Meridian Bancorp (EBSB) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	EBSB
Entity Registrant Name	Meridian Bancorp, Inc.
Entity Central Index Key	1,600,125
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,970,209

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
ASSETS
Cash and due from banks	$ 300,297	$ 236,423
Certificates of deposit	75,192	80,323
Securities available for sale, at fair value	44,661	67,663
Federal Home Loan Bank stock, at cost	22,976	18,175
Loans held for sale	3,707	3,944
Loans, net of fees and costs	4,547,511	3,938,817
Less: allowance for loan losses	(45,643)	(40,149)
Loans, net	4,501,868	3,898,668
Bank-owned life insurance	40,052	40,745
Foreclosed real estate, net	1,690
Premises and equipment, net	40,077	41,427
Accrued interest receivable	11,580	10,381
Deferred tax asset, net	21,487	21,461
Goodwill	13,687	13,687
Other assets	9,140	3,105
Total assets	5,086,414	4,436,002
Deposits:
Non interest-bearing	455,540	431,222
Interest-bearing	3,489,929	3,044,615
Total deposits	3,945,469	3,475,837
Long-term debt	471,069	322,512
Accrued expenses and other liabilities	29,472	30,356
Total liabilities	4,446,010	3,828,705
Stockholders' equity:
Preferred stock, $0.01 par value, 50,000,000 shares authorized; none issued
Common stock, $0.01 par value, 100,000,000 shares authorized; 53,947,394 and 53,596,105 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	539	536
Additional paid-in capital	393,903	390,065
Retained earnings	262,079	234,290
Accumulated other comprehensive income	2,622	1,806
Unearned compensation-ESOP, 2,587,477 and 2,678,800 shares at September 30, 2017 and December 31, 2016, respectively	(18,739)	(19,400)
Total stockholders' equity	640,404	607,297
Total liabilities and stockholders' equity	$ 5,086,414	$ 4,436,002

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	53,947,394	53,596,105
Common stock, shares outstanding	53,947,394	53,596,105
Unearned compensation, ESOP	2,587,477	2,678,800

Consolidated Statements of Net

Consolidated Statements of Net Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest and dividend income:
Interest and fees on loans	$ 46,597	$ 37,444	$ 130,281	$ 105,369
Interest on debt securities:
Taxable	58	203	260	707
Tax-exempt		30	18	95
Dividends on equity securities	275	365	843	1,183
Interest on certificates of deposit	221	75	629	380
Other interest and dividend income	819	303	2,200	709
Total interest and dividend income	47,970	38,420	134,231	108,443
Interest expense:
Interest on deposits	8,528	6,273	23,882	17,162
Interest on short-term borrowings			4	6
Interest on long-term debt	1,388	845	3,482	2,139
Total interest expense	9,916	7,118	27,368	19,307
Net interest income	38,054	31,302	106,863	89,136
Provision for loan losses	2,458	858	5,574	5,876
Net interest income, after provision for loan losses	35,596	30,444	101,289	83,260
Non-interest income:
Customer service fees	2,081	2,172	6,347	6,258
Loan fees	180	293	1,882	583
Mortgage banking gains, net	176	274	348	448
Gain on sales of securities, net	865	266	3,247	393
Income from bank-owned life insurance	294	296	874	894
Gain on life insurance distribution	1,657		1,657
Total non-interest income	5,253	3,301	14,355	8,576
Non-interest expenses:
Salaries and employee benefits	12,973	12,169	39,400	36,661
Occupancy and equipment	2,676	2,577	8,735	7,928
Data processing	1,528	1,293	4,381	3,804
Marketing and advertising	715	832	2,522	2,244
Professional services	624	663	2,865	1,996
Deposit insurance	660	572	2,164	1,556
Merger and acquisition	271		271
Other general and administrative	1,367	1,058	3,758	3,527
Total non-interest expenses	20,814	19,164	64,096	57,716
Income before income taxes	20,035	14,581	51,548	34,120
Provision for income taxes	6,702	5,084	17,624	11,239
Net income	$ 13,333	$ 9,497	$ 33,924	$ 22,881
Earnings per share:
Basic	$ 0.26	$ 0.19	$ 0.66	$ 0.45
Diluted	$ 0.25	$ 0.18	$ 0.65	$ 0.44
Weighted average shares:
Basic	51,229,203	50,982,633	51,061,959	51,192,332
Diluted	52,672,962	52,093,009	52,541,752	52,297,367

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income		$ 13,333	$ 9,497	$ 33,924	$ 22,881
Securities available for sale:
Unrealized holding gain		2,067	1,781	4,621	5,653
Reclassification adjustment for gains realized in income	[1]	(865)	(266)	(3,247)	(393)
Net unrealized gain		1,202	1,515	1,374	5,260
Tax effect		(485)	(570)	(558)	(2,124)
Total other comprehensive income		717	945	816	3,136
Comprehensive income		$ 14,050	$ 10,442	$ 34,740	$ 26,017
[1]	Amounts are included in gain on sales of securities, net in the Consolidated Statements of Net Income. Provisions for income tax associated with the reclassification adjustments for the three months ended September 30, 2017 and 2016 were $349,000 and $100,000, respectively, and for the nine months ended September 30, 2017 and 2016 were $1.3 million and $159,000, respectively.

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Income tax associated with reclassification adjustments	$ 349,000	$ 100,000	$ 1,300,000	$ 159,000

Consolidated Statements of Chan

Consolidated Statements of Changes In Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Unearned Compensation - ESOP [Member]
Beginning Balance at Dec. 31, 2015	$ 588,126	$ 549	$ 403,737	$ 206,214	$ (2,092)	$ (20,282)
Beginning balance, shares at Dec. 31, 2015		54,875,237
Comprehensive income	26,017			22,881	3,136
Dividends declared	(4,586)			(4,586)
Repurchased stock related to buyback program	(16,955)	$ (12)	(16,943)
Repurchased stock related to buyback program, shares		(1,220,711)
ESOP shares earned	1,322		661			661
Share-based compensation expense - restricted stock, net of awards forfeited	1,553		1,553
Share-based compensation expense - restricted stock, net of awards forfeited, shares		(20,248)
Share-based compensation expense - stock options, net of awards forfeited	872		872
Excess tax benefits in connection with share-based compensation	502		502
Stock options exercised	205		205
Stock options exercised, shares		79,913
Ending Balance at Sep. 30, 2016	597,056	$ 537	390,587	224,509	1,044	(19,621)
Ending balance, shares at Sep. 30, 2016		53,714,191
Beginning Balance at Dec. 31, 2016	$ 607,297	$ 536	390,065	234,290	1,806	(19,400)
Beginning balance, shares at Dec. 31, 2016	53,596,105	53,596,105
Comprehensive income	$ 34,740			33,924	816
Dividends declared	(6,135)			(6,135)
ESOP shares earned	1,629		968			661
Share-based compensation expense - restricted stock, net of awards forfeited	1,631	$ 2	1,629
Share-based compensation expense - restricted stock, net of awards forfeited, shares		255,196
Share-based compensation expense - stock options, net of awards forfeited	923		923
Stock options exercised	319	$ 1	318
Stock options exercised, shares		96,093
Ending Balance at Sep. 30, 2017	$ 640,404	$ 539	$ 393,903	$ 262,079	$ 2,622	$ (18,739)
Ending balance, shares at Sep. 30, 2017	53,947,394	53,947,394

Consolidated Statements of Cha8

Consolidated Statements of Changes In Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323
Common Stock [Member]
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323
Additional Paid-in Capital [Member]
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323
Retained Earnings [Member]
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323
Accumulated Other Comprehensive Income (Loss) [Member]
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323
Unearned Compensation - ESOP [Member]
Dividends declared per share	$ 0.12	$ 0.09
ESOP shares earned	91,323	91,323

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 33,924	$ 22,881
Adjustments to reconcile net income to net cash provided by operating activities:
Accretion of acquisition fair value adjustments	(122)	(107)
ESOP shares earned expense	1,629	1,322
Provision for loan losses	5,574	5,876
Accretion of net deferred loan origination fees	(913)	(787)
Net accretion of securities available for sale	(5)	(45)
Depreciation and amortization expense	2,333	2,224
Gain on sales of securities, net	(3,247)	(393)
Net loss and provision for foreclosed real estate		15
Deferred income tax benefit	(584)	(713)
Income from bank-owned life insurance	(874)	(894)
Gain on life insurance distribution	(1,657)
Share-based compensation expense	2,554	2,425
Net changes in:
Loans held for sale	237	1,815
Accrued interest receivable	(1,199)	(635)
Other assets	(5,719)	(3,638)
Accrued expenses and other liabilities	(1,410)	1,083
Net cash provided by operating activities	30,521	30,429
Cash flows from investing activities:
Purchases of certificates of deposit	(5,000)	(20,292)
Maturities of certificates of deposit	10,131	89,012
Activity in securities available for sale:
Proceeds from maturities, calls and principal payments	16,454	23,336
Purchase of mutual funds, net	(8)	(29,846)
Proceeds from sales	17,221	17,517
Purchases	(6,353)	(10,479)
Loans originated, net of principal payments received	(609,507)	(622,051)
Proceeds from the distribution of bank-owned life insurance	3,224
Purchases of premises and equipment	(921)	(2,661)
Purchase of Federal Home Loan Bank stock	(4,801)	(6,887)
Proceeds from sale of foreclosed real estate		623
Net cash used in investing activities	(579,560)	(561,728)
Cash flows from financing activities:
Net increase in deposits	469,646	486,565
Net change in borrowings with maturities less than three months		(20,000)
Proceeds from Federal Home Loan Bank advances with maturities of three months or more	260,625	210,000
Repayment of Federal Home Loan Bank advances with maturities of three months or more	(112,068)	(37,406)
Cash dividends paid on common stock	(5,609)	(4,621)
Stock options exercised	319	205
Repurchase of common stock		(16,955)
Net cash provided by financing activities	612,913	617,788
Net change in cash and cash equivalents	63,874	86,489
Cash and cash equivalents at beginning of period	236,423	96,363
Cash and cash equivalents at end of period	300,297	182,852
Supplemental cash flow information:
Interest paid on deposits	23,690	16,920
Interest paid on borrowings	3,312	2,032
Income taxes paid, net of refunds	21,285	15,521
Non-cash investing and financing activities:
Transfers from loans to foreclosed real estate	1,690	$ 638
Net amounts due from broker on security transactions	$ 316

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	1 . BASIS OF PRESENTATION The consolidated financial statements include the accounts of Meridian Bancorp, Inc. (the “Company”) and all other entities in which it has a controlling financial interest. The Company owns 100% of the outstanding shares of East Boston Savings Bank (the “Bank”). The Bank’s subsidiaries include: (1) Prospect, Inc., which engages in securities transactions on its own behalf; (2) EBOSCO, LLC, which holds foreclosed real estate; and (3) East Boston Investment Services, Inc., which is authorized for third-party investment sales and is currently inactive. All significant intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited interim consolidated financial statements of the Company have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q 10-01 S-X. 10-K www.sec.gov. In preparing consolidated financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the consolidated balance sheet and reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to the determination of the allowance for loan losses and the evaluation of securities for other-than-temporary impairment. Change in accounting principle—Share-based compensation In March 2016, the Financial Accounting Standards Board (the “FASB”) issued an Accounting Standards Update (“ASU”), No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting Accounting for Income Taxes Entities will no longer record the excess tax benefits or deficiencies related to share-based compensation in additional paid-in paid-in

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2017
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	2. RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments — Overall, (Subtopic 825-10). In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) right-to-use In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) held-to-maturity available-for-sale In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share	3. EARNINGS PER SHARE Basic earnings per share excludes dilution and is calculated by dividing net income available to common stockholders by the weighted-average number of common shares outstanding during the period. Rights to dividends on unvested stock awards are non-forfeitable, Basic and diluted earnings per share have been computed based on the following: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (Dollars in thousands, expect per share amounts) Net income available to common stockholders $ 13,333 $ 9,497 $ 33,924 $ 22,881 Basic weighted average shares outstanding 51,229,203 50,982,633 51,061,959 51,192,332 Effect of dilutive stock options 1,443,759 1,110,376 1,479,793 1,105,035 Diluted weighted average shares outstanding $ 52,672,962 52,093,009 $ 52,541,752 52,297,367 Earnings per share: Basic $ 0.26 $ 0.19 $ 0.66 $ 0.45 Diluted $ 0.25 $ 0.18 $ 0.65 $ 0.44 For the three and nine months ended September 30, 2017 options for the exercise of 79,802 shares and 26,601 shares, respectively, were not included in the calculation of diluted earnings per share because to do so would have been anti-dilutive. An anti-dilutive option exists when the average stock price for the period is less than the exercise price of the option. For the three and nine months ended September 30, 2016, options for the exercise of 153,760 shares and 265,139 shares, respectively, were not included in the calculation of diluted earnings per share because to do so would have been anti-dilutive. On July 31, 2017, the Company granted 682,750 stock options and 272,750 restricted stock awards under the 2015 Equity Incentive Plan to its directors and officers, including named executive officers of the Company. Awards vest 20% per year over a period of five years beginning one year from the date of grant.

Securities Available for Sale

Securities Available for Sale	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Securities Available for Sale	4. SECURITIES AVAILABLE FOR SALE The amortized cost and fair values of securities available for sale, with gross unrealized gains and losses, follows: Amortized Gross Gross Fair (In thousands) September 30, 2017 Debt securities: Municipal bonds $ 341 $ 6 $ — $ 347 Residential mortgage-backed securities: Government-sponsored enterprises 4,393 288 (2 ) 4,679 Private label 73 5 — 78 Total debt securities 4,807 299 (2 ) 5,104 Marketable equity securities: Common stocks: Basic materials 4,518 338 (230 ) 4,626 Consumer products and services 10,492 1,231 (745 ) 10,978 Financial services 4,471 1,296 (21 ) 5,746 Healthcare 7,827 1,688 (6 ) 9,509 Industrials 4,484 770 (4 ) 5,250 Technology 3,041 551 (154 ) 3,438 Total common stocks 34,833 5,874 (1,160 ) 39,547 Money market mutual funds 10 — — 10 Total marketable equity securities 34,843 5,874 (1,160 ) 39,557 Total securities available for sale $ 39,650 $ 6,173 $ (1,162 ) $ 44,661 December 31, 2016 Debt securities: Corporate bonds: Financial services $ 12,989 $ 16 $ (3 ) $ 13,002 Industrials 1,000 3 — 1,003 Total corporate bonds 13,989 19 (3 ) 14,005 Municipal bonds 1,202 17 — 1,219 Residential mortgage-backed securities: Government-sponsored enterprises 5,284 325 (3 ) 5,606 Private label 779 22 — 801 Total debt securities 21,254 383 (6 ) 21,631 Marketable equity securities: Common stocks: Basic materials 6,763 901 (232 ) 7,432 Consumer products and services 13,567 1,093 (382 ) 14,278 Financial services 5,953 970 — 6,923 Healthcare 8,225 533 (456 ) 8,302 Industrials 4,181 624 (11 ) 4,794 Technology 4,081 440 (220 ) 4,301 Total common stocks 42,770 4,561 (1,301 ) 46,030 Money market mutual funds 2 — — 2 Total marketable equity securities 42,772 4,561 (1,301 ) 46,032 Total securities available for sale $ 64,026 $ 4,944 $ (1,307 ) $ 67,663 At September 30, 2017, securities with an amortized cost of $3.5 million and $472,000 were pledged as collateral for Federal Home Loan Bank of Boston (“FHLB”) borrowings and for the Federal Reserve Bank discount window borrowings, respectively. The amortized cost and fair value of debt securities by contractual maturity at September 30, 2017 are as follows. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without prepayment penalties. One Year or Less After One Year After Five Years Total Amortized Fair Amortized Fair Amortized Fair Amortized Fair (In thousands) Municipal bonds $ 341 $ 347 $ — $ — $ — $ — $ 341 $ 347 Residential mortgage-backed securities: Government-sponsored enterprises — — 1 1 4,392 4,678 4,393 4,679 Private label — — — — 73 78 73 78 Total $ 341 $ 347 $ 1 $ 1 $ 4,465 $ 4,756 $ 4,807 $ 5,104 For the three months ended September 30, 2017 and 2016, proceeds from sales of securities available for sale amounted to $5.6 million and $12.5 million, respectively. Gross gains of $937,000 and $2.4 million and gross losses of $72,000 and $2.1 million, respectively, were realized on those sales. For the nine months ended September 30, 2017 and 2016, proceeds from the sales of securities available for sale amounted to $17.2 million and $17.5 million, respectively. Gross gains of $3.3 million and $3.6 million and gross losses of $93,000 and $3.2 million, respectively, were realized on those sales. Information pertaining to securities available for sale as of September 30, 2017 and December 31, 2016, with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: Less Than Twelve Months Twelve Months or Longer Gross Fair Gross Fair (In thousands) September 30, 2017 Debt securities: Residential mortgage-backed securities: Government-sponsored enterprises $ — $ — $ 2 $ 174 Total debt securities — — 2 174 Marketable equity securities: Common stocks: Basic materials 46 833 184 1,573 Consumer products and services 136 1,192 609 1,929 Financial services 21 492 — — Healthcare 6 406 — — Industrials 4 971 — — Technology 146 1,227 8 337 Total common stocks and marketable equity securities 359 5,121 801 3,839 Total temporarily impaired securities $ 359 $ 5,121 $ 803 $ 4,013 Less Than Twelve Months Twelve Months or Longer Gross Fair Gross Fair (In thousands) December 31, 2016 Debt securities: Corporate bonds-financial services $ 3 $ 5,000 $ — $ — Residential mortgage-backed securities: Government-sponsored enterprises — — 3 205 Total debt securities 3 5,000 3 205 Marketable equity securities: Common stocks: Basic materials — — 232 1,568 Consumer products and services 237 3,496 145 1,618 Healthcare 259 2,039 197 1,377 Industrials 11 450 — — Technology — — 220 1,681 Total common stocks and marketable equity securities 507 5,985 794 6,244 Total temporarily impaired securities $ 510 $ 10,985 $ 797 $ 6,449 The Company determined no securities were other-than-temporarily impaired for the nine months ended September 30, 2017, and 2016. Management evaluates securities for other-than-temporary impairment on a quarterly basis, with more frequent evaluation for selected issuers or when economic or market concerns warrant such evaluations. At September 30, 2017, 18 marketable equity securities with a fair value of $9.0 million had gross unrealized losses totaling $1.2 million, or an aggregate depreciation of 11.5% from the Company’s cost basis. These marketable equity securities consisted of 11 securities with a fair value of $5.1 million and a gross unrealized loss of $359,000 for less than 12 months and seven securities with a fair value of $3.8 million and a gross unrealized loss of $801,000 for 12 months or longer. The marketable equity securities in a gross unrealized loss position for 12 months or longer were comprised of two securities in the basic materials sector with a fair value of $1.6 million and a gross unrealized loss of $184,000, four securities in the consumer products and services sector with a fair value of $1.9 million and a gross unrealized loss of $609,000, and one security in the technology sector with a fair value of $337,000 and a gross unrealized loss of $8,000. In analyzing an equity issuer’s financial condition, management considers industry analysts’ reports, financial performance and projected target prices of investment analysts within a one-year Although issuers within the marketable equity securities portfolio had price declines resulting in unrealized losses, management does not believe these declines in market value are other than temporary, and the Company currently has the ability and intent to hold these investments until a recovery of fair value.

Loans

Loans	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Loans	5. LOANS A summary of loans follows: September 30, 2017 December 31, 2016 Amount Percent Amount Percent (Dollars in thousands) Real estate loans: Residential real estate: One- $ 560,393 12.3 % $ 532,450 13.5 % Home equity lines of credit 42,042 0.9 42,913 1.1 Multi-family 702,631 15.4 562,948 14.3 Commercial real estate 2,070,761 45.5 1,776,601 45.1 Construction 604,487 13.3 502,753 12.8 Total real estate loans 3,980,314 87.4 3,417,665 86.8 Commercial and industrial 561,769 12.4 515,430 13.0 Consumer 10,222 0.2 9,712 0.2 Total loans 4,552,305 100.0 % 3,942,807 100.0 % Allowance for loan losses (45,643 ) (40,149 ) Net deferred loan origination fees (4,794 ) (3,990 ) Loans, net $ 4,501,868 $ 3,898,668 The Company has transferred a portion of its originated commercial real estate loans to participating lenders. The amounts transferred have been accounted for as sales and are therefore not included in the Company’s accompanying balance sheets. The Company and participating lenders share ratably in any gains or losses that may result from a borrower’s lack of compliance with contractual terms of the loan. The Company continues to service the loans on behalf of the participating lenders and, as such, collects cash payments from the borrowers, remits payments to participating lenders and disburses required escrow funds to relevant parties. At September 30, 2017 and December 31, 2016, the Company was servicing loans for participants aggregating $238.4 million and $210.5 million, respectively. At September 30, 2017, multi-family and commercial real estate loans with carrying values totaling $161.6 million and $757.9 million, respectively, were pledged as collateral for FHLB borrowings. An analysis of the allowance for loan losses and related information follows: Three Months Ended September 30, 2017 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,167 $ 5,549 $ 71 $ 20,598 $ 8,846 $ 6,901 $ 97 $ 43,229 Provision (credit) for loan losses (100 ) (44 ) (9 ) 1,343 1,245 (52 ) 75 2,458 Charge-offs — — — — — — (99 ) (99 ) Recoveries — — — — 1 30 24 55 Ending balance $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Three Months Ended September 30, 2016 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,320 $ 4,002 $ 92 $ 16,950 $ 9,090 $ 6,751 $ 112 $ 38,317 Provision (credit) for loan losses 141 302 (6 ) 300 560 (482 ) 43 858 Charge-offs — — — — (486 ) — (72 ) (558 ) Recoveries — — — — 7 52 21 80 Ending balance $ 1,461 $ 4,304 $ 86 $ 17,250 $ 9,171 $ 6,321 $ 104 $ 38,697 Nine Months Ended September 30, 2017 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,367 $ 4,514 $ 73 $ 18,725 $ 8,931 $ 6,452 $ 87 $ 40,149 Provision (credit) for loan losses (333 ) 990 (11 ) 3,216 1,112 397 203 5,574 Charge-offs — — — — (2 ) — (265 ) (267 ) Recoveries 33 1 — — 51 30 72 187 Ending balance $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Nine Months Ended September 30, 2016 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,354 $ 3,385 $ 144 $ 14,497 $ 8,313 $ 5,620 $ 92 $ 33,405 Provision (credit) for loan losses 107 919 (58 ) 2,753 1,323 685 147 5,876 Charge-offs — — — — (486 ) (44 ) (206 ) (736 ) Recoveries — — — — 21 60 71 152 Ending balance $ 1,461 $ 4,304 $ 86 $ 17,250 $ 9,171 $ 6,321 $ 104 $ 38,697 One- four-family Multi- family Home equity lines of credit Commercial real estate Construction Commercial and industrial Consumer Total (In thousands) September 30, 2017 Amount of allowance for loan losses for loans deemed to be impaired $ 67 $ 105 $ — $ — $ — $ — $ — $ 172 Amount of allowance for loan losses for loans not deemed to be impaired 1,000 5,400 62 21,941 10,092 6,879 97 45,471 $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Loans deemed to be impaired $ 1,598 $ 1,327 $ — $ 862 $ 173 $ 1,577 $ — $ 5,537 Loans not deemed to be impaired 558,795 701,304 42,042 2,069,899 604,314 560,192 10,222 4,546,768 $560,393 $702,631 $42,042 $2,070,761 $604,487 $561,769 $10,222 $4,552,305 December 31, 2016 Amount of allowance for loan losses for loans deemed to be impaired $ 49 $ 137 $ — $ — $ — $ — $ — $ 186 Amount of allowance for loan losses for loans not deemed to be impaired 1,318 4,377 73 18,725 8,931 6,452 87 39,963 $ 1,367 $ 4,514 $ 73 $ 18,725 $ 8,931 $ 6,452 $ 87 $ 40,149 Loans deemed to be impaired $ 1,422 $ 1,359 $ — $ 2,807 $ 988 $ 1,808 $ — $ 8,384 Loans not deemed to be impaired 531,028 561,589 42,913 1,773,794 501,765 513,622 9,712 3,934,423 $532,450 $562,948 $42,913 $1,776,601 $502,753 $515,430 $9,712 $3,942,807 The following table provides information about the Company’s past due and non-accrual 30-59 60-89 90 Days Total Loans on Non-accrual (In thousands) September 30, 2017 Real estate loans: Residential real estate: One- $ 1,113 $ 984 $ 1,380 $ 3,477 $ 7,055 Home equity lines of credit 371 67 395 833 563 Commercial real estate 100 — — 100 862 Construction — 173 — 173 173 Total real estate loans 1,584 1,224 1,775 4,583 8,653 Commercial and industrial — — 525 525 525 Consumer 489 664 — 1,153 — Total $ 2,073 $ 1,888 $ 2,300 $ 6,261 $ 9,178 December 31, 2016 Real estate loans: Residential real estate: One- $ 641 $ 834 $ 2,902 $ 4,377 $ 8,487 Home equity lines of credit 707 131 672 1,510 674 Commercial real estate 105 — 1,904 2,009 2,807 Construction — — 815 815 815 Total real estate loans 1,453 965 6,293 8,711 12,783 Commercial and industrial — — 653 653 653 Consumer 679 392 — 1,071 — Total $ 2,132 $ 1,357 $ 6,946 $ 10,435 $ 13,436 At September 30, 2017 and December 31, 2016, the Company did not have any accruing loans past due 90 days or more. The following tables provide information with respect to the Company’s impaired loans: September 30, 2017 December 31, 2016 Recorded Unpaid Related Recorded Unpaid Related (In thousands) Impaired loans without a valuation allowance: One- $ 1,031 $ 1,488 $ 841 $ 1,281 Multi-family 63 63 74 74 Commercial real estate 862 862 2,807 3,102 Construction 173 173 988 1,083 Commercial and industrial 1,577 1,907 1,808 2,138 Total 3,706 4,493 6,518 7,678 Impaired loans with a valuation allowance: One- 567 567 $ 67 581 581 $ 49 Multi-family 1,264 1,264 105 1,285 1,285 137 Commercial real estate — — — — — — Total 1,831 1,831 172 1,866 $ 1,866 186 Total impaired loans $ 5,537 $ 6,324 $ 172 $ 8,384 $ 9,544 $ 186 Three Months Ended September 30, 2017 2016 Average Interest Interest Average Interest Interest (In thousands) One- $ 1,607 $ 18 $ 13 $ 1,843 $ 18 $ 13 Multi-family 1,331 13 — 1,374 14 — Commercial real estate 2,547 10 10 2,965 19 19 Construction 173 2 2 13,620 8 4 Commercial and industrial 1,600 16 — 1,941 18 — Total impaired loans $ 7,258 $ 59 $ 25 $ 21,743 $ 77 $ 36 Nine Months Ended September 30, 2017 2016 Average Interest Interest Average Interest Interest (In thousands) One- $ 1,488 $ 63 $ 47 $ 1,857 $ 54 $ 38 Multi-family 1,342 40 — 1,385 41 — Commercial real estate 2,695 43 43 3,432 72 72 Construction 445 6 6 14,410 25 14 Commercial and industrial 1,676 48 — 1,570 67 13 Total impaired loans $ 7,646 $ 200 $ 96 $ 22,654 $ 259 $ 137 At September 30, 2017, additional funds committed to be advanced in connection with impaired construction loans were immaterial. The following table summarizes troubled debt restructurings (“TDRs”) at the dates indicated: September 30, December 31, (In thousands) TDRs on accrual status: One- $ 2,163 $ 2,219 Multi-family 1,326 1,359 Home equity lines of credit — 18 Commercial real estate 9,266 9,460 Construction — 174 Commercial and industrial 22 27 Total TDRs on accrual status 12,777 13,257 TDRs on non-accrual One- 1,315 1,123 Construction 173 — Total TDRs on non-accrual 1,488 1,123 Total TDRs $ 14,265 $ 14,380 The Company generally places loans modified as TDRs on non-accrual The Company utilizes a ten-grade • Loans rated 1, 2, 3, 4, 5 and 6: • Loans rated 7: • Loans rated 8: • Loans rated 9: • Loans rated 10: On an annual basis, or more often if needed, the Company formally reviews the ratings on multi-family, commercial real estate, construction, and commercial and industrial loans. The Company also engages an independent third-party to review a significant portion of loans within these segments on at least an annual basis. Management uses the results of these reviews as part of its annual review process. The following tables provide the Company’s risk-rated loans by class: September 30, 2017 December 31, 2016 Multi-family Commercial Construction Commercial Multi-family Commercial Construction Commercial (In thousands) Loans rated 1 - 6 $ 697,858 $ 2,052,756 $ 604,314 $ 509,977 $ 556,892 $ 1,771,671 $ 500,565 $ 465,979 Loans rated 7 277 17,143 — 25,654 841 2,123 — 22,820 Loans rated 8 4,496 862 173 26,138 5,215 2,807 2,188 26,631 Loans rated 9 — — — — — — — — Loans rated 10 — — — — — — — — Total $ 702,631 $ 2,070,761 $ 604,487 $ 561,769 $ 562,948 $ 1,776,601 $ 502,753 $ 515,430 For one-

Deposits

Deposits	9 Months Ended
	Sep. 30, 2017
Banking and Thrift [Abstract]
Deposits	6. DEPOSITS A summary of deposit balances, by type, follows: September 30, December 31, (In thousands) Demand deposits $ 455,540 $ 431,222 Interest-bearing checking deposits 896,561 630,413 Money market deposits 975,246 980,344 Regular savings and other deposits 324,895 305,632 Total non-certificate 2,652,242 2,347,611 Term certificates less than $250,000 962,755 850,565 Term certificates $250,000 and greater 330,472 277,661 Total certificate accounts 1,293,227 1,128,226 Total deposits $ 3,945,469 $ 3,475,837 A summary of term certificates, by maturity, follows: September 30, 2017 December 31, 2016 Maturing Amount Weighted Amount Weighted (Dollars in thousands) Within 1 year $ 597,795 1.22 % $ 539,903 1.16 % Over 1 year to 2 years 294,158 1.42 306,120 1.29 Over 2 years to 3 years 270,173 2.00 122,952 1.69 Over 3 years to 4 years 83,080 1.97 133,256 2.02 Over 4 years to 5 years 44,434 2.06 22,483 1.61 Greater than 5 years 3,587 5.50 3,512 5.50 $ 1,293,227 1.52 % $ 1,128,226 1.38 % The Company had brokered certificates of deposit, which are included in term certificates in the tables above, totaling $243.8 million with a weighted average rate of 1.70% and $158.5 million with a weighted average rate of 1.33% at September 30, 2017 and December 31, 2016, respectively. At September 30, 2017 and December 31, 2016, the Company also had brokered interest-bearing checking deposits totaling $402.4 million and $296.3 million representing reciprocal deposits received from other financial institutions through an Authorized Bank Deposit Placement Network Sponsor to facilitate full federal deposit insurance coverage for certain Bank customers. In addition, the Company had $100.0 million in non-reciprocal

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Borrowings	7. BORROWINGS The Company had no short-term borrowings at September 30, 2017 or December 31, 2016. The Company has an available line of credit of $9.4 million with the FHLB at an interest rate that adjusts daily and $472,000 of borrowing capacity at the Federal Reserve Bank discount window. No amounts were drawn on the line of credit and no borrowings were outstanding with the Federal Reserve Bank discount window as of September 30, 2017 or December 31, 2016. Long-term debt consists of FHLB advances as follows: September 30, 2017 December 31, 2016 Amount Weighted Amount Weighted (Dollars in thousands) Fixed rate advances maturing: 2017 $ 15,000 1.02 % $ 89,632 1.32 % 2018 43,000 1.25 43,000 1.25 2019 3,532 1.23 4,891 1.23 2020 53,912 1.80 4,989 1.22 2021 45,000 1.46 45,000 1.46 2022 80,625 1.72 — — 2023 10,000 2.10 10,000 2.10 2026 10,000 0.69 20,000 0.59 2027 25,000 1.38 — — 2031 20,000 0.88 20,000 0.88 2032 45,000 1.03 — — 351,069 1.43 237,512 1.26 Variable rate advances maturing: 2020 — — 25,000 0.27 2021 35,000 0.71 60,000 0.31 2022 65,000 0.22 — — 2024 20,000 0.32 — — 120,000 0.38 85,000 0.29 Total advances $ 471,069 1.16 % $ 322,512 1.01 % At September 30, 2017, advances amounting to $330.0 million are callable by the FHLB prior to maturity, including advances totaling $35.0 million with variable rates based on the 3-Month 3-month 3-Month 3-Month All borrowings from the FHLB are secured by investment securities and qualified collateral, consisting of a blanket lien on one-

Other Commitments and Contingen

Other Commitments and Contingencies and Derivatives	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Other Commitments and Contingencies and Derivatives	8. OTHER COMMITMENTS AND CONTINGENCIES AND DERIVATIVES In the normal course of business, there are outstanding commitments and contingencies which are not reflected in the accompanying consolidated financial statements. Loan Commitments The Company is party to financial instruments with off-balance The Company’s exposure to credit loss in the event of nonperformance by the counterparty to the financial instrument for loan commitments is represented by the contractual amount of those instruments. The Company uses the same credit policies in making commitments as it does for on-balance A summary of outstanding loan commitments whose contract amounts represent credit risk is as follows: September 30, December 31, (In thousands) Unadvanced portion of existing loans: Construction $ 557,232 $ 503,586 Home equity lines of credit 41,499 36,722 Other lines and letters of credit 275,787 314,225 Commitments to originate: One- 20,048 18,272 Commercial real estate 75,726 42,141 Construction 241,985 231,274 Commercial and industrial 12,197 31,463 Other loans 115 350 Total loan commitments outstanding $ 1,224,589 $ 1,178,033 Commitments to originate loans are agreements to lend to a customer provided 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. Since a portion of the commitments are expected to expire without being drawn upon, the total commitments do not necessarily represent future cash requirements. The Company evaluates each customer’s credit worthiness on a case by case basis. The amount of collateral obtained, if deemed necessary by the Company for the extension of credit, is based upon management’s credit evaluation of the borrower. Collateral held includes, but is not limited to, residential real estate and deposit accounts. Unfunded commitments under lines of credit are commitments for possible future extensions of credit to existing customers. These lines of credit are collateralized if deemed necessary and usually do not contain a specified maturity date and may not be drawn upon to the total extent to which the Company is committed. Letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. Those letters of credit are primarily issued to support borrowing arrangements. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. Interest Rate Swaps The Company is a party to interest rate derivatives that are not designated as hedging instruments. These derivatives relate to interest rate swaps that the Company enters into with commercial business customers to synthetically convert their loans from a variable rate to a fixed rate. The Company pays interest to the customer at a floating rate on the notional amount and receives interest from the customer at a fixed rate for the same notional amount. Concurrently, the Company enters into an offsetting interest rate swap with a third party financial institution. In the offsetting swap, the Company pays the other financial institution interest at the same fixed rate on the same notional amount as the swap entered into with the customer, and receives interest from the financial institution for the same floating rate on the same notional amount. The changes in the fair value of the swaps offset each other, except for the credit risk of the counterparties, which is determined by taking into consideration the risk rating and probability of default. At September 30, 2017 and December 31, 2016, the Company had $3.7 million and $1.8 million, respectively, in cash pledged for collateral on its interest rate swaps with the third-party financial institution. Summary information regarding these derivatives is presented below: September 30, 2017 December 31, 2016 Maturity Interest Rate Paid Interest Rate Received Notional Fair Notional Fair (Dollars in thousands) Customer interest rate swap 06/07/32 1 Mo. LIBOR + 200bp Fixed (4.40%) $ 65,883 $ 1,106 $ — $ — Third-party interest rate swap 06/07/32 Fixed (4.40%) 1 Mo. LIBOR + 200bp 65,883 (1,106 ) — — Customer interest rate swap 10/17/33 1 Mo. LIBOR + 175bp Fixed (4.1052%) $ 10,767 $ 815 $ 10,922 $ 839 Third-party interest rate swap 10/17/33 Fixed (4.1052%) 1 Mo. LIBOR + 175bp 10,767 (815 ) 10,922 (839 ) Customer interest rate swap 12/13/26 1 Mo. LIBOR + 205bp Fixed (3.82%) $ 2,923 $ (51 ) $ 3,036 $ (60 ) Third-party interest rate swap 12/13/26 Fixed (3.82%) 1 Mo. LIBOR + 205bp 2,923 51 3,036 60 Other Commitments As of September 30, 2017, the Company has an outstanding commitment of $18.4 million with its core data processing provider through December 2021. Employment and Change in Control Agreements The Company has entered into employment agreements with certain senior executives which provide for a minimum annual salary, subject to increase at the discretion of the Board of Directors, and other benefits, including a severance payment in the event employment is terminated in conjunction with a defined change in control. The agreements may be terminated for cause by the Company without further liability on the part of the Company, or by the executives with prior written notice to the Board of Directors. The Company also has change in control agreements with several officers which provide a severance payment in the event employment is terminated in conjunction with a defined change in control. Legal Claims Various legal claims may arise from time to time in the normal course of business, but in the opinion of management, these claims are not expected to have a material effect on the Company’s consolidated financial statements.

Fair Values of Assets and Liabi

Fair Values of Assets and Liabilities	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Values of Assets and Liabilities	9. FAIR VALUES OF ASSETS AND LIABILITIES Determination of Fair Value The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The fair value of assets and liabilities 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 available for sale FHLB stock Loans held for sale Loans non-accrual Deposits non-certificate Borrowings Accrued interest Loan level interest rate swaps Off-balance off-balance-sheet, Assets and Liabilities Measured at Fair Value on a Recurring Basis Assets measured at fair value on a recurring basis are summarized as follows. There were no liabilities measured at fair value on a recurring basis. Level 1 Level 2 Level 3 Total Fair (In thousands) September 30, 2017 Assets: Debt securities $ — $ 5,104 $ — $ 5,104 Marketable equity securities 39,557 — — 39,557 Loan level interest rate swaps — 1,972 — 1,972 Total assets $ 39,557 $ 7,076 $ — $ 46,633 Liabilities: Loan level interest rate swaps — 1,972 — 1,972 Total liabilities $ — $ 1,972 $ — $ 1,972 Level 1 Level 2 Level 3 Total Fair (In thousands) December 31, 2016 Assets: Debt securities $ — $ 21,631 $ — $ 21,631 Marketable equity securities 46,032 — — 46,032 Loan level interest rate swaps — 899 — 899 Total assets $ 46,032 $ 22,530 $ — $ 68,562 Liabilities: Loan level interest rate swaps — 899 — 899 Total liabilities $ — $ 899 $ — $ 899 Assets Measured at Fair Value on a Non-recurring The Company may also be required, from time to time, to measure certain other assets on a non-recurring lower-of-cost-or Certain impaired loans were adjusted to fair value, less cost to sell, of the underlying collateral securing these loans resulting in losses. The loss is not recorded directly as an adjustment to current earnings, but rather as a component in determining the allowance for loan losses. Fair value was measured using appraised values of collateral and adjusted as necessary by management based on unobservable inputs for specific properties. Impaired loans measured at fair value at September 30, 2017 and December 31, 2016 were $2.1 million and $4.9 million, respectively. The related gains and losses were immaterial for the three and nine months ended September 30, 2017 and 2016. Summary of Fair Values of Financial Instruments The estimated fair values, and related carrying amounts, of the Company’s financial instruments are as follows. Certain financial instruments and all nonfinancial instruments are exempt from disclosure requirements. Accordingly, the aggregate fair value amounts presented herein do not represent the underlying fair value of the Company. Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) September 30, 2017 Financial assets: Cash and due from banks $ 300,297 $ 300,297 $ — $ — $ 300,297 Certificates of deposit 75,192 — 75,393 — 75,393 Securities available for sale 44,661 39,557 5,104 — 44,661 Federal Home Loan Bank stock 22,976 — — 22,976 22,976 Loans and loans held for sale, net 4,505,575 — — 4,467,739 4,467,739 Accrued interest receivable 11,580 — — 11,580 11,580 Financial liabilities: Deposits 3,945,469 — — 3,838,979 3,838,979 Borrowings 471,069 — 468,067 — 468,067 Accrued interest payable 1,765 — — 1,765 1,765 On-balance Assets: Loan level interest rate swaps 1,972 — 1,972 — 1,972 Liabilities: Loan level interest rate swaps 1,972 — 1,972 — 1,972 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) December 31, 2016 Financial assets: Cash and due from banks $ 236,423 $ 236,423 $ — $ — $ 236,423 Certificates of deposit 80,323 — 80,710 — 80,710 Securities available for sale 67,663 46,032 21,631 — 67,663 Federal Home Loan Bank stock 18,175 — — 18,175 18,175 Loans and loans held for sale, net 3,902,612 — — 3,970,896 3,970,896 Accrued interest receivable 10,381 — — 10,381 10,381 Financial liabilities: Deposits 3,475,837 — — 3,485,618 3,485,618 Borrowings 322,512 — 322,928 — 322,928 Accrued interest payable 1,384 — — 1,384 1,384 On-balance Assets: Loan level interest rate swaps 899 — 899 — 899 Liabilities: Loan level interest rate swaps 899 — 899 — 899

Pending Acquisition

Pending Acquisition	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Pending Acquisition	10. PENDING ACQUISITION On June 26, 2017, the Company announced the signing of a definitive merger agreement to acquire Meetinghouse Bancorp, Inc. (“Meetinghouse”) and for the Bank to acquire Meetinghouse Bank. The transaction has been unanimously approved by the boards of directors of both companies. Under the terms of the agreement, Meetinghouse shareholders will receive $26.00 in cash for each of their outstanding shares of Meetinghouse common stock, representing a total transaction value of approximately $17.8 million. Meetinghouse Bank has approximately $114 million in assets, $77 million in loans and $95 million in deposits as of September 30, 2017 and conducts its operations from two offices located in the Boston communities of Dorchester and Roslindale. The closing of the acquisition is anticipated to occur during the fourth quarter of 2017, subject to the receipt of required regulatory approvals and the satisfaction of other customary closing conditions. For more information, refer to our Current Reports on Form 8-K

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Changes and Error Corrections [Abstract]
Change in accounting principle - Share-based compensation	Change in accounting principle—Share-based compensation In March 2016, the Financial Accounting Standards Board (the “FASB”) issued an Accounting Standards Update (“ASU”), No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting Accounting for Income Taxes Entities will no longer record the excess tax benefits or deficiencies related to share-based compensation in additional paid-in paid-in
Recent Accounting Pronouncements	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments — Overall, (Subtopic 825-10). In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) right-to-use In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) held-to-maturity available-for-sale In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	Basic and diluted earnings per share have been computed based on the following: Three Months Ended Nine Months Ended 2017 2016 2017 2016 (Dollars in thousands, expect per share amounts) Net income available to common stockholders $ 13,333 $ 9,497 $ 33,924 $ 22,881 Basic weighted average shares outstanding 51,229,203 50,982,633 51,061,959 51,192,332 Effect of dilutive stock options 1,443,759 1,110,376 1,479,793 1,105,035 Diluted weighted average shares outstanding $ 52,672,962 52,093,009 $ 52,541,752 52,297,367 Earnings per share: Basic $ 0.26 $ 0.19 $ 0.66 $ 0.45 Diluted $ 0.25 $ 0.18 $ 0.65 $ 0.44

Securities Available for Sale (

Securities Available for Sale (Tables)	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Values of Securities Available for Sale	The amortized cost and fair values of securities available for sale, with gross unrealized gains and losses, follows: Amortized Gross Gross Fair (In thousands) September 30, 2017 Debt securities: Municipal bonds $ 341 $ 6 $ — $ 347 Residential mortgage-backed securities: Government-sponsored enterprises 4,393 288 (2 ) 4,679 Private label 73 5 — 78 Total debt securities 4,807 299 (2 ) 5,104 Marketable equity securities: Common stocks: Basic materials 4,518 338 (230 ) 4,626 Consumer products and services 10,492 1,231 (745 ) 10,978 Financial services 4,471 1,296 (21 ) 5,746 Healthcare 7,827 1,688 (6 ) 9,509 Industrials 4,484 770 (4 ) 5,250 Technology 3,041 551 (154 ) 3,438 Total common stocks 34,833 5,874 (1,160 ) 39,547 Money market mutual funds 10 — — 10 Total marketable equity securities 34,843 5,874 (1,160 ) 39,557 Total securities available for sale $ 39,650 $ 6,173 $ (1,162 ) $ 44,661 December 31, 2016 Debt securities: Corporate bonds: Financial services $ 12,989 $ 16 $ (3 ) $ 13,002 Industrials 1,000 3 — 1,003 Total corporate bonds 13,989 19 (3 ) 14,005 Municipal bonds 1,202 17 — 1,219 Residential mortgage-backed securities: Government-sponsored enterprises 5,284 325 (3 ) 5,606 Private label 779 22 — 801 Total debt securities 21,254 383 (6 ) 21,631 Marketable equity securities: Common stocks: Basic materials 6,763 901 (232 ) 7,432 Consumer products and services 13,567 1,093 (382 ) 14,278 Financial services 5,953 970 — 6,923 Healthcare 8,225 533 (456 ) 8,302 Industrials 4,181 624 (11 ) 4,794 Technology 4,081 440 (220 ) 4,301 Total common stocks 42,770 4,561 (1,301 ) 46,030 Money market mutual funds 2 — — 2 Total marketable equity securities 42,772 4,561 (1,301 ) 46,032 Total securities available for sale $ 64,026 $ 4,944 $ (1,307 ) $ 67,663
Amortized Cost and Fair Value of Debt Securities by Contractual Maturity	The amortized cost and fair value of debt securities by contractual maturity at September 30, 2017 are as follows. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without prepayment penalties. One Year or Less After One Year After Five Years Total Amortized Fair Amortized Fair Amortized Fair Amortized Fair (In thousands) Municipal bonds $ 341 $ 347 $ — $ — $ — $ — $ 341 $ 347 Residential mortgage-backed securities: Government-sponsored enterprises — — 1 1 4,392 4,678 4,393 4,679 Private label — — — — 73 78 73 78 Total $ 341 $ 347 $ 1 $ 1 $ 4,465 $ 4,756 $ 4,807 $ 5,104
Schedule of Information Pertaining to Securities Available for Sale	Information pertaining to securities available for sale as of September 30, 2017 and December 31, 2016, with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: Less Than Twelve Months Twelve Months or Longer Gross Fair Gross Fair (In thousands) September 30, 2017 Debt securities: Residential mortgage-backed securities: Government-sponsored enterprises $ — $ — $ 2 $ 174 Total debt securities — — 2 174 Marketable equity securities: Common stocks: Basic materials 46 833 184 1,573 Consumer products and services 136 1,192 609 1,929 Financial services 21 492 — — Healthcare 6 406 — — Industrials 4 971 — — Technology 146 1,227 8 337 Total common stocks and marketable equity securities 359 5,121 801 3,839 Total temporarily impaired securities $ 359 $ 5,121 $ 803 $ 4,013 Less Than Twelve Months Twelve Months or Longer Gross Fair Gross Fair (In thousands) December 31, 2016 Debt securities: Corporate bonds-financial services $ 3 $ 5,000 $ — $ — Residential mortgage-backed securities: Government-sponsored enterprises — — 3 205 Total debt securities 3 5,000 3 205 Marketable equity securities: Common stocks: Basic materials — — 232 1,568 Consumer products and services 237 3,496 145 1,618 Healthcare 259 2,039 197 1,377 Industrials 11 450 — — Technology — — 220 1,681 Total common stocks and marketable equity securities 507 5,985 794 6,244 Total temporarily impaired securities $ 510 $ 10,985 $ 797 $ 6,449

Loans (Tables)

Loans (Tables)	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Summary of Loans	A summary of loans follows: September 30, 2017 December 31, 2016 Amount Percent Amount Percent (Dollars in thousands) Real estate loans: Residential real estate: One- $ 560,393 12.3 % $ 532,450 13.5 % Home equity lines of credit 42,042 0.9 42,913 1.1 Multi-family 702,631 15.4 562,948 14.3 Commercial real estate 2,070,761 45.5 1,776,601 45.1 Construction 604,487 13.3 502,753 12.8 Total real estate loans 3,980,314 87.4 3,417,665 86.8 Commercial and industrial 561,769 12.4 515,430 13.0 Consumer 10,222 0.2 9,712 0.2 Total loans 4,552,305 100.0 % 3,942,807 100.0 % Allowance for loan losses (45,643 ) (40,149 ) Net deferred loan origination fees (4,794 ) (3,990 ) Loans, net $ 4,501,868 $ 3,898,668
Allowance for Loan Losses	An analysis of the allowance for loan losses and related information follows: Three Months Ended September 30, 2017 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,167 $ 5,549 $ 71 $ 20,598 $ 8,846 $ 6,901 $ 97 $ 43,229 Provision (credit) for loan losses (100 ) (44 ) (9 ) 1,343 1,245 (52 ) 75 2,458 Charge-offs — — — — — — (99 ) (99 ) Recoveries — — — — 1 30 24 55 Ending balance $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Three Months Ended September 30, 2016 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,320 $ 4,002 $ 92 $ 16,950 $ 9,090 $ 6,751 $ 112 $ 38,317 Provision (credit) for loan losses 141 302 (6 ) 300 560 (482 ) 43 858 Charge-offs — — — — (486 ) — (72 ) (558 ) Recoveries — — — — 7 52 21 80 Ending balance $ 1,461 $ 4,304 $ 86 $ 17,250 $ 9,171 $ 6,321 $ 104 $ 38,697 Nine Months Ended September 30, 2017 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,367 $ 4,514 $ 73 $ 18,725 $ 8,931 $ 6,452 $ 87 $ 40,149 Provision (credit) for loan losses (333 ) 990 (11 ) 3,216 1,112 397 203 5,574 Charge-offs — — — — (2 ) — (265 ) (267 ) Recoveries 33 1 — — 51 30 72 187 Ending balance $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Nine Months Ended September 30, 2016 One- four-family Multi- family Home equity of credit Commercial real estate Construction Commercial industrial Consumer Total (In thousands) Beginning balance $ 1,354 $ 3,385 $ 144 $ 14,497 $ 8,313 $ 5,620 $ 92 $ 33,405 Provision (credit) for loan losses 107 919 (58 ) 2,753 1,323 685 147 5,876 Charge-offs — — — — (486 ) (44 ) (206 ) (736 ) Recoveries — — — — 21 60 71 152 Ending balance $ 1,461 $ 4,304 $ 86 $ 17,250 $ 9,171 $ 6,321 $ 104 $ 38,697 One- four-family Multi- family Home equity lines of credit Commercial real estate Construction Commercial and industrial Consumer Total (In thousands) September 30, 2017 Amount of allowance for loan losses for loans deemed to be impaired $ 67 $ 105 $ — $ — $ — $ — $ — $ 172 Amount of allowance for loan losses for loans not deemed to be impaired 1,000 5,400 62 21,941 10,092 6,879 97 45,471 $ 1,067 $ 5,505 $ 62 $ 21,941 $ 10,092 $ 6,879 $ 97 $ 45,643 Loans deemed to be impaired $ 1,598 $ 1,327 $ — $ 862 $ 173 $ 1,577 $ — $ 5,537 Loans not deemed to be impaired 558,795 701,304 42,042 2,069,899 604,314 560,192 10,222 4,546,768 $560,393 $702,631 $42,042 $2,070,761 $604,487 $561,769 $10,222 $4,552,305 December 31, 2016 Amount of allowance for loan losses for loans deemed to be impaired $ 49 $ 137 $ — $ — $ — $ — $ — $ 186 Amount of allowance for loan losses for loans not deemed to be impaired 1,318 4,377 73 18,725 8,931 6,452 87 39,963 $ 1,367 $ 4,514 $ 73 $ 18,725 $ 8,931 $ 6,452 $ 87 $ 40,149 Loans deemed to be impaired $ 1,422 $ 1,359 $ — $ 2,807 $ 988 $ 1,808 $ — $ 8,384 Loans not deemed to be impaired 531,028 561,589 42,913 1,773,794 501,765 513,622 9,712 3,934,423 $532,450 $562,948 $42,913 $1,776,601 $502,753 $515,430 $9,712 $3,942,807
Past Due and Non Accrual	The following table provides information about the Company’s past due and non-accrual 30-59 60-89 90 Days Total Loans on Non-accrual (In thousands) September 30, 2017 Real estate loans: Residential real estate: One- $ 1,113 $ 984 $ 1,380 $ 3,477 $ 7,055 Home equity lines of credit 371 67 395 833 563 Commercial real estate 100 — — 100 862 Construction — 173 — 173 173 Total real estate loans 1,584 1,224 1,775 4,583 8,653 Commercial and industrial — — 525 525 525 Consumer 489 664 — 1,153 — Total $ 2,073 $ 1,888 $ 2,300 $ 6,261 $ 9,178 December 31, 2016 Real estate loans: Residential real estate: One- $ 641 $ 834 $ 2,902 $ 4,377 $ 8,487 Home equity lines of credit 707 131 672 1,510 674 Commercial real estate 105 — 1,904 2,009 2,807 Construction — — 815 815 815 Total real estate loans 1,453 965 6,293 8,711 12,783 Commercial and industrial — — 653 653 653 Consumer 679 392 — 1,071 — Total $ 2,132 $ 1,357 $ 6,946 $ 10,435 $ 13,436
Impaired Loans of Company	The following tables provide information with respect to the Company’s impaired loans: September 30, 2017 December 31, 2016 Recorded Unpaid Related Recorded Unpaid Related (In thousands) Impaired loans without a valuation allowance: One- $ 1,031 $ 1,488 $ 841 $ 1,281 Multi-family 63 63 74 74 Commercial real estate 862 862 2,807 3,102 Construction 173 173 988 1,083 Commercial and industrial 1,577 1,907 1,808 2,138 Total 3,706 4,493 6,518 7,678 Impaired loans with a valuation allowance: One- 567 567 $ 67 581 581 $ 49 Multi-family 1,264 1,264 105 1,285 1,285 137 Commercial real estate — — — — — — Total 1,831 1,831 172 1,866 $ 1,866 186 Total impaired loans $ 5,537 $ 6,324 $ 172 $ 8,384 $ 9,544 $ 186 Three Months Ended September 30, 2017 2016 Average Interest Interest Average Interest Interest (In thousands) One- $ 1,607 $ 18 $ 13 $ 1,843 $ 18 $ 13 Multi-family 1,331 13 — 1,374 14 — Commercial real estate 2,547 10 10 2,965 19 19 Construction 173 2 2 13,620 8 4 Commercial and industrial 1,600 16 — 1,941 18 — Total impaired loans $ 7,258 $ 59 $ 25 $ 21,743 $ 77 $ 36 Nine Months Ended September 30, 2017 2016 Average Interest Interest Average Interest Interest (In thousands) One- $ 1,488 $ 63 $ 47 $ 1,857 $ 54 $ 38 Multi-family 1,342 40 — 1,385 41 — Commercial real estate 2,695 43 43 3,432 72 72 Construction 445 6 6 14,410 25 14 Commercial and industrial 1,676 48 — 1,570 67 13 Total impaired loans $ 7,646 $ 200 $ 96 $ 22,654 $ 259 $ 137
Summary of Troubled Debt Restructurings	The following table summarizes troubled debt restructurings (“TDRs”) at the dates indicated: September 30, December 31, (In thousands) TDRs on accrual status: One- $ 2,163 $ 2,219 Multi-family 1,326 1,359 Home equity lines of credit — 18 Commercial real estate 9,266 9,460 Construction — 174 Commercial and industrial 22 27 Total TDRs on accrual status 12,777 13,257 TDRs on non-accrual One- 1,315 1,123 Construction 173 — Total TDRs on non-accrual 1,488 1,123 Total TDRs $ 14,265 $ 14,380
Risk Rated Loans by Class	The following tables provide the Company’s risk-rated loans by class: September 30, 2017 December 31, 2016 Multi-family Commercial Construction Commercial Multi-family Commercial Construction Commercial (In thousands) Loans rated 1 - 6 $ 697,858 $ 2,052,756 $ 604,314 $ 509,977 $ 556,892 $ 1,771,671 $ 500,565 $ 465,979 Loans rated 7 277 17,143 — 25,654 841 2,123 — 22,820 Loans rated 8 4,496 862 173 26,138 5,215 2,807 2,188 26,631 Loans rated 9 — — — — — — — — Loans rated 10 — — — — — — — — Total $ 702,631 $ 2,070,761 $ 604,487 $ 561,769 $ 562,948 $ 1,776,601 $ 502,753 $ 515,430

Deposits (Tables)

Deposits (Tables)	9 Months Ended
	Sep. 30, 2017
Banking and Thrift [Abstract]
Summary of Deposit Balances, by Type	A summary of deposit balances, by type, follows: September 30, December 31, (In thousands) Demand deposits $ 455,540 $ 431,222 Interest-bearing checking deposits 896,561 630,413 Money market deposits 975,246 980,344 Regular savings and other deposits 324,895 305,632 Total non-certificate 2,652,242 2,347,611 Term certificates less than $250,000 962,755 850,565 Term certificates $250,000 and greater 330,472 277,661 Total certificate accounts 1,293,227 1,128,226 Total deposits $ 3,945,469 $ 3,475,837
Summary of Term Certificates, by Maturity	A summary of term certificates, by maturity, follows: September 30, 2017 December 31, 2016 Maturing Amount Weighted Amount Weighted (Dollars in thousands) Within 1 year $ 597,795 1.22 % $ 539,903 1.16 % Over 1 year to 2 years 294,158 1.42 306,120 1.29 Over 2 years to 3 years 270,173 2.00 122,952 1.69 Over 3 years to 4 years 83,080 1.97 133,256 2.02 Over 4 years to 5 years 44,434 2.06 22,483 1.61 Greater than 5 years 3,587 5.50 3,512 5.50 $ 1,293,227 1.52 % $ 1,128,226 1.38 %

Borrowings (Tables)

Borrowings (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-term Debt, FHLB Advances	Long-term debt consists of FHLB advances as follows: September 30, 2017 December 31, 2016 Amount Weighted Amount Weighted (Dollars in thousands) Fixed rate advances maturing: 2017 $ 15,000 1.02 % $ 89,632 1.32 % 2018 43,000 1.25 43,000 1.25 2019 3,532 1.23 4,891 1.23 2020 53,912 1.80 4,989 1.22 2021 45,000 1.46 45,000 1.46 2022 80,625 1.72 — — 2023 10,000 2.10 10,000 2.10 2026 10,000 0.69 20,000 0.59 2027 25,000 1.38 — — 2031 20,000 0.88 20,000 0.88 2032 45,000 1.03 — — 351,069 1.43 237,512 1.26 Variable rate advances maturing: 2020 — — 25,000 0.27 2021 35,000 0.71 60,000 0.31 2022 65,000 0.22 — — 2024 20,000 0.32 — — 120,000 0.38 85,000 0.29 Total advances $ 471,069 1.16 % $ 322,512 1.01 %

Other Commitments and Conting26

Other Commitments and Contingencies and Derivatives (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Loan Commitments Outstanding	A summary of outstanding loan commitments whose contract amounts represent credit risk is as follows: September 30, December 31, (In thousands) Unadvanced portion of existing loans: Construction $ 557,232 $ 503,586 Home equity lines of credit 41,499 36,722 Other lines and letters of credit 275,787 314,225 Commitments to originate: One- 20,048 18,272 Commercial real estate 75,726 42,141 Construction 241,985 231,274 Commercial and industrial 12,197 31,463 Other loans 115 350 Total loan commitments outstanding $ 1,224,589 $ 1,178,033
Summary Information Regarding the Derivatives	Summary information regarding these derivatives is presented below: September 30, 2017 December 31, 2016 Maturity Interest Rate Paid Interest Rate Received Notional Fair Notional Fair (Dollars in thousands) Customer interest rate swap 06/07/32 1 Mo. LIBOR + 200bp Fixed (4.40%) $ 65,883 $ 1,106 $ — $ — Third-party interest rate swap 06/07/32 Fixed (4.40%) 1 Mo. LIBOR + 200bp 65,883 (1,106 ) — — Customer interest rate swap 10/17/33 1 Mo. LIBOR + 175bp Fixed (4.1052%) $ 10,767 $ 815 $ 10,922 $ 839 Third-party interest rate swap 10/17/33 Fixed (4.1052%) 1 Mo. LIBOR + 175bp 10,767 (815 ) 10,922 (839 ) Customer interest rate swap 12/13/26 1 Mo. LIBOR + 205bp Fixed (3.82%) $ 2,923 $ (51 ) $ 3,036 $ (60 ) Third-party interest rate swap 12/13/26 Fixed (3.82%) 1 Mo. LIBOR + 205bp 2,923 51 3,036 60

Fair Values of Assets and Lia27

Fair Values of Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value on a Recurring Basis	Assets measured at fair value on a recurring basis are summarized as follows. There were no liabilities measured at fair value on a recurring basis. Level 1 Level 2 Level 3 Total Fair (In thousands) September 30, 2017 Assets: Debt securities $ — $ 5,104 $ — $ 5,104 Marketable equity securities 39,557 — — 39,557 Loan level interest rate swaps — 1,972 — 1,972 Total assets $ 39,557 $ 7,076 $ — $ 46,633 Liabilities: Loan level interest rate swaps — 1,972 — 1,972 Total liabilities $ — $ 1,972 $ — $ 1,972 Level 1 Level 2 Level 3 Total Fair (In thousands) December 31, 2016 Assets: Debt securities $ — $ 21,631 $ — $ 21,631 Marketable equity securities 46,032 — — 46,032 Loan level interest rate swaps — 899 — 899 Total assets $ 46,032 $ 22,530 $ — $ 68,562 Liabilities: Loan level interest rate swaps — 899 — 899 Total liabilities $ — $ 899 $ — $ 899
Summary of Fair Values of Financial Instruments	Accordingly, the aggregate fair value amounts presented herein do not represent the underlying fair value of the Company. Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) September 30, 2017 Financial assets: Cash and due from banks $ 300,297 $ 300,297 $ — $ — $ 300,297 Certificates of deposit 75,192 — 75,393 — 75,393 Securities available for sale 44,661 39,557 5,104 — 44,661 Federal Home Loan Bank stock 22,976 — — 22,976 22,976 Loans and loans held for sale, net 4,505,575 — — 4,467,739 4,467,739 Accrued interest receivable 11,580 — — 11,580 11,580 Financial liabilities: Deposits 3,945,469 — — 3,838,979 3,838,979 Borrowings 471,069 — 468,067 — 468,067 Accrued interest payable 1,765 — — 1,765 1,765 On-balance Assets: Loan level interest rate swaps 1,972 — 1,972 — 1,972 Liabilities: Loan level interest rate swaps 1,972 — 1,972 — 1,972 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) December 31, 2016 Financial assets: Cash and due from banks $ 236,423 $ 236,423 $ — $ — $ 236,423 Certificates of deposit 80,323 — 80,710 — 80,710 Securities available for sale 67,663 46,032 21,631 — 67,663 Federal Home Loan Bank stock 18,175 — — 18,175 18,175 Loans and loans held for sale, net 3,902,612 — — 3,970,896 3,970,896 Accrued interest receivable 10,381 — — 10,381 10,381 Financial liabilities: Deposits 3,475,837 — — 3,485,618 3,485,618 Borrowings 322,512 — 322,928 — 322,928 Accrued interest payable 1,384 — — 1,384 1,384 On-balance Assets: Loan level interest rate swaps 899 — 899 — 899 Liabilities: Loan level interest rate swaps 899 — 899 — 899

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Share in East Boston Savings Bank	100.00%		100.00%
Provision for income taxes	$ 6,702,000	$ 5,084,000	$ 17,624,000	$ 11,239,000
Accounting Standards Update 2016-09 [Member]
Schedule of Available-for-sale Securities [Line Items]
Provision for income taxes			$ (365,000)

Recent Accounting Pronounceme29

Recent Accounting Pronouncements - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Deferred tax provision (benefit)	$ (584,000)	$ (713,000)
Future minimum lease payments under operating lease agreements			$ 15,000,000
Change in Accounting Method Accounted for as Change in Estimate [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized gain on equity investment	1,500,000
Deferred tax provision (benefit)	$ 509,000

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income available to common stockholders	$ 13,333	$ 9,497	$ 33,924	$ 22,881
Basic weighted average shares outstanding	51,229,203	50,982,633	51,061,959	51,192,332
Effect of dilutive stock options	1,443,759	1,110,376	1,479,793	1,105,035
Diluted weighted average shares outstanding	52,672,962	52,093,009	52,541,752	52,297,367
Earnings per share:
Basic	$ 0.26	$ 0.19	$ 0.66	$ 0.45
Diluted	$ 0.25	$ 0.18	$ 0.65	$ 0.44

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	Jul. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
2015 EIP [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of stock options granted	682,750
Award vesting percentage	20.00%
Stock options and restricted shares granted date	5 years
Stock Option [Member]
Schedule of Available-for-sale Securities [Line Items]
Anti-dilutive Options		79,802	153,760	26,601	265,139
Restricted Stock [Member] | 2015 EIP [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of shares granted	272,750

Securities Available for Sale -

Securities Available for Sale - Amortized Cost and Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total	$ 4,807	$ 21,254
Debt Securities, Gross Unrealized Gains	299	383
Debt Securities, Gross Unrealized Losses	(2)	(6)
Debt Securities, Fair Value	5,104	21,631
Marketable Equity Securities, Amortized Cost	34,843	42,772
Marketable Equity Securities, Gross Unrealized Gains	5,874	4,561
Marketable Equity Securities, Gross Unrealized Losses	(1,160)	(1,301)
Marketable Equity Securities, Fair Value	39,557	46,032
Total Securities Available for Sale, Amortized Cost	39,650	64,026
Total Securities Available for Sale, Gross Unrealized Gains	6,173	4,944
Total Securities Available for Sale, Gross Unrealized Losses	(1,162)	(1,307)
Total Securities Available for Sale, Fair Value	44,661	67,663
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total		13,989
Debt Securities, Gross Unrealized Gains		19
Debt Securities, Gross Unrealized Losses		(3)
Debt Securities, Fair Value		14,005
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total	341	1,202
Debt Securities, Gross Unrealized Gains	6	17
Debt Securities, Fair Value	347	1,219
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	10	2
Marketable Equity Securities, Fair Value	10	2
Residential Mortgage-backed Securities, Government - sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total	4,393	5,284
Debt Securities, Gross Unrealized Gains	288	325
Debt Securities, Gross Unrealized Losses	(2)	(3)
Debt Securities, Fair Value	4,679	5,606
Residential Mortgage-backed Securities, Private Label [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total	73	779
Debt Securities, Gross Unrealized Gains	5	22
Debt Securities, Fair Value	78	801
Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	34,833	42,770
Marketable Equity Securities, Gross Unrealized Gains	5,874	4,561
Marketable Equity Securities, Gross Unrealized Losses	(1,160)	(1,301)
Marketable Equity Securities, Fair Value	39,547	46,030
Financial Services [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total		12,989
Debt Securities, Gross Unrealized Gains		16
Debt Securities, Gross Unrealized Losses		(3)
Debt Securities, Fair Value		13,002
Financial Services [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	4,471	5,953
Marketable Equity Securities, Gross Unrealized Gains	1,296	970
Marketable Equity Securities, Gross Unrealized Losses	(21)
Marketable Equity Securities, Fair Value	5,746	6,923
Industrials [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total		1,000
Debt Securities, Gross Unrealized Gains		3
Debt Securities, Fair Value		1,003
Industrials [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	4,484	4,181
Marketable Equity Securities, Gross Unrealized Gains	770	624
Marketable Equity Securities, Gross Unrealized Losses	(4)	(11)
Marketable Equity Securities, Fair Value	5,250	4,794
Basic Materials [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	4,518	6,763
Marketable Equity Securities, Gross Unrealized Gains	338	901
Marketable Equity Securities, Gross Unrealized Losses	(230)	(232)
Marketable Equity Securities, Fair Value	4,626	7,432
Consumer Products and Services [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	10,492	13,567
Marketable Equity Securities, Gross Unrealized Gains	1,231	1,093
Marketable Equity Securities, Gross Unrealized Losses	(745)	(382)
Marketable Equity Securities, Fair Value	10,978	14,278
Healthcare [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	7,827	8,225
Marketable Equity Securities, Gross Unrealized Gains	1,688	533
Marketable Equity Securities, Gross Unrealized Losses	(6)	(456)
Marketable Equity Securities, Fair Value	9,509	8,302
Technology [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Equity Securities, Amortized Cost	3,041	4,081
Marketable Equity Securities, Gross Unrealized Gains	551	440
Marketable Equity Securities, Gross Unrealized Losses	(154)	(220)
Marketable Equity Securities, Fair Value	$ 3,438	$ 4,301

Securities Available for Sale33

Securities Available for Sale - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)SecurityLoanSecurity	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)SecurityLoanSecurityshares	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of securities available for sale	$ 5,600,000	$ 12,500,000	$ 17,221,000	$ 17,517,000
Gross gains	937,000	2,400,000	3,300,000	3,600,000
Gross losses	72,000	$ 2,100,000	93,000	$ 3,200,000
Marketable equity securities in an unrealized loss position for less than 12 months, fair value	5,121,000		5,121,000		$ 10,985,000
Marketable equity securities in an unrealized loss position for 12 months or longer, fair value	$ 4,013,000		$ 4,013,000		$ 6,449,000
Declined percentage of equity securities unrealized losses	10.00%		10.00%
Other-than-temporarily impaired securities | shares			0
Unrealized losses on marketable equity securities, declined percentage			25.00%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities, fair value	$ 9,000,000		$ 9,000,000
Marketable equity securities, total unrealized losses			$ 1,200,000
Number of securities in unrealized loss position | SecurityLoan	18		18
Unrealized losses with equity aggregate depreciation, percentage	11.50%		11.50%
Marketable equity securities in an unrealized loss position for less than 12 months, fair value	$ 5,100,000		$ 5,100,000
Marketable equity securities in an unrealized loss position for less than 12 months, unrealized losses			$ 359,000
Marketable equity securities in an unrealized loss position for less than 12 months, number of securities | Security	11		11
Marketable equity securities in an unrealized loss position for 12 months or longer, fair value	$ 3,800,000		$ 3,800,000
Marketable equity securities in an unrealized loss position for 12 months or longer, unrealized losses			$ 801,000
Marketable equity securities in an unrealized loss position for 12 months or longer, number of securities | Security	7		7
Equity Securities [Member] | Basic Materials [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities in an unrealized loss position for 12 months or longer, fair value	$ 1,600,000		$ 1,600,000
Marketable equity securities in an unrealized loss position for 12 months or longer, unrealized losses			$ 184,000
Marketable equity securities in an unrealized loss position for 12 months or longer, number of securities | Security	4		4
Equity Securities [Member] | Consumer Products and Services [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities in an unrealized loss position for 12 months or longer, fair value	$ 1,900,000		$ 1,900,000
Marketable equity securities in an unrealized loss position for 12 months or longer, unrealized losses			$ 609,000
Marketable equity securities in an unrealized loss position for 12 months or longer, number of securities | Security	4		4
Equity Securities [Member] | Technology [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities in an unrealized loss position for 12 months or longer, fair value	$ 337,000		$ 337,000
Marketable equity securities in an unrealized loss position for 12 months or longer, unrealized losses			$ 8,000
Marketable equity securities in an unrealized loss position for 12 months or longer, number of securities | Security	1		1
Federal Reserve Bank Discount Window Borrowings [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities with amortized cost, pledged as collateral	$ 472,000		$ 472,000
Federal Home Loan Bank of Boston Borrowings [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities with amortized cost, pledged as collateral	$ 3,500,000		$ 3,500,000

Securities Available for Sale34

Securities Available for Sale - Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, within 1 year	$ 341
Fair Value, within 1 year	347
Amortized Cost, over 1 year to 5 years	1
Fair Value, over 1 year to 5 years	1
Amortized Cost, over 5 years	4,465
Fair Value, over 5 years	4,756
Amortized Cost, Total	4,807	$ 21,254
Fair Value, Total	5,104	21,631
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, within 1 year	341
Fair Value, within 1 year	347
Amortized Cost, Total	341	1,202
Fair Value, Total	347	1,219
Residential Mortgage-backed Securities, Government - sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, over 1 year to 5 years	1
Fair Value, over 1 year to 5 years	1
Amortized Cost, over 5 years	4,392
Fair Value, over 5 years	4,678
Amortized Cost, Total	4,393	5,284
Fair Value, Total	4,679	5,606
Residential Mortgage-backed Securities, Private Label [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, over 5 years	73
Fair Value, over 5 years	78
Amortized Cost, Total	73	779
Fair Value, Total	$ 78	$ 801

Securities Available for Sale35

Securities Available for Sale - Schedule of Information Pertaining to Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	$ 359	$ 510
Fair value, less than twelve months	5,121	10,985
Gross unrealized losses, over twelve months	803	797
Fair value, over twelve months	4,013	6,449
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months		3
Fair value, less than twelve months		5,000
Gross unrealized losses, over twelve months	2	3
Fair value, over twelve months	174	205
Debt Securities [Member] | Residential Mortgage-backed Securities, Government - sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, over twelve months	2	3
Fair value, over twelve months	174	205
Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	359	507
Fair value, less than twelve months	5,121	5,985
Gross unrealized losses, over twelve months	801	794
Fair value, over twelve months	3,839	6,244
Financial Services [Member] | Debt Securities [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months		3
Fair value, less than twelve months		5,000
Financial Services [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	21
Fair value, less than twelve months	492
Basic Materials [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	46
Fair value, less than twelve months	833
Gross unrealized losses, over twelve months	184	232
Fair value, over twelve months	1,573	1,568
Consumer Products and Services [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	136	237
Fair value, less than twelve months	1,192	3,496
Gross unrealized losses, over twelve months	609	145
Fair value, over twelve months	1,929	1,618
Healthcare [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	6	259
Fair value, less than twelve months	406	2,039
Gross unrealized losses, over twelve months		197
Fair value, over twelve months		1,377
Industrials [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	4	11
Fair value, less than twelve months	971	450
Technology [Member] | Marketable Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, less than twelve months	146
Fair value, less than twelve months	1,227
Gross unrealized losses, over twelve months	8	220
Fair value, over twelve months	$ 337	$ 1,681

Loans - Summary of Loans (Detai

Loans - Summary of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 26, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 4,552,305		$ 3,942,807
Total loans, Percent	100.00%		100.00%
Allowance for loan losses	$ (45,643)	$ (43,229)	$ (40,149)	$ (38,697)	$ (38,317)	$ (33,405)
Net deferred loan origination fees	(4,794)		(3,990)
Loans, net	4,501,868		3,898,668
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 561,769		$ 515,430
Total loans, Percent	12.40%		13.00%
Allowance for loan losses	$ (6,879)	(6,901)	$ (6,452)	(6,321)	(6,751)	(5,620)
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 604,487		$ 502,753
Total loans, Percent	13.30%		12.80%
Allowance for loan losses	$ (10,092)	(8,846)	$ (8,931)	(9,171)	(9,090)	(8,313)
Total Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 3,980,314		$ 3,417,665
Total loans, Percent	87.40%		86.80%
Residential Portfolio Segment [Member] | Multi-Family Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 702,631		$ 562,948
Total loans, Percent	15.40%		14.30%
Allowance for loan losses	$ (5,505)	(5,549)	$ (4,514)	(4,304)	(4,002)	(3,385)
Residential Portfolio Segment [Member] | One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 560,393		$ 532,450
Total loans, Percent	12.30%		13.50%
Allowance for loan losses	$ (1,067)	(1,167)	$ (1,367)	(1,461)	(1,320)	(1,354)
Residential Portfolio Segment [Member] | Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 42,042		$ 42,913
Total loans, Percent	0.90%		1.10%
Allowance for loan losses	$ (62)	(71)	$ (73)	(86)	(92)	(144)
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 2,070,761		$ 1,776,601
Total loans, Percent	45.50%		45.10%
Allowance for loan losses	$ (21,941)	(20,598)	$ (18,725)	(17,250)	(16,950)	(14,497)
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans, Amount	$ 10,222		$ 9,712
Total loans, Percent	0.20%		0.20%
Allowance for loan losses	$ (97)	$ (97)	$ (87)	$ (104)	$ (112)	$ (92)

Loans - Additional Information

Loans - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017USD ($)SecurityLoan	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Servicing loans for participants	$ 238,400,000		$ 210,500,000
Number of accruing loans | SecurityLoan	0		0
Loans modified as TDRs on non-accrual status, minimum period	6 months
Loans modified as TDRs qualify for return to accrual status if demonstrated performance with modified terms of loan agreement, minimum period	6 months
Allocated component included in allowance for loan losses	$ 172,000		$ 186,000
Charge-offs related to the TDRs modified	0	$ 0
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loan pledged	757,900,000
Multi-Family Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loan pledged	$ 161,600,000

Loans - Allowance for Loan Loss

Loans - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 43,229	$ 38,317	$ 40,149	$ 33,405
Provision (credit) for loan losses	2,458	858	5,574	5,876
Charge-offs	(99)	(558)	(267)	(736)
Recoveries	55	80	187	152
Ending balance	45,643	38,697	45,643	38,697
Amount of allowance for loan losses for loans deemed to be impaired					$ 172	$ 186
Amount of allowance for loan losses for loans not deemed to be impaired					45,471	39,963
Total, Amount of allowance	43,229	38,317	45,643	38,697	45,643	40,149
Loans deemed to be impaired					5,537	8,384
Loans not deemed to be impaired					4,546,768	3,934,423
Total, Amount of allowance impaired					4,552,305	3,942,807
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	6,901	6,751	6,452	5,620
Provision (credit) for loan losses	(52)	(482)	397	685
Charge-offs				(44)
Recoveries	30	52	30	60
Ending balance	6,879	6,321	6,879	6,321
Amount of allowance for loan losses for loans not deemed to be impaired					6,879	6,452
Total, Amount of allowance	6,901	6,751	6,879	6,321	6,879	6,452
Loans deemed to be impaired					1,577	1,808
Loans not deemed to be impaired					560,192	513,622
Total, Amount of allowance impaired					561,769	515,430
Multi-Family Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Amount of allowance for loan losses for loans deemed to be impaired					105	137
One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Amount of allowance for loan losses for loans deemed to be impaired					67	49
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,846	9,090	8,931	8,313
Provision (credit) for loan losses	1,245	560	1,112	1,323
Charge-offs		(486)	(2)	(486)
Recoveries	1	7	51	21
Ending balance	10,092	9,171	10,092	9,171
Amount of allowance for loan losses for loans not deemed to be impaired					10,092	8,931
Total, Amount of allowance	8,846	9,090	10,092	9,171	10,092	8,931
Loans deemed to be impaired					173	988
Loans not deemed to be impaired					604,314	501,765
Total, Amount of allowance impaired					604,487	502,753
Residential Portfolio Segment [Member] | Multi-Family Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,549	4,002	4,514	3,385
Provision (credit) for loan losses	(44)	302	990	919
Recoveries			1
Ending balance	5,505	4,304	5,505	4,304
Amount of allowance for loan losses for loans deemed to be impaired					105	137
Amount of allowance for loan losses for loans not deemed to be impaired					5,400	4,377
Total, Amount of allowance	5,549	4,002	5,505	4,304	5,505	4,514
Loans deemed to be impaired					1,327	1,359
Loans not deemed to be impaired					701,304	561,589
Total, Amount of allowance impaired					702,631	562,948
Residential Portfolio Segment [Member] | One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,167	1,320	1,367	1,354
Provision (credit) for loan losses	(100)	141	(333)	107
Recoveries			33
Ending balance	1,067	1,461	1,067	1,461
Amount of allowance for loan losses for loans deemed to be impaired					67	49
Amount of allowance for loan losses for loans not deemed to be impaired					1,000	1,318
Total, Amount of allowance	1,167	1,320	1,067	1,461	1,067	1,367
Loans deemed to be impaired					1,598	1,422
Loans not deemed to be impaired					558,795	531,028
Total, Amount of allowance impaired					560,393	532,450
Residential Portfolio Segment [Member] | Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	71	92	73	144
Provision (credit) for loan losses	(9)	(6)	(11)	(58)
Ending balance	62	86	62	86
Amount of allowance for loan losses for loans not deemed to be impaired					62	73
Total, Amount of allowance	71	92	62	86	62	73
Loans not deemed to be impaired					42,042	42,913
Total, Amount of allowance impaired					42,042	42,913
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	20,598	16,950	18,725	14,497
Provision (credit) for loan losses	1,343	300	3,216	2,753
Ending balance	21,941	17,250	21,941	17,250
Amount of allowance for loan losses for loans not deemed to be impaired					21,941	18,725
Total, Amount of allowance	20,598	16,950	21,941	17,250	21,941	18,725
Loans deemed to be impaired					862	2,807
Loans not deemed to be impaired					2,069,899	1,773,794
Total, Amount of allowance impaired					2,070,761	1,776,601
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	97	112	87	92
Provision (credit) for loan losses	75	43	203	147
Charge-offs	(99)	(72)	(265)	(206)
Recoveries	24	21	72	71
Ending balance	97	104	97	104
Amount of allowance for loan losses for loans not deemed to be impaired					97	87
Total, Amount of allowance	$ 97	$ 112	$ 97	$ 104	97	87
Loans not deemed to be impaired					10,222	9,712
Total, Amount of allowance impaired					$ 10,222	$ 9,712

Loans - Past Due and Non Accrua

Loans - Past Due and Non Accrual (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	$ 6,261	$ 10,435
Loans on Non-accrual	9,178	13,436
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	525	653
Loans on Non-accrual	525	653
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	4,583	8,711
Loans on Non-accrual	8,653	12,783
One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	3,477	4,377
Loans on Non-accrual	7,055	8,487
Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	833	1,510
Loans on Non-accrual	563	674
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	100	2,009
Loans on Non-accrual	862	2,807
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	173	815
Loans on Non-accrual	173	815
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,153	1,071
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	2,073	2,132
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,584	1,453
Financing Receivables, 30 to 59 Days Past Due [Member] | One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,113	641
Financing Receivables, 30 to 59 Days Past Due [Member] | Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	371	707
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	100	105
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	489	679
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,888	1,357
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,224	965
Financing Receivables, 60 to 89 Days Past Due [Member] | One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	984	834
Financing Receivables, 60 to 89 Days Past Due [Member] | Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	67	131
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	173
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	664	392
Financing Receivables, 90 Days or Greater Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	2,300	6,946
Financing Receivables, 90 Days or Greater Past Due [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	525	653
Financing Receivables, 90 Days or Greater Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,775	6,293
Financing Receivables, 90 Days or Greater Past Due [Member] | One-to Four-Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	1,380	2,902
Financing Receivables, 90 Days or Greater Past Due [Member] | Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	$ 395	672
Financing Receivables, 90 Days or Greater Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due		1,904
Financing Receivables, 90 Days or Greater Past Due [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due		$ 815

Loans - Impaired Loans of Compa

Loans - Impaired Loans of Company (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total	$ 5,537		$ 5,537		$ 8,384
Impaired Loans Without Valuation Allowance, Recorded Investment	3,706		3,706		6,518
Impaired Loans With Valuation Allowance, Recorded Investment	1,831		1,831		1,866
Unpaid Principal Balance, Total	6,324		6,324		9,544
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	4,493		4,493		7,678
Impaired Loans With Valuation Allowance, Unpaid Principal Balance	1,831		1,831		1,866
Impaired Loans With Valuation Allowance, Related Allowance	172		172		186
Average Recorded Investment	7,258	$ 21,743	7,646	$ 22,654
Interest Income Recognized	59	77	200	259
Interest Income Recognized on Cash Basis	25	36	96	137
Multi-Family Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans Without Valuation Allowance, Recorded Investment	63		63		74
Impaired Loans With Valuation Allowance, Recorded Investment	1,264		1,264		1,285
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	63		63		74
Impaired Loans With Valuation Allowance, Unpaid Principal Balance	1,264		1,264		1,285
Impaired Loans With Valuation Allowance, Related Allowance	105		105		137
Average Recorded Investment	1,331	1,374	1,342	1,385
Interest Income Recognized	13	14	40	41
One-to Four-Family [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans Without Valuation Allowance, Recorded Investment	1,031		1,031		841
Impaired Loans With Valuation Allowance, Recorded Investment	567		567		581
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	1,488		1,488		1,281
Impaired Loans With Valuation Allowance, Unpaid Principal Balance	567		567		581
Impaired Loans With Valuation Allowance, Related Allowance	67		67		49
Average Recorded Investment	1,607	1,843	1,488	1,857
Interest Income Recognized	18	18	63	54
Interest Income Recognized on Cash Basis	13	13	47	38
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total	173		173		988
Impaired Loans Without Valuation Allowance, Recorded Investment	173		173		988
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	173		173		1,083
Average Recorded Investment	173	13,620	445	14,410
Interest Income Recognized	2	8	6	25
Interest Income Recognized on Cash Basis	2	4	6	14
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total	1,577		1,577		1,808
Impaired Loans Without Valuation Allowance, Recorded Investment	1,577		1,577		1,808
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	1,907		1,907		2,138
Average Recorded Investment	1,600	1,941	1,676	1,570
Interest Income Recognized	16	18	48	67
Interest Income Recognized on Cash Basis				13
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total	862		862		2,807
Impaired Loans Without Valuation Allowance, Recorded Investment	862		862		2,807
Impaired Loans Without Valuation Allowance, Unpaid Principal Balance	862		862		$ 3,102
Average Recorded Investment	2,547	2,965	2,695	3,432
Interest Income Recognized	10	19	43	72
Interest Income Recognized on Cash Basis	$ 10	$ 19	$ 43	$ 72

Loans - Summary of Troubled Deb

Loans - Summary of Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status	$ 12,777	$ 13,257
Total TDRs on non-accrual status	1,488	1,123
Total TDRs	14,265	14,380
Multi-Family Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status	1,326	1,359
One-to Four-Family [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status	2,163	2,219
Total TDRs on non-accrual status	1,315	1,123
Home Equity Lines of Credit [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status		18
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status	9,266	9,460
Construction [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status		174
Total TDRs on non-accrual status	173
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Total TDRs on accrual status	$ 22	$ 27

Loans - Risk Rated Loans by Cla

Loans - Risk Rated Loans by Class (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Multi-Family Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	$ 702,631	$ 562,948
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	2,070,761	1,776,601
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	604,487	502,753
Loans Rated 1-6 [Member] | Multi-Family Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	697,858	556,892
Loans Rated 1-6 [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	2,052,756	1,771,671
Loans Rated 1-6 [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	604,314	500,565
Loans Rated 7 [Member] | Multi-Family Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	277	841
Loans Rated 7 [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	17,143	2,123
Loans Rated 8 [Member] | Multi-Family Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	4,496	5,215
Loans Rated 8 [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	862	2,807
Loans Rated 8 [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	173	2,188
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	561,769	515,430
Commercial and Industrial [Member] | Loans Rated 1-6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	509,977	465,979
Commercial and Industrial [Member] | Loans Rated 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	25,654	22,820
Commercial and Industrial [Member] | Loans Rated 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Credit Quality Rating	$ 26,138	$ 26,631

Deposits - Summary of Deposit B

Deposits - Summary of Deposit Balances, by Type (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Banking and Thrift [Abstract]
Demand deposits	$ 455,540	$ 431,222
Interest-bearing checking deposits	896,561	630,413
Money market deposits	975,246	980,344
Regular savings and other deposits	324,895	305,632
Total non-certificate accounts	2,652,242	2,347,611
Term certificates less than $250,000	962,755	850,565
Term certificates $250,000 and greater	330,472	277,661
Total certificate accounts	1,293,227	1,128,226
Total deposits	$ 3,945,469	$ 3,475,837

Deposits - Summary of Term Cert

Deposits - Summary of Term Certificates, by Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Banking and Thrift [Abstract]
Within 1 year, Amount	$ 597,795	$ 539,903
Over 1 year to 2 years, Amount	294,158	306,120
Over 2 years to 3 years, Amount	270,173	122,952
Over 3 years to 4 years, Amount	83,080	133,256
Over 4 years to 5 years, Amount	44,434	22,483
Greater than 5 years, Amount	3,587	3,512
Total certificate accounts	$ 1,293,227	$ 1,128,226
Within 1 year, Weighted Average Rate	1.22%	1.16%
Over 1 year to 2 years, Weighted Average Rate	1.42%	1.29%
Over 2 year to 3 years, Weighted Average Rate	2.00%	1.69%
Over 3 year to 4 years, Weighted Average Rate	1.97%	2.02%
Over 4 years to 5 years, Weighted Average Rate	2.06%	1.61%
Greater than 5 Years, Weighted Average Rate	5.50%	5.50%
Weighted average rate on term certificates	1.52%	1.38%

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Deposits [Line Items]
Brokered certificate of deposit included in term certificates	$ 243,800	$ 158,500
Weighted average rate of deposit included in term certificates	1.70%	1.33%
Interest-bearing checking deposits	$ 896,561	$ 630,413
Reciprocal Deposits [Member]
Deposits [Line Items]
Interest-bearing checking deposits	402,400	$ 296,300
Authorized Brokerage Firm [Member]
Deposits [Line Items]
Interest-bearing checking deposits	$ 100,000

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Debt Disclosure [Line Items]
Available line of credit with the FHLB	$ 9,400,000
Short-term borrowings	0	$ 0
Amounts drawn on the line of credit	0	0
Available borrowings under Federal Reserve Bank discount window	472,000,000
Outstanding borrowings under Federal Reserve Bank discount window	0	$ 0
Amount of advances callable by the FHLB prior to maturity	330,000,000
Multi-Family Residential Real Estate [Member]
Debt Disclosure [Line Items]
Carrying value of commercial real estate loans pledged	161,600,000
LIBOR Less 60 Basis Points [Member] | First Two Years [Member]
Debt Disclosure [Line Items]
FHLB advances	$ 35,000,000
LIBOR, Basis points	0.60%
Interest rate, Description	3-Month London Interbank Offered Rate ("LIBOR"), less 60 basis points
Interest rate, Term	Variable
Period of LIBOR measurement	3 months
Libor Less 130 Basis Points Member | First Year [Member]
Debt Disclosure [Line Items]
FHLB advances	$ 20,000,000
LIBOR, Basis points	1.30%
Interest rate, Description	3-month LIBOR, less 130 basis points
Interest rate, Term	Variable
Period of LIBOR measurement	3 months
LIBOR Less 100 Basis Points [Member] | First Two Years [Member]
Debt Disclosure [Line Items]
FHLB advances	$ 20,000,000
LIBOR, Basis points	1.00%
Interest rate, Description	3-Month LIBOR, less 100 basis point
Interest rate, Term	Variable
Period of LIBOR measurement	3 months
LIBOR Less 100 Basis Points [Member] | First Year [Member]
Debt Disclosure [Line Items]
FHLB advances	$ 45,000,000
LIBOR, Basis points	1.00%
Interest rate, Description	3-Month LIBOR, less 100 basis point
Interest rate, Term	Variable
Period of LIBOR measurement	3 months
Commercial Real Estate Portfolio Segment [Member]
Debt Disclosure [Line Items]
Carrying value of commercial real estate loans pledged	$ 757,900,000

Borrowings - Long-term Debt, FH

Borrowings - Long-term Debt, FHLB Advances (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total advances	$ 471,069	$ 322,512
Weighted Average [Member]
Debt Instrument [Line Items]
Weighted Average Rate	1.16%	1.01%
Fixed Interest Rate [Member]
Debt Instrument [Line Items]
2,017	$ 15,000	$ 89,632
2,018	43,000	43,000
2,019	3,532	4,891
2,020	53,912	4,989
2,021	45,000	45,000
2,022	80,625
2,023	10,000	10,000
2,026	10,000	20,000
2,027	25,000
2,031	20,000	20,000
2,032	45,000
Total advances	$ 351,069	$ 237,512
Weighted Average Rate, 2017	1.02%	1.32%
Weighted Average Rate, 2018	1.25%	1.25%
Weighted Average Rate, 2019	1.23%	1.23%
Weighted Average Rate, 2020	1.80%	1.22%
Weighted Average Rate, 2021	1.46%	1.46%
Weighted Average Rate, 2022	1.72%
Weighted Average Rate, 2023	2.10%	2.10%
Weighted Average Rate, 2026	0.69%	0.59%
Weighted Average Rate, 2027	1.38%
Weighted Average Rate, 2031	0.88%	0.88%
Weighted Average Rate, 2032	1.03%
Fixed Interest Rate [Member] | Weighted Average [Member]
Debt Instrument [Line Items]
Weighted Average Rate	1.43%	1.26%
Variable Interest Rate [Member]
Debt Instrument [Line Items]
2,020		$ 25,000
2,021	$ 35,000	60,000
2,022	65,000
2,024	20,000
Total advances	$ 120,000	$ 85,000
Weighted Average Rate, 2020		0.27%
Weighted Average Rate, 2021	0.71%	0.31%
Weighted Average Rate, 2022	0.22%
Weighted Average Rate, 2024	0.32%
Variable Interest Rate [Member] | Weighted Average [Member]
Debt Instrument [Line Items]
Weighted Average Rate	0.38%	0.29%

Other Commitments and Conting48

Other Commitments and Contingencies and Derivatives - Loan Commitments Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Total loan commitments outstanding	$ 1,224,589	$ 1,178,033
Construction [Member] | Unadvanced Portion of Existing Loans [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	557,232	503,586
Construction [Member] | Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	241,985	231,274
Home Equity Lines of Credit [Member] | Unadvanced Portion of Existing Loans [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	41,499	36,722
One-to Four-Family [Member] | Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	20,048	18,272
Commercial Real Estate Portfolio Segment [Member] | Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	75,726	42,141
Unallocated Financing Receivables [Member] | Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	115	350
Other Lines and Letters of Credit [Member] | Unadvanced Portion of Existing Loans [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	275,787	314,225
Commercial and Industrial [Member] | Unfunded Loan Commitment [Member]
Loss Contingencies [Line Items]
Total loan commitments outstanding	$ 12,197	$ 31,463

Other Commitments and Conting49

Other Commitments and Contingencies and Derivatives - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Cash pledged for collateral interest rate swap	$ 3.7	$ 1.8
Core Data Processing Provider [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other outstanding commitments	$ 18.4

Other Commitments and Conting50

Other Commitments and Contingencies and Derivatives - Summary Information Regarding the Derivatives (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Customer Interest Rate Swap Maturing on 06/06/32 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 65,883,000
Fair value	$ 1,106,000
Maturity	Jun. 7, 2032
Interest rate paid	1 Mo. LIBOR + 200bp
Interest rate received	Fixed (4.40%)
Third Party Interest Rate Swap Maturing on 06/06/32 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 65,883,000
Fair value	$ (1,106,000)
Maturity	Jun. 7, 2032
Interest rate paid	Fixed (4.40%)
Interest rate received	1 Mo. LIBOR + 200bp
Customer Interest Rate Swap Maturing on 10/17/33 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 10,767,000	$ 10,922,000
Fair value	$ 815,000	839,000
Maturity	Oct. 17, 2033
Interest rate paid	1 Mo. LIBOR + 175bp
Interest rate received	Fixed (4.1052%)
Third Party Interest Rate Swap Maturing on 10/17/33 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 10,767,000	10,922,000
Fair value	$ (815,000)	(839,000)
Maturity	Oct. 17, 2033
Interest rate paid	Fixed (4.1052%)
Interest rate received	1 Mo. LIBOR + 175bp
Customer Interest Rate Swap Maturing on 12/13/26 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 2,923,000	3,036,000
Fair value	$ (51,000)	(60,000)
Maturity	Dec. 13, 2026
Interest rate paid	1 Mo. LIBOR + 205bp
Interest rate received	Fixed (3.82%)
Third Party Interest Rate Swap Maturing on 12/13/26 [Member]
Loss Contingencies [Line Items]
Notional amount	$ 2,923,000	3,036,000
Fair value	$ 51,000	$ 60,000
Maturity	Dec. 13, 2026
Interest rate paid	Fixed (3.82%)
Interest rate received	1 Mo. LIBOR + 205bp

Fair Values of Assets and Lia51

Fair Values of Assets and Liabilities - Assets Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 5,104	$ 21,631
Marketable equity securities	39,557	46,032
Total assets	46,633	68,562
Total liabilities	1,972	899
Loan Level Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,972	899
Total liabilities	1,972	899
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	39,557	46,032
Total assets	39,557	46,032
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	5,104	21,631
Total assets	7,076	22,530
Total liabilities	1,972	899
Fair Value, Inputs, Level 2 [Member] | Loan Level Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,972	899
Total liabilities	$ 1,972	$ 899

Fair Values of Assets and Lia52

Fair Values of Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans measured at fair value	$ 2.1	$ 4.9

Fair Values of Assets and Lia53

Fair Values of Assets and Liabilities - Summary of Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Cash and due from banks, fair value	$ 300,297	$ 236,423
Cash and due from banks, carrying amount	300,297	236,423
Certificates of deposit, fair value	75,393	80,710
Certificates of deposit, carrying amount	75,192	80,323
Securities available for sale, carrying amount	44,661	67,663
Federal Home Loan Bank stock, carrying amount	22,976	18,175
Federal Home Loan Bank stock, fair value	22,976	18,175
Loans and loans held for sale, net, carrying amount	4,505,575	3,902,612
Loans and loans held for sale, net, fair value	4,467,739	3,970,896
Accrued interest receivable, carrying amount	11,580	10,381
Accrued interest receivable, fair value	11,580	10,381
Financial liabilities:
Deposits, fair value	3,838,979	3,485,618
Deposits, carrying amount	3,945,469	3,475,837
Borrowings, fair value	468,067	322,928
Borrowings, carrying amount	471,069	322,512
Accrued interest payable, fair value	1,765	1,384
Accrued interest payable, carrying amount	1,765	1,384
Reported Value Measurement [Member]
Financial assets:
Securities available for sale, carrying amount	44,661	67,663
Interest Rate Swaps Asset [Member]
Financial liabilities:
Derivative Financial Assets, fair value	1,972	899
Derivative Financial Assets, carrying amount	1,972	899
Interest Rate Swaps Liability [Member]
Financial liabilities:
Derivative Financial Liability, fair value	1,972	899
Derivative Financial Liability, carrying amount	1,972	899
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks, fair value	300,297	236,423
Securities available for sale, carrying amount	39,557	46,032
Fair Value, Inputs, Level 2 [Member]
Financial assets:
Certificates of deposit, fair value	75,393	80,710
Securities available for sale, carrying amount	5,104	21,631
Financial liabilities:
Borrowings, fair value	468,067	322,928
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swaps Asset [Member]
Financial liabilities:
Derivative Financial Assets, fair value	1,972	899
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swaps Liability [Member]
Financial liabilities:
Derivative Financial Liability, fair value	1,972	899
Fair Value, Inputs, Level 3 [Member]
Financial assets:
Federal Home Loan Bank stock, fair value	22,976	18,175
Loans and loans held for sale, net, fair value	4,467,739	3,970,896
Accrued interest receivable, fair value	11,580	10,381
Financial liabilities:
Deposits, fair value	3,838,979	3,485,618
Accrued interest payable, fair value	$ 1,765	$ 1,384

Pending Acquisition - Additiona

Pending Acquisition - Additional Information (Detail) - Meetinghouse Bancorp, Inc. [Member] $ / shares in Units, $ in Millions	Jun. 26, 2017USD ($)$ / shares	Sep. 30, 2017USD ($)Office
Business Acquisition [Line Items]
Business acquisition, agreement date		Jun. 26, 2017
Business acquisition, share price | $ / shares	$ 26
Total transaction value	$ 17.8
Assets		$ 114
Loans		77
Deposits		$ 95
Number of offices operated | Office		2
Business acquisition, closing date		Dec. 31, 2017