fair Value	547	3,756
Debt Securities [Member] | Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses		(11)
Less Than Twelve Months, Fair Value		1,919
Over Twelve Months, Gross Unrealized Losses		(7)
Over Twelve Months, Fair Value		479
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Over Twelve Months, Gross Unrealized Losses	(32)	(12)
Over Twelve Months, Fair Value	$ 513	$ 533

Loans and Allowance for Loan _3

Loans and Allowance for Loan Losses - Summary of Loans Held for Investment at Dates Indicated (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 471,336	$ 402,658
Allowance for loan losses	(3,890)	(3,737)
Net deferred loan costs and fees, and purchase premiums	1,492	1,452
Net loans	468,938	400,373
Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	434,313	364,555
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	108,817	101,755
Commercial Real Estate Loans [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	108,817	101,755
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,948	21,766
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,075	16,337
One-to-Four Family [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	254,279	198,475
One-to-Four Family [Member] | Residential Real Estate [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	254,279	198,475
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	42,401	38,968
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	28,816	25,357
Construction [Member] | Real Estate Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 28,816	$ 25,357

Loans and Allowance for Loan _4

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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 3,742	$ 3,557	$ 3,737	$ 3,271
Provision (credit) for loan losses	178		183	335
Loans charged-off	(41)	(25)	(80)	(134)
Recoveries	11	13	50	73
Ending balance	3,890	3,545	3,890	3,545
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,505	1,536	1,620	1,410
Provision (credit) for loan losses	12	42	(103)	168
Ending balance	1,517	1,578	1,517	1,578
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	298	276	335	37
Provision (credit) for loan losses	(26)	(15)	(63)	189
Recoveries				35
Ending balance	272	261	272	261
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	247	198	218	145
Provision (credit) for loan losses	22	2	82	151
Loans charged-off	(41)	(25)	(80)	(134)
Recoveries	4	6	12	19
Ending balance	232	181	232	181
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	969	820	854	1,018
Provision (credit) for loan losses	142	15	226	(195)
Recoveries	7	7	38	19
Ending balance	1,118	842	1,118	842
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	280	338	359	436
Provision (credit) for loan losses	11	6	(68)	(92)
Ending balance	291	344	291	344
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	443	389	351	225
Provision (credit) for loan losses	17	(50)	109	114
Ending balance	$ 460	$ 339	$ 460	$ 339

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Summary of Additional Information Pertaining to the Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	$ 97		$ 162
Allowance for non-impaired loans	3,793		3,575
Total allowance for loan losses	3,890	$ 3,742	3,737	$ 3,545	$ 3,557	$ 3,271
Impaired loans	5,731		5,833
Non-impaired loans	465,605		396,825
Total loans	471,336		402,658
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans			1
Allowance for non-impaired loans	1,517		1,619
Total allowance for loan losses	1,517	1,505	1,620	1,578	1,536	1,410
Impaired loans	247		352
Non-impaired loans	108,570		101,403
Total loans	108,817		101,755
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	272		335
Total allowance for loan losses	272	298	335	261	276	37
Non-impaired loans	18,948		21,766
Total loans	18,948		21,766
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	232		218
Total allowance for loan losses	232	247	218	181	198	145
Non-impaired loans	18,075		16,337
Total loans	18,075		16,337
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans	97		160
Allowance for non-impaired loans	1,021		694
Total allowance for loan losses	1,118	969	854	842	820	1,018
Impaired loans	5,241		5,205
Non-impaired loans	249,038		193,270
Total loans	254,279		198,475
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for impaired loans			1
Allowance for non-impaired loans	291		358
Total allowance for loan losses	291	280	359	344	338	436
Impaired loans	243		276
Non-impaired loans	42,158		38,692
Total loans	42,401		38,968
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for non-impaired loans	460		351
Total allowance for loan losses	460	$ 443	351	$ 339	$ 389	$ 225
Non-impaired loans	28,816		25,357
Total loans	$ 28,816		$ 25,357

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Schedule of Past Due and Non-Accrual Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 2,662	$ 833
Non-accrual Loans	2,008	2,251
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	53
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,408	737
Non-accrual Loans	1,765	1,975
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	201	96
Non-accrual Loans	243	276
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,847	833
30 - 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	40
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	1,773	737
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	34	$ 96
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	96
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	96
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	719
90 Days or More Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13
90 Days or More Past Due [Member] | One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	635
90 Days or More Past Due [Member] | Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 71

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	$ 3,494	$ 3,189
Unpaid Principal Balance without a valuation allowance	3,494	3,145
Recorded Investment with a valuation allowance		2,708
Unpaid Principal Balance with a valuation allowance		2,688
Related Allowance, Total impaired loans	97	162
Recorded Investment, Total impaired loans	5,731	5,897
Unpaid Principal Balance, Total impaired loans	5,731	5,833
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	247	257
Unpaid Principal Balance without a valuation allowance	247	257
Recorded Investment with a valuation allowance		95
Unpaid Principal Balance with a valuation allowance		95
Related Allowance, Total impaired loans		1
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	3,004	2,685
Unpaid Principal Balance without a valuation allowance	3,004	2,641
Recorded Investment with a valuation allowance	2,237	2,584
Unpaid Principal Balance with a valuation allowance	2,237	2,564
Related Allowance, Total impaired loans	97	160
Home Equity Loans and Lines of Credit [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment without a valuation allowance	243	247
Unpaid Principal Balance without a valuation allowance	$ 243	247
Recorded Investment with a valuation allowance		29
Unpaid Principal Balance with a valuation allowance		29
Related Allowance, Total impaired loans		$ 1

Loans and Allowance for Loan _8

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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 5,754	$ 6,021	$ 5,747	$ 5,904
Interest Income Recognized	57	49	208	167
Cash Basis Interest Recognized	27	16	91	63
Residential Real Estate [Member] | One-to-Four Family [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	5,252	5,124	5,197	4,896
Interest Income Recognized	51	44	168	143
Cash Basis Interest Recognized	24	16	63	62
Residential Real Estate [Member] | Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	243	276	256	276
Interest Income Recognized	3		28	1
Cash Basis Interest Recognized	3		28	1
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	259	621	294	732
Interest Income Recognized	$ 3	$ 5	$ 12	$ 23

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)TDR	Sep. 30, 2017USD ($)TDR	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans, additional funds committed	$ 0		$ 0
Loans subject to troubled debt restructurings | TDR			1	0
Troubled debt restructuring amount			$ 3,530,000	$ 4,567,000
Changes to allowance for loan losses	0	$ 0	$ 0	0
Minimum past due days for loan rating			90 days
Total loans	471,336,000		$ 471,336,000		$ 402,658,000
Consumer Loans [Member] | Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	51,000		51,000
Residential Mortgage [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	699,000		699,000		712,000
Residential Mortgage [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,551,000		2,551,000		2,512,000
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			369,000	$ 1,139,000
Home Equity Loans and Lines of Credit [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	243,000		$ 243,000		247,000
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR			17	20
Loans subject to troubled debt restructurings, amount	3,721,000	4,382,000	$ 3,721,000	$ 4,382,000
Residential Real Estate [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, interest rate concession period			3 months
Residential Real Estate [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, interest rate concession period			30 years
Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans subject to troubled debt restructurings | TDR			1	2
Loans subject to troubled debt restructurings, amount	54,000	$ 185,000	$ 54,000	$ 185,000
Total loans	108,817,000		108,817,000		101,755,000
Commercial Real Estate Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 195,000		$ 195,000		$ 199,000
Commercial Real Estate Loans [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, interest rate concession period			1 year

Loans and Allowance for Loan_10

Loans and Allowance for Loan Losses - Summary of Company's Loans by Risk Rating (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 471,336	$ 402,658
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	28,816	25,357
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	108,817	101,755
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	18,948	21,766
Pass [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	28,816	25,357
Pass [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	108,622	101,556
Pass [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	18,948	21,766
Substandard [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 195	$ 199

Loan Servicing - Additional Inf

Loan Servicing - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Transfers And Servicing [Abstract]
Unpaid principal balance of residential mortgage loans serviced for others	$ 873,933,000		$ 771,407,000
Increase (decrease) in valuation allowance of mortgage servicing rights	$ (84,000)	$ (134,000)

Loan Servicing - Summary of Act

Loan Servicing - Summary of Activity Relating to Mortgage Servicing Rights (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Mortgage servicing rights:
Balance at beginning of year	$ 6,487	$ 8,910
Additions through originations	1,726	1,486
Sales		(3,126)
Amortization	(891)	(941)
Balance at end of period	7,322	6,329
Valuation allowance:
Balance at beginning of year	90	424
Provision (credit)	(84)	(134)
Balance at end of period	6	290
Amortized cost, net	7,316	6,039	$ 6,397
Fair value	$ 8,028	$ 6,051

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Deferred income tax provision (benefit)	$ 0	$ 129,000	$ 0	$ (151,000)
Current state tax expense			14,000	$ 3,000
Net operating loss carryforward	13,400,000		13,400,000
Valuation allowance on deferred tax assets	$ 3,200,000		$ 3,200,000

On-Balance Sheet Derivative I_2

On-Balance Sheet Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative, Notional amount	$ 34,476,000	$ 24,222,000
Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative, Notional amount	34,034,000	29,613,000
Other Assets [Member] | Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative fair value, Asset	419,000	363,000
Other Assets [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative fair value, Asset	74,000	4,000
Other Liabilities [Member] | Derivative Loan Commitments [Member]
Derivative [Line Items]
Derivative fair value, Liability	10,000
Other Liabilities [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivative fair value, Liability	$ 62,000	$ 19,000

Employee Stock Ownership Plan -

Employee Stock Ownership Plan - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Loan repaid term			25 years
Number of allocated shares	18,780		18,780
Annual allocation of shares, expiration year			2,040
ESOP expense	$ 79,000	$ 69,000	$ 229,000	$ 214,000
Unallocated shares	417,853		417,853
Unallocated shares, value	$ 6,907,000		$ 6,907,000
Common Stock [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of stock, price per share	$ 10		$ 10
The Randolph Savings Charitable Foundation, Inc. [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of share in employee stock ownership plan			469,498

Share Repurchase Program - Addi

Share Repurchase Program - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Class Of Stock [Line Items]
Cost of shares repurchased		$ 631,000	$ 3,000
September 2017 Share Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program percentage of outstanding shares repurchased	10.00%
Number of shares authorized to repurchase	586,854		586,854
Number of shares repurchased		47,500
Cost of shares repurchased		$ 748,000

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Detail) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Potentially dilutive common stock equivalents outstanding	0	0
Stock options outstanding	325,707	325,707	316,009

Earnings (Loss) Per Share - Sch

Earnings (Loss) Per Share - Schedule of Calculation of Average Number of Shares Outstanding Used to Calculate Basic and Diluted Earnings (Loss) Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Average number of common shares outstanding	5,987,796	5,868,545	6,010,467	5,870,938
Less: Average unallocated ESOP shares	(420,200)	(438,981)	(424,896)	(443,676)
Average number of common shares outstanding (basic and diluted)	5,567,596	5,429,564	5,585,571	5,427,262

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)shares	Sep. 30, 2018USD ($)shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted to purchase of shares of common stock		27,000
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options term		9 years
Stock-based compensation expense | $	$ 81,000	$ 226,000
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $	$ 129,000	$ 371,000
Two Thousand Seventeen Stock Option and Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and awards vesting period		5 years
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	586,872	586,872
Stock options term		10 years
Two Thousand Seventeen Stock Option and Incentive Plan [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	234,749	234,749

Stock Based Compensation - Summ

Stock Based Compensation - Summary of Granted Options to Purchase Shares of Common Stock (Detail)	9 Months Ended
	Sep. 30, 2018$ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option fair value	$ 3.92
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period (years)	9 years
Expected volatility	29.87%
Expected life (years)	3 years 10 months 24 days
Risk free interest rate, minimum	2.68%
Risk free interest rate, maximum	2.77%
Minimum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (years)	3 years
Maximum [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (years)	6 years 6 months

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Stock Option Grants
Beginning Balance	316,009
Granted	27,000
Forfeited	(17,302)
Ending Balance	325,707	316,009
Exercisable at September 30, 2018	0
Unrecognized compensation cost	$ 1,218,000
Weighted Average Exercise Price
Beginning Balance	$ 14.66
Granted	16.15
Forfeited	14.74
Ending Balance	$ 14.78	$ 14.66
Weighted Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term	9 years 25 days	9 years 1 month 6 days
Weighted Average Remaining Contractual Term, Granted	6 years 6 months
Aggregate Intrinsic Value, Outstanding	$ 280,423
Aggregate Intrinsic Value, Outstanding	570,267	$ 280,423
Aggregate Intrinsic Value, Exercisable	$ 0
Stock Options [Member]
Stock Option Grants
Weighted average remaining recognition period (years)	3 years 10 months 17 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Activity in Restricted Stock Awards Under Equity Plan (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Restricted Stock Awards
Beginning Balance | shares	176,239
Forfeited | shares	(7,042)
Ending Balance | shares	169,197
Unrecognized compensation cost | $	$ 1,987,000
Weighted Average Grant Price
Beginning Balance | $ / shares	$ 14.66
Forfeited | $ / shares	14.66
Ending Balance | $ / shares	$ 14.66
Restricted Stock [Member]
Restricted Stock Awards
Weighted average remaining recognition period (years)	3 years 11 months 4 days

Fair Value of Assets and Liab_3

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, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	$ 54,405	$ 61,576
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	53,892	61,043
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	513	533
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	54,405	61,576
Fair value, Loans held for sale	24,120	25,390
Derivative assets	493	367
Derivative liabilities	62	19
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Loans held for sale	24,120	25,390
Fair value, Loans held for investment	1,894	6,412
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	53,891	61,043
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	513	533
Fair Value, Measurements, Recurring [Member] | Derivative Loan Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	419	363
Derivative liabilities	10
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	74	4
Derivative liabilities	62	19
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	24,120	25,390
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	53,891	61,043
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	513	533
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	419	363
Derivative liabilities	10
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	74	4
Derivative liabilities	62	19
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, Loans held for investment	$ 1,894	$ 6,412

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Schedule of Assets Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, fair value	$ 8,028		$ 6,051
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (losses) on assets held, mortgage servicing rights	84
Gains (losses) on assets held for sale	230
Gains (losses) on assets held, foreclosed real estate	(25)
Gains (Losses) on assets held	289
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	7,316	$ 6,397
Assets, Fair Value Disclosure	7,316	6,397
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	1,248	1,630
Fair value, Assets held for sale	2,897	828
Fair value, Foreclosed real estate	82	193
Assets, Fair Value Disclosure	$ 4,227	$ 2,651

Fair Value of Assets and Liab_5

Fair Value of Assets and Liabilities - Additional information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in valuation allowance of mortgage servicing rights	$ (84,000)	$ (134,000)
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on nonrecurring basis	0		$ 0
Branch Office [Member] | North Randolph [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) recognized from sale of property	0
Branch Office [Member] | Stoughton [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) recognized from sale of property	230,000
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of assets held for sale	$ 2,897,000

Fair Value of Assets and Liab_6

Fair Value of Assets and Liabilities - Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Securities available for sale	$ 54,405	$ 61,576
Level 2 [Member]
Financial assets:
Certificates of deposit	2,681	2,932
Securities available for sale	54,405	61,576
Loans held for sale	24,120	25,390
Derivative assets	493	367
Financial liabilities:
Deposits	425,481	365,997
FHLBB advances	77,197	75,821
Derivative liabilities	62	19
Level 3 [Member]
Financial assets:
Loans, net	457,349	398,407
Carrying Amount [Member]
Financial assets:
Certificates of deposit	2,695	2,940
Securities available for sale	54,405	61,576
Loans held for sale	24,120	25,390
Loans, net	468,938	400,373
Derivative assets	493	367
Financial liabilities:
Deposits	427,173	366,836
FHLBB advances	77,411	75,954
Derivative liabilities	62	19
Fair Value [Member]
Financial assets:
Certificates of deposit	2,681	2,932
Securities available for sale	54,405	61,576
Loans held for sale	24,120	25,390
Loans, net	457,349	398,407
Derivative assets	493	367
Financial liabilities:
Deposits	425,481	365,997
FHLBB advances	77,197	75,821
Derivative liabilities	$ 62	$ 19

Commitments and Contingencies -

Commitments and Contingencies - Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commitments to Originate Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 48,678	$ 35,549
Unused Lines and Letters of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	42,939	39,968
Unadvanced Funds on Construction Loans [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	11,571	6,967
Overdraft Lines of Credit [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk	$ 8,615	$ 8,996

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)SegmentOffice	Sep. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Number of business segments | Segment			2
Number of branch offices | Office			6
Servicing fees amount	$ (310,000)	$ (199,000)	$ (935,000)	$ (1,149,000)
Envision Mortgage [Member]
Segment Reporting Information [Line Items]
Premium percentage for new loans			1.50%	1.50%
Premium income	307,000	204,000	$ 971,000	$ 638,000
Percentage of fees for HELOC			1.00%	1.00%
Servicing fees amount	(391,000)	(266,000)	$ (1,157,000)	$ (1,338,000)
Envision Bank [Member]
Segment Reporting Information [Line Items]
Percentage of loan servicing fees			0.14%	0.14%
Servicing fees amount	$ 81,000	$ 67,000	$ 222,000	$ 189,000

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income		$ 4,260,000	$ 3,816,000	$ 12,276,000	$ 10,990,000
Provision for loan losses		178,000		183,000	335,000
Net interest income after provision for loan losses		4,082,000	3,816,000	12,093,000	10,655,000
Non-interest income:
Customer service fees		357,000	359,000	1,096,000	1,109,000
Gain on loan origination and sale activities, net	[1]	2,263,000	2,909,000	6,327,000	7,902,000
Mortgage servicing fees, net		310,000	199,000	935,000	1,149,000
Other		585,000	308,000	1,011,000	893,000
Total non-interest income		3,515,000	3,775,000	9,369,000	11,053,000
Non-interest expenses:
Salaries and employee benefits		4,788,000	4,668,000	14,166,000	14,059,000
Occupancy and equipment		728,000	682,000	2,157,000	1,957,000
Merger and integration costs			7,000		531,000
Other non-interest expenses		1,911,000	1,852,000	6,013,000	5,219,000
Total non-interest expenses		7,427,000	7,209,000	22,336,000	21,766,000
Income (loss) before income taxes and elimination of inter-segment profit		170,000	382,000	(874,000)	(58,000)
Elimination of inter-segment profit		(307,000)	(204,000)	(971,000)	(638,000)
Income (loss) before income taxes		(137,000)	178,000	(1,845,000)	(696,000)
Income tax expense (benefit)		5,000	129,000	14,000	(148,000)
Net income (loss)		(142,000)	49,000	(1,859,000)	(548,000)
Total assets, September 30, 2018		589,682,000	505,512,000	589,682,000	505,512,000	$ 531,892,000
Envision Bank [Member]
Segment Reporting Information [Line Items]
Net interest income		4,002,000	3,566,000	11,541,000	10,215,000
Provision for loan losses		178,000		183,000	335,000
Net interest income after provision for loan losses		3,824,000	3,566,000	11,358,000	9,880,000
Non-interest income:
Customer service fees		324,000	329,000	1,035,000	1,036,000
Mortgage servicing fees, net		(81,000)	(67,000)	(222,000)	(189,000)
Other		400,000	34,000	648,000	524,000
Total non-interest income		643,000	296,000	1,461,000	1,371,000
Non-interest expenses:
Salaries and employee benefits		1,601,000	1,454,000	4,849,000	4,690,000
Occupancy and equipment		317,000	336,000	1,090,000	1,008,000
Merger and integration costs					19,000
Other non-interest expenses		1,117,000	1,001,000	3,355,000	2,758,000
Total non-interest expenses		3,035,000	2,791,000	9,294,000	8,475,000
Income (loss) before income taxes and elimination of inter-segment profit		1,432,000	1,071,000	3,525,000	2,776,000
Total assets, September 30, 2018		521,139,000	444,372,000	521,139,000	444,372,000
Envision Mortgage [Member]
Segment Reporting Information [Line Items]
Net interest income		258,000	250,000	735,000	775,000
Net interest income after provision for loan losses		258,000	250,000	735,000	775,000
Non-interest income:
Customer service fees		33,000	30,000	61,000	73,000
Gain on loan origination and sale activities, net	[1]	2,263,000	2,909,000	6,327,000	7,902,000
Mortgage servicing fees, net		391,000	266,000	1,157,000	1,338,000
Other		185,000	274,000	363,000	369,000
Total non-interest income		2,872,000	3,479,000	7,908,000	9,682,000
Non-interest expenses:
Salaries and employee benefits		3,187,000	3,214,000	9,317,000	9,369,000
Occupancy and equipment		411,000	346,000	1,067,000	949,000
Merger and integration costs			7,000		512,000
Other non-interest expenses		794,000	851,000	2,658,000	2,461,000
Total non-interest expenses		4,392,000	4,418,000	13,042,000	13,291,000
Income (loss) before income taxes and elimination of inter-segment profit		(1,262,000)	(689,000)	(4,399,000)	(2,834,000)
Total assets, September 30, 2018		$ 68,543,000	$ 61,140,000	$ 68,543,000	$ 61,140,000
[1]	Before elimination of inter-segment profit

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	Jul. 31, 2018	Oct. 31, 2018PositionEmployee	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)ft²	Oct. 23, 2018USD ($)
Consolidation of Mortgage Banking Operations [Member]
Subsequent Event [Line Items]
Percentage of land occupied under sublease agreement	27.00%
Termination of lease	2,023
Remaining minimum lease obligation, net of sublease payments			$ 1,223,000
Andover [Member] | Scenario, Forecast [Member] | Consolidation of Mortgage Banking Operations [Member]
Subsequent Event [Line Items]
Severance costs				$ 235,000
Remaining space available to sublease | ft²				3,000
Andover [Member] | Subsequent Events [Member] | Consolidation of Mortgage Banking Operations [Member]
Subsequent Event [Line Items]
Number of administrative positions eliminated | Position		15
Number of employees remained | Employee		25
North Attleboro [Member] | Subsequent Events [Member] | Consolidation of Mortgage Banking Operations [Member]
Subsequent Event [Line Items]
Number of administrative positions to be added | Position		8
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member]
Subsequent Event [Line Items]
Pending sale of property, Description			During the third quarter of 2018, the Company began to actively market for sale its branch office in Boston and on October 23, 2018 entered into a purchase and sale agreement to sell the property for $5,000,000. Consummation of this transaction is subject to an inspection review by the buyer, removal of asbestos in accordance with an environmental engineering report and certain other customary closing conditions, including receipt of regulatory approval to close the branch. This transaction is expected to close in the fourth quarter of 2018.
Net book value of property reclassified to assets held for sale			$ 2,897,000
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member] | Scenario, Forecast [Member]
Subsequent Event [Line Items]
Insurance recovery for personal property				$ 90,000
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member] | Subsequent Events [Member]
Subsequent Event [Line Items]
Consideration receivable					$ 5,000,000
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member] | Subsequent Events [Member] | Insurance Settlements [Member] | Minimum [Member]
Subsequent Event [Line Items]
Recognizable gain on sale					2,000,000
Branch Office [Member] | Boston [Member] | Purchase and Sale Agreement [Member] | Subsequent Events [Member] | Insurance Settlements [Member] | Maximum [Member]
Subsequent Event [Line Items]
Recognizable gain on sale					$ 2,150,000