Blue Hills Bancorp (BHBK) 10-Q 2 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 01, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Blue Hills Bancorp, Inc.
Entity Central Index Key	1,601,545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		26,901,347

Consolidated Balance Sheets (un

Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 17,566	$ 16,149
Short-term investments	34,383	30,018
Total cash and cash equivalents	51,949	46,167
Equity securities, at fair value	5,331	0
Securities available for sale, at fair value	0	9,720
Securities held to maturity, at amortized cost	303,137	303,716
Federal Home Loan Bank stock, at cost	14,375	12,105
Loans held for sale	10,005	8,992
Loans, net of allowance for loan losses of $20,125 at June 30, 2018 and $20,877 at December 31, 2017	2,241,746	2,186,147
Premises and equipment, net	20,192	21,573
Other real estate owned	3,649	0
Accrued interest receivable	6,531	6,438
Goodwill	9,160	9,160
Core deposit intangible	278	557
Net deferred tax asset	6,480	6,000
Bank-owned life insurance	33,610	33,078
Other assets	34,719	24,867
Total assets	2,741,162	2,668,520
Deposits:
Non-interest bearing	213,017	219,984
Interest bearing	1,899,050	1,819,885
Total deposits	2,112,067	2,039,869
Short-term borrowings	110,000	100,000
Long-term debt	90,000	105,000
Accrued expenses and other liabilities	28,850	25,845
Total liabilities	2,340,917	2,270,714
Stockholders' Equity:
Preferred stock, zero par value, (50,000,000 shares authorized; none issued and outstanding)	0	0
Common stock, $0.01 par value, (100,000,000 shares authorized; 26,874,071 and 26,827,660 issued and outstanding at June 30, 2018 and December 31, 2017, respectively)	268	268
Additional paid-in capital	258,225	254,750
Unearned compensation-ESOP	(19,357)	(19,737)
Retained earnings	162,948	163,978
Accumulated other comprehensive loss	(1,839)	(1,453)
Total stockholders' equity	400,245	397,806
Total liabilities and stockholders' equity	$ 2,741,162	$ 2,668,520

Consolidated Balance Sheets (u3

Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Loans, net of allowance for loan losses of $20,125 at June 30, 2018 and $20,877 at December 31, 2017	$ 20,125	$ 20,877
Preferred stock, par value (dollars per share)	$ 0	$ 0
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	26,874,071	26,827,660
Common stock, shares outstanding	26,874,071	26,827,660

Consolidated Statements of Net

Consolidated Statements of Net Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest and dividend income:
Interest and fees on loans	$ 23,081	$ 18,715	$ 44,890	$ 36,097
Interest on securities	1,809	1,572	3,666	3,782
Dividends	195	193	399	350
Other	62	94	140	126
Total interest and dividend income	25,147	20,574	49,095	40,355
Interest expense:
Interest on deposits	5,252	3,523	10,027	6,777
Interest on borrowings	912	643	1,726	1,289
Total interest expense	6,164	4,166	11,753	8,066
Net interest and dividend income	18,983	16,408	37,342	32,289
Provision (credit) for loan losses	101	1,118	(359)	1,175
Net interest and dividend income, after provision (credit) for loan losses	18,882	15,290	37,701	31,114
Non-interest income:
Deposit account fees	422	341	777	661
Interchange and ATM fees	454	388	845	736
Mortgage banking	1,033	1,219	1,773	1,959
Loan level derivative income	143	1,367	383	1,531
Net unrealized gains on equity securities	452	0	383	0
Gain (loss) on sales of available for sale securities, net	0	928	0	(94)
Gain on exchange of investment in Northeast Retirement Services	0	0	653	5,947
Bank-owned life insurance income	256	261	532	518
Gain on sale of premises and equipment	0	0	271	0
Miscellaneous	872	6	1,913	68
Total non-interest income	3,632	4,510	7,530	11,326
Non-interest expense:
Salaries and employee benefits	8,264	7,664	16,646	15,227
Occupancy and equipment	2,050	2,030	4,133	4,145
Data processing	1,054	1,022	2,098	2,066
Professional fees	450	526	903	1,395
Advertising	499	489	803	856
FDIC deposit insurance	230	223	463	435
Directors’ fees	362	428	771	802
Amortization of core deposit intangible	127	222	278	469
Other general and administrative	655	762	1,467	1,371
Total non-interest expense	13,691	13,366	27,562	26,766
Income before income taxes	8,823	6,434	17,669	15,674
Provision for income taxes	2,366	2,566	4,629	4,319
Net income	$ 6,457	$ 3,868	$ 13,040	$ 11,355
Earnings per common share:
Basic (dollars per share)	$ 0.27	$ 0.16	$ 0.54	$ 0.47
Diluted (dollars per share)	$ 0.26	$ 0.16	$ 0.52	$ 0.47
Weighted average shares outstanding:
Basic (shares)	24,230,098	23,952,443	24,201,328	23,932,044
Diluted (shares)	24,991,958	24,346,553	24,910,065	24,311,222

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income		$ 6,457	$ 3,868	$ 13,040	$ 11,355
Securities available for sale:
Change in unrealized holding gains		0	2,190	0	3,993
Reclassification adjustment for net losses realized in net income	[1]	0	(928)	0	94
Net change in unrealized gains		0	1,262	0	4,087
Tax effect		0	(523)	0	(1,427)
Net-of-tax amount		0	739	0	2,660
Securities held to maturity:
Reclassification adjustment for amortization of amounts previously recorded upon transfer from available-for-sale	[2]	(21)	(22)	(40)	(45)
Tax effect		5	9	11	5
Net-of-tax amount		(16)	(13)	(29)	(40)
Defined benefit pension plan:
Reclassification adjustment for net actuarial loss recognized in net periodic benefit cost	[3]	67	89	133	178
Tax effect		(19)	(31)	(38)	(90)
Net-of-tax amount		48	58	95	88
Other comprehensive income		32	784	66	2,708
Comprehensive income		$ 6,489	$ 4,652	$ 13,106	$ 14,063
[1]	Amounts are included in gain (loss) on sales of available for sale securities, net, in the consolidated statements of net income. Income tax expense (benefit) associated with the reclassification adjustment for the three and six months ended June 30, 2017 was $324,000 and (32,000).
[2]	Amounts are included in interest income on securities in the consolidated statements of net income.
[3]	Amounts are included in salaries and employee benefits expense in the consolidated statements of net income.

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Reclassification adjustment for net losses realized in net income, tax	$ 324	$ (32)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity (unaudited) - USD ($)	Total	Common Stock	Additional paid-in capital	Unearned compensation- ESOP	Retained earnings	Accumulated other comprehensive (loss) income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2)			$ 27,000		$ (27,000)
Beginning balance at Dec. 31, 2016		$ 268,000	249,308,000	$ (20,496,000)	161,896,000	$ (4,069,000)
Beginning balance (shares) at Dec. 31, 2016		26,759,953
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	$ 14,063,000				11,355,000	2,708,000
ESOP shares committed to be released	684,000		305,000	379,000
Common stock dividends declared ($0.08 and $0.45 per common share for the nine months ended September 30, 2016 and 2017, respectively)	(7,191,000)				(7,191,000)
Restricted stock awards granted (shares)		175,695
Restricted stock awards granted	0
Restricted stock awards forfeited (shares)		(84,417)
Restricted stock awards forfeited	0
Share-based compensation expense	2,745,000		2,745,000
Share redemption for tax withholdings for restricted stock vesting (shares)		(5,903)
Share redemption for tax withholdings for restricted stock vesting			(107,000)
Proceeds from exercise of options (shares)		15,660
Proceeds from exercise of options	217,000		217,000
Ending balance at Jun. 30, 2017	397,318,000	$ 268,000	252,495,000	(20,117,000)	166,033,000	(1,361,000)
Ending balance (shares) at Jun. 30, 2017		26,860,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2) | ASU 2016-01					173,000	(173,000)
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2) | ASU 2018-02					279,000	(279,000)
Beginning balance at Dec. 31, 2017	397,806,000	$ 268,000	254,750,000	(19,737,000)	163,978,000	(1,453,000)
Beginning balance (shares) at Dec. 31, 2017		26,827,660
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	13,106,000				13,040,000	66,000
ESOP shares committed to be released	775,000		395,000	380,000
Common stock dividends declared ($0.08 and $0.45 per common share for the nine months ended September 30, 2016 and 2017, respectively)	(14,522,000)				(14,522,000)
Restricted stock awards granted (shares)		36,500
Restricted stock awards forfeited (shares)		(23,450)
Share-based compensation expense	2,714,000		2,714,000
Share redemption for tax withholdings for restricted stock vesting (shares)		(15,969)
Share redemption for tax withholdings for restricted stock vesting	$ (325,000)		(325,000)
Proceeds from exercise of options (shares)	49,330	49,330
Proceeds from exercise of options	$ 691,000		691,000
Ending balance at Jun. 30, 2018	$ 400,245,000	$ 268,000	$ 258,225,000	$ (19,357,000)	$ 162,948,000	$ (1,839,000)
Ending balance (shares) at Jun. 30, 2018		26,874,071

Consolidated Statements of Cha8

Consolidated Statements of Changes in Stockholders' Equity (unaudited) (Parenthetical) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Stockholders' Equity [Abstract]
Common stock paid (dollars per share)	$ 0.60	$ 0.30

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 13,040	$ 11,355
Adjustments to reconcile net income to net cash provided by operating activities:
Provision (credit) for loan losses	(359)	1,175
Net amortization of securities	476	1,007
Loss on sales of available for sale securities, net	0	94
Net unrealized gains on equity securities	(383)	0
Net change in loans held for sale	(1,013)	(4,028)
Losses on sales of portfolio loans, net	41	74
Net amortization of net deferred loan origination costs and discounts	(538)	31
Depreciation and amortization of premises and equipment	1,020	1,062
Amortization of core deposit intangible	278	469
Bank-owned life insurance income	(532)	(518)
ESOP expense	775	684
Deferred income tax (benefit) provision	(507)	450
Share-based compensation expense	2,714	2,745
Gain on exchange of investment in Northeast Retirement Services	(653)	(5,947)
Gain on sale of premises and equipment	(271)	0
Net change in:
Accrued interest receivable	(93)	695
Other assets	(10,159)	(3,284)
Accrued expenses and other liabilities	3,791	(2,245)
Net cash provided by operating activities	7,627	3,819
Activity in securities available for sale:
Purchases	0	(13,951)
Sales	0	213,084
Principal paydowns	0	5,049
Activity in securities held to maturity:
Purchases	(19,239)	(97,591)
Principal paydowns	19,302	14,324
Proceeds from sale of equity securities	4,772	0
Loan originations and purchases, net of paydowns	(65,599)	(166,992)
Proceeds from sales of portfolios	7,207	32,406
Net disposals (purchases) of premises and equipment	(632)	1,032
Purchase of FHLBB stock	(7,254)	(4,309)
Redemption of FHLBB stock	4,984	5,718
Proceeds from exchange of investment in Northeast Retirement Services	308	1,595
Net cash used in investing activities	(54,887)	(11,699)
Cash flows from financing activities:
Net change in deposits, excluding brokered deposits	46,139	135,405
Net change in brokered deposits	26,059	21,171
Net change in short-term borrowings	10,000	(146,000)
Net (repayments) proceeds from long-term debt	(15,000)	25,000
Share redemption for tax withholdings for restricted stock vesting	(325)	(107)
Proceeds from exercise of stock options	691	217
Common stock dividends paid	(14,522)	(7,191)
Net cash provided by financing activities	53,042	28,495
Net change in cash and cash equivalents	5,782	20,615
Cash and cash equivalents at beginning of period	46,167	30,496
Cash and cash equivalents at end of period	51,949	51,111
Supplementary information:
Interest paid	11,448	7,978
Income taxes paid, net of refunds	3,931	4,240
Other real estate owned acquired in settlement of loans	$ 3,649	$ 202

Basis of Presentation and Conso

Basis of Presentation and Consolidation	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation	BASIS OF PRESENTATION AND CONSOLIDATION Basis of Presentation The accompanying unaudited interim consolidated financial statements include the accounts of Blue Hills Bancorp, Inc. (the "Company"), its wholly-owned subsidiaries, Blue Hills Funding Corporation and Blue Hills Bank (the "Bank"), the principal operating entity, and the Bank's wholly-owned subsidiaries, B.H. Security Corporation, HP Security Corporation and 1196 Corporation, which are Massachusetts security corporations, and Nantucket Property Acquisition Company LLC, the Bank's subsidiary that holds other real estate owned. All significant intercompany balances and transactions have been eliminated in consolidation. The unaudited consolidated financial statements of the Company presented herein have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information and pursuant to the rules of the Securities and Exchange Commission ("SEC") for quarterly reports on Form 10-Q and Article 10 of Regulation S-X and do not include all of the information and note disclosures required by GAAP for a complete set of financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) and disclosures necessary for the fair presentation of the accompanying consolidated financial statements have been included. Interim results are not necessarily reflective of the results of the year. The accompanying unaudited financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017, included in the Company's annual report on Form 10-K. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and reported amounts of revenues and expenses during the reporting 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 valuation of deferred tax assets. Loan policies The Company has historically granted mortgage and consumer loans to its customers and a substantial portion of the loan portfolio consists of mortgage loans in communities including and near the locations of its banking offices. The ability of the Company’s debtors to honor their contracts is dependent upon the real estate and general economic conditions in these areas. The Company’s loan portfolio includes 1-4 family residential real estate, home equity, commercial real estate, construction, commercial business, and consumer segments. Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off generally are reported at their outstanding unpaid principal balances adjusted for the allowance for loan losses, charge-offs, deferred origination fees and costs, and discounts on purchased loans. Interest income is accrued on the unpaid principal balance. Deferred loan origination fees/costs and discounts on purchased loans are recognized as an adjustment of the related loan yield using the interest method. It is the policy of the Company to discontinue the accrual of interest on loans past due in excess of 90 days, unless the loan is well-secured and in the process of collection. Accrual may be discontinued sooner when in the judgment of management, the ultimate collectability of the principal or interest becomes doubtful. Upon discontinuance of accrual, all interest previously accrued is reversed against interest income. Past due status is based on contractual terms of the loan. The interest on non-accrual loans is accounted for on the cash-basis until qualifying for return to accrual. Loans are returned to accrual status when all the principal and interest amounts contractually due have been current for six consecutive months and future payments are reasonably assured. Allowance for loan losses The allowance for loan losses is based on the size and the composition of the loan portfolio, delinquency levels, loss experience, economic conditions and other factors related to the collectability of the loan portfolio. Loss experience is updated at least quarterly with consideration given to unusual circumstances in the portfolio. Loan losses are charged against the allowance when management believes the uncollectability of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The allowance for loan losses is evaluated regularly by management and reflects consideration of all significant factors that affect the collectability of the loan portfolio. The evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available. It is the intention of management to maintain an allowance that is prudently commensurate with the growth in the loan portfolio. The allowance consists of general and allocated components, as further described below. General component The general component of the allowance for loan losses is based on a combination of the Company's own loss history and an extrapolated historical loss experience based on FDIC data for depository institutions with assets of one billion to five billion dollars dating back to 2010, adjusted for qualitative and environmental factors including changes to lending policies and procedures, economic and business conditions, portfolio characteristics, staff experience, problem loan trends, collateral values, concentrations and the competitive, legal and regulatory environment. The qualitative factors are determined based on the various risk characteristics of each loan segment. Risk characteristics relevant to each portfolio segment are as follows: Residential real estate - The Company does not generally originate loans with a loan-to-value ratio greater than 80 percent and does not generally grant loans that would be classified as subprime upon origination. When the Company does extend credit either on a first- or second-lien basis at a loan-to-value ratio greater than 80 percent , such loans are supported by either mortgage insurance or state guarantee programs. All loans in this segment are collateralized by owner-occupied, 1-4 family residential real estate and repayment is dependent on the credit quality of the individual borrower. The health of the national and state economy, including unemployment rates and housing prices, will have an effect on the credit quality of loans in this segment. Home equity - Loans in this segment are generally secured by first or second liens on residential real estate. Repayment is dependent on the credit quality of the individual borrower. The Company evaluates each loan application based on factors including the borrower’s credit score, income, length of employment, and other factors to establish the creditworthiness of the borrower. Commercial real estate - Loans in this segment include investment real estate and are generally secured by assignments of leases, real estate collateral and owner-occupied properties. In cases where there is a concentration of exposure to a single large tenant, underwriting standards include analysis of the tenant’s ability to support lease payments over the duration of the loan. The underlying cash flows generated by the properties may be adversely impacted by a downturn in the economy due to increased vacancy rates, which in turn can have an effect on the credit quality in this segment. Payments on loans secured by income-producing properties often depend on the successful operation and management of the properties. Management continually monitors the cash flows of these loans. Construction - Loans in this segment primarily include real estate development loans for which payment is derived from permanent financing or sale of the property. Credit risk is affected by cost overruns, time to sell at an adequate price, and market conditions. Commercial business - Loans in this segment are generally secured by business assets, including accounts receivable, inventory, real estate and intangible assets. Strict underwriting standards include considerations of the borrower’s ability to support the debt service requirements from the underlying historical and projected cash flows of the business, collateral values, the borrower’s credit history and the ultimate collectability of the de bt. Economic conditions, real estate values, commodity prices, unemployment trends and other factors will affect the credit quality of loans in these segments. Consumer - Loans in this segment primarily include used classic and collector automobile loans. A significant portion of the used automobile loan portfolio is comprised of geographically diverse loans originated by and purchased from a third party, who also provides collection services and shares equally in any losses incurred. Allocated component The allocated component relates to loans that are considered impaired. Impairment is measured by either the present value of expected future cash flows discounted at the loan’s effective interest rate or the fair value of the collateral if the loan is collateral dependent. An allowance is established when the discounted cash flows (or collateral value) of the impaired loan is lower than the carrying value of that loan. A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Management reviews all loan types for individual impairment. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed. The Company periodically may agree to modify the contractual terms of loans. When a loan is modified and a concession is made to a borrower experiencing financial difficulty, the modification is considered a troubled debt restructuring (“TDR”). All TDRs are initially classified as impaired and generally remain impaired for the remaining life of the loan. The impaired classification may be removed if the borrower demonstrates compliance with the modified terms and the restructuring agreement specifies an interest rate equal to that which would be provided to a borrower with similar credit at the time of restructuring.

Accounting Standards Updates

Accounting Standards Updates	6 Months Ended
	Jun. 30, 2018
Accounting Changes and Error Corrections [Abstract]
Accounting Standards Updates	ACCOUNTING STANDARDS UPDATES Accounting Standards Adopted in the Period In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The purpose of this Update is to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The Company adopted the Update on January 1, 2018. The effect of applying the provisions of this Update resulted in an increase to retained earnings and a corresponding decrease in accumulated other comprehensive loss in the amount of $279,000 . Effective January 1, 2018, the Company adopted ASU 2016-01, Financial Instruments – Overall, (Subtopic 825-10) . The amendments in this Update address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Targeted improvements to generally accepted accounting principles include the requirement for equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income and the elimination of the requirement for public business entities to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost. The Update also requires Companies to utilize an "exit price" fair value methodology when measuring the fair value of financial instruments. The cumulative effect of applying the provisions of this Update resulted in an increase to retained earnings and a corresponding decrease to accumulated other comprehensive loss in the amount of $173,000 . Effective January 1, 2018, the Company adopted ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory . The amendments in this Update require an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . The amendments in this Update require that in the statement of cash flows, amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers . This Update provides a revenue recognition framework for any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets unless those contracts are within the scope of other accounting standards. The Company's revenue relates principally to financial instruments, which are explicitly excluded from the scope of the new guidance. The Company adopted this Update on January 1, 2018 and the impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting which amends the scope of modification accounting for share-based payment arrangements. The Update provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. The Update should be applied prospectively to awards modified on or after the effective date. The impact to the consolidated financial statements upon adopting was not material. Recently Issued In June 2018 the FASB issued ASU 2018-07 Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The Updates expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. An entity should apply the requirements of Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the attribution of cost (that is, the period of time over which share-based payment awards vest and the pattern of cost recognition over that period). The Update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company does not anticipate the adoption of ASU 2018-07 will have a material impact on its consolidated financial statements. Future Application of Accounting Pronouncements Previously Issued In March 2018, the FASB issued ASU 2018-04, Investments-Debt Securities (Topic 320) and Regulated Operations (Topic 980) . Amendments to SEC paragraph Pursuant to SEC Staff Accounting Bulletin No. 177 and SEC Release No 33-9273, the amendment of ASU 2018-04 adds, amends and supersedes variance paragraphs that contain SEC guidance in ASC 320, Investments-Debt Securities and ASC 980, Regulated Operations. The Company does not anticipate the adoption of ASU 2018-04 will have a material impact on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities . The purpose of this Update is to better align a company’s financial reporting for hedging activities with the economic objectives of those activities. This Update is effective for public business entities for fiscal years beginning after December 15, 2018, with early adoption, including adoption in an interim period permitted. The Update requires a modified retrospective transition method in which the Company will recognize the cumulative effect of the change on the opening balance of each affected component of equity in the statement of financial position as of the date of adoption. While the Company continues to assess all potential impacts of the standard, we currently expect the adoption to have an immaterial impact on our consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . This Update is intended to improve financial reporting about leasing transactions and the key provision impacting the Company is the requirement for a lessee to record a right-to-use asset and a liability representing the obligation to make lease payments for long-term operating leases. Additionally, the Update includes additional quantitative and qualitative disclosures required by lessees and lessors to help users better understand the amount, timing, and uncertainty of cash flows arising from leases. This Update is effective for fiscal years beginning after December 31, 2018, and interim periods within those fiscal years. Lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The modified retrospective approach includes a number of optional practical expedients that entities may elect to apply as well as transition guidance specific to nonstandard leasing transactions. The Company's assets and liabilities will increase based on the present value of remaining lease payments for leases in place at the adoption date; however, this is not expected to be material to the Company's results of operations or financial position. Future lease commitments as of at June 30, 2018 amounted to $20.5 million . In June, 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which removes the thresholds that companies apply to measure credit losses on financial instruments measured at amortized cost, such as loans, receivables, and held-to-maturity debt securities. Under current U.S. GAAP, companies generally recognize credit losses when it is probable that the loss has been incurred. The revised guidance will remove previously established recognition thresholds based on probability, and will require companies to recognize an allowance for credit losses for the difference between the amortized cost basis of a financial instrument and the net amount that the company expects to collect over the instrument’s contractual life. ASU 2016-13 also amends the credit loss measurement guidance for available-for-sale debt securities and will require that credit losses be recorded through an allowance for credit losses. Additionally, this Update may reduce the carrying value of the Company's held-to-maturity investment securities as it will require an allowance on the expected losses over the life of these securities to be recorded upon adoption. The ASU is effective for public business entities fiscal years beginning after December 15, 2019 and for interim periods within those fiscal years. Any increase in our allowance for loan losses or expenses may have a material adverse effect on our financial condition and results of operations. The Company is actively working through the provisions of the Update. Management has established a steering committee which has identified the methodologies and the additional data requirements necessary to implement the Update and has engaged a third-party software service provider to assist in the Company's implementation.

Securities

Securities	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Securities	SECURITIES The amortized cost and estimated fair value of securities available for sale and securities held to maturity, with gross unrealized gains and losses, follows: June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ 30,683 $ — $ (1,312 ) $ 29,371 Government-sponsored mortgage-backed and collateralized mortgage obligations 245,849 8 (8,061 ) 237,796 SBA asset-backed securities 26,605 — (832 ) 25,773 Total securities held to maturity $ 303,137 $ 8 $ (10,205 ) $ 292,940 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Securities Available for Sale: Marketable equity securities $ 9,437 $ 755 $ (472 ) $ 9,720 Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ 30,673 $ — $ (894 ) $ 29,779 Government-sponsored mortgage-backed and collateralized mortgage obligations 244,668 30 (3,437 ) 241,261 SBA asset-backed securities 28,375 28 (329 ) 28,074 Total securities held to maturity $ 303,716 $ 58 $ (4,660 ) $ 299,114 The amortized cost and estimated fair value of debt securities by contractual maturity at June 30, 2018 are included in the following table. Expected maturities will differ from contractual maturities because the issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Based on expected maturities, the mortgage and asset-backed securities and collateralized mortgage obligations, included below, have a 4.0 year weighted average duration. Amortized Cost Fair Value (In thousands) After 1 year through 5 years $ 18,635 $ 17,999 After 5 years through 10 years 12,048 11,372 30,683 29,371 Mortgage and asset-backed securities and collateralized mortgage obligations 272,454 263,569 $ 303,137 $ 292,940 At June 30, 2018 , net unrealized gains on equity securities held at the end of the period are $654,000 . For the three and six months ended June 30, 2018 , proceeds from the sale of equity securities amounted to $4.8 million . For the three months ended June 30, 2017 , proceeds from sale of securities available for sale amounted to $168.2 million , gross realized gains amounted to $2.0 million , and gross realized losses amount to $1.0 million . For the six months ended June 30, 2017 , proceeds from sales of securities available for sale amounted to $213.1 million , gross realized gains amounted $2.2 million , and gross realized losses amounted to $2.3 million . Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: June 30, 2018 Less Than Twelve Months More Than Twelve Months Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (In thousands) Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ (244 ) $ 8,394 $ (1,068 ) $ 20,976 Government-sponsored mortgage-backed and collateralized mortgage obligations (2,066 ) 79,335 (5,995 ) 157,606 SBA asset-backed securities (141 ) 6,333 (691 ) 19,440 Total temporarily impaired held-to-maturity securities $ (2,451 ) $ 94,062 $ (7,754 ) $ 198,022 The Company continually reviews securities for the existence of other-than-temporary impairment ("OTTI"), taking into consideration current market conditions, the extent and nature of changes in fair value, issuer rating changes and trends, the credit worthiness of the obligor of the security, volatility of earnings, current analysts’ evaluations, the Company’s intent to sell the security, or whether it is more likely than not that the Company will be required to sell the security before its anticipated recovery, as well as other qualitative factors. The term “other-than-temporary” is not intended to indicate that the decline is permanent, but indicates that the prospects for a near-term recovery of value is not necessarily favorable, or that there is a lack of evidence to support a realizable value equal to or greater than the carrying value of the investment. At June 30, 2018 , multiple debt securities have unrealized losses with aggregate depreciation of approximately 3.4% from the Company’s amortized cost basis. The unrealized losses were primarily caused by interest rate fluctuations. It is expected that none of these securities would be settled at a price less than the par value of the investment. Because the decline in fair value is attributable to changes in interest rates and not to credit quality and it is more likely than not that the Company will recover their amortized cost bases by maturity, the Company does not consider these securities to be other-than-temporarily impaired at June 30, 2018 . Management has the ability and intent to hold the securities until maturity. December 31, 2017 Less Than Twelve Months More Than Twelve Months Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (In thousands) Securities Available for Sale: Temporarily impaired marketable equity securities $ (449 ) $ 4,310 $ (23 ) $ 443 Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ (109 ) $ 8,521 $ (785 ) $ 21,258 Government-sponsored mortgage-backed and collateralized mortgage obligations (1,563 ) 119,782 (1,874 ) 111,712 SBA asset-backed securities (34 ) 9,897 (295 ) 11,423 Total temporarily impaired securities held to maturity $ (1,706 ) $ 138,200 $ (2,954 ) $ 144,393

Loans and The Allowance for Loa

Loans and The Allowance for Loan Losses	6 Months Ended
	Jun. 30, 2018
Receivables [Abstract]
Loans and The Allowance for Loan Losses	LOANS AND THE ALLOWANCE FOR LOAN LOSSES A summary of the balances of loans follows: June 30, December 31, 2018 2017 (In thousands) Real estate: 1-4 family residential $ 985,901 $ 922,627 Home equity 71,956 80,662 Commercial real estate 824,731 834,264 Construction 88,337 91,050 1,970,925 1,928,603 Commercial business 268,963 253,509 Consumer 18,262 21,698 Total loans 2,258,150 2,203,810 Allowance for loan losses (20,125 ) (20,877 ) Discount and fair value adjustments on purchased loans (1,177 ) (1,477 ) Deferred loan costs and fees, net 4,898 4,691 Loans, net $ 2,241,746 $ 2,186,147 Activity in the allowance for loan losses for the three and six months ended June 30, 2018 and 2017 , by loan segment, follows: 1-4 Family Home Commercial Construction Commercial Consumer Total (In thousands) Three Months Ended June 30, 2018 Allowance at March 31, 2018 $ 5,099 $ 631 $ 9,511 $ 1,281 $ 3,353 $ 310 $ 20,185 Provision (credit) for loan losses 273 (28 ) (519 ) 198 178 (1 ) 101 Loans charged-off — — — — (153 ) (19 ) (172 ) Recoveries — — — — 11 — 11 Allowance at June 30, 2018 $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Three Months Ended June 30, 2017 Allowance at March 31, 2017 $ 5,000 $ 558 $ 8,333 $ 1,457 $ 3,126 $ 401 $ 18,875 Provision (credit) for loan losses 25 51 654 153 226 9 1,118 Loans charged-off (52 ) — — — — (24 ) (76 ) Recoveries — — — — — — — Allowance at June 30, 2017 $ 4,973 $ 609 $ 8,987 $ 1,610 $ 3,352 $ 386 $ 19,917 Six Months Ended June 30, 2018 Allowance at December 31, 2017 $ 5,076 $ 699 $ 9,584 $ 1,708 $ 3,473 $ 337 $ 20,877 Provision (credit) for loan losses 296 (96 ) (398 ) (229 ) 83 (15 ) (359 ) Loans charged-off — — (194 ) — (178 ) (40 ) (412 ) Recoveries — — — — 11 8 19 Allowance at June 30, 2018 $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Six Months Ended June 30, 2017 Allowance at December 31, 2016 $ 4,846 $ 537 $ 8,374 $ 1,353 $ 3,206 $ 434 $ 18,750 Provision (credit) for loan losses 105 72 613 257 137 (9 ) 1,175 Loans charged-off (52 ) — — — — (39 ) (91 ) Recoveries 74 — — — 9 — 83 Allowance at June 30, 2017 $ 4,973 $ 609 $ 8,987 $ 1,610 $ 3,352 $ 386 $ 19,917 Additional information pertaining to the allowance for loan losses at June 30, 2018 and December 31, 2017 is as follows: 1-4 Family Home Commercial Construction Commercial Consumer Total (In thousands) June 30, 2018 Allowance related to impaired loans $ 48 $ — $ — $ — $ — $ 7 $ 55 Allowance related to non-impaired loans 5,324 603 8,992 1,479 3,389 283 20,070 Total allowance for loan losses $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Impaired loans $ 5,860 $ 2,224 $ 2,357 $ — $ 179 $ 96 $ 10,716 Non-impaired loans 980,041 69,732 822,374 88,337 268,784 18,166 2,247,434 Total loans $ 985,901 $ 71,956 $ 824,731 $ 88,337 $ 268,963 $ 18,262 $ 2,258,150 December 31, 2017 Allowance related to impaired loans $ 80 $ — $ — $ — $ — $ 1 $ 81 Allowance related to non-impaired loans 4,996 699 9,584 1,708 3,473 336 20,796 Total allowance for loan losses $ 5,076 $ 699 $ 9,584 $ 1,708 $ 3,473 $ 337 $ 20,877 Impaired loans $ 5,949 $ 1,387 $ 4,744 $ — $ — $ 202 $ 12,282 Non-impaired loans 916,678 79,275 829,520 91,050 253,509 21,496 2,191,528 Total loans $ 922,627 $ 80,662 $ 834,264 $ 91,050 $ 253,509 $ 21,698 $ 2,203,810 The following is a summary of past due and non-accrual loans, by loan class, at June 30, 2018 and December 31, 2017 : 30-59 Days Past Due 60-89 Days Past Due Past Due 90 Days or More Total Past Due Loans on Non-accrual (In thousands) June 30, 2018 Real estate: 1-4 family residential $ 733 $ 425 $ 1,664 $ 2,822 $ 5,393 Home equity 677 — 605 1,282 2,224 Commercial real estate — — — — 2,357 Commercial business — — — — 179 Consumer 134 — 7 141 96 Total $ 1,544 $ 425 $ 2,276 $ 4,245 $ 10,249 December 31, 2017 Real estate: 1-4 family residential $ 381 $ 348 $ 2,184 $ 2,913 $ 5,190 Home equity 509 13 656 1,178 1,387 Commercial real estate — — 3,893 3,893 4,744 Consumer 107 7 92 206 202 Total $ 997 $ 368 $ 6,825 $ 8,190 $ 11,523 There were no loans past due 90 days or more and still accruing interest at June 30, 2018 and December 31, 2017 . The following is a summary of information pertaining to impaired loans by loan class at the dates indicated: Recorded Investment Unpaid Principal Balance Related Allowance June 30, 2018 (In thousands) Impaired loans without a valuation allowance: Real estate: 1-4 family residential $ 4,337 $ 4,733 $ — Home equity 2,224 2,407 — Commercial real estate 2,357 2,488 — Commercial business 179 325 — Consumer 89 101 — Total 9,186 10,054 — Impaired loans with a valuation allowance: 1-4 family residential 1,523 1,523 48 Consumer 7 7 7 Total 1,530 1,530 55 Total impaired loans $ 10,716 $ 11,584 $ 55 December 31, 2017 Impaired loans without a valuation allowance: Real estate: 1-4 family residential $ 4,501 $ 4,897 $ — Home equity 1,387 1,523 — Commercial real estate 4,744 5,206 — Commercial business — 11 — Consumer 191 243 — Total 10,823 11,880 — Impaired loans with a valuation allowance: Real estate: 1-4 family residential 1,448 1,448 80 Consumer 11 11 1 Total 1,459 1,459 81 Total impaired loans $ 12,282 $ 13,339 $ 81 The following tables set forth information regarding average balances and interest income recognized (the majority of which is on a cash basis) on impaired loans by class, for the periods indicated: Average Recorded Investment Interest Income Recognized Three Months Ended June 30, 2018 (In thousands) Real estate: 1-4 family residential $ 5,943 $ 72 Home equity 1,775 36 Commercial real estate 2,377 22 Commercial business 242 4 Consumer 94 1 Total $ 10,431 $ 135 Three Months Ended June 30, 2017 Real estate: 1-4 family residential $ 6,395 $ 82 Home equity 1,294 15 Commercial real estate 5,048 27 Commercial business 200 2 Consumer 287 4 Total $ 13,224 $ 130 Six Months Ended June 30, 2018 Real estate: 1-4 family residential $ 5,945 $ 150 Home equity 1,357 45 Commercial real estate 3,166 46 Commercial business 162 8 Consumer 147 3 Total $ 10,777 $ 252 Six Months Ended June 30, 2017 Real estate: 1-4 family residential $ 6,505 $ 160 Home equity 1,247 29 Commercial real estate 3,679 35 Commercial business 214 5 Consumer 249 5 Total $ 11,894 $ 234 No additional funds are committed to be advanced in connection with impaired loans. Troubled debt restructurings entered into during the three and six months ended June 30, 2018 are as follows: Three Months Ended June 30, 2018 Number of contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Real estate: Home equity 1 $ 359 $ 359 Total 1 $ 359 $ 359 Six Months Ended June 30, 2018 Number of contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Real estate: 1-4 family residential 3 $ 469 $ 475 Home equity 1 359 359 Commercial real estate 1 1,563 1,563 Total 5 $ 2,391 $ 2,397 There were no material troubled debt restructurings recorded during the three and six months ended June 30, 2017 . Loans modified during the three and six months ended June 30, 2018 were modified to capitalize past due interest for residential loans and extend interest only periods for commercial real estate loans. Credit Quality Information The Company utilizes a ten-grade internal loan rating system for all loans as follows: Loans rated 1 – 6 are considered “acceptable” rated loans that are performing as agreed, and generally require only routine supervision. Loans rated 7 are considered “special mention.” These loans are starting to show signs of potential weakness and are being closely monitored by management. Loans rated 8 are considered “substandard.” Generally, a loan is considered substandard if it is inadequately protected by the current net worth and paying capacity of the obligors and/or the collateral pledged. There is a distinct possibility that the Company will sustain some loss if the weakness is not corrected. Generally, all loans 90 days delinquent are rated 8. Loans rated 9 are considered “doubtful.” Serious problems exist to the point where a partial loss of principal is likely. Weakness is so pronounced that on the basis of current information, conditions and values, collection in full is highly improbable. Loans rated 10 are considered "loss" and the credit extended to the customer is considered uncollectible or of such little value that it does not warrant consideration as an active asset. The Company assigns a 6 risk-rating to otherwise performing, satisfactorily collateralized consumer and residential loans where the Bank becomes aware of deterioration in a FICO score or other indication of potential inability to service the debt. The Company assigns risk ratings of 7-10 to residential or consumer loans that have a well-defined weakness that may jeopardize the collection of the contractual principal and interest, are contractually past due 90 days or more or legal action has commenced against the borrower. All other residential mortgage and consumer loans have no risk rating. On an annual basis, or more often if needed, the Company formally reviews the ratings on all commercial and commercial construction loans. At least annually, the Company engages an independent third party to review a significant portion of loans within these segments. Management uses the results of these reviews as part of its annual review process. In addition, management utilizes delinquency reports, the watch list and other loan reports to monitor credit quality of other loan segments. The following tables present the Company’s loans by risk rating at June 30, 2018 and December 31, 2017 : 1-4 Family Residential Home Equity Commercial Real Estate Construction Commercial Business Consumer Total Loans (In thousands) June 30, 2018 Loans rated 1 - 6 $ 1,001 $ 335 $ 815,688 $ 88,337 $ 261,966 $ 3 $ 1,167,330 Loans rated 7 2,815 2,224 5,608 — 5,974 96 16,717 Loans rated 8 2,682 — 3,435 — 1,023 — 7,140 Loans rated 9 245 — — — — — 245 Loans rated 10 — — — — — — — Loans not rated 979,158 69,397 — — — 18,163 1,066,718 $ 985,901 $ 71,956 $ 824,731 $ 88,337 $ 268,963 $ 18,262 $ 2,258,150 December 31, 2017 Loans rated 1 - 6 $ 1,022 $ 270 $ 821,815 $ 91,050 $ 252,765 $ 3 $ 1,166,925 Loans rated 7 2,848 1,523 4,660 — 744 121 9,896 Loans rated 8 2,566 — 7,789 — — — 10,355 Loans rated 9 250 — — — — — 250 Loans rated 10 — — — — — — — Loans not rated 915,941 78,869 — — — 21,574 1,016,384 $ 922,627 $ 80,662 $ 834,264 $ 91,050 $ 253,509 $ 21,698 $ 2,203,810

Other Real Estate Owned

Other Real Estate Owned	6 Months Ended
	Jun. 30, 2018
Banking and Thrift [Abstract]
Other Real Estate Owned	OTHER REAL ESTATE OWNED Assets acquired through, or in lieu of, loan foreclosure are held for sale and are initially recorded at fair value, less cost to sell, at the date of foreclosure, establishing a new cost basis. Subsequent to foreclosure, valuations are periodically performed by management and the assets are carried at the lower of carrying amount or fair value less cost to sell. Revenue and expenses from operations, changes in the valuation allowance and any direct writedowns are included in net expenses from foreclosed assets. At June 30, 2018 , other real estate owned consists of one commercial real estate property that the Company foreclosed on during the six months ended June 30, 2018 . The balance was $3.6 million as of June 30, 2018 . There was no balance as of December 31, 2017 . Noninterest expenses applicable to foreclosed assets were $54,000 and $72,000 during the three and six months ended June 30, 2018 , respectively. Noninterest expenses applicable to foreclosed assets were $9,000 for the three and six months ended June 30, 2017 .

Derivatives

Derivatives	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	DERIVATIVES Interest Rate Swap Agreements The Company is party to derivative financial instruments in the normal course of business to manage exposure to fluctuations in interest rates and to meet the needs of commercial customers. These financial instruments have been generally limited to loan level interest rate swap agreements, which are entered into with counterparties that meet established credit standards. These transactions involve both credit and market risk. The notional amounts are amounts on which calculations, payments, and the value of the derivatives are based. Notional amounts do not represent direct credit exposures. The fair value of the derivative instruments is reflected on the Company’s consolidated balance sheet as other assets or accrued expenses and other liabilities as appropriate. Changes in the fair value of these agreements are recorded in miscellaneous income in the consolidated statements of net income. The table below presents information about derivative financial instruments not designated as hedging instruments at June 30, 2018 and December 31, 2017 . Derivative Gains Derivative Losses Notional Amount Fair Value Notional Amount Fair Value (In thousands) June 30, 2018 Economic hedges: Commercial loan level interest rate swap agreements $ 572,285 $ 15,308 $ 572,285 $ 15,308 Other contracts 37,350 28 53,931 18 Total derivatives $ 609,635 $ 15,336 $ 626,216 $ 15,326 December 31, 2017 Economic hedges: Commercial loan level interest rate swap agreements $ 582,388 $ 8,741 $ 582,388 $ 8,741 Other contracts 27,689 25 54,293 44 Total derivatives $ 610,077 $ 8,766 $ 636,681 $ 8,785 The Company is exposed to credit-related losses in the event of nonperformance by the counterparties to these agreements. The Company controls the credit risk of its financial contracts through credit approvals, limits and monitoring procedures, and does not expect any counterparties to fail their obligations. The Company has minimum collateral posting thresholds with certain of its interest rate swap derivative counterparties. Other contracts represent risk participation agreements on commercial loan level interest rate swap agreements. The Company has entered into risk participation agreements with the correspondent institutions to share in any interest rate swap gains or losses incurred as a result of the commercial loan customers’ termination of a loan level interest rate swap agreement prior to maturity. The Company records these risk participation agreements at fair value. Mortgage Banking Derivatives The Company enters into commitments to fund residential mortgage loans at specified rates and times in the future, with the intention that loans will subsequently be sold in the secondary market. Mortgage loan commitments are referred to as derivative loan commitments if the loan that will result from exercise of the commitment will be held for sale upon funding. These commitments are recognized at fair value on the consolidated balance sheet in other assets and other liabilities with changes in their fair values recorded in non-interest income. Outstanding loan commitments expose the Company to the risk that the price of the loans arising from exercise of the loan commitment might change from inception of the rate lock to funding of the loan due to changes in mortgage interest rates. If interest rates increase, the value of these loan commitments decreases. Conversely, if interest rates decrease, the value of these loan commitments increases. To protect against the price risk inherent in derivative loan commitments, the Company utilizes both "mandatory delivery" and "best efforts" forward loan sale commitments to mitigate the risk of potential decreases in the values of loans that would result from the exercise of the derivative loan commitments. Mandatory delivery contracts are accounted for as derivative instruments. Included in the mandatory delivery forward commitments are To Be Announced securities (“TBAs”). Mandatory delivery forward loan sale commitments are recognized at fair value on the consolidated balance sheet in other assets and other liabilities with changes in their fair values recorded in other non-interest income. With best effort contracts, the Company commits to deliver an individual mortgage loan of a specified principal amount and quality to an investor if the loan to the underlying borrower closes. Generally best efforts cash contracts have no pair off risk regardless of market movement. The price the investor will pay the seller for an individual loan is specified prior to the loan being funded (e.g., on the same day the lender commits to lend funds to a potential borrower). The Company expects that these best efforts forward loan sale commitments will experience a net neutral shift in fair value with related derivative loan commitments. With mandatory delivery contracts, the Company commits to deliver a certain principal amount of mortgage loans to an investor at a specified price on or before a specified date. If the Company fails to deliver the amount of mortgages necessary to fulfill the commitment by the specified date, it is obligated to pay a “pair-off” fee, based on then-current market prices, to the investor/counterparty to compensate the investor for the shortfall. Generally the Company makes this type of commitment once mortgage loans have been funded and are held for sale, in order to minimize the risk of failure to deliver the requisite volume of loans to the investor and paying pair-off fees as a result. The Company also sells TBA securities to offset potential changes in the fair value of derivative loan commitments. Generally the Company sells TBA securities upon entering derivative loan commitments for settlement in 30 to 90 days . The Company expects that mandatory delivery contracts, including TBA securities, will experience changes in fair value opposite to the changes in the fair value of derivative loan commitments. At June 30, 2018 , the Company had $14.4 million of interest rate lock commitments to borrowers and loans held for sale of $2.5 million with $17.0 million of forward commitments for the future delivery of residential mortgage loans on a best efforts basis. At June 30, 2018 , the Company had $27.9 million of interest rate lock commitments to borrowers and loans held for sale of $7.4 million with $35.3 million of forward commitments for the future delivery of residential mortgage loans on a mandatory delivery basis. Included in the forward commitments are open TBAs with a notional amount of $24.3 million and $14.5 million of closed hedge instruments that are not settled at June 30, 2018 . At December 31, 2017 , the Company had $16.4 million of loan commitments to borrowers and loans held for sale of $8.9 million with $25.3 million of forward commitments for the future delivery of residential mortgage loans on a best efforts basis. The Company did no t have any commitments under mandatory delivery at December 31, 2017 . The fair value of such commitments as of June 30, 2018 and December 31, 2017 are outlined below: Assets Liabilities Balance sheet location Fair Value Balance sheet location Fair Value (In thousands) June 30, 2018 Derivative loan commitments: Mortgage loan commitments best efforts Other assets $ 142 Other liabilities $ 46 Mortgage loan commitments mandatory delivery Other assets 323 Other liabilities — Total mortgage derivative commitments $ 465 $ 46 Forward loan sale commitments: Forward loan sale commitments best efforts Other assets $ 51 Other liabilities $ 17 Forward loan sale commitments mandatory delivery Other assets 15 Other liabilities 85 Total forward loan sale commitments $ 66 $ 102 Total $ 531 $ 148 December 31, 2017 Derivative loan commitments: Mortgage loan commitments best efforts Other assets $ 210 Other liabilities $ 36 Total mortgage derivative commitments $ 210 $ 36 Forward loan sale commitments: Forward loan sale commitments best efforts Other assets $ 22 Other liabilities $ 69 Total forward loan sale commitments $ 22 $ 69 Total $ 232 $ 105

Deposits

Deposits	6 Months Ended
	Jun. 30, 2018
Banking and Thrift [Abstract]
Deposits	DEPOSITS A summary of deposit balances, by type, is as follows: June 30, December 31, 2018 2017 (In thousands) NOW and demand $ 375,934 $ 381,316 Regular savings 213,205 221,004 Money market 628,718 646,603 Brokered money market 85,951 92,798 Total non-certificate accounts 1,303,808 1,341,721 Term certificates of $250,000 or more 164,081 134,649 Term certificates less than $250,000 361,506 313,733 Brokered term certificates 282,672 249,766 Total term certificate accounts 808,259 698,148 Total deposits $ 2,112,067 $ 2,039,869 At June 30, 2018 , the scheduled maturities of term certificate accounts, including brokered deposits, are as follows: Amount Weighted Average Rate (Dollars in thousands) Within 1 year $ 481,235 1.62 % 1-2 years 239,227 1.93 2-3 years 49,974 1.99 3-4 years 20,521 1.79 4 years and beyond 17,302 2.15 $ 808,259 1.75 %

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Determination of fair value The Company uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various assets and liabilities. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the asset or liability. Assets and liabilities measured at fair value on a recurring basis Assets and liabilities measured at fair value on a recurring basis are summarized below: Level 1 Level 2 Level 3 Total Fair Value (In thousands) June 30, 2018 Assets Equity securities, at fair value $ 5,331 $ — $ — $ 5,331 Derivative assets: Interest rate swap agreements — 15,336 — 15,336 Forward loan sale commitments - best efforts — — 51 51 Forward loan sale commitments - mandatory delivery — — 15 15 Mortgage loan commitments - best efforts — — 142 142 Mortgage loan commitments - mandatory delivery — — 323 323 Total assets $ 5,331 $ 15,336 $ 531 $ 21,198 Liabilities Derivative liabilities: Interest rate swap agreements $ — $ 15,326 $ — $ 15,326 Forward loan sale commitments - best efforts — — 17 17 Mortgage loan commitments - best efforts — — 46 46 Forward loan sale commitments-mandatory delivery — — 85 85 Total liabilities $ — $ 15,326 $ 148 $ 15,474 December 31, 2017 Assets Securities available for sale: Marketable equity securities $ 9,720 $ — $ — $ 9,720 Derivative assets: Interest rate swap agreements — 8,766 — 8,766 Forward loan sale commitments - best efforts — — 22 22 Mortgage loan commitments - best efforts — — 210 210 Total assets $ 9,720 $ 8,766 $ 232 $ 18,718 Liabilities Derivative liabilities: Interest rate swap agreements $ — $ 8,785 $ — $ 8,785 Forward loan sale commitments - best efforts — — 69 69 Mortgage loan commitments - best efforts — — 36 36 Total liabilities $ — $ 8,785 $ 105 $ 8,890 The following methods and assumptions were used by the Company in estimating fair value: Securities : All fair value measurements are obtained from a third-party pricing service and are not adjusted by management. The securities measured at fair value in Level 1 are based on quoted market prices in an active exchange market. These securities include U.S. Treasury securities and marketable equity securities. All other securities are measured at fair value in Level 2 based on pricing models that consider standard input factors such as observable market data, benchmark yields, interest rate volatilities, broker/dealer quotes, credit spreads and new issue data. Interest rate swap agreements : The fair values of interest rate swap agreements are based on a valuation model that uses primarily observable inputs, such as benchmark yield curves and interest rates and also include the value associated with counterparty credit risk. Credit risk adjustments consider factors such as the likelihood of default by the Company and its counterparties, its net exposures and remaining contractual life. To date, the Company has not realized any losses due to a counterparty's inability to pay any net uncollateralized position. Forward loan sale commitments and derivative loan commitments : Fair values of forward loan sale commitments and derivative loan commitments are based on changes in the fair values of the underlying mortgage loans from inception and, for derivative loan commitments, fair values also include the value of servicing, deferred origination fees/costs and the probability of such commitments being exercised. Significant management judgment and estimation is required in determining these fair value measurements. Assets measured at fair value on a non-recurring basis The Company may also be required, from time to time, to measure certain assets at fair value on a non-recurring basis in accordance with generally accepted accounting principles. These adjustments to fair value usually result from application of lower-of-cost-or-market accounting or write-downs of individual assets. There are no liabilities measured at fair value on a non-recurring basis. The following table summarizes the fair value hierarchy applicable to assets measured at fair value on a non-recurring basis: June 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 (In thousands) Impaired loans $ — $ — $ 1,606 $ — $ — $ 2,214 Other real estate owned — — 3,649 — — — $ — $ — $ 5,255 $ — $ — $ 2,214 The following table summarizes the total losses on assets measured at fair value on a non-recurring basis for the three and six months ended June 30, 2018 and 2017 . Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 (In thousands) Impaired loans $ (156 ) $ (86 ) $ (350 ) $ (9 ) Gains and losses applicable to impaired loans are based on the appraised value of the underlying collateral, discounted as necessary due to management’s estimates of changes in market conditions. The gains and losses applicable to impaired loans are not recorded as a direct adjustment to current earnings or comprehensive income, but rather as a component in determining the overall adequacy of the allowance for loan losses. Adjustments to the estimated fair value of impaired loans may result in increases or decreases to the provision for loan losses. 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) June 30, 2018 Financial assets: Cash and cash equivalents $ 51,949 $ 51,949 $ — $ — $ 51,949 Equity securities at fair value 5,331 5,331 — — 5,331 Securities held to maturity 303,137 — 292,940 — 292,940 Federal Home Loan Bank stock 14,375 — — 14,375 14,375 Loans and loans held for sale, net 2,251,751 — — 2,222,753 2,222,753 Accrued interest receivable 6,531 — — 6,531 6,531 Financial liabilities: Deposits 2,112,067 — — 2,106,630 2,106,630 Borrowings 200,000 — 198,890 — 198,890 On-balance sheet derivative financial instruments: Derivative assets: Interest rate swap agreements 15,336 — 15,336 — 15,336 Forward loan sale commitments-best efforts 51 — — 51 51 Forward loan sale commitments-mandatory delivery 15 — — 15 15 Mortgage loan commitments-best efforts 142 — — 142 142 Mortgage loan commitments-mandatory delivery 323 — — 323 323 Derivative liabilities: Interest rate swap agreements 15,326 — 15,326 — 15,326 Forward loan sale commitments-best efforts 17 — — 17 17 Mortgage loan commitments-best efforts 46 — — 46 46 Forward loan sale commitments-mandatory delivery 85 — — 85 85 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) December 31, 2017 Financial assets: Cash and cash equivalents $ 46,167 $ 46,167 $ — $ — $ 46,167 Securities available for sale 9,720 9,720 — — 9,720 Securities held to maturity 303,716 — 299,114 — 299,114 Federal Home Loan Bank stock 12,105 — — 12,105 12,105 Loans and loans held for sale 2,195,139 — — 2,174,871 2,174,871 Accrued interest receivable 6,438 — — 6,438 6,438 Financial liabilities: Deposits 2,039,869 — — 2,036,150 2,036,150 Borrowings 205,000 — 203,913 — 203,913 On-balance sheet derivative financial instruments: Derivative assets: Interest rate swap agreements 8,766 — 8,766 — 8,766 Forward loan sale commitments-best efforts 22 — — 22 22 Mortgage loan commitments-best efforts 210 — — 210 210 Derivative liabilities: Interest rate swap agreements 8,785 — 8,785 — 8,785 Forward loan sale commitments-best efforts 69 — — 69 69 Mortgage loan commitments-best efforts 36 — — 36 36

Comprehensive Income

Comprehensive Income	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Comprehensive Income	COMPREHENSIVE INCOME Accounting principles generally require that recognized revenues, expenses, gains and losses be included in net income. Although certain changes in assets and liabilities are reported as a separate component of stockholders' equity on the consolidated balance sheets, such items, along with net income, are components of comprehensive income. The components of accumulated other comprehensive loss, included in stockholders' equity, are as follows: June 30, December 31, 2018 2017 (In thousands) Securities available for sale: Net unrealized gain $ — $ 283 Tax effect — (140 ) Net-of-tax amount — 143 Securities held to maturity: Net unrealized gain on transferred securities 210 250 Tax effect (21 ) (66 ) Net-of-tax amount 189 184 Defined benefit pension plan: Unrecognized net actuarial loss (2,561 ) (2,694 ) Tax effect 533 914 Net-of-tax amount (2,028 ) (1,780 ) $ (1,839 ) $ (1,453 )

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Stockholders' Equity	STOCKHOLDERS' EQUITY Minimum regulatory capital requirements The Company (on a consolidated basis) and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory, and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s and the Bank’s consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and the Bank must meet specific capital guidelines that involve quantitative measures of their assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Prompt corrective action provisions are not applicable to bank holding companies. Federal banking regulations include minimum capital ratios as displayed in the following table. Additionally, community banking institutions must maintain a capital conservation buffer of common equity Tier 1 capital in an amount greater than 2.5% of total risk-weighted assets to avoid being subject to limitations on capital distributions and discretionary bonuses. The capital conservation buffer is being phased in over multiple years, with an initial phase-in of 0.625% . Beginning on January 1, 2018, the capital conservation buffer is 1.875% . Also, certain deductions from and adjustments to regulatory capital are being phased in over several years. Management believes that the Company will remain characterized as “well capitalized” throughout the phase-in periods. The application of the capital conservation buffer resulted in no limitations to payout of retained earnings as of June 30, 2018 . As of June 30, 2018 , the most recent notification from the Federal Deposit Insurance Corporation categorized the Bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized, an institution must maintain minimum ratios as set forth in the following tables. There are no conditions or events since the notification that management believes have changed the Bank's category. Management believes, as of June 30, 2018 and December 31, 2017 , that the Company and the Bank meet all capital adequacy requirements to which they are subject. The Company's and the Bank's actual capital amounts and ratios as of June 30, 2018 and December 31, 2017 are also presented in the following table. Actual Minimum Capital Requirement Minimum To Be Well Capitalized Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) Blue Hills Bancorp, Inc.: June 30, 2018 Total capital (to risk weighted assets) $ 413,430 18.8 % $ 176,112 8.0 % $ 220,140 10.0 % Tier 1 capital (to risk weighted assets) 393,305 17.9 132,084 6.0 176,112 8.0 Common equity Tier 1 (to risk weighted assets) 393,305 17.9 99,063 4.5 143,091 6.5 Tier 1 capital (to average assets) 393,305 14.9 105,775 4.0 132,219 5.0 December 31, 2017 Total capital (to risk weighted assets) $ 410,088 19.7 % $ 166,635 8.0 % $ 208,294 10.0 % Tier 1 capital (to risk weighted assets) 389,211 18.7 124,977 6.0 166,635 8.0 Common equity Tier 1 (to risk weighted assets) 389,211 18.7 93,732 4.5 135,391 6.5 Tier 1 capital (to average assets) 389,211 14.9 104,278 4.0 130,348 5.0 Blue Hills Bank: June 30, 2018 Total capital (to risk weighted assets) $ 357,224 16.2 % $ 176,025 8.0 % $ 220,032 10.0 % Tier 1 capital (to risk weighted assets) 337,099 15.3 132,019 6.0 176,025 8.0 Common equity Tier 1 (to risk weighted assets) 337,099 15.3 99,014 4.5 143,020 6.5 Tier 1 capital (to average assets) 337,099 12.8 105,673 4.0 132,092 5.0 December 31, 2017 Total capital (to risk weighted assets) $ 341,175 16.4 % $ 166,391 8.0 % $ 207,988 10.0 % Tier 1 capital (to risk weighted assets) 320,298 15.4 124,793 6.0 166,391 8.0 Common equity Tier 1 (to risk weighted assets) 320,298 15.4 93,595 4.5 135,192 6.5 Tier 1 capital (to average assets) 320,298 12.3 104,137 4.0 130,171 5.0 As a result of the recently enacted Economic Growth, Regulatory Relief, and Consumer Protection Act (the “Act”), banking regulatory agencies must adopt a revised definition of “well capitalized” for financial institutions and holding companies with assets of less than $10 billion and that are not determined to be ineligible by their primary federal regulator due to their risk profile (a “qualifying community bank”). The new definition will expand the ways that a qualifying community bank may meet its capital requirements and be deemed “well capitalized.” The new rule will establish a “community bank leverage ratio” equal to the tangible equity capital divided by the average total consolidated assets. A qualifying community bank that exceeds a to-be-determined threshold for this new leverage ratio, which regulators must set at between 8% and 10%, will be considered to be well capitalized and to have met generally applicable leverage capital requirements, generally applicable risk-based capital requirements, and any other capital or leverage requirements to which such financial institution or holding company is subject. In addition, as a result of the Act, the Federal Reserve Board is required to amend its small bank holding company and savings and loan holding company policy statement to provide that holding companies with consolidated assets of less than $3 billion that are (i) not engaged in significant nonbanking activities, (ii) do not conduct significant off-balance sheet activities, and (3) do not have a material amount of SEC-registered debt or equity securities, other than trust preferred securities, that contribute to an organization’s complexity, will no longer be subject to regulatory capital requirements, effective no later than November 2018.

Employee Stock Ownership Plan

Employee Stock Ownership Plan	6 Months Ended
	Jun. 30, 2018
Retirement Benefits [Abstract]
Employee Stock Ownership Plan	EMPLOYEE STOCK OWNERSHIP PLAN The Company maintains an Employee Stock Ownership Plan (“ESOP”) to provide eligible employees the opportunity to own Company stock. This plan is a tax-qualified retirement plan for the benefit of Company employees. Contributions are allocated to eligible participants on the basis of compensation, subject to federal tax limits. The number of shares committed to be released per year is 75,912 through 2043. Shares held by the ESOP include the following: June 30, 2018 December 31, 2017 Allocated 293,670 219,860 Committed to be allocated 37,644 75,912 Unallocated 1,936,053 1,973,699 2,267,367 2,269,471 The fair value of unallocated shares was $43.0 million and $39.7 million at June 30, 2018 and December 31, 2017 , respectively. Total compensation expense recognized in connection with the ESOP for the three months ended June 30, 2018 and 2017 was $397,000 and $343,000 , respectively. Total compensation expense recognized in connection with the ESOP for the six months ended June 30, 2018 and 2017 was $775,000 and $684,000 , respectively.

Earnings Per Common Share

Earnings Per Common Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	EARNINGS PER COMMON SHARE Basic earnings per common share represents income available to common stockholders divided by the weighted-average number of common shares outstanding during the period. Unallocated ESOP shares are not deemed outstanding for earnings per share calculations. Three Months Ended June 30, 2018 2017 (In thousands, except share amounts) Net income applicable to common stock $ 6,457 $ 3,868 Average number of common shares outstanding 26,870,770 26,859,345 Less: Average unallocated ESOP shares (1,945,516 ) (2,021,427 ) Less: Average unvested restricted stock awards (695,156 ) (885,475 ) Average number of common shares outstanding used to calculate basic earnings per common share 24,230,098 23,952,443 Effect of dilutive stock options 506,138 155,938 Effect of dilutive unvested restricted stock awards 255,722 238,172 Average number of common shares outstanding used to calculate diluted earnings per common share 24,991,958 24,346,553 Earnings per common share: Basic $ 0.27 $ 0.16 Diluted $ 0.26 $ 0.16 Six Months Ended June 30, 2018 2017 (In thousands, except share amounts) Net income applicable to common stock $ 13,040 $ 11,355 Average number of common shares outstanding 26,845,536 26,851,143 Less: Average unallocated ESOP shares (1,954,875 ) (2,030,786 ) Less: Average unvested restricted stock awards (689,333 ) (888,313 ) Average number of common shares outstanding used to calculate basic earnings per common share 24,201,328 23,932,044 Effect of dilutive stock options 469,213 147,665 Effect of dilutive unvested restricted stock awards 239,524 231,513 Average number of common shares outstanding used to calculate diluted earnings per common share 24,910,065 24,311,222 Earnings per common share: Basic $ 0.54 $ 0.47 Diluted $ 0.52 $ 0.47 Options for 550,634 and 552,950 shares were not included in the computation of diluted earnings per common share because to do so would have been anti-dilutive for the three and six months ended June 30, 2018 . Options for 384,100 were not included in the computation of diluted earnings per common share because to do so would have been anti-dilutive for the three and six months ended June 30, 2017 .

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION Under the Blue Hills Bancorp, Inc. 2015 Equity Incentive Plan (the "Equity Plan"), the Company may grant options, restricted stock, restricted units or performance awards to its directors, officers and employees. Both incentive stock options and non-qualified stock options may be granted under the Equity Plan, with the total shares reserved for options equaling 2,846,681 . Board members may only receive non-qualified stock options. The exercise price of each option equals the market price of the Company’s stock on the date of grant and the maximum term of each option is ten years. A total of 1,138,673 shares are reserved for awards of restricted stock or restricted units. The vast majority of options and awards vest ratably over five years. The fair value of shares awarded is based on the market price at the date of grant. Expense related to options and restricted stock granted to directors is recognized as directors' fees within noninterest expense. The Company has standard form agreements used for stock option and restricted stock awards. The standard form agreements used for the Chief Executive Officer and all other Executive Officers have previously been disclosed in Securities and Exchange Commission filings and generally provide that: (1) any unvested options or unvested restricted stock vest upon a Change in Control; and, that (2) any stock options which vest pursuant to a Change in Control, which is an event described in Section 280G of the Internal Revenue Code of 1986, will be cashed out at the difference between the acquisition price and the exercise price of the stock option. Stock Options The fair value of each option grant is estimated on the date of the grant using the Black-Scholes option-pricing model with the following assumptions: • Volatility is based on peer group volatility because the Company does not have a sufficient trading history. • Expected life represents the period of time that the option is expected to be outstanding, taking into account the contractual term, and the vesting period. • Expected dividend yield is based on the Company's history and expectation of dividend payouts. • The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for a period equivalent to the expected life of the option. The Company made the following awards of options to purchase shares of common stock during the six months ended June 30, 2018 : Options granted 145,000 Vesting period (years) 5 Term (years) 10 Fair value calculation assumptions: Expected volatility 26.47 % Expected life (years) 6.5 Expected dividend yield 3.21 % Risk free interest rate 2.39 % Weighted average grant date fair value $4.12 A summary of the status of the Company's stock option grants for the six months ended June 30, 2018 , is presented in the table below: Stock Option Awards Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2017 2,684,650 $ 14.70 Granted 145,000 20.70 Forfeited (74,440 ) 14.07 Exercised (49,330 ) 14.01 342,000 Outstanding at June 30, 2018 2,705,880 $ 15.05 7.59 $ 19,352,000 Exercisable at June 30, 2018 966,250 $ 14.39 7.31 $ 7,549,000 Unrecognized compensation cost inclusive of directors' options at June 30, 2018 $ 6,096,000 Weighted average remaining recognition period (years) 2.82 For the three months ended June 30, 2018 and 2017 , share-based compensation expense applicable to the stock options was $571,000 and $ 568,000 , respectively, and the recognized tax benefit related to this expense was $101,000 and $135,000 , respectively. For the six months ended June 30, 2018 and 2017 , share-based compensation expense applicable to the stock options was $1.1 million and $1.2 million , respectively, and the recognized tax benefit related to this expense was $203,000 and $290,000 . Restricted Stock Shares issued upon vesting may be either authorized but unissued shares or reacquired shares held by the Company. Any shares not issued because vesting requirements are not met will again be available for issuance under the plan. The fair market value of shares awarded, based on the market price at the date of grant, is recorded as unearned compensation and amortized over the applicable vesting period. Of the restricted shares granted to date, 40,000 are performance based, of which 12,000 have vested, 4,000 have been forfeited and 24,000 remain unvested. There were 2,000 performance shares forfeited during the six months ended June 30, 2018 . The following table presents the activity in non-vested stock awards under the Equity Plan for the six months ended June 30, 2018 : Outstanding Restricted Stock Awards Weighted Average Grant Price Nonvested stock awards at December 31, 2017 730,420 $ 15.11 Granted 36,500 20.70 Vested (48,749 ) 17.03 Forfeited (23,450 ) 14.07 Nonvested stock awards at June 30, 2018 694,721 $ 15.31 Unrecognized compensation cost inclusive of directors' awards at June 30, 2018 $8,566,000 Weighted average remaining recognition period (years) 2.86 For the three months ended June 30, 2018 and 2017 , share-based compensation expense applicable to restricted stock awards was $ 795,000 and $770,000 , respectively, and the recognized tax benefit related to this expense was $207,000 and $269,000 , respectively. For the six months ended June 30, 2018 and 2017, share-based compensation expense applicable to restricted stock awards was $1.6 million and $1.6 million , respectively, and the recognized tax benefit related to this expense was $409,000 and $574,000 respectively.

Basis of Presentation and Con23

Basis of Presentation and Consolidation (Policies)	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim consolidated financial statements include the accounts of Blue Hills Bancorp, Inc. (the "Company"), its wholly-owned subsidiaries, Blue Hills Funding Corporation and Blue Hills Bank (the "Bank"), the principal operating entity, and the Bank's wholly-owned subsidiaries, B.H. Security Corporation, HP Security Corporation and 1196 Corporation, which are Massachusetts security corporations, and Nantucket Property Acquisition Company LLC, the Bank's subsidiary that holds other real estate owned. All significant intercompany balances and transactions have been eliminated in consolidation. The unaudited consolidated financial statements of the Company presented herein have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information and pursuant to the rules of the Securities and Exchange Commission ("SEC") for quarterly reports on Form 10-Q and Article 10 of Regulation S-X and do not include all of the information and note disclosures required by GAAP for a complete set of financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) and disclosures necessary for the fair presentation of the accompanying consolidated financial statements have been included. Interim results are not necessarily reflective of the results of the year. The accompanying unaudited financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017, included in the Company's annual report on Form 10-K. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and reported amounts of revenues and expenses during the reporting 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 valuation of deferred tax assets.
Loan policies	Loan policies The Company has historically granted mortgage and consumer loans to its customers and a substantial portion of the loan portfolio consists of mortgage loans in communities including and near the locations of its banking offices. The ability of the Company’s debtors to honor their contracts is dependent upon the real estate and general economic conditions in these areas. The Company’s loan portfolio includes 1-4 family residential real estate, home equity, commercial real estate, construction, commercial business, and consumer segments. Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off generally are reported at their outstanding unpaid principal balances adjusted for the allowance for loan losses, charge-offs, deferred origination fees and costs, and discounts on purchased loans. Interest income is accrued on the unpaid principal balance. Deferred loan origination fees/costs and discounts on purchased loans are recognized as an adjustment of the related loan yield using the interest method. It is the policy of the Company to discontinue the accrual of interest on loans past due in excess of 90 days, unless the loan is well-secured and in the process of collection. Accrual may be discontinued sooner when in the judgment of management, the ultimate collectability of the principal or interest becomes doubtful. Upon discontinuance of accrual, all interest previously accrued is reversed against interest income. Past due status is based on contractual terms of the loan. The interest on non-accrual loans is accounted for on the cash-basis until qualifying for return to accrual. Loans are returned to accrual status when all the principal and interest amounts contractually due have been current for six consecutive months and future payments are reasonably assured.
Allowance for Loan Losses	Allowance for loan losses The allowance for loan losses is based on the size and the composition of the loan portfolio, delinquency levels, loss experience, economic conditions and other factors related to the collectability of the loan portfolio. Loss experience is updated at least quarterly with consideration given to unusual circumstances in the portfolio. Loan losses are charged against the allowance when management believes the uncollectability of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The allowance for loan losses is evaluated regularly by management and reflects consideration of all significant factors that affect the collectability of the loan portfolio. The evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available. It is the intention of management to maintain an allowance that is prudently commensurate with the growth in the loan portfolio. The allowance consists of general and allocated components, as further described below. General component The general component of the allowance for loan losses is based on a combination of the Company's own loss history and an extrapolated historical loss experience based on FDIC data for depository institutions with assets of one billion to five billion dollars dating back to 2010, adjusted for qualitative and environmental factors including changes to lending policies and procedures, economic and business conditions, portfolio characteristics, staff experience, problem loan trends, collateral values, concentrations and the competitive, legal and regulatory environment. The qualitative factors are determined based on the various risk characteristics of each loan segment. Risk characteristics relevant to each portfolio segment are as follows: Residential real estate - The Company does not generally originate loans with a loan-to-value ratio greater than 80 percent and does not generally grant loans that would be classified as subprime upon origination. When the Company does extend credit either on a first- or second-lien basis at a loan-to-value ratio greater than 80 percent , such loans are supported by either mortgage insurance or state guarantee programs. All loans in this segment are collateralized by owner-occupied, 1-4 family residential real estate and repayment is dependent on the credit quality of the individual borrower. The health of the national and state economy, including unemployment rates and housing prices, will have an effect on the credit quality of loans in this segment. Home equity - Loans in this segment are generally secured by first or second liens on residential real estate. Repayment is dependent on the credit quality of the individual borrower. The Company evaluates each loan application based on factors including the borrower’s credit score, income, length of employment, and other factors to establish the creditworthiness of the borrower. Commercial real estate - Loans in this segment include investment real estate and are generally secured by assignments of leases, real estate collateral and owner-occupied properties. In cases where there is a concentration of exposure to a single large tenant, underwriting standards include analysis of the tenant’s ability to support lease payments over the duration of the loan. The underlying cash flows generated by the properties may be adversely impacted by a downturn in the economy due to increased vacancy rates, which in turn can have an effect on the credit quality in this segment. Payments on loans secured by income-producing properties often depend on the successful operation and management of the properties. Management continually monitors the cash flows of these loans. Construction - Loans in this segment primarily include real estate development loans for which payment is derived from permanent financing or sale of the property. Credit risk is affected by cost overruns, time to sell at an adequate price, and market conditions. Commercial business - Loans in this segment are generally secured by business assets, including accounts receivable, inventory, real estate and intangible assets. Strict underwriting standards include considerations of the borrower’s ability to support the debt service requirements from the underlying historical and projected cash flows of the business, collateral values, the borrower’s credit history and the ultimate collectability of the de bt. Economic conditions, real estate values, commodity prices, unemployment trends and other factors will affect the credit quality of loans in these segments. Consumer - Loans in this segment primarily include used classic and collector automobile loans. A significant portion of the used automobile loan portfolio is comprised of geographically diverse loans originated by and purchased from a third party, who also provides collection services and shares equally in any losses incurred. Allocated component The allocated component relates to loans that are considered impaired. Impairment is measured by either the present value of expected future cash flows discounted at the loan’s effective interest rate or the fair value of the collateral if the loan is collateral dependent. An allowance is established when the discounted cash flows (or collateral value) of the impaired loan is lower than the carrying value of that loan. A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Management reviews all loan types for individual impairment. Factors considered by management in determining impairment include payment status, collateral value, and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on a case-by-case basis, taking into consideration all of the circumstances surrounding the loan and the borrower, including the length of the delay, the reasons for the delay, the borrower’s prior payment record, and the amount of the shortfall in relation to the principal and interest owed. The Company periodically may agree to modify the contractual terms of loans. When a loan is modified and a concession is made to a borrower experiencing financial difficulty, the modification is considered a troubled debt restructuring (“TDR”). All TDRs are initially classified as impaired and generally remain impaired for the remaining life of the loan. The impaired classification may be removed if the borrower demonstrates compliance with the modified terms and the restructuring agreement specifies an interest rate equal to that which would be provided to a borrower with similar credit at the time of restructuring.
Recent Accounting Standards Updates	Accounting Standards Adopted in the Period In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The purpose of this Update is to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The Company adopted the Update on January 1, 2018. The effect of applying the provisions of this Update resulted in an increase to retained earnings and a corresponding decrease in accumulated other comprehensive loss in the amount of $279,000 . Effective January 1, 2018, the Company adopted ASU 2016-01, Financial Instruments – Overall, (Subtopic 825-10) . The amendments in this Update address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Targeted improvements to generally accepted accounting principles include the requirement for equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income and the elimination of the requirement for public business entities to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost. The Update also requires Companies to utilize an "exit price" fair value methodology when measuring the fair value of financial instruments. The cumulative effect of applying the provisions of this Update resulted in an increase to retained earnings and a corresponding decrease to accumulated other comprehensive loss in the amount of $173,000 . Effective January 1, 2018, the Company adopted ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory . The amendments in this Update require an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . The amendments in this Update require that in the statement of cash flows, amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers . This Update provides a revenue recognition framework for any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets unless those contracts are within the scope of other accounting standards. The Company's revenue relates principally to financial instruments, which are explicitly excluded from the scope of the new guidance. The Company adopted this Update on January 1, 2018 and the impact to the consolidated financial statements upon adopting was not material. Effective January 1, 2018, the Company adopted ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting which amends the scope of modification accounting for share-based payment arrangements. The Update provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. The Update should be applied prospectively to awards modified on or after the effective date. The impact to the consolidated financial statements upon adopting was not material. Recently Issued In June 2018 the FASB issued ASU 2018-07 Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The Updates expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. An entity should apply the requirements of Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the attribution of cost (that is, the period of time over which share-based payment awards vest and the pattern of cost recognition over that period). The Update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company does not anticipate the adoption of ASU 2018-07 will have a material impact on its consolidated financial statements. Future Application of Accounting Pronouncements Previously Issued In March 2018, the FASB issued ASU 2018-04, Investments-Debt Securities (Topic 320) and Regulated Operations (Topic 980) . Amendments to SEC paragraph Pursuant to SEC Staff Accounting Bulletin No. 177 and SEC Release No 33-9273, the amendment of ASU 2018-04 adds, amends and supersedes variance paragraphs that contain SEC guidance in ASC 320, Investments-Debt Securities and ASC 980, Regulated Operations. The Company does not anticipate the adoption of ASU 2018-04 will have a material impact on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities . The purpose of this Update is to better align a company’s financial reporting for hedging activities with the economic objectives of those activities. This Update is effective for public business entities for fiscal years beginning after December 15, 2018, with early adoption, including adoption in an interim period permitted. The Update requires a modified retrospective transition method in which the Company will recognize the cumulative effect of the change on the opening balance of each affected component of equity in the statement of financial position as of the date of adoption. While the Company continues to assess all potential impacts of the standard, we currently expect the adoption to have an immaterial impact on our consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . This Update is intended to improve financial reporting about leasing transactions and the key provision impacting the Company is the requirement for a lessee to record a right-to-use asset and a liability representing the obligation to make lease payments for long-term operating leases. Additionally, the Update includes additional quantitative and qualitative disclosures required by lessees and lessors to help users better understand the amount, timing, and uncertainty of cash flows arising from leases. This Update is effective for fiscal years beginning after December 31, 2018, and interim periods within those fiscal years. Lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The modified retrospective approach includes a number of optional practical expedients that entities may elect to apply as well as transition guidance specific to nonstandard leasing transactions. The Company's assets and liabilities will increase based on the present value of remaining lease payments for leases in place at the adoption date; however, this is not expected to be material to the Company's results of operations or financial position. Future lease commitments as of at June 30, 2018 amounted to $20.5 million . In June, 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which removes the thresholds that companies apply to measure credit losses on financial instruments measured at amortized cost, such as loans, receivables, and held-to-maturity debt securities. Under current U.S. GAAP, companies generally recognize credit losses when it is probable that the loss has been incurred. The revised guidance will remove previously established recognition thresholds based on probability, and will require companies to recognize an allowance for credit losses for the difference between the amortized cost basis of a financial instrument and the net amount that the company expects to collect over the instrument’s contractual life. ASU 2016-13 also amends the credit loss measurement guidance for available-for-sale debt securities and will require that credit losses be recorded through an allowance for credit losses. Additionally, this Update may reduce the carrying value of the Company's held-to-maturity investment securities as it will require an allowance on the expected losses over the life of these securities to be recorded upon adoption. The ASU is effective for public business entities fiscal years beginning after December 15, 2019 and for interim periods within those fiscal years. Any increase in our allowance for loan losses or expenses may have a material adverse effect on our financial condition and results of operations. The Company is actively working through the provisions of the Update. Management has established a steering committee which has identified the methodologies and the additional data requirements necessary to implement the Update and has engaged a third-party software service provider to assist in the Company's implementation.

Securities (Tables)

Securities (Tables)	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Securities Available for Sale: Marketable equity securities $ 9,437 $ 755 $ (472 ) $ 9,720 Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ 30,673 $ — $ (894 ) $ 29,779 Government-sponsored mortgage-backed and collateralized mortgage obligations 244,668 30 (3,437 ) 241,261 SBA asset-backed securities 28,375 28 (329 ) 28,074 Total securities held to maturity $ 303,716 $ 58 $ (4,660 ) $ 299,114
Held-to-maturity Securities	December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Securities Available for Sale: Marketable equity securities $ 9,437 $ 755 $ (472 ) $ 9,720 Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ 30,673 $ — $ (894 ) $ 29,779 Government-sponsored mortgage-backed and collateralized mortgage obligations 244,668 30 (3,437 ) 241,261 SBA asset-backed securities 28,375 28 (329 ) 28,074 Total securities held to maturity $ 303,716 $ 58 $ (4,660 ) $ 299,114 The amortized cost and estimated fair value of securities available for sale and securities held to maturity, with gross unrealized gains and losses, follows: June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ 30,683 $ — $ (1,312 ) $ 29,371 Government-sponsored mortgage-backed and collateralized mortgage obligations 245,849 8 (8,061 ) 237,796 SBA asset-backed securities 26,605 — (832 ) 25,773 Total securities held to maturity $ 303,137 $ 8 $ (10,205 ) $ 292,940
Investments Classified by Contractual Maturity Date	The amortized cost and estimated fair value of debt securities by contractual maturity at June 30, 2018 are included in the following table. Expected maturities will differ from contractual maturities because the issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Based on expected maturities, the mortgage and asset-backed securities and collateralized mortgage obligations, included below, have a 4.0 year weighted average duration. Amortized Cost Fair Value (In thousands) After 1 year through 5 years $ 18,635 $ 17,999 After 5 years through 10 years 12,048 11,372 30,683 29,371 Mortgage and asset-backed securities and collateralized mortgage obligations 272,454 263,569 $ 303,137 $ 292,940
Unrealized Gain (Loss) and Fair Value of Investments - Available-for-sale Securities	December 31, 2017 Less Than Twelve Months More Than Twelve Months Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (In thousands) Securities Available for Sale: Temporarily impaired marketable equity securities $ (449 ) $ 4,310 $ (23 ) $ 443
Unrealized Gain (Loss) and Fair Value of Investments - Held-to-maturity Securities	Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, follows: June 30, 2018 Less Than Twelve Months More Than Twelve Months Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value (In thousands) Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ (244 ) $ 8,394 $ (1,068 ) $ 20,976 Government-sponsored mortgage-backed and collateralized mortgage obligations (2,066 ) 79,335 (5,995 ) 157,606 SBA asset-backed securities (141 ) 6,333 (691 ) 19,440 Total temporarily impaired held-to-maturity securities $ (2,451 ) $ 94,062 $ (7,754 ) $ 198,022 Securities Held to Maturity: Debt securities: Government-sponsored enterprises $ (109 ) $ 8,521 $ (785 ) $ 21,258 Government-sponsored mortgage-backed and collateralized mortgage obligations (1,563 ) 119,782 (1,874 ) 111,712 SBA asset-backed securities (34 ) 9,897 (295 ) 11,423 Total temporarily impaired securities held to maturity $ (1,706 ) $ 138,200 $ (2,954 ) $ 144,393

Loans and The Allowance for L25

Loans and The Allowance for Loan Losses (Tables)	6 Months Ended
	Jun. 30, 2018
Receivables [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	A summary of the balances of loans follows: June 30, December 31, 2018 2017 (In thousands) Real estate: 1-4 family residential $ 985,901 $ 922,627 Home equity 71,956 80,662 Commercial real estate 824,731 834,264 Construction 88,337 91,050 1,970,925 1,928,603 Commercial business 268,963 253,509 Consumer 18,262 21,698 Total loans 2,258,150 2,203,810 Allowance for loan losses (20,125 ) (20,877 ) Discount and fair value adjustments on purchased loans (1,177 ) (1,477 ) Deferred loan costs and fees, net 4,898 4,691 Loans, net $ 2,241,746 $ 2,186,147
Activity in Allowance for Loan Losses	Activity in the allowance for loan losses for the three and six months ended June 30, 2018 and 2017 , by loan segment, follows: 1-4 Family Home Commercial Construction Commercial Consumer Total (In thousands) Three Months Ended June 30, 2018 Allowance at March 31, 2018 $ 5,099 $ 631 $ 9,511 $ 1,281 $ 3,353 $ 310 $ 20,185 Provision (credit) for loan losses 273 (28 ) (519 ) 198 178 (1 ) 101 Loans charged-off — — — — (153 ) (19 ) (172 ) Recoveries — — — — 11 — 11 Allowance at June 30, 2018 $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Three Months Ended June 30, 2017 Allowance at March 31, 2017 $ 5,000 $ 558 $ 8,333 $ 1,457 $ 3,126 $ 401 $ 18,875 Provision (credit) for loan losses 25 51 654 153 226 9 1,118 Loans charged-off (52 ) — — — — (24 ) (76 ) Recoveries — — — — — — — Allowance at June 30, 2017 $ 4,973 $ 609 $ 8,987 $ 1,610 $ 3,352 $ 386 $ 19,917 Six Months Ended June 30, 2018 Allowance at December 31, 2017 $ 5,076 $ 699 $ 9,584 $ 1,708 $ 3,473 $ 337 $ 20,877 Provision (credit) for loan losses 296 (96 ) (398 ) (229 ) 83 (15 ) (359 ) Loans charged-off — — (194 ) — (178 ) (40 ) (412 ) Recoveries — — — — 11 8 19 Allowance at June 30, 2018 $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Six Months Ended June 30, 2017 Allowance at December 31, 2016 $ 4,846 $ 537 $ 8,374 $ 1,353 $ 3,206 $ 434 $ 18,750 Provision (credit) for loan losses 105 72 613 257 137 (9 ) 1,175 Loans charged-off (52 ) — — — — (39 ) (91 ) Recoveries 74 — — — 9 — 83 Allowance at June 30, 2017 $ 4,973 $ 609 $ 8,987 $ 1,610 $ 3,352 $ 386 $ 19,917
Allowance for Credit Losses on Financing Receivables	Additional information pertaining to the allowance for loan losses at June 30, 2018 and December 31, 2017 is as follows: 1-4 Family Home Commercial Construction Commercial Consumer Total (In thousands) June 30, 2018 Allowance related to impaired loans $ 48 $ — $ — $ — $ — $ 7 $ 55 Allowance related to non-impaired loans 5,324 603 8,992 1,479 3,389 283 20,070 Total allowance for loan losses $ 5,372 $ 603 $ 8,992 $ 1,479 $ 3,389 $ 290 $ 20,125 Impaired loans $ 5,860 $ 2,224 $ 2,357 $ — $ 179 $ 96 $ 10,716 Non-impaired loans 980,041 69,732 822,374 88,337 268,784 18,166 2,247,434 Total loans $ 985,901 $ 71,956 $ 824,731 $ 88,337 $ 268,963 $ 18,262 $ 2,258,150 December 31, 2017 Allowance related to impaired loans $ 80 $ — $ — $ — $ — $ 1 $ 81 Allowance related to non-impaired loans 4,996 699 9,584 1,708 3,473 336 20,796 Total allowance for loan losses $ 5,076 $ 699 $ 9,584 $ 1,708 $ 3,473 $ 337 $ 20,877 Impaired loans $ 5,949 $ 1,387 $ 4,744 $ — $ — $ 202 $ 12,282 Non-impaired loans 916,678 79,275 829,520 91,050 253,509 21,496 2,191,528 Total loans $ 922,627 $ 80,662 $ 834,264 $ 91,050 $ 253,509 $ 21,698 $ 2,203,810
Past Due Financing Receivables	The following is a summary of past due and non-accrual loans, by loan class, at June 30, 2018 and December 31, 2017 : 30-59 Days Past Due 60-89 Days Past Due Past Due 90 Days or More Total Past Due Loans on Non-accrual (In thousands) June 30, 2018 Real estate: 1-4 family residential $ 733 $ 425 $ 1,664 $ 2,822 $ 5,393 Home equity 677 — 605 1,282 2,224 Commercial real estate — — — — 2,357 Commercial business — — — — 179 Consumer 134 — 7 141 96 Total $ 1,544 $ 425 $ 2,276 $ 4,245 $ 10,249 December 31, 2017 Real estate: 1-4 family residential $ 381 $ 348 $ 2,184 $ 2,913 $ 5,190 Home equity 509 13 656 1,178 1,387 Commercial real estate — — 3,893 3,893 4,744 Consumer 107 7 92 206 202 Total $ 997 $ 368 $ 6,825 $ 8,190 $ 11,523
Impaired Financing Receivables	The following tables set forth information regarding average balances and interest income recognized (the majority of which is on a cash basis) on impaired loans by class, for the periods indicated: Average Recorded Investment Interest Income Recognized Three Months Ended June 30, 2018 (In thousands) Real estate: 1-4 family residential $ 5,943 $ 72 Home equity 1,775 36 Commercial real estate 2,377 22 Commercial business 242 4 Consumer 94 1 Total $ 10,431 $ 135 Three Months Ended June 30, 2017 Real estate: 1-4 family residential $ 6,395 $ 82 Home equity 1,294 15 Commercial real estate 5,048 27 Commercial business 200 2 Consumer 287 4 Total $ 13,224 $ 130 Six Months Ended June 30, 2018 Real estate: 1-4 family residential $ 5,945 $ 150 Home equity 1,357 45 Commercial real estate 3,166 46 Commercial business 162 8 Consumer 147 3 Total $ 10,777 $ 252 Six Months Ended June 30, 2017 Real estate: 1-4 family residential $ 6,505 $ 160 Home equity 1,247 29 Commercial real estate 3,679 35 Commercial business 214 5 Consumer 249 5 Total $ 11,894 $ 234 The following is a summary of information pertaining to impaired loans by loan class at the dates indicated: Recorded Investment Unpaid Principal Balance Related Allowance June 30, 2018 (In thousands) Impaired loans without a valuation allowance: Real estate: 1-4 family residential $ 4,337 $ 4,733 $ — Home equity 2,224 2,407 — Commercial real estate 2,357 2,488 — Commercial business 179 325 — Consumer 89 101 — Total 9,186 10,054 — Impaired loans with a valuation allowance: 1-4 family residential 1,523 1,523 48 Consumer 7 7 7 Total 1,530 1,530 55 Total impaired loans $ 10,716 $ 11,584 $ 55 December 31, 2017 Impaired loans without a valuation allowance: Real estate: 1-4 family residential $ 4,501 $ 4,897 $ — Home equity 1,387 1,523 — Commercial real estate 4,744 5,206 — Commercial business — 11 — Consumer 191 243 — Total 10,823 11,880 — Impaired loans with a valuation allowance: Real estate: 1-4 family residential 1,448 1,448 80 Consumer 11 11 1 Total 1,459 1,459 81 Total impaired loans $ 12,282 $ 13,339 $ 81
Troubled Debt Restructurings	Troubled debt restructurings entered into during the three and six months ended June 30, 2018 are as follows: Three Months Ended June 30, 2018 Number of contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Real estate: Home equity 1 $ 359 $ 359 Total 1 $ 359 $ 359 Six Months Ended June 30, 2018 Number of contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Real estate: 1-4 family residential 3 $ 469 $ 475 Home equity 1 359 359 Commercial real estate 1 1,563 1,563 Total 5 $ 2,391 $ 2,397
Financing Receivable Credit Quality Indicators	The following tables present the Company’s loans by risk rating at June 30, 2018 and December 31, 2017 : 1-4 Family Residential Home Equity Commercial Real Estate Construction Commercial Business Consumer Total Loans (In thousands) June 30, 2018 Loans rated 1 - 6 $ 1,001 $ 335 $ 815,688 $ 88,337 $ 261,966 $ 3 $ 1,167,330 Loans rated 7 2,815 2,224 5,608 — 5,974 96 16,717 Loans rated 8 2,682 — 3,435 — 1,023 — 7,140 Loans rated 9 245 — — — — — 245 Loans rated 10 — — — — — — — Loans not rated 979,158 69,397 — — — 18,163 1,066,718 $ 985,901 $ 71,956 $ 824,731 $ 88,337 $ 268,963 $ 18,262 $ 2,258,150 December 31, 2017 Loans rated 1 - 6 $ 1,022 $ 270 $ 821,815 $ 91,050 $ 252,765 $ 3 $ 1,166,925 Loans rated 7 2,848 1,523 4,660 — 744 121 9,896 Loans rated 8 2,566 — 7,789 — — — 10,355 Loans rated 9 250 — — — — — 250 Loans rated 10 — — — — — — — Loans not rated 915,941 78,869 — — — 21,574 1,016,384 $ 922,627 $ 80,662 $ 834,264 $ 91,050 $ 253,509 $ 21,698 $ 2,203,810

Derivatives (Tables)

Derivatives (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Interest Rate Derivatives	The table below presents information about derivative financial instruments not designated as hedging instruments at June 30, 2018 and December 31, 2017 . Derivative Gains Derivative Losses Notional Amount Fair Value Notional Amount Fair Value (In thousands) June 30, 2018 Economic hedges: Commercial loan level interest rate swap agreements $ 572,285 $ 15,308 $ 572,285 $ 15,308 Other contracts 37,350 28 53,931 18 Total derivatives $ 609,635 $ 15,336 $ 626,216 $ 15,326 December 31, 2017 Economic hedges: Commercial loan level interest rate swap agreements $ 582,388 $ 8,741 $ 582,388 $ 8,741 Other contracts 27,689 25 54,293 44 Total derivatives $ 610,077 $ 8,766 $ 636,681 $ 8,785
Summary of Fair Value and Location of Mortgage Loan and Forward Loan Sale Commitments	The fair value of such commitments as of June 30, 2018 and December 31, 2017 are outlined below: Assets Liabilities Balance sheet location Fair Value Balance sheet location Fair Value (In thousands) June 30, 2018 Derivative loan commitments: Mortgage loan commitments best efforts Other assets $ 142 Other liabilities $ 46 Mortgage loan commitments mandatory delivery Other assets 323 Other liabilities — Total mortgage derivative commitments $ 465 $ 46 Forward loan sale commitments: Forward loan sale commitments best efforts Other assets $ 51 Other liabilities $ 17 Forward loan sale commitments mandatory delivery Other assets 15 Other liabilities 85 Total forward loan sale commitments $ 66 $ 102 Total $ 531 $ 148 December 31, 2017 Derivative loan commitments: Mortgage loan commitments best efforts Other assets $ 210 Other liabilities $ 36 Total mortgage derivative commitments $ 210 $ 36 Forward loan sale commitments: Forward loan sale commitments best efforts Other assets $ 22 Other liabilities $ 69 Total forward loan sale commitments $ 22 $ 69 Total $ 232 $ 105

Deposits (Tables)

Deposits (Tables)	6 Months Ended
	Jun. 30, 2018
Banking and Thrift [Abstract]
Schedule of Deposit Balances	A summary of deposit balances, by type, is as follows: June 30, December 31, 2018 2017 (In thousands) NOW and demand $ 375,934 $ 381,316 Regular savings 213,205 221,004 Money market 628,718 646,603 Brokered money market 85,951 92,798 Total non-certificate accounts 1,303,808 1,341,721 Term certificates of $250,000 or more 164,081 134,649 Term certificates less than $250,000 361,506 313,733 Brokered term certificates 282,672 249,766 Total term certificate accounts 808,259 698,148 Total deposits $ 2,112,067 $ 2,039,869
Schedule of Contractual Maturities of Deposits and Weighted Average Rate	At June 30, 2018 , the scheduled maturities of term certificate accounts, including brokered deposits, are as follows: Amount Weighted Average Rate (Dollars in thousands) Within 1 year $ 481,235 1.62 % 1-2 years 239,227 1.93 2-3 years 49,974 1.99 3-4 years 20,521 1.79 4 years and beyond 17,302 2.15 $ 808,259 1.75 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis are summarized below: Level 1 Level 2 Level 3 Total Fair Value (In thousands) June 30, 2018 Assets Equity securities, at fair value $ 5,331 $ — $ — $ 5,331 Derivative assets: Interest rate swap agreements — 15,336 — 15,336 Forward loan sale commitments - best efforts — — 51 51 Forward loan sale commitments - mandatory delivery — — 15 15 Mortgage loan commitments - best efforts — — 142 142 Mortgage loan commitments - mandatory delivery — — 323 323 Total assets $ 5,331 $ 15,336 $ 531 $ 21,198 Liabilities Derivative liabilities: Interest rate swap agreements $ — $ 15,326 $ — $ 15,326 Forward loan sale commitments - best efforts — — 17 17 Mortgage loan commitments - best efforts — — 46 46 Forward loan sale commitments-mandatory delivery — — 85 85 Total liabilities $ — $ 15,326 $ 148 $ 15,474 December 31, 2017 Assets Securities available for sale: Marketable equity securities $ 9,720 $ — $ — $ 9,720 Derivative assets: Interest rate swap agreements — 8,766 — 8,766 Forward loan sale commitments - best efforts — — 22 22 Mortgage loan commitments - best efforts — — 210 210 Total assets $ 9,720 $ 8,766 $ 232 $ 18,718 Liabilities Derivative liabilities: Interest rate swap agreements $ — $ 8,785 $ — $ 8,785 Forward loan sale commitments - best efforts — — 69 69 Mortgage loan commitments - best efforts — — 36 36 Total liabilities $ — $ 8,785 $ 105 $ 8,890
Fair Value Measurements, Nonrecurring	The following table summarizes the fair value hierarchy applicable to assets measured at fair value on a non-recurring basis: June 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 (In thousands) Impaired loans $ — $ — $ 1,606 $ — $ — $ 2,214 Other real estate owned — — 3,649 — — — $ — $ — $ 5,255 $ — $ — $ 2,214 The following table summarizes the total losses on assets measured at fair value on a non-recurring basis for the three and six months ended June 30, 2018 and 2017 . Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 (In thousands) Impaired loans $ (156 ) $ (86 ) $ (350 ) $ (9 )
Fair Value, by Balance Sheet Grouping	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) June 30, 2018 Financial assets: Cash and cash equivalents $ 51,949 $ 51,949 $ — $ — $ 51,949 Equity securities at fair value 5,331 5,331 — — 5,331 Securities held to maturity 303,137 — 292,940 — 292,940 Federal Home Loan Bank stock 14,375 — — 14,375 14,375 Loans and loans held for sale, net 2,251,751 — — 2,222,753 2,222,753 Accrued interest receivable 6,531 — — 6,531 6,531 Financial liabilities: Deposits 2,112,067 — — 2,106,630 2,106,630 Borrowings 200,000 — 198,890 — 198,890 On-balance sheet derivative financial instruments: Derivative assets: Interest rate swap agreements 15,336 — 15,336 — 15,336 Forward loan sale commitments-best efforts 51 — — 51 51 Forward loan sale commitments-mandatory delivery 15 — — 15 15 Mortgage loan commitments-best efforts 142 — — 142 142 Mortgage loan commitments-mandatory delivery 323 — — 323 323 Derivative liabilities: Interest rate swap agreements 15,326 — 15,326 — 15,326 Forward loan sale commitments-best efforts 17 — — 17 17 Mortgage loan commitments-best efforts 46 — — 46 46 Forward loan sale commitments-mandatory delivery 85 — — 85 85 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total (In thousands) December 31, 2017 Financial assets: Cash and cash equivalents $ 46,167 $ 46,167 $ — $ — $ 46,167 Securities available for sale 9,720 9,720 — — 9,720 Securities held to maturity 303,716 — 299,114 — 299,114 Federal Home Loan Bank stock 12,105 — — 12,105 12,105 Loans and loans held for sale 2,195,139 — — 2,174,871 2,174,871 Accrued interest receivable 6,438 — — 6,438 6,438 Financial liabilities: Deposits 2,039,869 — — 2,036,150 2,036,150 Borrowings 205,000 — 203,913 — 203,913 On-balance sheet derivative financial instruments: Derivative assets: Interest rate swap agreements 8,766 — 8,766 — 8,766 Forward loan sale commitments-best efforts 22 — — 22 22 Mortgage loan commitments-best efforts 210 — — 210 210 Derivative liabilities: Interest rate swap agreements 8,785 — 8,785 — 8,785 Forward loan sale commitments-best efforts 69 — — 69 69 Mortgage loan commitments-best efforts 36 — — 36 36

Comprehensive Income (Tables)

Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The components of accumulated other comprehensive loss, included in stockholders' equity, are as follows: June 30, December 31, 2018 2017 (In thousands) Securities available for sale: Net unrealized gain $ — $ 283 Tax effect — (140 ) Net-of-tax amount — 143 Securities held to maturity: Net unrealized gain on transferred securities 210 250 Tax effect (21 ) (66 ) Net-of-tax amount 189 184 Defined benefit pension plan: Unrecognized net actuarial loss (2,561 ) (2,694 ) Tax effect 533 914 Net-of-tax amount (2,028 ) (1,780 ) $ (1,839 ) $ (1,453 )

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	The Company's and the Bank's actual capital amounts and ratios as of June 30, 2018 and December 31, 2017 are also presented in the following table. Actual Minimum Capital Requirement Minimum To Be Well Capitalized Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) Blue Hills Bancorp, Inc.: June 30, 2018 Total capital (to risk weighted assets) $ 413,430 18.8 % $ 176,112 8.0 % $ 220,140 10.0 % Tier 1 capital (to risk weighted assets) 393,305 17.9 132,084 6.0 176,112 8.0 Common equity Tier 1 (to risk weighted assets) 393,305 17.9 99,063 4.5 143,091 6.5 Tier 1 capital (to average assets) 393,305 14.9 105,775 4.0 132,219 5.0 December 31, 2017 Total capital (to risk weighted assets) $ 410,088 19.7 % $ 166,635 8.0 % $ 208,294 10.0 % Tier 1 capital (to risk weighted assets) 389,211 18.7 124,977 6.0 166,635 8.0 Common equity Tier 1 (to risk weighted assets) 389,211 18.7 93,732 4.5 135,391 6.5 Tier 1 capital (to average assets) 389,211 14.9 104,278 4.0 130,348 5.0 Blue Hills Bank: June 30, 2018 Total capital (to risk weighted assets) $ 357,224 16.2 % $ 176,025 8.0 % $ 220,032 10.0 % Tier 1 capital (to risk weighted assets) 337,099 15.3 132,019 6.0 176,025 8.0 Common equity Tier 1 (to risk weighted assets) 337,099 15.3 99,014 4.5 143,020 6.5 Tier 1 capital (to average assets) 337,099 12.8 105,673 4.0 132,092 5.0 December 31, 2017 Total capital (to risk weighted assets) $ 341,175 16.4 % $ 166,391 8.0 % $ 207,988 10.0 % Tier 1 capital (to risk weighted assets) 320,298 15.4 124,793 6.0 166,391 8.0 Common equity Tier 1 (to risk weighted assets) 320,298 15.4 93,595 4.5 135,192 6.5 Tier 1 capital (to average assets) 320,298 12.3 104,137 4.0 130,171 5.0

Employee Stock Ownership Plan (

Employee Stock Ownership Plan (Tables)	6 Months Ended
	Jun. 30, 2018
Retirement Benefits [Abstract]
Employee Stock Ownership Plan (ESOP) Disclosures	Shares held by the ESOP include the following: June 30, 2018 December 31, 2017 Allocated 293,670 219,860 Committed to be allocated 37,644 75,912 Unallocated 1,936,053 1,973,699 2,267,367 2,269,471

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Three Months Ended June 30, 2018 2017 (In thousands, except share amounts) Net income applicable to common stock $ 6,457 $ 3,868 Average number of common shares outstanding 26,870,770 26,859,345 Less: Average unallocated ESOP shares (1,945,516 ) (2,021,427 ) Less: Average unvested restricted stock awards (695,156 ) (885,475 ) Average number of common shares outstanding used to calculate basic earnings per common share 24,230,098 23,952,443 Effect of dilutive stock options 506,138 155,938 Effect of dilutive unvested restricted stock awards 255,722 238,172 Average number of common shares outstanding used to calculate diluted earnings per common share 24,991,958 24,346,553 Earnings per common share: Basic $ 0.27 $ 0.16 Diluted $ 0.26 $ 0.16 Six Months Ended June 30, 2018 2017 (In thousands, except share amounts) Net income applicable to common stock $ 13,040 $ 11,355 Average number of common shares outstanding 26,845,536 26,851,143 Less: Average unallocated ESOP shares (1,954,875 ) (2,030,786 ) Less: Average unvested restricted stock awards (689,333 ) (888,313 ) Average number of common shares outstanding used to calculate basic earnings per common share 24,201,328 23,932,044 Effect of dilutive stock options 469,213 147,665 Effect of dilutive unvested restricted stock awards 239,524 231,513 Average number of common shares outstanding used to calculate diluted earnings per common share 24,910,065 24,311,222 Earnings per common share: Basic $ 0.54 $ 0.47 Diluted $ 0.52 $ 0.47

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The Company made the following awards of options to purchase shares of common stock during the six months ended June 30, 2018 : Options granted 145,000 Vesting period (years) 5 Term (years) 10 Fair value calculation assumptions: Expected volatility 26.47 % Expected life (years) 6.5 Expected dividend yield 3.21 % Risk free interest rate 2.39 % Weighted average grant date fair value $4.12
Schedule of Share-based Compensation, Stock Options, Activity	A summary of the status of the Company's stock option grants for the six months ended June 30, 2018 , is presented in the table below: Stock Option Awards Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2017 2,684,650 $ 14.70 Granted 145,000 20.70 Forfeited (74,440 ) 14.07 Exercised (49,330 ) 14.01 342,000 Outstanding at June 30, 2018 2,705,880 $ 15.05 7.59 $ 19,352,000 Exercisable at June 30, 2018 966,250 $ 14.39 7.31 $ 7,549,000 Unrecognized compensation cost inclusive of directors' options at June 30, 2018 $ 6,096,000 Weighted average remaining recognition period (years) 2.82
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table presents the activity in non-vested stock awards under the Equity Plan for the six months ended June 30, 2018 : Outstanding Restricted Stock Awards Weighted Average Grant Price Nonvested stock awards at December 31, 2017 730,420 $ 15.11 Granted 36,500 20.70 Vested (48,749 ) 17.03 Forfeited (23,450 ) 14.07 Nonvested stock awards at June 30, 2018 694,721 $ 15.31 Unrecognized compensation cost inclusive of directors' awards at June 30, 2018 $8,566,000 Weighted average remaining recognition period (years) 2.86

Basis of Presentation and Con34

Basis of Presentation and Consolidation - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Retained earnings
Subsidiary or Equity Method Investee [Line Items]
Cumulative effect on change in accounting principle			$ (27,000)
ASU 2018-02 | Retained earnings
Subsidiary or Equity Method Investee [Line Items]
Cumulative effect on change in accounting principle		$ 279,000
ASU 2016-01 | Retained earnings
Subsidiary or Equity Method Investee [Line Items]
Cumulative effect on change in accounting principle		$ 173,000
1-4 Family Residential
Subsidiary or Equity Method Investee [Line Items]
Origination covenants, maximum loan-to-value ratio (greater than) (percent)	80.00%

Accounting Standards Updates -

Accounting Standards Updates - Narrative (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future lease commitments	$ 20,500,000
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2)			$ (27,000)
Retained earnings | ASU 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2)		$ 279,000
Retained earnings | ASU 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle ASU 2016-01 (Note 2)		$ 173,000

Securities - Available-for-sale

Securities - Available-for-sale Securities (Details) $ in Thousands	Dec. 31, 2017USD ($)
Marketable equity securities
Amortized Cost	$ 9,437
Gross Unrealized Gains	755
Gross Unrealized Losses	(472)
Fair Value	$ 9,720

Securities - Held-to-maturity S

Securities - Held-to-maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt securities:
Amortized Cost	$ 303,137	$ 303,716
Gross Unrealized Gains	8	58
Gross Unrealized Losses	(10,205)	(4,660)
Fair Value	292,940	299,114
Government-sponsored enterprises
Debt securities:
Amortized Cost	30,683	30,673
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,312)	(894)
Fair Value	29,371	29,779
Government-sponsored mortgage-backed and collateralized mortgage obligations
Debt securities:
Amortized Cost	245,849	244,668
Gross Unrealized Gains	8	30
Gross Unrealized Losses	(8,061)	(3,437)
Fair Value	237,796	241,261
SBA asset-backed securities
Debt securities:
Amortized Cost	26,605	28,375
Gross Unrealized Gains	0	28
Gross Unrealized Losses	(832)	(329)
Fair Value	$ 25,773	$ 28,074

Securities - Schedule of Contra

Securities - Schedule of Contractual Maturities of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
After 1 year through 5 years, Held to Maturity, Amortized Cost	$ 18,635
After 5 years through 10 years, Held to Maturity, Amortized Cost	12,048
Single Maturity Date, Held to Maturity, Amortized Cost	30,683
Mortgage- and asset-backed securities and collateralized mortgage obligations - Amortized Basis	272,454
Amortized Cost	303,137	$ 303,716
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
After 1 year through 5 years, Held to Maturity, Fair Value	17,999
After 5 years through 10 years, Held to Maturity, Fair Value	11,372
Single Maturity Date, Held to Maturity, Fair Value	29,371
Mortgage- and asset-backed securities and collateralized mortgage obligations - Fair Value	263,569
Held-to-maturity securities, total debt securities	$ 292,940	$ 299,114

Securities - Available-for-sa39

Securities - Available-for-sale Securities Unrealized Loss (Details) $ in Thousands	Dec. 31, 2017USD ($)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months	$ (449)
Gross Unrealized Losses - More than twelve months	(23)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months	4,310
Fair Value - More than twelve months	$ 443

Securities - Held-to-maturity40

Securities - Held-to-maturity Securities Unrealized Loss (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months	$ (2,451)	$ (1,706)
Gross Unrealized Losses - More than twelve months	(7,754)	(2,954)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months	94,062	138,200
Fair Value - More than twelve months	198,022	144,393
Total mortgage- and other asset-backed securities
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months	(244)
Gross Unrealized Losses - More than twelve months	(1,068)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months	8,394
Fair Value - More than twelve months	20,976
Municipal bonds
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months	(2,066)
Gross Unrealized Losses - More than twelve months	(5,995)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months	79,335
Fair Value - More than twelve months	157,606
Government-sponsored enterprises
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months		(109)
Gross Unrealized Losses - More than twelve months		(785)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months		8,521
Fair Value - More than twelve months		21,258
Government-sponsored mortgage-backed and collateralized mortgage obligations
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months		(1,563)
Gross Unrealized Losses - More than twelve months		(1,874)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months		119,782
Fair Value - More than twelve months		111,712
SBA asset-backed securities
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Gross Unrealized Losses - Less than twelve months	(141)	(34)
Gross Unrealized Losses - More than twelve months	(691)	(295)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than twelve months	6,333	9,897
Fair Value - More than twelve months	$ 19,440	$ 11,423

Securities - Narrative (Details

Securities - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from sale of equity securities	$ 4,772		$ 4,772	$ 0
Mortgage and asset-backed securities and collateralized mortgage obligations, weighted average duration			4 years
Net unrealized gains on equity securities	$ 654
Proceeds from sale of available-for-sale securities		$ 168,200	$ 0	213,084
Available-for-sale securities, gross realized gains		2,000		2,200
Available-for-sale securities, gross realized losses		$ (1,000)		$ (2,300)
Held-to-maturity securities, depreciation, percentage of amortized cost basis	3.40%		3.40%

Loans and The Allowance for L42

Loans and The Allowance for Loan Losses - Summary of Loan Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 2,258,150		$ 2,203,810
Allowance for loan losses	(20,125)	$ (20,185)	(20,877)	$ (19,917)	$ (18,875)	$ (18,750)
Discount and fair value adjustments on purchased loans	(1,177)		(1,477)
Deferred loan costs and fees, net	4,898		4,691
Loans, net	2,241,746		2,186,147
Consumer and Commercial Portfolio Segment | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	88,337		91,050
Allowance for loan losses	(1,479)	(1,281)	(1,708)	(1,610)	(1,457)	(1,353)
Consumer, Excluding Consumer Other Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,970,925		1,928,603
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	985,901		922,627
Allowance for loan losses	(5,372)	(5,099)	(5,076)	(4,973)	(5,000)	(4,846)
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	71,956		80,662
Allowance for loan losses	(603)	(631)	(699)	(609)	(558)	(537)
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	824,731		834,264
Allowance for loan losses	(8,992)	(9,511)	(9,584)	(8,987)	(8,333)	(8,374)
Commercial business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	268,963		253,509
Allowance for loan losses	(3,389)	(3,353)	(3,473)	(3,352)	(3,126)	(3,206)
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,262		21,698
Allowance for loan losses	$ (290)	$ (310)	$ (337)	$ (386)	$ (401)	$ (434)

Loans and The Allowance for L43

Loans and The Allowance for Loan Losses - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	$ 20,185	$ 18,875	$ 20,877	$ 18,750
Provision (credit) for loan losses	101	1,118	(359)	1,175
Loans charged-off	(172)	(76)	(412)	(91)
Recoveries	11	0	19	83
Loans and Leases Receivable, Ending Allowance	20,125	19,917	20,125	19,917
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	5,099	5,000	5,076	4,846
Provision (credit) for loan losses	273	25	296	105
Loans charged-off	0	(52)	0	(52)
Recoveries	0	0	0	74
Loans and Leases Receivable, Ending Allowance	5,372	4,973	5,372	4,973
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	631	558	699	537
Provision (credit) for loan losses	(28)	51	(96)	72
Loans charged-off	0	0	0	0
Recoveries	0	0	0	0
Loans and Leases Receivable, Ending Allowance	603	609	603	609
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	9,511	8,333	9,584	8,374
Provision (credit) for loan losses	(519)	654	(398)	613
Loans charged-off	0	0	(194)	0
Recoveries	0	0	0	0
Loans and Leases Receivable, Ending Allowance	8,992	8,987	8,992	8,987
Consumer and Commercial Portfolio Segment | Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	1,281	1,457	1,708	1,353
Provision (credit) for loan losses	198	153	(229)	257
Loans charged-off	0	0	0	0
Recoveries	0	0	0	0
Loans and Leases Receivable, Ending Allowance	1,479	1,610	1,479	1,610
Commercial business
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	3,353	3,126	3,473	3,206
Provision (credit) for loan losses	178	226	83	137
Loans charged-off	(153)	0	(178)	0
Recoveries	11	0	11	9
Loans and Leases Receivable, Ending Allowance	3,389	3,352	3,389	3,352
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans and Leases Receivable, Beginning Allowance	310	401	337	434
Provision (credit) for loan losses	(1)	9	(15)	(9)
Loans charged-off	(19)	(24)	(40)	(39)
Recoveries	0	0	8	0
Loans and Leases Receivable, Ending Allowance	$ 290	$ 386	$ 290	$ 386

Loans and The Allowance for L44

Loans and The Allowance for Loan Losses - Additional Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	$ 55		$ 81
Allowance related to non-impaired loans	20,070		20,796
Total allowance for loan losses	20,125	$ 20,185	20,877	$ 19,917	$ 18,875	$ 18,750
Impaired loans	10,716		12,282
Non-impaired loans	2,247,434		2,191,528
Total loans	2,258,150		2,203,810
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	48		80
Allowance related to non-impaired loans	5,324		4,996
Total allowance for loan losses	5,372	5,099	5,076	4,973	5,000	4,846
Impaired loans	5,860		5,949
Non-impaired loans	980,041		916,678
Total loans	985,901		922,627
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	0		0
Allowance related to non-impaired loans	603		699
Total allowance for loan losses	603	631	699	609	558	537
Impaired loans	2,224		1,387
Non-impaired loans	69,732		79,275
Total loans	71,956		80,662
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	0		0
Allowance related to non-impaired loans	8,992		9,584
Total allowance for loan losses	8,992	9,511	9,584	8,987	8,333	8,374
Impaired loans	2,357		4,744
Non-impaired loans	822,374		829,520
Total loans	824,731		834,264
Consumer and Commercial Portfolio Segment | Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	0		0
Allowance related to non-impaired loans	1,479		1,708
Total allowance for loan losses	1,479	1,281	1,708	1,610	1,457	1,353
Impaired loans	0		0
Non-impaired loans	88,337		91,050
Total loans	88,337		91,050
Commercial business
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	0		0
Allowance related to non-impaired loans	3,389		3,473
Total allowance for loan losses	3,389	3,353	3,473	3,352	3,126	3,206
Impaired loans	179		0
Non-impaired loans	268,784		253,509
Total loans	268,963		253,509
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance related to impaired loans	7		1
Allowance related to non-impaired loans	283		336
Total allowance for loan losses	290	$ 310	337	$ 386	$ 401	$ 434
Impaired loans	96		202
Non-impaired loans	18,166		21,496
Total loans	$ 18,262		$ 21,698

Loans and The Allowance for L45

Loans and The Allowance for Loan Losses - Summary of Past Due and Non-accrual loans, by class (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 4,245	$ 8,190
Loans on Non-accrual	10,249	11,523
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,544	997
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	425	368
Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,276	6,825
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,822	2,913
Loans on Non-accrual	5,393	5,190
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,282	1,178
Loans on Non-accrual	2,224	1,387
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	3,893
Loans on Non-accrual	2,357	4,744
Consumer, Excluding Consumer Other Portfolio Segment | 30-59 Days Past Due | 1-4 Family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	733	381
Consumer, Excluding Consumer Other Portfolio Segment | 30-59 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	677	509
Consumer, Excluding Consumer Other Portfolio Segment | 30-59 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Consumer, Excluding Consumer Other Portfolio Segment | 60-89 Days Past Due | 1-4 Family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	425	348
Consumer, Excluding Consumer Other Portfolio Segment | 60-89 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	13
Consumer, Excluding Consumer Other Portfolio Segment | 60-89 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Past Due 90 Days or More | 1-4 Family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,664	2,184
Consumer, Excluding Consumer Other Portfolio Segment | Past Due 90 Days or More | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	605	656
Consumer, Excluding Consumer Other Portfolio Segment | Past Due 90 Days or More | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	3,893
Commercial business
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0
Loans on Non-accrual	179
Commercial business | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0
Commercial business | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0
Commercial business | Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	141	206
Loans on Non-accrual	96	202
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	134	107
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	7
Consumer | Past Due 90 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 7	$ 92

Loans and The Allowance for L46

Loans and The Allowance for Loan Losses - Summary of Impaired Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Recorded Investment
Recorded Investment, without valuation allowance	$ 9,186	$ 10,823
Recorded Investment, with a valuation allowance	1,530	1,459
Recorded Investment, total	10,716	12,282
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	10,054	11,880
Unpaid Principal Balance, with a valuation allowance	1,530	1,459
Unpaid Principal Balance, total	11,584	13,339
Related Allowance	55	81
1-4 Family Residential
Recorded Investment
Recorded Investment, with a valuation allowance	1,523	1,448
Unpaid Principal Balance
Unpaid Principal Balance, with a valuation allowance	1,523	1,448
Related Allowance	48	80
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Recorded Investment
Recorded Investment, without valuation allowance	4,337	4,501
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	4,733	4,897
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Recorded Investment
Recorded Investment, without valuation allowance	2,224	1,387
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	2,407	1,523
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Recorded Investment
Recorded Investment, without valuation allowance	2,357	4,744
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	2,488	5,206
Commercial business
Recorded Investment
Recorded Investment, without valuation allowance	179	0
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	325	11
Consumer
Recorded Investment
Recorded Investment, without valuation allowance	89	191
Recorded Investment, with a valuation allowance	7	11
Unpaid Principal Balance
Unpaid Principal Balance, without a valuation allowance	101	243
Unpaid Principal Balance, with a valuation allowance	7	11
Related Allowance	$ 7	$ 1

Loans and The Allowance for L47

Loans and The Allowance for Loan Losses - Summary of Average Recorded Investments and Interest Income of Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 10,431	$ 13,224	$ 10,777	$ 11,894
Interest Income Recognized	135	130	252	234
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	5,943	6,395	5,945	6,505
Interest Income Recognized	72	82	150	160
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,775	1,294	1,357	1,247
Interest Income Recognized	36	15	45	29
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,377	5,048	3,166	3,679
Interest Income Recognized	22	27	46	35
Consumer
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	94	287	147	249
Interest Income Recognized	1	4	3	5
Commercial business
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	242	200	162	214
Interest Income Recognized	$ 4	$ 2	$ 8	$ 5

Loans and The Allowance for L48

Loans and The Allowance for Loan Losses - Summary of Troubled Debt Restructurings (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2018USD ($)contract	Jun. 30, 2018USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	5
Pre-Modification Outstanding Recorded Investment	$ 359,000	$ 2,391,000
Post-Modification Outstanding Recorded Investment	$ 359,000	$ 2,397,000
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of contracts | contract		1
Pre-Modification Outstanding Recorded Investment		$ 1,563,000
Post-Modification Outstanding Recorded Investment		$ 1,563,000
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Modifications [Line Items]
Number of contracts | contract		3
Pre-Modification Outstanding Recorded Investment		$ 469,000
Post-Modification Outstanding Recorded Investment		$ 475,000
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	1
Pre-Modification Outstanding Recorded Investment	$ 359,000	$ 359,000
Post-Modification Outstanding Recorded Investment	$ 359,000	$ 359,000

Loans and The Allowance for L49

Loans and The Allowance for Loan Losses - Summary of Loan by Risk Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 2,258,150	$ 2,203,810
Loans rated 1 - 6
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,167,330	1,166,925
Loans rated 7
Financing Receivable, Recorded Investment [Line Items]
Total loans	16,717	9,896
Loans rated 8
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,140	10,355
Loans rated 9
Financing Receivable, Recorded Investment [Line Items]
Total loans	245	250
Loans rated 10
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loans not rated
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,066,718	1,016,384
Consumer, Excluding Consumer Other Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,970,925	1,928,603
Consumer, Excluding Consumer Other Portfolio Segment | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	985,901	922,627
Consumer, Excluding Consumer Other Portfolio Segment | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	71,956	80,662
Consumer, Excluding Consumer Other Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	824,731	834,264
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 1 - 6 | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,001	1,022
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 1 - 6 | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	335	270
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 1 - 6 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	815,688	821,815
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 7 | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,815	2,848
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 7 | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,224	1,523
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 7 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,608	4,660
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 8 | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,682	2,566
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 8 | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,435	7,789
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 9 | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	245	250
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 9 | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 9 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 10 | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 10 | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans rated 10 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer, Excluding Consumer Other Portfolio Segment | Loans not rated | 1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	979,158	915,941
Consumer, Excluding Consumer Other Portfolio Segment | Loans not rated | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	69,397	78,869
Consumer, Excluding Consumer Other Portfolio Segment | Loans not rated | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer and Commercial Portfolio Segment | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	88,337	91,050
Consumer and Commercial Portfolio Segment | Loans rated 1 - 6 | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	88,337	91,050
Consumer and Commercial Portfolio Segment | Loans rated 7 | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer and Commercial Portfolio Segment | Loans rated 8 | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer and Commercial Portfolio Segment | Loans rated 9 | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer and Commercial Portfolio Segment | Loans rated 10 | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer and Commercial Portfolio Segment | Loans not rated | Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial business
Financing Receivable, Recorded Investment [Line Items]
Total loans	268,963	253,509
Commercial business | Loans rated 1 - 6
Financing Receivable, Recorded Investment [Line Items]
Total loans	261,966	252,765
Commercial business | Loans rated 7
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,974	744
Commercial business | Loans rated 8
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,023	0
Commercial business | Loans rated 9
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial business | Loans rated 10
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial business | Loans not rated
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	18,262	21,698
Consumer | Loans rated 1 - 6
Financing Receivable, Recorded Investment [Line Items]
Total loans	3	3
Consumer | Loans rated 7
Financing Receivable, Recorded Investment [Line Items]
Total loans	96	121
Consumer | Loans rated 8
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer | Loans rated 9
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer | Loans rated 10
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Consumer | Loans not rated
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 18,163	$ 21,574

Other Real Estate Owned - Narra

Other Real Estate Owned - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)property	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)property	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Banking and Thrift [Abstract]
Other real estate owned properties | property	1		1
Other real estate owned	$ 3,649,000		$ 3,649,000		$ 0
Noninterest expenses applicable to foreclosed assets	$ 54,000	$ 9,000	$ 72,000	$ 9,000

Derivatives - Derivative Financ

Derivatives - Derivative Financial Instruments Not Designated as hedging Instruments (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Gains, notional amount	$ 609,635	$ 610,077
Derivative Gains, fair value	15,336	8,766
Derivative Losses, notional amount	626,216	636,681
Derivative Losses, fair value	15,326	8,785
Commercial loan level interest rate swap agreements
Derivatives, Fair Value [Line Items]
Derivative Gains, notional amount	572,285	582,388
Derivative Gains, fair value	15,308	8,741
Derivative Losses, notional amount	572,285	582,388
Derivative Losses, fair value	15,308	8,741
Other contracts
Derivatives, Fair Value [Line Items]
Derivative Gains, notional amount	37,350	27,689
Derivative Gains, fair value	28	25
Derivative Losses, notional amount	53,931	54,293
Derivative Losses, fair value	$ 18	$ 44

Derivatives - Narrative (Detail

Derivatives - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
TBA Securities
Derivative [Line Items]
Notional amount	$ 24,300,000
Closed hedge not settled	14,500,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Best Efforts
Derivative [Line Items]
Notional amount	17,000,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Loans Held-for-sale - Best Efforts
Derivative [Line Items]
Notional amount	2,500,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Borrowers - Best Efforts
Derivative [Line Items]
Notional amount	$ 14,400,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Mandatory Delivery
Derivative [Line Items]
Notional amount		$ 35,300,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Borrowers - Mandatory Delivery
Derivative [Line Items]
Notional amount		27,900,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments - Loans Held-for-sale - Mandatory Delivery
Derivative [Line Items]
Notional amount		7,400,000
Not Designated as Hedging Instrument | Mortgage loan commitments best efforts
Derivative [Line Items]
Notional amount		25,300,000
Not Designated as Hedging Instrument | Mortgage Loan Commitments - Borrowers - Best Efforts
Derivative [Line Items]
Notional amount		16,400,000
Not Designated as Hedging Instrument | Mortgage Loan Commitments - Loans Held-for-sale - Best Efforts
Derivative [Line Items]
Notional amount		8,900,000
Not Designated as Hedging Instrument | Mortgage loan commitments mandatory delivery
Derivative [Line Items]
Notional amount		$ 0
Minimum | TBA Securities
Derivative [Line Items]
Settlement term	30 days
Maximum | TBA Securities
Derivative [Line Items]
Settlement term	90 days

Derivatives - Summary of Fair V

Derivatives - Summary of Fair Value and Location for Rate-Lock and Forward Loan Sale Commitments (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative assets:	$ 15,336	$ 8,766
Derivative liabilities:	15,326	8,785
Mortgage Banking Derivatives
Derivative [Line Items]
Derivative assets:		232
Derivative liabilities:		105
Other assets
Derivative [Line Items]
Derivative assets:	531
Other assets | Total mortgage derivative commitments
Derivative [Line Items]
Derivative assets:	465	210
Other assets | Mortgage loan commitments best efforts
Derivative [Line Items]
Derivative assets:	142	210
Other assets | Mortgage loan commitments mandatory delivery
Derivative [Line Items]
Derivative assets:	323
Other assets | Total forward loan sale commitments
Derivative [Line Items]
Derivative assets:	66	22
Other assets | Forward loan sale commitments best efforts
Derivative [Line Items]
Derivative assets:	51	22
Other assets | Forward loan sale commitments mandatory delivery
Derivative [Line Items]
Derivative assets:	15
Other liabilities
Derivative [Line Items]
Derivative liabilities:	148
Other liabilities | Total mortgage derivative commitments
Derivative [Line Items]
Derivative liabilities:	46	36
Other liabilities | Mortgage loan commitments best efforts
Derivative [Line Items]
Derivative liabilities:	46	36
Other liabilities | Mortgage loan commitments mandatory delivery
Derivative [Line Items]
Derivative liabilities:	0
Other liabilities | Total forward loan sale commitments
Derivative [Line Items]
Derivative liabilities:	102	69
Other liabilities | Forward loan sale commitments best efforts
Derivative [Line Items]
Derivative liabilities:	17	$ 69
Other liabilities | Forward loan sale commitments mandatory delivery
Derivative [Line Items]
Derivative liabilities:	$ 85

Deposits - Summary of Deposit B

Deposits - Summary of Deposit Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
NOW and demand	$ 375,934	$ 381,316
Regular savings	213,205	221,004
Money market	628,718	646,603
Brokered money market	85,951	92,798
Total non-certificate accounts	1,303,808	1,341,721
Term certificates of $250,000 or more	164,081	134,649
Term certificates less than $250,000	361,506	313,733
Brokered term certificates	282,672	249,766
Total term certificate accounts	808,259	698,148
Total deposits	$ 2,112,067	$ 2,039,869

Deposits - Schedule of Contract

Deposits - Schedule of Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Amount
Amount - Within 1 year	$ 481,235
Amount - 1-2 years	239,227
Amount - 2-3 years	49,974
Amount - 3-4 years	20,521
Amount - 4 years and beyond	17,302
Total term certificate accounts	$ 808,259	$ 698,148
Weighted Average Rate
Weighted Average Rate - Within 1 year	1.62%
Weighted Average Rate - 1-2 years	1.93%
Weighted Average Rate - 2-3 years	1.99%
Weighted Average Rate - 3-4 years	1.79%
Weighted Average Rate - 4 years and beyond	2.15%
Weighted Average Rate	1.75%

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Equity securities at fair value	$ 5,331	$ 0
Marketable equity securities		9,720
Level 1
Assets
Equity securities at fair value	5,331
Level 2
Assets
Equity securities at fair value	0
Level 3
Assets
Equity securities at fair value	0
Recurring
Assets
Equity securities at fair value	5,331
Marketable equity securities		9,720
Total assets	21,198	18,718
Liabilities
Interest rate swap agreements	15,474	8,890
Recurring | Level 1
Assets
Equity securities at fair value	5,331
Marketable equity securities		9,720
Total assets	5,331	9,720
Liabilities
Interest rate swap agreements	0	0
Recurring | Level 2
Assets
Equity securities at fair value	0
Marketable equity securities		0
Total assets	15,336	8,766
Liabilities
Interest rate swap agreements	15,326	8,785
Recurring | Level 3
Assets
Equity securities at fair value	0
Marketable equity securities		0
Total assets	531	232
Liabilities
Interest rate swap agreements	148	105
Interest rate swap agreements | Level 1
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Interest rate swap agreements | Level 2
Assets
Interest rate swap agreements	15,336	8,766
Liabilities
Interest rate swap agreements	15,326	8,785
Interest rate swap agreements | Level 3
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Interest rate swap agreements | Recurring
Assets
Interest rate swap agreements	15,336	8,766
Liabilities
Interest rate swap agreements	15,326	8,785
Interest rate swap agreements | Recurring | Level 1
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Interest rate swap agreements | Recurring | Level 2
Assets
Interest rate swap agreements	15,336	8,766
Liabilities
Interest rate swap agreements	15,326	8,785
Interest rate swap agreements | Recurring | Level 3
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Forward loan sale commitments - best efforts | Level 1
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Forward loan sale commitments - best efforts | Level 2
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Forward loan sale commitments - best efforts | Level 3
Assets
Interest rate swap agreements	51	22
Liabilities
Interest rate swap agreements	17	69
Forward loan sale commitments - best efforts | Recurring
Assets
Interest rate swap agreements	51	22
Liabilities
Interest rate swap agreements	17	69
Forward loan sale commitments - best efforts | Recurring | Level 1
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Forward loan sale commitments - best efforts | Recurring | Level 2
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Forward loan sale commitments - best efforts | Recurring | Level 3
Assets
Interest rate swap agreements	51	22
Liabilities
Interest rate swap agreements	17	69
Forward loan sale commitments mandatory delivery | Level 1
Assets
Interest rate swap agreements	0
Liabilities
Interest rate swap agreements	0
Forward loan sale commitments mandatory delivery | Level 2
Assets
Interest rate swap agreements	0
Liabilities
Interest rate swap agreements	0
Forward loan sale commitments mandatory delivery | Level 3
Assets
Interest rate swap agreements	15
Liabilities
Interest rate swap agreements	85
Forward loan sale commitments mandatory delivery | Recurring
Assets
Interest rate swap agreements	15
Liabilities
Interest rate swap agreements	85
Forward loan sale commitments mandatory delivery | Recurring | Level 1
Assets
Interest rate swap agreements	0
Liabilities
Interest rate swap agreements	0
Forward loan sale commitments mandatory delivery | Recurring | Level 2
Assets
Interest rate swap agreements	0
Liabilities
Interest rate swap agreements	0
Forward loan sale commitments mandatory delivery | Recurring | Level 3
Assets
Interest rate swap agreements	15
Liabilities
Interest rate swap agreements	85
Mortgage loan commitments best efforts | Level 1
Assets
Interest rate swap agreements	0
Mortgage loan commitments best efforts | Level 2
Assets
Interest rate swap agreements	0
Mortgage loan commitments best efforts | Level 3
Assets
Interest rate swap agreements	142
Mortgage loan commitments best efforts | Recurring
Assets
Interest rate swap agreements	142	210
Liabilities
Interest rate swap agreements	46	36
Mortgage loan commitments best efforts | Recurring | Level 1
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Mortgage loan commitments best efforts | Recurring | Level 2
Assets
Interest rate swap agreements	0	0
Liabilities
Interest rate swap agreements	0	0
Mortgage loan commitments best efforts | Recurring | Level 3
Assets
Interest rate swap agreements	142	210
Liabilities
Interest rate swap agreements	46	$ 36
Mortgage loan commitments mandatory delivery | Level 1
Assets
Interest rate swap agreements	0
Mortgage loan commitments mandatory delivery | Level 2
Assets
Interest rate swap agreements	0
Mortgage loan commitments mandatory delivery | Level 3
Assets
Interest rate swap agreements	323
Mortgage loan commitments mandatory delivery | Recurring
Assets
Interest rate swap agreements	323
Mortgage loan commitments mandatory delivery | Recurring | Level 1
Assets
Interest rate swap agreements	0
Mortgage loan commitments mandatory delivery | Recurring | Level 2
Assets
Interest rate swap agreements	0
Mortgage loan commitments mandatory delivery | Recurring | Level 3
Assets
Interest rate swap agreements	$ 323

Fair Value Measurements - Ass57

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ (156)	$ (86)	$ (350)	$ (9)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		0		$ 0
Other real estate owned	0		0		0
Total assets	0		0		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		0		0
Other real estate owned	0		0		0
Total assets	0		0		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	1,606		1,606		2,214
Other real estate owned	3,649		3,649		0
Total assets	$ 5,255		$ 5,255		$ 2,214

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value, Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial assets:
Equity securities at fair value	$ 5,331	$ 0
Equity securities at fair value	0	9,720
Securities held to maturity	303,137	303,716
Estimate of Fair Value Measurement
Financial assets:
Cash and cash equivalents	51,949	46,167
Equity securities at fair value	5,331
Equity securities at fair value		9,720
Securities held to maturity	292,940	299,114
Federal Home Loan Bank stock	14,375	12,105
Loans and loans held for sale, net	2,222,753	2,174,871
Accrued interest receivable	6,531	6,438
Financial liabilities:
Deposits	2,106,630	2,036,150
Borrowings	198,890	203,913
Carrying Amount
Financial assets:
Cash and cash equivalents	51,949	46,167
Equity securities at fair value	5,331
Equity securities at fair value		9,720
Securities held to maturity	303,137	303,716
Federal Home Loan Bank stock	14,375	12,105
Loans and loans held for sale, net	2,251,751	2,195,139
Accrued interest receivable	6,531	6,438
Financial liabilities:
Deposits	2,112,067	2,039,869
Borrowings	200,000	205,000
Level 1
Financial assets:
Cash and cash equivalents	51,949	46,167
Equity securities at fair value	5,331
Equity securities at fair value		9,720
Securities held to maturity	0	0
Federal Home Loan Bank stock	0	0
Loans and loans held for sale, net	0	0
Accrued interest receivable	0	0
Financial liabilities:
Deposits	0	0
Borrowings	0	0
Level 2
Financial assets:
Cash and cash equivalents	0	0
Equity securities at fair value	0
Equity securities at fair value		0
Securities held to maturity	292,940	299,114
Federal Home Loan Bank stock	0	0
Loans and loans held for sale, net	0	0
Accrued interest receivable	0	0
Financial liabilities:
Deposits	0	0
Borrowings	198,890	203,913
Level 3
Financial assets:
Cash and cash equivalents	0	0
Equity securities at fair value	0
Equity securities at fair value		0
Securities held to maturity	0	0
Federal Home Loan Bank stock	14,375	12,105
Loans and loans held for sale, net	2,222,753	2,174,871
Accrued interest receivable	6,531	6,438
Financial liabilities:
Deposits	2,106,630	2,036,150
Borrowings	0	0
Interest rate swap agreements | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:	15,336	8,766
Derivative liabilities:	15,326	8,785
Interest rate swap agreements | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:	15,336	8,766
Derivative liabilities:	15,326	8,785
Interest rate swap agreements | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:	0	0
Derivative liabilities:	0	0
Interest rate swap agreements | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:	15,336	8,766
Derivative liabilities:	15,326	8,785
Interest rate swap agreements | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:	0	0
Derivative liabilities:	0	0
Mortgage loan commitments best efforts | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:	142
Mortgage loan commitments best efforts | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:	142
Mortgage loan commitments best efforts | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:	0
Mortgage loan commitments best efforts | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:	0
Mortgage loan commitments best efforts | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:	142
Mortgage loan commitments mandatory delivery | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:	323
Mortgage loan commitments mandatory delivery | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:	323
Mortgage loan commitments mandatory delivery | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:	0
Mortgage loan commitments mandatory delivery | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:	0
Mortgage loan commitments mandatory delivery | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:	323
Mortgage loan commitments-best efforts | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:		210
Derivative liabilities:	46	36
Mortgage loan commitments-best efforts | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:		210
Derivative liabilities:	46	36
Mortgage loan commitments-best efforts | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:		0
Derivative liabilities:	0	0
Mortgage loan commitments-best efforts | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:		0
Derivative liabilities:	0	0
Mortgage loan commitments-best efforts | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:		210
Derivative liabilities:	46	36
Forward loan sale commitments best efforts | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:	51	22
Derivative liabilities:	17	69
Forward loan sale commitments best efforts | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:	51	22
Derivative liabilities:	17	69
Forward loan sale commitments best efforts | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:	0	0
Derivative liabilities:	0	0
Forward loan sale commitments best efforts | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:	0	0
Derivative liabilities:	0	0
Forward loan sale commitments best efforts | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:	51	22
Derivative liabilities:	17	$ 69
Forward loan sale commitments mandatory delivery | Estimate of Fair Value Measurement
On-balance sheet derivative financial instruments:
Derivative assets:	15
Derivative liabilities:	85
Forward loan sale commitments mandatory delivery | Carrying Amount
On-balance sheet derivative financial instruments:
Derivative assets:	15
Derivative liabilities:	85
Forward loan sale commitments mandatory delivery | Level 1
On-balance sheet derivative financial instruments:
Derivative assets:	0
Derivative liabilities:	0
Forward loan sale commitments mandatory delivery | Level 2
On-balance sheet derivative financial instruments:
Derivative assets:	0
Derivative liabilities:	0
Forward loan sale commitments mandatory delivery | Level 3
On-balance sheet derivative financial instruments:
Derivative assets:	15
Derivative liabilities:	$ 85

Comprehensive Income - Componen

Comprehensive Income - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	$ (1,839)	$ (1,453)
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized actuarial gain (loss)	(2,561)	(2,694)
Tax effect	533	914
Accumulated other comprehensive income	(2,028)	(1,780)
Securities Available for Sale | Accumulated Net Investment Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized actuarial gain (loss)	0	283
Tax effect	0	(140)
Accumulated other comprehensive income	0	143
Securities Held to Maturity | Accumulated Net Investment Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized actuarial gain (loss)	210	250
Tax effect	(21)	(66)
Accumulated other comprehensive income	$ 189	$ 184

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details)	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2015
Equity [Abstract]
Tier one capital conservation buffer common equity capital to risk weighted assets (greater than)	1.875%	0.625%	2.50%

Stockholders' Equity - Minimum

Stockholders' Equity - Minimum Required Capital (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Total capital (to risk weighted assets)
Actual - Total Capital to Risk Weighted Assets	$ 413,430	$ 410,088
Actual - Total Capital to Risk Weighted Assets Ratio (percentage)	18.80%	19.70%
Minimum Capital Requirement - Total Capital	$ 176,112	$ 166,635
Minimum Capital Requirement - Total Capital to Risk Weighted Assets Ratio (percentage)	8.00%	8.00%
Minimum to Be Well Capitalized - Total Capital	$ 220,140	$ 208,294
Minimum to Be Well Capitalized - Total Capital to Risk Weighted Assets Ratio (percentage)	10.00%	10.00%
Tier 1 capital (to risk weighted assets)
Actual - Tier 1 Capital to Risk Weighted Assets	$ 393,305	$ 389,211
Actual - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	17.90%	18.70%
Minimum Capital Requirement - Tier 1 Capital to Risk Weighted Assets	$ 132,084	$ 124,977
Minimum Capital Requirement - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	6.00%	6.00%
Minimum to Be Well Capitalized - Tier 1 Capital to Risk Weighted Assets	$ 176,112	$ 166,635
Minimum to Be Well Capitalized - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	8.00%	8.00%
Common equity Tier 1 (to risk weighted assets)
Actual - Common Equity to Risk Weighted Assets	$ 393,305	$ 389,211
Actual - Common Equity to Risk Weighted Assets Ratio (percentage)	17.90%	18.70%
Minimum Capital Requirement - Common Equity to Risk Weighted Assets	$ 99,063	$ 93,732
Minimum Capital Requirement - Common Equity to Risk Weighted Assets Ratio (percentage)	4.50%	4.50%
Minimum to Be Well Capitalized - Common Equity to Risk Weighted Assets	$ 143,091	$ 135,391
Minimum to Be Well Capitalized - Common Equity to Risk Weighted Assets Ratio (percentage)	6.50%	6.50%
Tier 1 capital (to average assets)
Actual - Tier 1 Capital to Average Assets	$ 393,305	$ 389,211
Actual - Tier 1 Capital to Average Assets Ratio (percentage)	14.90%	14.90%
Minimum Capital Requirement - Tier 1 Capital to Average Assets	$ 105,775	$ 104,278
Minimum Capital Requirement - Tier 1 Capital to Average Assets Ratio (percentage)	4.00%	4.00%
Minimum to Be Well Capitalized - Tier 1 Capital to Average Assets	$ 132,219	$ 130,348
Minimum to Be Well Capitalized - Tier 1 Capital to Average Assets Ratio (percentage)	5.00%	5.00%
Blue Hills Bank
Total capital (to risk weighted assets)
Actual - Total Capital to Risk Weighted Assets	$ 357,224	$ 341,175
Actual - Total Capital to Risk Weighted Assets Ratio (percentage)	16.20%	16.40%
Minimum Capital Requirement - Total Capital	$ 176,025	$ 166,391
Minimum Capital Requirement - Total Capital to Risk Weighted Assets Ratio (percentage)	8.00%	8.00%
Minimum to Be Well Capitalized - Total Capital	$ 220,032	$ 207,988
Minimum to Be Well Capitalized - Total Capital to Risk Weighted Assets Ratio (percentage)	10.00%	10.00%
Tier 1 capital (to risk weighted assets)
Actual - Tier 1 Capital to Risk Weighted Assets	$ 337,099	$ 320,298
Actual - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	15.30%	15.40%
Minimum Capital Requirement - Tier 1 Capital to Risk Weighted Assets	$ 132,019	$ 124,793
Minimum Capital Requirement - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	6.00%	6.00%
Minimum to Be Well Capitalized - Tier 1 Capital to Risk Weighted Assets	$ 176,025	$ 166,391
Minimum to Be Well Capitalized - Tier 1 Capital to Risk Weighted Assets Ratio (percentage)	8.00%	8.00%
Common equity Tier 1 (to risk weighted assets)
Actual - Common Equity to Risk Weighted Assets	$ 337,099	$ 320,298
Actual - Common Equity to Risk Weighted Assets Ratio (percentage)	15.30%	15.40%
Minimum Capital Requirement - Common Equity to Risk Weighted Assets	$ 99,014	$ 93,595
Minimum Capital Requirement - Common Equity to Risk Weighted Assets Ratio (percentage)	4.50%	4.50%
Minimum to Be Well Capitalized - Common Equity to Risk Weighted Assets	$ 143,020	$ 135,192
Minimum to Be Well Capitalized - Common Equity to Risk Weighted Assets Ratio (percentage)	6.50%	6.50%
Tier 1 capital (to average assets)
Actual - Tier 1 Capital to Average Assets	$ 337,099	$ 320,298
Actual - Tier 1 Capital to Average Assets Ratio (percentage)	12.80%	12.30%
Minimum Capital Requirement - Tier 1 Capital to Average Assets	$ 105,673	$ 104,137
Minimum Capital Requirement - Tier 1 Capital to Average Assets Ratio (percentage)	4.00%	4.00%
Minimum to Be Well Capitalized - Tier 1 Capital to Average Assets	$ 132,092	$ 130,171
Minimum to Be Well Capitalized - Tier 1 Capital to Average Assets Ratio (percentage)	5.00%	5.00%

Employee Stock Ownership Plan -

Employee Stock Ownership Plan - Employee Stock Ownership Plan (Details) - shares	Jun. 30, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Allocated	293,670	219,860
Committed to be allocated	37,644	75,912
Unallocated	1,936,053	1,973,699
Total	2,267,367	2,269,471

Employee Stock Ownership Plan63

Employee Stock Ownership Plan - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Retirement Benefits [Abstract]
ESOP, Number of shares committed to be released annually (shares)	75,912		75,912
Fair Value of unallocated shares	$ 43,000		$ 43,000		$ 39,700
ESOP expense	$ 397	$ 343	$ 775	$ 684

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net income applicable to common stock	$ 6,457	$ 3,868	$ 13,040	$ 11,355
Average number of common shares outstanding	26,870,770	26,859,345	26,845,536	26,851,143
Less: Average unallocated ESOP shares	(1,945,516)	(2,021,427)	(1,954,875)	(2,030,786)
Less: Average unvested restricted stock awards	(695,156)	(885,475)	(689,333)	(888,313)
Average number of common shares outstanding used to calculate basic earnings per common share	24,230,098	23,952,443	24,201,328	23,932,044
Average number of common shares outstanding used to calculate diluted earnings per common share	24,991,958	24,346,553	24,910,065	24,311,222
Earnings per common share:
Basic (dollars per share)	$ 0.27	$ 0.16	$ 0.54	$ 0.47
Diluted (dollars per share)	$ 0.26	$ 0.16	$ 0.52	$ 0.47
Antidilutive securities excluded from computation of earnings per share (shares)	550,634	372,100	552,950	384,100
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of dilutive share-based compensation awards (in shares)	506,138	155,938	469,213	147,665
Unvested Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of dilutive share-based compensation awards (in shares)	255,722	238,172	239,524	231,513

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		42 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	2,846,681		2,846,681		2,846,681
Term (years)			10 years
Vesting period (years)			5 years
Share-based compensation expense	$ 571	$ 568	$ 1,100	$ 1,200
Tax benefit related to share-based compensation expense	$ 101	135	$ 203	290
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	1,138,673		1,138,673		1,138,673
Share-based compensation expense	$ 795	770	$ 1,600	1,600
Tax benefit related to share-based compensation expense	$ 207	$ 269	$ 409	$ 574
Granted (shares)			36,500
Vested (shares)			48,749
Nonvested (shares)	694,721		694,721		694,721	730,420
Forfeited (shares)			23,450
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (shares)					40,000
Vested (shares)					12,000
Nonvested (shares)	24,000		24,000		24,000
Forfeited (shares)			2,000		4,000
Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term (years)			10 years

Share-Based Compensation - Fair

Share-Based Compensation - Fair Value Assumptions (Details)	6 Months Ended
	Jun. 30, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (shares)	145,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (shares)	145,000
Vesting period (years)	5 years
Term (years)	10 years
Expected volatility (percent)	26.47%
Expected life (years)	6 years 6 months
Expected dividend yield (percent)	3.21%
Risk free interest rate (percent)	2.39%
Weighted average grant date fair value (dollars per share) | $ / shares	$ 4.12
Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term (years)	10 years

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (shares)	2,684,650
Granted (shares)	145,000
Forfeited (shares)	(74,440)
Exercised (shares)	(49,330)
Ending balance (shares)	2,705,880
Exercisable at end of period (shares)	966,250
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance, weighted average exercise price (dollars per share) | $ / shares	$ 14.70
Granted, weighted average exercise price (dollars per share) | $ / shares	20.70
Forfeited, weighted average exercise price (dollars per share) | $ / shares	14.07
Exercised, weighted average exercise price (dollars per share) | $ / shares	14.01
Ending balance, weighted average exercise price (dollars per share) | $ / shares	15.05
Exercisable at end of period, weighted average exercise price (dollars per share) | $ / shares	$ 14.39
Outstanding, weighted average remaining contractual term (years)	7 years 7 months 2 days
Exercisable at period end, weighted average remaining contractual term (years)	7 years 3 months 22 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercised, aggregate intrinsic value | $	$ 342,000
Outstanding, aggregate intrinsic value | $	19,352,000
Exercisable, aggregate intrinsic value | $	$ 7,549,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (shares)	145,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Unrecognized compensation cost | $	$ 6,096,000
Weighted average remaining recognition period (years)	2 years 300 days

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (shares)	730,420
Granted (shares)	36,500
Vested (shares)	(48,749)
Forfeited (shares)	(23,450)
Ending balance (shares)	694,721
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, weighted average exercise price (dollars per share)	$ 15.11
Granted, weighted average exercise price (dollars per share)	20.70
Vested, weighted average exercise price (dollars per share)	17.03
Forfeited, weighted average exercise price (dollars per share)	14.07
Ending balance, weighted average exercise price (dollars per share)	$ 15.31
Unrecognized compensation cost inclusive of directors' fees	$ 8,566
Weighted average remaining recognition period (years)	2 years 9 months 40 days