Enterprise Bancorp (EBTC) 10-K 13 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	ENTERPRISE BANCORP INC /MA/
Entity Central Index Key	1,018,399
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		11,635,044
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 345,319,719

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cash and cash equivalents:
Cash and due from banks	$ 40,310	$ 33,047
Interest-earning deposits	14,496	17,428
Total cash and cash equivalents	54,806	50,475
Investment securities at fair value	405,206	374,790
Federal Home Loan Bank Stock	5,215	2,094
Loans held for sale	208	1,569
Loans, less allowance for loan losses of $32,915 at December 31, 2017 and $31,342 at December 31, 2016	2,236,989	1,991,387
Premises and equipment, net	37,022	33,540
Accrued interest receivable	10,614	8,792
Deferred income taxes, net	10,751	17,020
Bank-owned life insurance	29,466	28,765
Prepaid income taxes	1,301	1,344
Prepaid expenses and other assets	20,330	10,837
Goodwill	5,656	5,656
Total assets	2,817,564	2,526,269
Liabilities
Deposits	2,441,362	2,268,921
Borrowed funds	89,000	10,671
Subordinated debt	14,847	14,834
Accrued expenses and other liabilities	40,067	16,794
Accrued interest payable	478	263
Total liabilities	2,585,754	2,311,483
Commitments and Contingencies
Stockholders' Equity
Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued	0	0
Common stock $0.01 par value per share; 40,000,000 shares authorized; 11,609,853 shares issued and outstanding at December 31, 2017 and 11,475,742 shares issued and outstanding at December 31, 2016	116	115
Additional paid-in capital	88,205	85,421
Retained earnings	143,073	130,008
Accumulated other comprehensive income (loss)	416	(758)
Total stockholders’ equity	231,810	214,786
Total liabilities and stockholders' equity	$ 2,817,564	$ 2,526,269

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	May 01, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Allowance for loan losses	$ 32,915		$ 31,342	$ 29,008	$ 27,121
Common stock, par value	$ 0.01		$ 0.01
Common stock, shares authorized	40,000,000	20,000,000
Common stock, shares issued	11,609,853		11,475,742
Common stock, shares outstanding	11,609,853		11,475,742
Preferred stock, par value	$ 0.01		$ 0.01
Preferred stock, shares authorized	1,000,000		1,000,000
Preferred stock, shares issued	0		0

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest and dividend income:
Loans and loans held for sale	$ 96,559	$ 85,390	$ 77,946
Investment securities	8,045	6,640	5,346
Other interest-earning assets	428	285	179
Total interest and dividend income	105,032	92,315	83,471
Interest expense:
Deposits	5,995	4,514	4,068
Borrowed funds	590	81	38
Subordinated debt	925	928	1,071
Total interest expense	7,510	5,523	5,177
Net interest income	97,522	86,792	78,294
Provision for loan losses	1,430	2,993	3,267
Net interest income after provision for loan losses	96,092	83,799	75,027
Non-interest income:
Investment advisory fees	5,149	4,774	4,750
Deposit and interchange fees	6,011	5,124	4,879
Income on bank-owned life insurance,net	701	747	553
Net gains on sales of investment securities	716	802	1,828
Net gains on sales of loans	460	601	492
Other income	2,637	2,393	2,465
Total non-interest income	15,674	14,441	14,967
Non-interest expense:
Salaries and employee benefits	48,379	43,886	40,285
Occupancy and equipment expenses	7,960	7,362	7,308
Technology and telecommunications expenses	6,372	6,080	5,710
Advertising and public relations expenses	2,855	2,833	2,719
Audit, legal and other professional fees	1,565	1,721	1,657
Deposit insurance premiums	1,535	1,387	1,214
Supplies and postage expenses	999	965	988
Other operating expenses	6,480	6,094	5,851
Total non-interest expense	76,145	70,328	65,732
Income before income taxes	35,621	27,912	24,262
Provision for income taxes	16,228	9,161	8,114
Net income	$ 19,393	$ 18,751	$ 16,148
Basic earnings per share	$ 1.68	$ 1.71	$ 1.56
Diluted earnings per share	$ 1.66	$ 1.70	$ 1.55
Basic weighted average common shares outstanding	11,568,430	10,966,333	10,323,016
Diluted weighted average common shares outstanding	11,651,763	11,039,511	10,389,934

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 19,393	$ 18,751	$ 16,148
Other comprehensive income (loss), net of taxes:
Gross unrealized holding gains (losses) on investments arising during the period	2,424	(3,876)	(518)
Income tax (expense) benefit	(855)	1,357	216
Net unrealized holding gains (losses), net of tax	1,569	(2,519)	(302)
Less: Reclassification adjustment for net gains included in net income
Net realized gains on sales of securities during the period	716	802	1,828
Income tax expense	(247)	(289)	(637)
Reclassification adjustment for gains realized, net of tax	469	513	1,191
Total other comprehensive income (loss), net	1,100	(3,032)	(1,493)
Comprehensive income	$ 20,493	$ 15,719	$ 14,655

Consolidated Statement of Chang

Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)
Balance, beginning at Dec. 31, 2014	$ 166,950	$ 102	$ 57,130	$ 105,951	$ 3,767
Balance, beginning, shares, outstanding at Dec. 31, 2014		10,207,943
Increase (Decrease) in Stockholders' Equity
Net income	16,148			16,148
Other comprehensive income (loss), net	(1,493)				(1,493)
Tax benefit from stock compensation	217		217
Common stock dividend paid	(5,158)			(5,158)
Common stock issued under dividend reinvestment plan, shares		58,529
Common stock issued under dividend reinvestment plan, value	1,277	$ 1	1,276
Common stock issued, shares, other, net of expenses		7,674
Common stock issued, other, net of expenses	171	$ 0	171
Stock-based compensation, shares		65,015
Stock-based compensation	1,784	$ 1	1,783
Stock options exercised, net, shares		38,626
Stock options exercised, net	431	$ 0	431
Balance, ending at Dec. 31, 2015	180,327	$ 104	61,008	116,941	2,274
Balance, ending, shares, outstanding at Dec. 31, 2015		10,377,787
Increase (Decrease) in Stockholders' Equity
Net income	18,751			18,751
Other comprehensive income (loss), net	(3,032)				(3,032)
Tax benefit from stock compensation	789		789
Common stock dividend paid	(5,684)			(5,684)
Common stock issued under dividend reinvestment plan, shares		53,516
Common stock issued under dividend reinvestment plan, value	1,381	$ 1	1,380
Common stock issued, shares, other, net of expenses		932,522
Common stock issued, other, net of expenses	19,802	$ 9	19,793
Stock-based compensation, shares		71,662
Stock-based compensation	2,348	$ 1	2,347
Net settlement for employee taxes on restricted stock and options, shares		(12,744)
Net settlement for employee taxes on restricted stock and options	(442)	$ 0	(442)
Stock options exercised, net, shares		52,999
Stock options exercised, net	546	$ 0	546
Balance, ending at Dec. 31, 2016	$ 214,786	$ 115	85,421	130,008	(758)
Balance, ending, shares, outstanding at Dec. 31, 2016	11,475,742	11,475,742
Increase (Decrease) in Stockholders' Equity
Net income	$ 19,393			19,393
Cumulative effect adjustment for adoption of new accounting pronouncements	0		13	(87)	74
Other comprehensive income (loss), net	1,100				1,100
Common stock dividend paid	(6,241)			(6,241)
Common stock issued under dividend reinvestment plan, shares		44,752
Common stock issued under dividend reinvestment plan, value	1,494	$ 0	1,494
Common stock issued, shares, other, net of expenses		2,798
Common stock issued, other, net of expenses	96	$ 0	96
Stock-based compensation, shares		58,037
Stock-based compensation	1,758	$ 1	1,757
Net settlement for employee taxes on restricted stock and options, shares		(15,185)
Net settlement for employee taxes on restricted stock and options	(931)	$ 0	(931)
Stock options exercised, net, shares		43,709
Stock options exercised, net	355	$ 0	355
Balance, ending at Dec. 31, 2017	$ 231,810	$ 116	$ 88,205	$ 143,073	$ 416
Balance, ending, shares, outstanding at Dec. 31, 2017	11,609,853	11,609,853

Consolidated Statement of Chan7

Consolidated Statement of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common stock dividend paid, per share	$ 0.54	$ 0.52	$ 0.50

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 19,393,000	$ 18,751,000	$ 16,148,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	1,430,000	2,993,000	3,267,000
Depreciation and amortization	7,028,000	6,081,000	5,603,000
Stock-based compensation expense	1,753,000	2,380,000	1,803,000
Income on bank-owned life insurance, net	(701,000)	(747,000)	(553,000)
Net gains on life insurance	0	0	(163,000)
Net gains on sales of investments	(716,000)	(802,000)	(1,828,000)
Mortgage loans originated for sale	(19,820,000)	(28,873,000)	(23,673,000)
Proceeds from mortgage loans sold	21,641,000	29,614,000	24,827,000
Net gains on sales of loans	(460,000)	(601,000)	(492,000)
Net gains on sales of OREO	0	0	(154,000)
Changes in:
Decrease (increase) in other assets	6,026,000	(2,174,000)	64,000
Increase in other liabilities	2,357,000	701,000	874,000
Net cash provided by operating activities	37,931,000	27,323,000	25,723,000
Cash flows from investing activities:
Proceeds from sales of investment securities	133,736,000	4,800,000	25,115,000
Net (purchases) proceeds from FHLB capital stock	(3,121,000)	956,000	307,000
Proceeds from maturities, calls and pay-downs of investment securities	32,643,000	30,930,000	26,731,000
Purchase of investment securities	(187,158,000)	(118,255,000)	(108,962,000)
Net increase in loans	(247,032,000)	(163,426,000)	(188,738,000)
Additions to premises and equipment, net	(8,211,000)	(7,918,000)	(3,938,000)
Proceeds from OREO sales and payments	0	0	1,015,000
Proceeds from bank-owned life insurance	0	405,000	0
Purchase of bank-owned life insurance	0	0	(11,390,000)
Net cash used in investing activities	(279,143,000)	(252,508,000)	(259,860,000)
Cash flows from financing activities:
Net increase in deposits	172,441,000	250,773,000	249,602,000
Net increase (decrease) in borrowed funds	78,329,000	(43,000,000)	(5,229,000)
Repayment of subordinated debt	0	0	(10,825,000)
Proceeds from the issuance of subordinated debt	0	0	15,000,000
Cash dividends paid	(6,241,000)	(5,684,000)	(5,158,000)
Proceeds from issuance of common stock, net of expenses	1,590,000	21,183,000	1,448,000
Net settlement for employee taxes on restricted stock and options	(931,000)	(442,000)	0
Proceeds from stock option exercises	355,000	546,000	431,000
Tax benefit from stock-based compensation	0	789,000	217,000
Net cash provided by financing activities	245,543,000	224,165,000	245,486,000
Net increase (decrease) in cash and cash equivalents	4,331,000	(1,020,000)	11,349,000
Cash and cash equivalents, beginning of year	50,475,000	51,495,000	40,146,000
Cash and cash equivalents, end of year	54,806,000	50,475,000	51,495,000
Supplemental financial data:
Cash Paid For: Interest	7,295,000	5,536,000	5,467,000
Cash Paid For: Income taxes	10,459,000	10,868,000	7,594,000
Supplemental schedule of non-cash activity:
Net purchases (sales) of investment securities not yet settled	9,154,000	(301,000)	2,296,000
Bank owned life insurance proceeds not yet received	0	0	403,000
Capital expenditures incurred not yet paid	$ 0	$ 0	$ 525,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) Organization of Holding Company and Basis of Presentation The consolidated financial statements of Enterprise Bancorp, Inc. (the "Company," "Enterprise," "we," or "our"), a Massachusetts corporation, include the accounts of the Company and its wholly owned subsidiary, Enterprise Bank and Trust Company commonly referred to as Enterprise Bank (the "Bank"). The Bank is a Massachusetts trust company and state chartered commercial bank organized in 1989. Substantially all of the Company’s operations are conducted through the Bank and its subsidiaries. The Bank’s subsidiaries include Enterprise Insurance Services, LLC and Enterprise Wealth Services, LLC, organized under the laws of the State of Delaware for the purposes of engaging in insurance sales activities and offering non-deposit investment products and services, respectively. In addition, the Bank has the following subsidiaries that are incorporated in the Commonwealth of Massachusetts and classified as security corporations in accordance with applicable Massachusetts General Laws: Enterprise Security Corporation; Enterprise Security Corporation II; and Enterprise Security Corporation III. The security corporations, which hold various types of qualifying securities, are limited to conducting securities investment activities that the Bank itself would be allowed to conduct under applicable laws. At December 31, 2017 , the Company had 24 full service branches serving the Greater Merrimack Valley and North Central regions of Massachusetts and Southern New Hampshire (Southern Hillsborough and Rockingham counties). Through the Bank and its subsidiaries, the Company offers a range of commercial, residential and consumer loan products, deposit products and cash management services, as well as investment advisory and wealth management, trust and insurance services. The services offered through the Bank and its subsidiaries are managed as one strategic unit and represent the Company’s only reportable operating segment. The Federal Deposit Insurance Corporation (the "FDIC") and the Massachusetts Division of Banks (the "Division") have regulatory authority over the Bank. The Bank is also subject to certain regulatory requirements of the Board of Governors of the Federal Reserve System (the "Federal Reserve Board") and, with respect to its New Hampshire branch operations, the New Hampshire Banking Department. The business and operations of the Company are subject to the regulatory oversight of the Federal Reserve Board. The Division also retains supervisory jurisdiction over the Company. The accompanying audited consolidated financial statements and notes thereto have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") and the instructions for Form 10-K through the rules and interpretive releases of the SEC under federal securities law. In the opinion of management, the accompanying audited consolidated financial statements reflect all necessary adjustments consisting of normal recurring accruals for a fair presentation. All significant intercompany balances and transactions have been eliminated in the accompanying audited consolidated financial statements. Certain previous years' amounts in the audited consolidated financial statements, and notes thereto, have been reclassified to conform to the current year's presentation. The Company has evaluated subsequent events and transactions from December 31, 2017 through the date this Annual Report on Form 10-K was filed with the SEC for potential recognition or disclosure as required by GAAP and determined that there were no material subsequent events requiring recognition or disclosure. (b) Uses of estimates In preparing the financial statements in conformity with GAAP, management is required to exercise judgment in determining many of the methodologies, assumptions and estimates to be utilized. These assumptions and estimates affect the reported values of assets and liabilities as of the balance sheet date and income and expenses for the years then ended. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates should the assumptions and estimates used be incorrect, or change over time due to changes in circumstances. Changes in those estimates resulting from continuing change in the economic environment and other factors will be reflected in the financial statements and results of operations in future periods. The three most significant areas in which management applies critical assumptions and estimates are the estimate of the allowance for loan losses, impairment review of investment securities and the impairment review of goodwill. (c) Cash and cash equivalents Cash equivalents are defined as highly liquid investments with original maturities of three months or less, that are readily convertible to known amounts of cash and present insignificant risk of changes in value due to changes in interest rates. The Company's cash and cash equivalents is comprised of cash on hand and cash items due from banks, interest-earning deposits (deposit accounts, excess reserve cash balances, money markets, and money market mutual fund accounts) and federal funds ("fed funds") sold. Balances in cash and cash equivalents will fluctuate due primarily to the timing of net deposit flows, borrowing and loan inflows and outflows, investment purchases and maturities, calls and sales proceeds, and the immediate liquidity needs of the Company. (d) Investments Investments that are intended to be held for indefinite periods of time but which may not be held to maturity or on a long-term basis are considered to be "available-for-sale" and are carried at fair value. Net unrealized appreciation and depreciation on investments available-for-sale, net of applicable income taxes, are reflected as a component of accumulated other comprehensive income (loss). Included as available-for-sale are securities that are purchased in connection with the Company’s asset-liability risk management strategy and that may be sold in response to changes in interest rates, resultant prepayment risk and other related factors. In instances where the Company has the positive intent to hold investment securities to maturity, investment securities will be classified as held-to-maturity and carried at amortized cost. As of the balance sheet dates, all of the Company’s investment securities were classified as available-for-sale and carried at fair value. There are inherent risks associated with the Company’s investment activities that could adversely impact the fair market value and the ultimate collectability of the Company’s investments. Management regularly reviews the portfolio for securities with unrealized losses to determine if any of the unrealized losses are other-than-temporarily impaired ("OTTI"). The determination of OTTI involves a high degree of judgment. While management uses available information to measure OTTI at the balance sheet date, future write-downs may be necessary based on extended duration of current unrealized losses, changing market conditions, or circumstances surrounding individual issuers. If an investment is deemed to have an unrealized loss that is OTTI, the Company is required to write-down the investment. For debt securities, OTTI is generally recognized through a charge to earnings as of the balance sheet date, while non-OTTI unrealized losses are recognized in other comprehensive income. Unrealized losses on debt securities are deemed OTTI if 1) the Company intends to sell the security, 2) it is more likely than not that the Company will be required to sell the security before recovery, or 3) a credit loss exists and the Company does not expect to recover the entire amortized cost. For debt securities that have a credit loss, any portion of the loss related to other factors is recorded in other comprehensive income. Once written-down, the previous charge on debt securities may not be recovered through earnings until sale or maturity, if in excess of its new cost basis. Any OTTI charges, depending upon the magnitude of the charges, could have a material adverse effect on the Company’s financial condition and results of operations. At December 31, 2017 the Company did not hold any equity investments. See "Accounting pronouncements not yet adopted by the Company" under "Recent Accounting Pronouncements" in Item (t) below in this Note 1 for treatment of unrealized losses on equities beginning in 2018. See also Note 2, "Investment Securities," for further information on management's OTTI assessment. Investment securities’ discounts are accreted and premiums are amortized over the period of estimated principal repayment using methods that approximate the interest method. Gains or losses on the sale of investment securities are recognized on the trade date on a specific identification basis. See "Accounting pronouncements adopted by the Company" within "Recent Accounting Pronouncements" in Item (t) below in this Note 1 for further information on the Company's amortization of premiums on callable debt securities. (e) Restricted Investments Certain of the Company's derivative agreements contain provisions for collateral to be posted if the derivative exposure exceeds a threshold amount. When the Company has pledged cash as collateral for this purpose, the cash is carried as restricted cash within cash and cash equivalents. See Note 8, "Derivatives and Hedging Activities" for more information about the Company's collateral related to its derivatives. The Bank is also required by the FRB to maintain in reserves certain amounts of vault cash and/or deposits with the FRB. The average daily reserve requirement included in “Cash and Due from Banks” was approximately $7.6 million and $6.8 million , based on the two week computation periods encompassing December 31, 2017 and 2016 , respectively. As a member of the Federal Home Loan Bank of Boston ("FHLB"), the Company is required to purchase certain levels of FHLB capital stock at par value in association with outstanding advances from the FHLB. From time-to-time, the FHLB may initiate the repurchase, at par value, of "excess" levels of its capital stock held by member banks. This stock is classified as a restricted investment and carried at cost, which management believes approximates fair value. FHLB stock represents the only restricted investment held by the Company. Management regularly reviews its holdings of FHLB stock for OTTI. Based on management’s periodic review, the Company has not recorded any OTTI charges on this investment to date. If it was determined that a write-down of FHLB stock was required, impairment would be recognized through a charge to earnings. See Note 2, "Investment Securities," for additional information on management's OTTI review of investments. (f) Loans Held for Sale Depending on the current interest rate environment, management projections of future interest rates and the overall asset-liability management program of the Company, management may elect to sell those fixed and adjustable rate residential mortgage loans which are eligible for sale in the secondary market or hold some or all of this residential loan production for the Company's portfolio. Mortgage loans are generally not pooled for sale, but instead sold on an individual basis. Enterprise may retain or sell the servicing when selling the loans. Loans sold are subject to standard secondary market underwriting and eligibility representations and warranties over the life of the loan and are subject to an early payment default period covering the first four payments for certain loan sales. Loans held for sale are carried at the lower of aggregate amortized cost or market value. Market value is based on comparable market prices for loans with similar rates and terms. When loans are sold, a gain or loss is recognized to the extent that the sales proceeds plus unamortized fees and costs exceed, or are less than, the carrying value of the loans. Gains and losses are determined using the specific identification method. (g) Loans Loans made by the Company to businesses include commercial mortgage loans, construction and land development loans, secured and unsecured commercial loans and lines of credit, and letters of credit. The Company also originates equipment lease financing for businesses. Loans made to individuals include conventional residential mortgage loans, home equity loans and lines, residential construction loans on owner-occupied primary and secondary residences, and secured and unsecured personal loans and lines of credit. Most loans granted by the Company are collateralized by real estate or equipment and/or are guaranteed by the principals of the borrower. The ability and willingness of the single family residential and consumer borrowers to honor their repayment commitments is generally dependent on the level of overall economic activity and real estate values within the borrowers’ geographic areas. The ability and willingness of commercial real estate, commercial and construction loan borrowers to honor their repayment commitments is generally dependent on the health of the real estate sector in the borrowers’ geographic areas and the general economy, among other factors. Loans are reported at the principal amount outstanding, net of deferred origination fees and costs. The aggregate amount of overdrawn deposit accounts are reclassified as loan balances. Loan origination fees received, offset by direct loan origination costs, are deferred and amortized using the straight line method over three to five years for lines of credit and demand notes or over the life of the related loans using the level-yield method for all other types of loans. When loans are paid off, the unamortized fees and costs are recognized as an adjustment to interest income. From time to time, the Company participates with other banks in the financing of certain commercial projects. In each case in which the Company participates in a loan, the rights and obligations of each participating bank are divided proportionately among the participating banks in an amount equal to their share of ownership and with equal priority among all banks. When the participation qualifies as a sale under GAAP, the balances participated out to other institutions are not carried as assets on the Company's consolidated financial statements. Loans originated by other banks in which the Company is the participating institution are carried in the loan portfolio at the Company's pro rata share of ownership. See also, "Commercial loans" under "Loan categories" in Note 3, 'Loans" for further information about the Company's participation loans. (h) Allowance for Loan Losses The allowance for loan losses is an estimate of probable credit risk inherent in the loan portfolio as of the specified balance sheet dates. The allowance for loan losses is established through a provision for loan losses, a direct charge to earnings. Loan losses are charged against the allowance when management believes that the collectability of the loan principal is unlikely. Recoveries on loans previously charged-off are credited to the allowance. The Company maintains the allowance at a level that it deems adequate to absorb all reasonably anticipated probable losses from specifically known and other credit risks associated with the portfolio. The Company uses a systematic methodology to measure the amount of estimated loan loss exposure inherent in the portfolio for purposes of establishing a sufficient allowance for loan losses. The methodology uses a two-tiered approach that makes use of specific reserves for loans individually evaluated and deemed impaired and general reserves for larger groups of homogeneous loans, which are collectively evaluated relying on a combination of qualitative and quantitative factors that may affect credit quality of the pool. On a quarterly basis, the Company prepares an estimate of the allowance necessary to cover estimated credit risk inherent in the portfolio as of the specified balance sheet dates. The adequacy of the allowance for loan losses is reviewed and evaluated on a regular basis by an internal management committee and the full Board. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to recognize additions to the allowance based on judgments different from those of management. See Note 4, "Allowance for Loan Losses," for additional accounting policies related to non-accrual, impaired and troubled debt restructured loans and to the allowance for loan losses. (i) Other Real Estate Owned Real estate acquired by the Company through foreclosure proceedings or the acceptance of a deed in lieu of foreclosure is classified as Other Real Estate Owned ("OREO"). When property is acquired, it is generally recorded at the lesser of the loan’s remaining principal balance, net of unamortized deferred fees, or the estimated fair value of the property acquired, less estimated costs to sell, establishing a new cost basis. The estimated fair value is based on market appraisals and the Company’s internal analysis. Any loan balance in excess of the estimated realizable fair value on the date of transfer is charged to the allowance for loan losses on that date. All costs incurred thereafter in maintaining the property, as well as subsequent declines in fair value are charged to non-interest expense. (j) Premises and Equipment Land is carried at cost. Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation or amortization is computed on a straight-line basis over the lesser of the estimated useful lives of the asset or the respective lease term (with reasonably assured renewal options) for leasehold improvements generally as follows: Bank premises and leasehold improvements 10 to 39 years Computer software and equipment 3 to 5 years Furniture, fixtures and equipment 3 to 10 years (k) Bank Owned Life Insurance The Company has purchased bank-owned life insurance ("BOLI') on certain current and former senior and executive officers. The cash surrender value carried on the consolidated balance sheets at December 31, 2017 and December 31, 2016 amounted to $29.5 million and $28.8 million , respectively. There are no associated surrender charges under the outstanding policies. (l) Impairment of Long-Lived Assets Other than Goodwill The Company reviews long-lived assets, including premises and equipment, for impairment on an ongoing basis or whenever events or changes in business circumstances indicate that the remaining useful life may warrant revision or that the carrying amount of the long-lived asset may not be fully recoverable. If impairment is determined to exist, any related impairment loss is recognized through a charge to earnings. Impairment losses on assets disposed of, if any, are based on the estimated proceeds to be received, less cost of disposal. (m) Goodwill Goodwill carried on the Company’s consolidated financial statements was $5.7 million at both December 31, 2017 and December 31, 2016 . This asset is related to the Company’s acquisition of two branch offices in July 2000. In accordance with GAAP, the Company does not amortize goodwill and instead, at least annually, evaluates whether the carrying value of goodwill has become impaired. Impairment of the goodwill may occur when the estimated fair value of the Company is less than its recorded book value. A determination that goodwill has become impaired results in an immediate write-down of goodwill to its determined value with a resulting charge to operations. The annual impairment test begins with a qualitative assessment of whether it is "more likely than not" that the reporting unit's fair value is less than its carrying amount. The assessment is performed at the reporting unit level. If an entity concludes it is not "more likely than not" that the fair value of a reporting unit is less than its carrying amount, it need not perform a two-step impairment test. In the case of the Company, the services offered through the Bank and subsidiaries are managed as one strategic unit and represent the Company’s only reportable operating segment. Management's qualitative assessment takes into consideration macroeconomic conditions, industry and market considerations, cost or margin factors, financial performance and share price. Based on this assessment, the Company determined that it is not "more likely than not" that the Company's fair value is less than its carrying amount and therefore goodwill was determined not to be impaired at December 31, 2017 . If the Company's qualitative assessment concluded that it is "more likely than not" that the fair value of a reporting unit is less than its carrying amount, it must perform the two-step impairment test to identify potential goodwill impairment and measure the amount of goodwill impairment loss to be recognized, if any. The first step of the goodwill impairment test compares the estimated fair value of the reporting unit with its carrying amount, or the book value of the reporting unit, including goodwill. If the estimated fair value of the reporting unit equals or exceeds its book value, goodwill is considered not impaired, and the second step of the impairment test is unnecessary. The second step, if necessary, measures the amount of goodwill impairment loss to be recognized. The reporting unit must determine fair values for all assets and liabilities, excluding goodwill. The net of the assigned fair value of assets and liabilities is then compared to the book value of the reporting unit, and any excess book value becomes the implied fair value of goodwill. If the carrying amount of the goodwill exceeds the newly calculated implied fair value of that goodwill, an impairment loss is recognized in the amount required to write down the goodwill to the implied fair value. (n) Investment Assets Under Management Investment assets under management, consisting of assets managed through Enterprise Wealth Management and Enterprise Wealth Services and commercial sweep products, totaled $845.0 million and $725.3 million at December 31, 2017 and 2016 , respectively. Fee income is recorded on an accrual basis and recognized over the period in which it is earned. Securities and other property held in a fiduciary or agency capacity are not included in the consolidated balance sheets because they are not assets of the Company. (o) Derivatives The Company recognizes all derivatives as either assets or liabilities on its consolidated balance sheet and measures those instruments at fair market value. Interest-rate-lock commitments related to the origination of mortgage loans that will be sold are considered derivative instruments. The commitments to sell loans are also considered derivative instruments. The Company generally does not pool mortgage loans for sale, but instead, sells the loans on an individual basis. To reduce the net interest rate exposure arising from its loan sale activity, the Company enters into the commitment to sell these loans at essentially the same time that the interest-rate lock commitment is quoted on the origination of the loan. The Company estimates the fair value of these derivatives based on current secondary mortgage market prices. At December 31, 2017 and 2016 , the estimated fair value of the Company's interest-rate lock commitments and commitments to sell these mortgage loans were deemed immaterial. The Company may use interest-rate-contract swaps as part of its interest-rate risk management strategy. Interest-rate- swap agreements are entered into as hedges against future interest-rate fluctuations on specifically identified assets or liabilities. The Company did not have derivative fair value hedges or derivative cash flow hedges at December 31, 2017 or 2016 . The Company has a "Back-to-Back Swap" program whereby the Bank enters into an interest-rate swap with a qualified commercial banking customer and simultaneously enters into an equal and opposite interest-rate swap with a swap counterparty. The customer interest-rate-swap agreement allows commercial banking customers to convert a floating-rate loan payment to a fixed-rate payment. The transaction structure effectively minimizes the Bank’s net risk exposure resulting from such transactions. Customer-related credit risk is minimized by the cross collateralization of the loan and the interest-rate-swap agreement. Back-to-Back Swaps are not speculative but rather, result from a service the Company provides to certain customers. Back-to-Back Swaps do not meet hedge accounting requirements and therefore changes in the fair value of both the customer swaps and the counterparty swaps, which have an offsetting relationship, are recognized directly in earnings. See Note 8, "Derivatives and Hedging Activities" for more information about the Company's derivatives. (p) Stock Based Compensation The Company’s consolidated financial statements include stock-based compensation expense for the portion of stock option awards and stock awards for which the requisite service has been rendered during the period. The compensation expense has been recorded based on the estimated grant-date fair value of the stock option awards, or in the case of stock awards, the market value of the common stock on the date of grant. Prior to the adoption of ASU 2016-09 "Compensation - Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting," in January 2017, forfeitures were estimated and netted against the expense. Upon adoption of this ASU, expense adjustments are made for actual forfeitures as they occur. See "Recent Accounting pronouncements" below in this Note 1, for further information related to the adoption of ASU 2016-09, including the change in recording excess tax benefits and deficiencies. The Company will recognize the remaining estimated compensation expense for the portion of outstanding awards and compensation expense for any future awards, net of actual forfeitures, as the requisite service is rendered (i.e., on a straight-line basis over the remaining vesting period of each award) or as performance objectives are met. Stock awards that do not require future service ("vested awards") will be expensed immediately. Stock-based compensation also includes Director stock compensation for stock awards and stock in lieu of cash fees, both included in other operating expenses, described in more detail in Note 12, "Stock-Based Compensation." (q) Income Taxes The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and in the states of Massachusetts and New Hampshire. The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax expense or benefit attributable to differences between the financial statement carrying amounts and the tax basis of assets and liabilities. The deferred tax assets and liabilities are reflected at currently enacted income tax rates applicable to the period in which the deferred tax assets or liabilities are expected to be realized or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities will be adjusted accordingly through the provision for income taxes in the period that includes the enactment date. The Company’s policy is to classify interest resulting from underpayment of income taxes as income tax expense in the first period the interest would begin accruing according to the provisions of the relevant tax law. The Company classifies penalties resulting from underpayment of income taxes as income tax expense in the period for which the Company claims or expects to claim an uncertain tax position or in the period in which the Company’s judgment changes regarding an uncertain tax position. The income tax provisions will differ from the expense that would result from applying the federal statutory rate to income before taxes, due primarily to the impact of tax-exempt interest from certain investment securities, loans and BOLI. The Company did not have any unrecognized tax benefits accrued as income tax liabilities or receivables or as deferred tax items at December 31, 2017 or December 31, 2016 . The Company is subject to U.S. federal and state income tax examinations by taxing authorities for the 2014 through 2017 tax years. See Note 13, "Income Taxes," for further information about the Company's income taxes and deferred tax assets, including the impact of the Tax Cuts and Jobs Acts (the "new federal tax bill"). (r) Earnings per Share Basic earnings per share are calculated by dividing net income available to common stockholders by the weighted average number of common shares outstanding (including participating securities) during the year. The Company's only participating securities are unvested restricted stock awards that contain non-forfeitable rights to dividends. Diluted earnings per share reflects the effect on weighted average shares outstanding of the number of additional shares outstanding if dilutive stock options were converted into common stock using the treasury stock method. (s) Reporting Comprehensive Income Comprehensive income is defined as all changes to stockholder's equity except investments by and distributions to stockholders. Net income is one component of comprehensive income, with other components referred to in the aggregate as other comprehensive income. The Company’s only other comprehensive income component is the net unrealized holding gains or losses on investments available-for-sale, net of deferred income taxes. Pursuant to GAAP, the Company initially excludes these unrealized holding gains and losses from net income; however, they are later reported as reclassifications out of accumulated other comprehensive income into net income when the securities are sold. When securities are sold, the reclassification of realized gains and losses on available-for-sale securities are included on the Consolidated Statements of Income under the "non-interest income" subheading on the line item "net gains on sales of investment securities" and the related income tax expense is included in the line item "provision for income taxes," both of which are also detailed on the Consolidated Statements of Comprehensive Income under the subheading "reclassification adjustment for net gains included in net income." (t) Recent Accounting Pronouncements Accounting pronouncements adopted by the Company In March 2016, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU" or "Update") No. 2016-09, "Compensation - Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting. " The new standard was effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The Company adopted ASU No. 2016-09 in the first quarter of 2017. Several aspects of the accounting are simplified including, generally: a) income tax consequences; b) classification of awards as either equity or liabilities; c) accounting for forfeitures; and d) classification on the statement of cash flows. Upon adoption, the most significant impact of this amendment resulted from the prospective application of current excess tax benefits and deficiencies being recognized in income tax expense, which would previously have been recognized in additional paid-in capital, in the reporting period in which they occur. For the year ended December 31, 2017, this reduced the Company's provision for income taxes, increasing earnings by approximately $922 thousand . For the years ended December 31, 2016 and 2015, the Company recognized $789 thousand and $217 thousand , respectively, in additional paid-in-capital in this regard, which, if under the new ASU, would have been recognized as income tax benefit in the income statement. This amount, treated as discrete items in the period in which they occur, will vary from year to year as a function of the volume of share-based payments vested or exercised and the then current market price of the Company's stock in comparison to the compensation cost recognized in the consolidated financial statements. Additionally upon adoption, the C

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities The amortized cost and fair values of investment securities at December 31, 2017 and 2016 are summarized as follows: 2017 (Dollars in thousands) Amortized cost Unrealized gains Unrealized losses Fair Value Federal agency obligations (1) $ 51,769 $ 30 $ 82 $ 51,717 Residential federal agency MBS (1) 141,054 71 971 140,154 Commercial federal agency MBS (1) 66,777 9 286 66,500 Municipal securities 132,603 2,097 354 134,346 Corporate bonds 11,546 63 67 11,542 Certificates of deposits (2) 950 — 3 947 Total investment securities, at fair value (3) $ 404,699 $ 2,270 $ 1,763 $ 405,206 2016 (Dollars in thousands) Amortized cost Unrealized gains Unrealized losses Fair Value Federal agency obligations (1) $ 74,682 $ 432 $ 45 $ 75,069 Residential federal agency MBS (1) 94,818 96 1,561 93,353 Commercial federal agency MBS (1) 71,993 15 1,730 70,278 Municipal securities 112,401 922 1,520 111,803 Corporate bonds 10,734 51 90 10,695 Certificates of deposits (2) 950 — 1 949 Total debt securities 365,578 1,516 4,947 362,147 Equity investments 10,413 2,532 302 12,643 Total investment securities, at fair value $ 375,991 $ 4,048 $ 5,249 $ 374,790 (1) These categories may include investments issued or guaranteed by government sponsored enterprises such as Fannie Mae ("FNMA"), Freddie Mac ("FHLMC"), Federal Farm Credit Bank ("FFCB"), or one of several Federal Home Loan Banks, as well as, investments guaranteed by Ginnie Mae ("GNMA"), a wholly-owned government entity. (2) Certificates of deposit ("CDs") represent term deposits issued by banks that are subject to FDIC insurance and purchased on the open market. (3) As of December 31, 2017, all investments were debt securities and the Company did not hold any available-for-sale equity securities. Included in the residential and commercial federal agency MBS category were collateralized mortgage obligations ("CMOs") issued by U.S. agencies with fair values totaling $171.7 million and $107.0 million at December 31, 2017 and 2016 , respectively. As of the dates reflected in the tables above, all of the Company's investment securities were classified as available-for-sale and carried at fair value. Net unrealized appreciation and depreciation on investments available-for-sale, net of applicable income taxes, are reflected as a component of accumulated other comprehensive income (loss). The net unrealized gain or loss in the Company's debt security portfolio fluctuates as market interest rates rise and fall. Due to the predominantly fixed rate nature of this portfolio, as market rates fall the value of the portfolio rises, and as market rates rise, the value of the portfolio declines. The unrealized gains or losses on debt securities will also decline as the securities approach maturity. Unrealized losses that are deemed OTTI are generally charged to earnings, as described further in Note 1, "Summary of Significant Accounting Policies," under Item (d) "Investments." Gains or losses will be recognized in the income statement if the securities are sold. The Company did not hold any available-for-sale equity securities at December 31, 2017 . The following tables summarize investments (debt and equity) having temporary impairment, due to the fair market values having declined below the amortized costs of the individual investments, and the period that the investments have been temporarily impaired at December 31, 2017 and 2016 . 2017 Less than 12 months 12 months or longer Total (Dollars in thousands) Fair Value Unrealized Losses Fair value Unrealized Losses Fair Value Unrealized Losses # of holdings Federal agency obligations $ 34,344 $ 82 $ — $ — $ 34,344 $ 82 9 Residential federal agency MBS 109,308 882 2,015 89 111,323 971 30 Commercial federal agency MBS 35,859 205 5,190 81 41,049 286 11 Municipal securities 16,983 129 10,210 225 27,193 354 50 Corporate bonds 2,802 23 2,913 44 5,715 67 33 Certificates of deposits 947 3 — — 947 3 4 Total temporarily impaired investment securities $ 200,243 $ 1,324 $ 20,328 $ 439 $ 220,571 $ 1,763 137 2016 Less than 12 months 12 months or longer Total (Dollars in thousands) Fair Value Unrealized Losses Fair value Unrealized Losses Fair Value Unrealized Losses # of holdings Federal agency obligations $ 13,956 $ 45 $ — $ — $ 13,956 $ 45 3 Residential federal agency MBS 68,138 1,236 8,008 325 76,146 1,561 31 Commercial federal agency MBS 60,060 1,730 — — 60,060 1,730 18 Municipal securities 60,436 1,520 — — 60,436 1,520 107 Corporate bonds 5,729 90 — — 5,729 90 37 Certificates of deposit 949 1 — — 949 1 4 Equity investments 1,185 20 2,743 282 3,928 302 3 Total temporarily impaired investment securities $ 210,453 $ 4,642 $ 10,751 $ 607 $ 221,204 $ 5,249 203 During the years ended December 31, 2017 and 2016 , the Company did not record any fair value impairment charges on its investments. Management regularly reviews the portfolio for securities with unrealized losses that are other-than-temporarily impaired. At December 31, 2017 , management did not consider it debt securities to have OTTI and attributes the unrealized losses to increases in current market yields compared to the yields at the time the investments were purchased by the Company. The process for assessing investments for OTTI may vary depending on the type of security. In assessing the Company's investments in federal agency mortgage-backed securities and federal agency obligations, the contractual cash flows of these investments are guaranteed by the respective government sponsored enterprise (FHLMC, FNMA, FFCB, or FHLB) or wholly-owned government corporation (GNMA). Accordingly, it is expected that the securities would not be settled at a price less than the par value of the Company's investments. Management's assessment of other debt securities within the portfolio includes reviews of market pricing, ongoing credit quality evaluations, assessment of the investments' materiality, and duration of the investments' unrealized loss position. In addition, the Company utilizes an outside registered investment adviser to manage the corporate and municipal bond portfolios, within prescribed guidelines set by management, and to provide assistance in assessing the credit risk of those portfolios. At December 31, 2017 , the Company's corporate and municipal bond portfolios did not contain any securities below investment grade, as reported by major credit rating agencies. For equities and funds, management's assessment includes the severity of the declines, whether it is unlikely that the security or fund will completely recover its unrealized loss within a reasonable time period and if the equity security or fund exhibits fundamental deterioration. The Company did not hold any equity securities at December 31, 2017 . As noted in the table above, a small portion of the portfolio was invested in CDs and was also in an unrealized loss position at December 31, 2017 due to market rates. The unrealized loss was not considered to be material and the securities are expected to mature at par value. The contractual maturity distribution at December 31, 2017 of total debt securities was as follows: (Dollars in thousands) Amortized Cost Fair Value Due in one year or less $ 19,095 $ 19,159 Due after one, but within five years 82,231 82,255 Due after five, but within ten years 134,395 134,959 Due after ten years 168,978 168,833 Total available-for-sale securities $ 404,699 $ 405,206 Scheduled contractual maturities shown above may not reflect the actual maturities of the investments. The actual MBS/CMO cash flows likely will be faster than presented above due to prepayments and amortization. Similarly, included in debt securities above are callable securities, comprised of municipal securities and corporate bonds with amortized costs and fair values of $74.5 million and $75.7 million , respectively, at December 31, 2017 , which can be redeemed by the issuers prior to the maturity presented above. Management considers these factors when evaluating the interest rate risk in the Company's asset-liability management program. From time to time the Company may pledge securities as collateral for deposit account balances of municipal customers, and for borrowing capacity with the FHLB and the Federal Reserve Bank of Boston (the "FRB"). The fair value of securities pledged as collateral for these purposes was $383.1 million at December 31, 2017 and $361.2 million at December 31, 2016 . Sales of investments, including pending trades based on trade date, if applicable, for the years ended December 31, 2017 , 2016 , and 2015 are summarized as follows: (Dollars in thousands) 2017 2016 2015 Amortized cost of investments sold (1) $ 145,472 $ 4,299 $ 23,287 Gross realized gains on sales 3,411 803 1,990 Gross realized losses on sales (2,695 ) (1 ) (162 ) Total proceeds from sales of investments $ 146,188 $ 5,101 $ 25,115 (1) Amortized cost of investments sold is determined on a specific identification basis. In 2017, the gross realized gains were primarily from equity sales, partially offset by losses predominately from a debt security portfolio restructuring. The proceeds from sales of investments were reinvested into the portfolio. Tax-exempt interest earned on the municipal securities portfolio was $4.0 million for the year ended December 31, 2017 , $3.6 million for the year ended December 31, 2016 , and $2.9 million for the year ended December 31, 2015 . The average balance of tax-exempt investments was $111.6 million and $100.0 million for the years ended December 31, 2017 and December 31, 2016 , respectively. See Item (d) "Investments," contained in Note 1, "Summary of Significant Accounting Policies," for additional information regarding the accounting for the Company’s investments portfolio. See also Note 15, "Fair Value Measurements," below for further information regarding the Company’s fair value measurements for available-for-sale securities.

Loans

Loans	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans	Loans The Company specializes in lending to business entities, non-profit organizations, professional practices and individuals. The Company’s primary lending focus is on the development of high quality commercial relationships achieved through active business development efforts, long-term relationships with established commercial developers, strong community involvement and focused marketing strategies. Loans made to businesses include commercial mortgage loans, construction and land development loans, secured and unsecured commercial loans and lines of credit, and letters of credit. The Company also originates equipment lease financing for businesses. Loans made to individuals include conventional residential mortgage loans, home equity loans and lines, residential construction loans on owner-occupied primary and secondary residences, and secured and unsecured personal loans and lines of credit. The Company manages its loan portfolio to avoid concentration by industry, relationship size and source of repayment to lessen its credit risk exposure. See Note 4, "Allowance for Loan Losses," for information on the Company's credit risk management, non-accrual, impaired and troubled debt restructured loans and the allowance for loan losses. Major classifications of loans at the periods indicated were as follows: (Dollars in thousands) December 31, 2017 December 31, 2016 Commercial real estate $ 1,201,351 $ 1,038,082 Commercial and industrial 498,802 490,799 Commercial construction 274,905 213,447 Total commercial loans 1,975,058 1,742,328 Residential mortgages 195,492 180,560 Home equity loans and lines 91,706 91,065 Consumer 10,293 10,845 Total retail loans 297,491 282,470 Gross loans 2,272,549 2,024,798 Deferred loan origination fees, net (2,645 ) (2,069 ) Total loans 2,269,904 2,022,729 Allowance for loan losses (32,915 ) (31,342 ) Net loans $ 2,236,989 $ 1,991,387 Loan Categories Commercial loans Commercial real estate loans include loans secured by both owner-use and non-owner occupied real estate. These loans are typically secured by a variety of commercial and industrial property types, including one-to-four family and multi-family apartment buildings, office, industrial or mixed-use facilities, strip shopping centers or other commercial properties, and are generally guaranteed by the principals of the borrower. Commercial real estate loans generally have repayment periods of approximately fifteen to twenty-five years. Variable interest rate loans have a variety of adjustment terms and underlying interest rate indices, and are generally fixed for an initial period before periodic rate adjustments begin. Commercial and industrial loans include seasonal revolving lines of credit, working capital loans, equipment financing (including equipment leases), and term loans. Also included in commercial and industrial loans are loans partially guaranteed by the U. S. Small Business Administration ("SBA"), and loans under various programs and agencies. Commercial and industrial credits may be unsecured loans and lines to financially strong borrowers, loans secured in whole or in part by real estate unrelated to the principal purpose of the loan or secured by inventories, equipment, or receivables, and are generally guaranteed by the principals of the borrower. Variable rate loans and lines in this portfolio have interest rates that are periodically adjusted, with loans generally having fixed initial periods. Commercial and industrial loans have average repayment periods of one to seven years. Commercial construction loans include the development of residential housing and condominium projects, the development of commercial and industrial use property, and loans for the purchase and improvement of raw land. These loans are secured in whole or in part by the underlying real estate collateral and are generally guaranteed by the principals of the borrowers. Construction lenders work to cultivate long-term relationships with established developers. The Company limits the amount of financing provided to any single developer for the construction of properties built on a speculative basis. Funds for construction projects are disbursed as pre-specified stages of construction are completed. Regular site inspections are performed, prior to advancing additional funds, at each construction phase, either by experienced construction lenders on staff or by independent outside inspection companies. Commercial construction loans generally are variable rate loans and lines with interest rates that are periodically adjusted and generally have terms of one to three years. From time to time, the Company participates with other banks in the financing of certain commercial projects. Participating loans with other institutions provide banks the opportunity to retain customer relationships and reduce credit risk exposure among each participating bank, while providing customers with larger credit vehicles than the individual bank might be willing or able to offer independently. In some cases, the Company may act as the lead lender, originating and servicing the loans, but participating out a portion of the funding to other banks. In other cases, the Company may participate in loans originated by other institutions. In each case, the participating bank funds a percentage of the loan commitment and takes on the related pro-rata risk. In each case in which the Company participates in a loan, the rights and obligations of each participating bank are divided proportionately among the participating banks in an amount equal to their share of ownership and with equal priority among all banks. When the participation qualifies as a sale under GAAP, the balances participated out to other institutions are not carried as assets on the Company's consolidated financial statements. The Company performs an independent credit analysis of each commitment and a review of the participating institution prior to participation in the loan, and an annual review thereafter of each participating institution. Loans originated by other banks in which the Company is a participating institution are carried in the loan portfolio at the Company's pro-rata share of ownership. Loans originated by other banks in which the Company is a participating institution amounted to $91.6 million at December 31, 2017 and $85.2 million at December 31, 2016 . See also "Loans serviced for others" below for information related to commercial loans participated out to various institutions. In addition, the Company participates in various community development loan funds in which local banks contribute to a loan pool which is independently managed. These loan pools make small dollar loans available to local businesses and start-ups that might otherwise not qualify for traditional small business loans directly from banks, with the potential risk spread among the participating banks. The goal of these partnerships with community development loan funds is to stimulate local economic development, create jobs, and help small businesses and entrepreneurs to become more viable, bankable and an integrated part of the local community. Letters of credit are conditional commitments issued by the Company to guarantee the financial obligation or performance of a customer to a third party. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. If the letter of credit is drawn upon, a loan is created for the customer, generally a commercial loan, with the same criteria associated with similar commercial loans. Residential mortgage loans Enterprise originates conventional mortgage loans on one-to-four family residential properties. These properties may serve as the borrower's primary residence, or as vacation homes or investment properties. Loan-to-value limits vary, generally from 75% for multi-family, owner-occupied properties, up to 97% for single family, owner-occupied properties, with mortgage insurance coverage required for loan-to-value ratios greater than 80% based on program parameters. In addition, financing is provided for the construction of owner-occupied primary and secondary residences. Residential mortgage loans may have terms of up to 30 years at either fixed or adjustable rates of interest. Fixed and adjustable rate residential mortgage loans are generally originated using secondary market underwriting and documentation standards. Depending on the current interest rate environment, management projections of future interest rates and the overall asset-liability management program of the Company, management may elect to sell those fixed and adjustable rate residential mortgage loans which are eligible for sale in the secondary market, or hold some or all of this residential loan production for the Company's portfolio. Mortgage loans are generally not pooled for sale, but instead sold on an individual basis. The Company may retain or sell the servicing when selling the loans. Loans sold are subject to standard secondary market underwriting and eligibility representations and warranties over the life of the loan and are subject to an early payment default period covering the first four payments for certain loan sales. Loans classified as held for sale are carried as a separate line item on the consolidated balance sheet. Home equity loans and lines of credit Home equity term loans have in the past been originated for one-to-four family residential properties with maximum original loan-to-value ratios generally up to 80% of the automated valuation or appraised value of the property securing the loan. Home equity loan payments consist of monthly principal and interest based on amortization ranging from three to fifteen years. The rates may be variable or fixed. The Company originates home equity revolving lines of credit for one-to-four family residential properties with maximum original loan-to-value ratios generally up to 80% of the automated valuation or appraised value of the property securing the loan. Home equity lines generally have interest rates that adjust monthly based on changes in the Wall Street Journal Prime Rate, although minimum rates may be applicable. Some home equity line rates may be fixed for a period of time and then adjusted monthly thereafter. The payment schedule for home equity lines requires interest only payments for the first ten years of the lines. Generally at the end of ten years, the line may be frozen to future advances, and principal plus interest payments are collected over a fifteen -year amortization schedule or, for eligible borrowers meeting certain requirements, the line availability may be extended for an additional interest only period. Consumer loans Consumer loans consist primarily of secured or unsecured personal loans, loans under energy efficiency financing programs in conjunction with Massachusetts public utilities, and overdraft protection lines on checking accounts extended to individual customers. The aggregate amounts of overdrawn deposit accounts are reclassified as loan balances. Related Party Loans Certain of the Company's directors, officers, principal stockholders and their associates are credit customers of the Company in the ordinary course of business. In addition, certain directors are also directors, trustees, officers or stockholders of corporations and non-profit entities or members of partnerships that are customers of the Bank and that enter into loan and other transactions with the Bank in the ordinary course of business. All loans and commitments included in such transactions are on such terms, including interest rates, repayment terms and collateral, as those prevailing at the time for comparable transactions with persons who are not affiliated with the Bank and do not involve more than a normal risk of collectability or present other features unfavorable to the Bank. As of December 31, 2017 and 2016 , the outstanding loan balances to directors, officers, principal stockholders and their associates were $33.9 million and $18.6 million , respectively. All loans to these related parties were current and accruing at those dates. Unadvanced portions of lines of credit available to these individuals were $16.8 million and $9.8 million , as of December 31, 2017 and 2016 , respectively. During 2017 , new loans and net increases in loan balances or lines of credit under existing commitments of $30.2 million were made and principal paydowns of $7.9 million were received. During 2016 , new loans and net increases in loan balances or lines of credit under existing commitments of $2.3 million were made and principal paydowns of $1.9 million were received. Loans Serviced for Others At December 31, 2017 and 2016 , the Company was servicing residential mortgage loans owned by investors amounting to $18.4 million and $18.7 million , respectively. Additionally, the Company was servicing commercial loans participated out to various other institutions amounting to $70.7 million and $62.3 million at December 31, 2017 and 2016 , respectively. See the discussion above under the heading "Commercial loans" for further information regarding commercial participations. Loans Serving as Collateral Loans designated as qualified collateral and pledged to the FHLB for borrowing capacity for the periods indicated are summarized below: (Dollars in thousands) December 31, 2017 December 31, 2016 Commercial real estate $ 224,703 $ 247,664 Residential mortgages 187,524 170,247 Home equity loans and lines 9,405 12,340 Total loans pledged to FHLB $ 421,632 $ 430,251 Tax-Exempt Interest Tax-exempt interest earned on qualified commercial loans was $2.1 million for both the years ended December 31, 2017 and 2016 and $1.6 million for the year ended December 31, 2015 , respectively. Average tax-exempt loan balances were $64.4 million and $63.9 million for the years ended December 31, 2017 and 2016 , respectively. See Note 15, "Fair Value Measurements," below for further information regarding the Company's fair value measurements for loans, and Note 8, "Derivatives and Hedging Activities," below for information regarding interest-rate-swap agreements related to certain commercial loans. For additional information on unadvanced loans and lines, commitments to originate loans, letters of credit and commitments to originate loans for sale or to sell loans see Note 9, "Commitments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk."

Allowance For Loan Losses

Allowance For Loan Losses	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for Loan Loss	Allowance for Loan Losses Inherent in the lending process is the risk of loss due to customer non-payment, or "credit risk." The Company's commercial lending focus may entail significant additional credit risks compared to long-term financing on existing, owner-occupied residential real estate. The Company seeks to lessen its credit risk exposure by managing its loan portfolio to avoid concentration by industry, relationship size and source of repayment, and through sound underwriting practices and the credit risk management function; however, management recognizes that loan losses will occur and that the amount of these losses will fluctuate depending on the risk characteristics of the loan portfolio and economic conditions. In making its assessment on the adequacy of the allowance, management considers several quantitative and qualitative factors that could have an effect on the credit quality of the portfolio including, individual review of larger and higher risk problem assets, the level of delinquent loans and non-performing loans, impaired loans, the level of net charge-offs, and the growth and composition of the loan portfolio, as well as trends in the general levels of these indicators. In addition management monitors expansion in geographic market area, the experience level of lenders and any changes in underwriting criteria, the strength of local and national economy, including general conditions in the multi-family, commercial real estate and development and construction markets in the local region. Allowance for Probable Loan Losses Methodology On a quarterly basis, management prepares an estimate of the allowance necessary to cover estimated probable credit losses. The Company uses a systematic methodology to measure the amount of estimated loan loss exposure inherent in the portfolio for purposes of establishing a sufficient allowance for loan losses. The methodology makes use of specific reserves for loans individually evaluated and deemed impaired, and general reserves for larger groups of homogeneous loans, which are collectively evaluated relying on a combination of qualitative and quantitative factors that may affect credit quality of the pool. Specific Reserves for loans individually evaluated for impairment When a loan is deemed to be impaired, management estimates the credit loss by comparing the loan's carrying value against either 1) the present value of the expected future cash flows discounted at the loan's effective interest rate; 2) the loan's observable market price; or 3) the expected realizable fair value of the collateral, in the case of collateral dependent loans. A specific allowance is assigned to the impaired loan for the amount of estimated credit loss. Impaired loans are charged-off, in whole or in part, when management believes that the recorded investment in the loan is uncollectible. General Reserves for loans collectively evaluated for impairment In assessing the general reserves management has segmented the portfolio for groups of loans with similar risk characteristics, by I. Non-classified loans, and II. Regulatory problem-asset segments. These groups are further subdivided by loan category or internal risk rating, respectively. The general loss allocation factors take into account the quantitative historic loss experience, qualitative or environmental factors such as those identified above, as well as regulatory guidance and industry data. I. Non-classified loans by credit type: Management has established the modified historic loss factor for non-classified loan segments by first calculating net charge-offs over a period of time, divided by the average loan balance over that same period. The time period utilized equates to the estimated loss emergence period for each loan segment. This average period may be changed from time to time to be reflective of the most appropriate corresponding conditions (market, economic, etc.). These historic loss factors are then adjusted up or down based on management’s assessment of current qualitative factors that are likely to cause estimated credit losses as of the evaluation date to differ from the segment’s historical loss experience. These key qualitative factors include the following broad categories: • Several key areas of expansion and growth, including geographic market, changes in lending staff, new or expanded product lines, changes in composition and portfolio concentrations; • Changes in the credit trend and current volume and severity of past due loans, non-accrual loans and the severity of adversely classified and impaired loans compared to historical levels; and • The current economic environment and conditions (local, state and national) and their general implications to each loan category. Management weighs the current effect of each of these areas on each particular non-classified loan segment in determining the allowance allocation factors. Management must exercise significant judgment when evaluating the effect of these qualitative factors on the amount of the allowance for loan losses on the non-classified segments because data may not be reasonably available or directly applicable to determine the precise impact of a factor on the collectability of the loan portfolio as of the evaluation date. The methodology contemplates a range of acceptable levels for these factors due to the subjective nature of the factors and the qualitative considerations related to the inherent credit risk in the portfolio. II. Regulatory problem-assets segments by credit rating: For determining the reserve percentages for problem-loans, management has segmented the portfolio following the regulatory problem-asset segments by risk rating: Criticized; Substandard; Doubtful; or Loss, after excluding loans that are individually evaluated for impairment. The modified historic loss factor for problem loan segments was determined by first tracking a sampling of these loans over a period of time, to determine the ultimate resolution. Those balances resulting in charge-offs were calculated as a percentage of the segment's loan balance and an average was calculated over that same period. This average period may be changed from time to time to be reflective of the most appropriate corresponding conditions (market, economic, etc.). These historic loss factors are then adjusted up or down based on management’s assessment of current qualitative factors that are likely to cause estimated credit losses as of the evaluation date to differ from the segment’s historical loss experience. Management also utilizes regulatory guidance and industry data in relation to the Company's own portfolio statistics as a basis for assessing the reasonableness of the allocation factors for each class of regulatory problem-assets. Management recognizes that additional issues may also impact the estimate of credit losses to some degree. From time to time management will re-evaluate the qualitative factors, regulatory guidance, and industry data in use in order to consider the impact of other issues which, based on changing circumstances, may become more significant in the future. The balances of loans as of December 31, 2017 by segment and evaluation method are summarized as follows: (Dollars in thousands) Loans individually evaluated for impairment Loans collectively evaluated for impairment Gross Loans Commercial real estate $ 13,739 $ 1,187,612 $ 1,201,351 Commercial and industrial 10,096 488,706 498,802 Commercial construction 1,624 273,281 274,905 Residential mortgages 397 195,095 195,492 Home equity loans and lines 371 91,335 91,706 Consumer 35 10,258 10,293 Total gross loans $ 26,262 $ 2,246,287 $ 2,272,549 The balances of loans as of December 31, 2016 by segment and evaluation method are summarized as follows: (Dollars in thousands) Loans individually evaluated for impairment Loans collectively evaluated for impairment Gross Loans Commercial real estate $ 14,261 $ 1,023,821 $ 1,038,082 Commercial and industrial 13,372 477,427 490,799 Commercial construction 3,364 210,083 213,447 Residential mortgages 289 180,271 180,560 Home equity loans and lines 509 90,556 91,065 Consumer 1 10,844 10,845 Total loans $ 31,796 $ 1,993,002 $ 2,024,798 Credit Risk Management As noted above, the credit risk management function focuses on a wide variety of factors and early detection of credit issues is critical to minimize credit losses. Accordingly, management regularly monitors these factors, among others, through ongoing credit reviews by the Credit Department, an external loan review service, reviews by members of senior management as well as reviews by the Loan Committee and the Board. This review includes the assessment of internal credit quality indicators such as, among others, the risk classification of adversely classified loans, past due and non-accrual loans, impaired and restructured loans, and the level of foreclosure activity. These credit quality indicators are discussed below. Credit Quality Indicators Adversely classified loans The Company's loan risk rating system classifies loans depending on risk of loss characteristics. The classifications range from "substantially risk free" for the highest quality loans and loans that are secured by cash collateral, through a satisfactory range of "minimal," "moderate," "better than average," and "average" risk, to the regulatory problem-asset classifications of "criticized," for loans that may need additional monitoring, and the more severe adverse classifications of "substandard," "doubtful," and "loss" based on criteria established under banking regulations. Loans which are evaluated to be of weaker credit quality are placed on the "watch credit list" and reviewed on a more frequent basis by management. Loans classified as substandard include those loans characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. These loans are inadequately protected by the sound net worth and paying capacity of the borrower; repayment has become increasingly reliant on collateral liquidation or reliance on guaranties; credit weaknesses are well-defined; borrower cash flow is insufficient to meet the required debt service specified in the loan terms and to meet other obligations, such as trade debt and tax payments. Loans classified as doubtful have all the weaknesses inherent in a substandard rated loan with the added characteristic that the weaknesses make collection or full payment from liquidation, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. The probability of loss is extremely high, but because of certain important and reasonably specific pending factors which may work to the advantage and strengthening of the loan, its classification as an estimated loss is deferred until more exact status may be determined. Loans classified as loss are generally considered uncollectible at present, although long term recovery of part or all of loan proceeds may be possible. These "loss" loans would require a specific loss reserve or charge-off. Adversely classified loans may be accruing or in non-accrual status and may be additionally designated as impaired or restructured, or some combination thereof. The following tables present the Company's credit risk profile for each class of loan in its portfolio by internally assigned adverse risk rating category as of the periods indicated. December 31, 2017 (Dollars in thousands) Adversely Classified Not Adversely Classified Gross Loans Substandard Doubtful Loss Commercial real estate $ 12,895 $ — $ — $ 1,188,456 $ 1,201,351 Commercial and industrial 9,915 48 1 488,838 498,802 Commercial construction 1,624 — — 273,281 274,905 Residential mortgages 1,355 — — 194,137 195,492 Home equity loans and lines 513 — — 91,193 91,706 Consumer 52 10 — 10,231 10,293 Total gross loans $ 26,354 $ 58 $ 1 $ 2,246,136 $ 2,272,549 December 31, 2016 (Dollars in thousands) Adversely Classified Not Adversely Classified Gross Loans Substandard Doubtful Loss Commercial real estate $ 16,003 $ — $ — $ 1,022,079 $ 1,038,082 Commercial and industrial 12,770 99 2 477,928 490,799 Commercial construction 3,364 — — 210,083 213,447 Residential mortgages 1,414 — — 179,146 180,560 Home equity loans and lines 666 — — 90,399 91,065 Consumer 30 — — 10,815 10,845 Total gross loans $ 34,247 $ 99 $ 2 $ 1,990,450 $ 2,024,798 Total adversely classified loans amounted to 1.16% of total loans at December 31, 2017 , as compared to 1.70% at December 31, 2016 . Past due and non-accrual loans Loans on which the accrual of interest has been discontinued are designated as non-accrual and the classified portions are credit downgraded to one of the adversely classified categories noted above. Accrual of interest on loans is generally discontinued when a loan becomes contractually past due, with respect to interest or principal, by 90 days, or when reasonable doubt exists as to the full and timely collection of interest or principal. Interest payments received on loans in a non-accrual status are generally applied to principal on the books of the Company. When a loan is placed on non-accrual status, all interest previously accrued but not collected is reversed against current period interest income. Interest accruals are resumed on such loans only when payments are brought current and have remained current for a period of 180 days and when, in the judgment of management, the collectability of both principal and interest is reasonably assured. Additionally, deposit accounts overdrawn for 90 or more days are included in the consumer non-accrual numbers below. The following tables present an age analysis of past due loans as of the dates indicated: Balance at December 31, 2017 (Dollars in thousands) Past Due 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Total Past Due Loans Current Loans Gross Loans Non-accrual Loans Commercial real estate $ 4,200 $ 69 $ 3,569 $ 7,838 $ 1,193,513 $ 1,201,351 $ 6,751 Commercial and industrial 374 527 327 1,228 497,574 498,802 1,294 Commercial construction 2,526 518 — 3,044 271,861 274,905 193 Residential mortgages 1,931 93 89 2,113 193,379 195,492 262 Home equity loans and lines 491 120 12 623 91,083 91,706 463 Consumer 51 5 45 101 10,192 10,293 69 Total gross loans $ 9,573 $ 1,332 $ 4,042 $ 14,947 $ 2,257,602 $ 2,272,549 $ 9,032 Balance at December 31, 2016 (Dollars in thousands) Past Due 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Total Past Due Loans Current Loans Gross Loans Non-accrual Loans Commercial real estate $ 5,993 $ 923 $ 1,399 $ 8,315 $ 1,029,767 $ 1,038,082 $ 4,876 Commercial and industrial 267 4 1,544 1,815 488,984 490,799 3,174 Commercial construction — — — — 213,447 213,447 519 Residential mortgages 648 — 99 747 179,813 180,560 289 Home equity loans and lines 270 — 269 539 90,526 91,065 616 Consumer 94 13 11 118 10,727 10,845 11 Total gross loans $ 7,272 $ 940 $ 3,322 $ 11,534 $ 2,013,264 $ 2,024,798 $ 9,485 At December 31, 2017 and December 31, 2016 , all loans past due 90 days or more were carried as non-accrual, in addition to those loans where reasonable doubt existed as to the full and timely collection of interest or principal that have also been designated as non-accrual, despite their payment due status shown in the tables above. Non-accrual loans that were not adversely classified amounted to $21 thousand at December 31, 2017 and $220 thousand at December 31, 2016 . These balances primarily represented the guaranteed portions of non-performing SBA loans. The majority of the non-accrual loan balances were also carried as impaired loans during the periods noted, and are discussed further below. The ratio of non-accrual loans to total loans amounted to 0.40% and 0.47% at December 31, 2017 and December 31, 2016 , respectively. The Company's obligation to fulfill the additional funding commitments on impaired loans is generally contingent on the borrower's compliance with the terms of the credit agreement. If the borrower is not in compliance, additional funding commitments may or may not be made at the Company's discretion. At December 31, 2017 , additional funding commitments for loans on non-accrual status totaled $25 thousand . The reduction in interest income for the years ended December 31, associated with non-accruing loans is summarized as follows: (Dollars in thousands) 2017 2016 2015 Income in accordance with original loan terms $ 1,906 $ 1,585 $ 1,052 Less income recognized 990 722 426 Reduction in interest income $ 916 $ 863 $ 626 Impaired loans Impaired loans are individually significant loans for which management considers it probable that not all amounts due (principal and interest) will be collected in accordance with the original contractual terms. The majority of impaired loans are included within the non-accrual balances; however, not every loan on non-accrual status has been designated as impaired. Impaired loans include loans that have been modified in a troubled debt restructuring ("TDR"), see "Troubled debt restructurings" below. Impaired loans are individually evaluated and exclude large groups of smaller-balance homogeneous loans, such as residential mortgage loans and consumer loans, which are collectively evaluated for impairment, and loans that are measured at fair value, unless the loan is amended in a TDR. Management does not set any minimum delay of payments as a factor in reviewing for impaired classification. Management considers the individual payment status, net worth and earnings potential of the borrower, and the value and cash flow of the collateral as factors to determine if a loan will be paid in accordance with its contractual terms. An impaired or TDR loan classification will be considered for upgrade based on the borrower's sustained performance over time and their improving financial condition. Consistent with the criteria for returning non-accrual loans to accrual status, the borrower must demonstrate the ability to continue to service the loan in accordance with the original or modified terms and, in the judgment of management, the collectability of the remaining balances, both principal and interest, are reasonably assured. In the case of TDR loans having had a modified interest rate, that rate must be at, or greater than, a market rate for a similar credit at the time of modification for an upgrade to be considered. Impaired loans are individually evaluated for credit loss and a specific allowance reserve is assigned for the amount of the estimated probable credit loss. Refer to heading “Allowance for probable loan losses methodology” contained within this Note 4 for further discussion of management’s methodology used to estimate specific reserves for impaired loans. The carrying value of impaired loans amounted to $26.3 million and $31.8 million at December 31, 2017 and December 31, 2016 , respectively. Total accruing impaired loans amounted to $17.4 million and $22.4 million at December 31, 2017 and December 31, 2016 , respectively, while non-accrual impaired loans amounted to $8.9 million and $9.4 million as of December 31, 2017 and December 31, 2016 , respectively. The following tables set forth the recorded investment in impaired loans and the related specific allowance allocated as of the dates indicated: Balance at December 31, 2017 (Dollars in thousands) Unpaid contractual principal balance Total recorded investment in impaired loans Recorded investment with no allowance Recorded investment with allowance Related specific allowance Commercial real estate $ 15,132 $ 13,739 $ 12,850 $ 889 $ 59 Commercial and industrial 10,458 10,096 7,053 3,043 1,284 Commercial construction 1,678 1,624 1,624 — — Residential mortgages 511 397 262 135 5 Home equity loans and lines 543 371 371 — — Consumer 36 35 — 35 35 Total $ 28,358 $ 26,262 $ 22,160 $ 4,102 $ 1,383 Balance at December 31, 2016 (Dollars in thousands) Unpaid contractual principal balance Total recorded investment in impaired loans Recorded investment with no allowance Recorded investment with allowance Related specific allowance Commercial real estate $ 16,010 $ 14,261 $ 12,444 $ 1,817 $ 370 Commercial and industrial 14,291 13,372 9,366 4,006 2,222 Commercial construction 3,408 3,364 3,051 313 28 Residential mortgages 388 289 289 — — Home equity loans and lines 665 509 509 — — Consumer 2 1 — 1 1 Total $ 34,764 $ 31,796 $ 25,659 $ 6,137 $ 2,621 The following table presents the average recorded investment in impaired loans and the related interest recognized during the year ends indicated: December 31, 2017 December 31, 2016 December 31, 2015 (Dollars in thousands) Average recorded investment Interest income (loss) recognized Average recorded investment Interest income (loss) recognized Average recorded investment Interest income recognized Commercial real estate $ 14,473 $ 363 $ 12,988 $ 332 $ 13,827 $ 196 Commercial and industrial 12,272 370 9,790 223 9,372 97 Commercial construction 1,818 92 3,137 150 2,202 83 Residential mortgages 320 2 301 — 449 — Home equity loans and lines 482 (1 ) 356 (4 ) 174 1 Consumer 25 (1 ) 14 — 45 — Total $ 29,390 $ 825 $ 26,586 $ 701 $ 26,069 $ 377 All payments received on impaired loans in non-accrual status are applied to principal. Interest income that was not recognized on loans that were deemed impaired as of December 31, 2017 , 2016 and 2015 , amounted to $890 thousand , $858 thousand , and $688 thousand , respectively. At December 31, 2017 , additional funding commitments for impaired loans totaled $416 thousand . The Company's obligation to fulfill the additional funding commitments on impaired loans is generally contingent on the borrower's compliance with the terms of the credit agreement. If the borrower is not in compliance, additional funding commitments may or may not be made at the Company's discretion. Troubled debt restructurings Loans are designated as a TDR when, as part of an agreement to modify the original contractual terms of the loan as a result of financial difficulties of the borrower, the Bank grants the borrower a concession on the terms, that would not otherwise be considered. Typically, such concessions may consist of a reduction in interest rate to a below market rate, taking into account the credit quality of the note, extension of additional credit based on receipt of adequate collateral, or a deferment or reduction of payments (principal or interest) which materially alters the Bank's position or significantly extends the note's maturity date, such that the present value of cash flows to be received is materially less than those contractually established at the loan's origination. All loans that are modified are reviewed by the Company to identify if a TDR has occurred. TDR loans are included in the impaired loan category and, as such, these loans are individually reviewed and evaluated and a specific reserve is assigned for the amount of the estimated probable credit loss. Total TDR loans, included in the impaired loan balances above, as of December 31, 2017 and December 31, 2016 , were $20.3 million and $27.0 million , respectively. TDR loans on accrual status amounted to $17.4 million and $22.4 million at December 31, 2017 and December 31, 2016 , respectively. TDR loans included in non-performing loans amounted to $2.9 million and $4.6 million at December 31, 2017 and December 31, 2016 , respectively. The Company continues to work with customers, particularly commercial relationships, and enters into loan modifications (which may or may not be TDRs) to the extent deemed to be necessary or appropriate while attempting to achieve the best mutual outcome given the individual financial circumstances and future prospects of the borrower. At December 31, 2017 , additional funding commitments for TDR loans totaled $391 thousand . The Company's obligation to fulfill the additional funding commitments on TDR loans is generally contingent on the borrower's compliance with the terms of the credit agreement. If the borrower is not in compliance, additional funding commitments may or may not be made at the Company's discretion. The following table sets forth the post modification balances of TDRs listed by type of modification for TDRs that occurred during the periods indicated. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of restructurings Amount Number of restructurings Amount Loan advances with adequate collateral — $ — 8 $ 10,533 Extended maturity date 1 175 4 548 Temporary payment reduction and payment re-amortization of remaining principal over extended term 6 790 — — Temporary interest-only payment plan 4 191 7 1,697 Total 11 $ 1,156 19 $ 12,778 Amount of specific reserves included in the allowance for loan losses associated with TDRs listed above $ 155 $ 1,418 Loans modified as TDRs during the year ended December 31, 2017 and December 31, 2016 are detailed below. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of restructurings Pre-modification outstanding recorded investment Post-modification outstanding recorded investment Number of restructurings Pre-modification outstanding recorded investment Post-modification outstanding recorded investment Commercial real estate 3 $ 696 $ 674 8 $ 6,212 $ 7,534 Commercial and industrial 6 386 346 11 5,231 5,244 Commercial construction — — — — — — Residential mortgages 1 136 135 — — — Home equity loans and lines — — — — — — Consumer 1 1 1 — — — Total 11 $ 1,219 $ 1,156 19 $ 11,443 $ 12,778 There were no subsequent charge-offs associated with the new TDRs noted in the table above during both 2017 and 2016 . Interest payments received on non-accruing 2017 and 2016 TDR loans which were applied to principal and not recognized as interest income were not material. Payment defaults during the years ended December 31, 2017 and December 31, 2016 on loans modified as TDRs within the preceding twelve months are detailed below. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of TDRs that defaulted Post-modification outstanding recorded investment Number of TDRs that defaulted Post-modification outstanding recorded investment Commercial real estate — $ — 1 $ 148 Commercial and industrial 2 20 — — Commercial construction — — — — Residential mortgages — — — — Home equity loans and lines — — — — Consumer — — — — Total 2 $ 20 1 $ 148 Other Real Estate Owned ("OREO") The Company carried no OREO at December 31, 2017 or December 31, 2016 . There were no additions, sales or write downs on OREO during 2017 or 2016 . There were $154 thousand gains on OREO sales and no subsequent write downs during 2015. At December 31, 2017 , the Company had consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings were in process according to local requirements of the applicable jurisdictions with carrying amounts totaling $101 thousand compared with $200 thousand at December 31, 2016 . Allowance for Loan Loss Activity The allowance for loan losses is established through a provision for loan losses, a direct charge to earnings. Loan losses are charged against the allowance when management believes that the collectability of the loan principal is unlikely. Recoveries on loans previously charged-off are credited to the allowance. The allowance for loan losses amounted to $32.9 million at December 31, 2017 , compared to $31.3 million at December 31, 2016 . For the years ended December 31, 2017 and 2016 , the provision for loan losses amounted to $1.4 million and $3.0 million , respectively. The decrease in the provision for 2017 was due primarily to generally improved credit quality metrics and underlying collateral values, partially offset by increased loan growth compared to the prior year. The allowance for loan losses to total loans ratio was 1.45% at December 31, 2017 , compared to 1.55% at December 31, 2016 . Based on management’s judgment as to the existing credit risks inherent in the loan portfolio, as discussed above under the heading "Credit Quality Indicators," management believes that the Company’s allowance for loan losses is adequate to absorb probable losses from specifically known and other probable credit risks associated with the portfolio as of December 31, 2017 . Changes in the allowance for loan losses for the years ended December 31, are summarized as follows: (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 31,342 $ 29,008 $ 27,121 Provision 1,430 2,993 3,267 Recoveries 755 709 409 Less: Charge-offs 612 1,368 1,789 Balance at end of year $ 32,915 $ 31,342 $ 29,008 Changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2017 , are presented below: (Dollars in thousands) Cmml Real Estate Cmml and Industrial Cmml Constr Resid. Mortgage Home Equity Cnsmr Total Beginning Balance, December 31, 2016 $ 14,902 $ 11,204 $ 3,406 $ 960 $ 634 $ 236 $ 31,342 Provision 2,628 (1,737 ) 541 (56 ) (30 ) 84 1,430 Recoveries 193 550 — — 4 8 755 Less: Charge-offs 178 348 — — — 86 612 Ending Balance, December 31, 2017 $ 17,545 $ 9,669 $ 3,947 $ 904 $ 608 $ 242 $ 32,915 Ending allowance balance: Allocated to loans individually evaluated for impairment $ 59 $ 1,284 $ — $ 5 $ — $ 35 $ 1,383 Allocated to loans collectively evaluated for impairment $ 17,486 $ 8,385 $ 3,947 $ 899 $ 608 $ 207 $ 31,532 Changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2016 , are presented below: (Dollars in thousands) Cmml Real Estate Cmml and Industrial Cmml Constr Resid. Mortgage Home Equity Cnsmr Total Beginning Balance, December 31, 2015 $ 13,514 $ 9,758 $ 3,905 $ 1,061 $ 540 $ 230 $ 29,008 Provision 1,696 1,745 (494 ) (101 ) 97 50 2,993 Recoveries 20 681 — — 3 5 709 Less: Charge-offs 328 980 5 — 6 49 1,368 Ending Balance, December 31, 2016 $ 14,902 $ 11,204 $ 3,406 $ 960 $ 634 $ 236 $ 31,342 Ending allowance balance: Allocated to loans individually evaluated for impairment $ 370 $ 2,222 $ 28 $ — $ — $ 1 $ 2,621 Allocated to loans collectively evaluated for impairment $ 14,532 $ 8,982 $ 3,378 $ 960 $ 634 $ 235 $ 28,721

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment Premises and equipment at December 31, are summarized as follows: (Dollars in thousands) 2017 2016 Land $ 5,488 $ 5,201 Bank premises and leasehold improvements 42,525 37,390 Computer software and equipment 9,303 9,250 Furniture, fixtures and equipment 20,347 18,243 Total premises and equipment, before accumulated depreciation 77,663 70,084 Less accumulated depreciation (40,641 ) (36,544 ) Total premises and equipment, net of accumulated depreciation $ 37,022 $ 33,540 Total depreciation expense related to premises and equipment amounted to $4.7 million , $4.4 million and $4.3 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Total rent expense for the years ended December 31, 2017 , 2016 and 2015 amounted to $1.4 million , $1.3 million and $1.2 million , respectively. The Company's leased facilities are contracted under various non-cancelable operating leases, most of which provide options to extend lease periods and periodic rent adjustments. Several leases provide the Company the right of first refusal should the property be offered for sale or purchase options at specified periods mutually agreeable to the parties. In February 2017, the Company purchased, at fair market value, a property which was previously a leased branch location, the location remains an active full service banking branch. At December 31, 2017 , minimum lease payments for these operating leases were as follows: (Dollars in thousands) Payable in: 2018 $ 1,609 2019 1,392 2020 1,136 2021 1,133 2022 1,131 Thereafter 9,285 Total minimum lease payments $ 15,686 The Company currently collects rent through leases for a small portion of the overall square-footage within its Lowell, MA campus headquarters and at one of its branch locations. Rental income was $133 thousand for the year ended December 31, 2017 , $159 thousand for the year ended December 31, 2016 and $153 thousand for the year ended December 31, 2015 .

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposits	Deposits Deposits at December 31, are summarized as follows: (Dollars in thousands) 2017 2016 Non-interest bearing demand deposits $ 705,846 $ 646,115 Interest-bearing checking 391,111 372,696 Savings 193,385 178,637 Money market 807,931 844,216 Certificates of deposit $250,000 or less 150,445 125,580 Certificates of deposit more than $250,000 45,154 42,315 Total customer deposits 2,293,872 2,209,559 Brokered deposits (1) 147,490 59,362 Total deposits $ 2,441,362 $ 2,268,921 (1) Brokered CDs $250,000 and under. Total customer deposits (deposits, excluding brokered deposits) include reciprocal money market deposits and CDs received from participating banks in nationwide deposit networks as a result of our customers electing to participate in Company offered programs which allow for full FDIC insurance. Essentially, the equivalent of the customers' original deposited funds comes back to the Company as customer deposits within the appropriate category under total deposits on the consolidated balance sheet. The Company's balances in these reciprocal products were $249.6 million and $281.6 million at December 31, 2017 and December 31, 2016 , respectively. The aggregate amount of overdrawn deposits that have been reclassified as loan balances were $359 thousand and $558 thousand at December 31, 2017 and 2016 , respectively. The following table shows the scheduled maturities of certificates of deposit (including brokered deposits with weighted average remaining lives of less than 6 months at December 31, 2017 and approximately 1.5 years as of December 31, 2016 ): (Dollars in thousands) December 31, 2017 December 31, 2016 Due in less than twelve months $ 240,995 $ 136,695 Due in over one year through two years 60,692 38,344 Due in over two years through three years 28,141 32,652 Due in over three years through four years 6,592 8,525 Due in over four years through five years 5,614 5,721 Due in over five years 1,055 5,320 Total certificates of deposit $ 343,089 $ 227,257 See Note 15, "Fair Value Measurements," below for further information regarding the Company's fair value measurements for deposits.

Borrowed Funds and Subordinated

Borrowed Funds and Subordinated Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowed Funds and Subordinated Debt	Borrowed Funds and Subordinated Debt Borrowed funds and subordinated debt outstanding at December 31, for the years indicated are summarized as follows: 2017 2016 2015 (Dollars in thousands) Amount Average Rate Amount Average Rate Amount Average Rate FHLB borrowings $ 89,000 1.54 % $ 10,671 0.80 % $ 40,671 0.51 % Other borrowings — — % — — % 13,000 0.60 % Total borrowed funds $ 89,000 1.54 % $ 10,671 0.80 % $ 53,671 0.53 % Subordinated debt 14,847 6.23 % 14,834 6.26 % 14,822 6.16 % Total borrowed funds and subordinated debt $ 103,847 2.21 % $ 25,505 3.98 % $ 68,493 1.75 % FHLB borrowings at December 31, 2017 consisted of $39.0 million in overnight borrowings, with a weighted average rate of 1.59% , and short-term borrowings of $50.0 million , with a weighted average rate of 1.50% , that matured in January 2018. Maximum FHLB and other borrowings outstanding at any month end during 2017 , 2016 , and 2015 were $149.3 million , $43.7 million , and $53.7 million , respectively. The following table summarizes the average balance and average cost of borrowed funds for the years indicated. Year ended December 31, 2017 2016 2015 (Dollars in thousands) Average Balance Average Cost Average Balance Average Cost Average Balance Average Cost FHLB advances $ 49,546 1.19 % $ 14,551 0.55 % $ 10,731 0.36 % Other borrowings — — % 107 0.61 % 36 0.61 % Total borrowed funds $ 49,546 1.19 % $ 14,658 0.55 % $ 10,767 0.36 % The Company’s primary borrowing source is the FHLB, but the Company may choose to borrow from other established business partners. "Other borrowings" represents overnight advances from the FRB or federal funds purchased from correspondent banks. As a member of the FHLB, the Bank has the potential capacity to borrow an amount up to the value of its discounted qualified collateral. Borrowings from the FHLB are secured by certain securities from the Company’s investment portfolio not otherwise pledged and certain residential and commercial real estate loans. At December 31, 2017 , based on qualifying collateral less outstanding advances, the Bank had the capacity to borrow additional funds from the FHLB of up to approximately $415.0 million . In addition, based on qualifying collateral, the Bank had the capacity to borrow funds from the FRB Discount Window up to approximately $120.0 million at December 31, 2017 . The Bank also has pre-approved borrowing arrangements with large correspondent banks in order to provide overnight and short-term borrowing capacity. See Note 2, "Investments," and Note 3, "Loans" above to these consolidated financial statements for further information regarding securities and loans pledged for borrowed funds. The Company also carried subordinated debt of $14.8 million (net of deferred issuance costs) at December 31, 2017 December 31, 2016 and December 31, 2015 , which consisted of $15.0 million in aggregate principal amount of Fixed-to-Floating Rate Subordinated Notes (the "Notes"), issued in January 2015 , in a private placement to an accredited investor. The Notes are intended to qualify as Tier 2 capital for regulatory purposes, mature on January 30, 2030 (the "Maturity Date") and are callable by the Company, subject to regulatory approval, at a premium beginning January 30, 2020 , and at par beginning January 30, 2025 . The Notes pay interest at a fixed rate of 6.00% per annum through January 30, 2025 , and beginning on January 31, 2025 through the Maturity Date, or any early redemption date, the interest rate on the Notes will adjust monthly at an interest rate of 3.90% plus 30-day LIBOR. Original debt issuance costs were $190 thousand and have been netted against the subordinated debt on the consolidated balance sheet in accordance with accounting guidance. These costs are being amortized to interest expense over the life of the Notes. In 2015 , the Company used a portion of the proceeds from the $15.0 million in Notes, to redeem the $10.8 million junior subordinated debt previously held by the Company. See Note 15, "Fair Value Measurements," below for further information regarding the Company's fair value measurements for borrowed funds and subordinated debt.

Derivatives and Hedging Activit

Derivatives and Hedging Activities	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities Interest-rate lock commitments related to the origination of mortgage loans that will be sold are considered derivative instruments. The commitments to sell loans are also considered derivative instruments. The Company generally does not pool mortgage loans for sale, but instead sells the loans on an individual basis. To reduce the net interest rate exposure arising from its loan sale activity, the Company enters into the commitment to sell these loans at essentially the same time that the interest-rate lock commitment is quoted on the origination of the loan. The Company estimates the fair value of these derivatives based on current secondary mortgage market prices. At December 31, 2017 and 2016 , the estimated fair value of the Company's interest-rate lock commitments and commitments to sell these mortgage loans were deemed immaterial. The Company may use interest-rate contract swaps as part of its interest-rate risk management strategy. Interest-rate swap agreements are entered into as hedges against future interest rate fluctuations on specifically identified assets or liabilities. The Company did not have derivative fair value hedges or derivative cash flow hedges at December 31, 2017 and 2016 . The Company has a "Back-to-Back Swap" program whereby the Bank enters into an interest-rate swap with a qualified commercial banking customer and simultaneously enters into an equal and opposite interest-rate swap with a swap counterparty. The customer interest-rate swap agreement allows commercial banking customers to convert a floating-rate loan payment to a fixed-rate payment. The transaction structure effectively minimizes the Bank's net risk exposure resulting from such transactions. Customer-related credit risk is minimized by the cross collateralization of the loan and the interest-rate swap agreement. As detailed in Note 1 "Summary of Significant Accounting Policies," under Item (o) "Derivatives," Back-to-Back Swaps are not speculative but rather, result from a service the Company provides to certain commercial customers. Back-to-Back swaps do not meet hedge accounting requirements and therefore changes in the fair value of both the customer swaps and the counterparty swaps, which have an offsetting relationship, are recognized directly in earnings. As a result of this offsetting relationship, there were no net gains or losses recognized in income on Back-to-Back Swaps during the years ended December 31, 2017 , December 31, 2016 or December 31, 2015 . Each Back-to-Back swap transaction consists of two interest-rate swaps (a customer swap and offsetting counterparty swap) and amounted to a total number of six and four interest-rate swaps outstanding at December 31, 2017 and December 31, 2016 , respectively, with an aggregate notional amount of $29.4 million and $26.7 million on those respective dates. Asset derivatives are included in the line item prepaid expenses and other assets and liability derivatives are included in the accrued expenses and other liabilities line item on the consolidated balance sheets, respectively. The table below presents the fair value and classification of the Company’s derivative financial instruments for the periods presented: As of December 31, 2017 As of December 31, 2016 (Dollars in thousands) Asset Derivatives Liability Derivatives Asset Derivatives Liability Derivatives Interest-rate contracts - pay floating, received fixed $ 25 $ 568 $ — $ 610 Interest-rate contracts - pay fixed, receive floating 543 — 610 — Total interest rate swaps $ 568 $ 568 $ 610 $ 610 By using derivative financial instruments, the Company exposes itself to counterparty-credit risk. Credit risk is the risk of failure by the counterparty to perform under the terms of the derivative contract. When the fair value of a derivative contract is positive, the counterparty owes the Company, which creates credit risk for the Company. When the fair value of a derivative is negative, the Company owes the counterparty and, therefore, it does not possess credit risk. The credit risk in derivative instruments is mitigated by entering into transactions with highly-rated counterparties that management believes to be creditworthy. The counterparty was rated A / A2 by S&P and Moody’s, respectively, at December 31, 2017 . Additionally, counterparty interest-rate swaps contain provisions for collateral to be posted if the derivative exposure exceeds a threshold amount. The Company had credit risk exposure amounting to $543 thousand and $610 thousand at December 31, 2017 and December 31, 2016 respectively, relating to interest-rate swaps with counterparties. The Company held cash collateral of $480 thousand at December 31, 2017 , and none at December 31, 2016 . Collateral held by the Company is restricted and not considered an asset of the Company. Therefore it is not carried on the Company's consolidated balance sheet. Interest-rate swaps with the counterparty are subject to master netting agreements. The table below presents the Company's asset derivative positions and the potential effect of those netting arrangements on its financial position, as of the periods presented. Interest-rate swaps with customers are not subject to master netting agreements and therefore are not included in the table below. As of December 31, 2017 (Dollars in thousands) Gross Amounts of Recognized Asset Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets Presented in the Statement of Financial Position Asset Derivatives Interest-rate contracts - pay fixed, receive floating $ 568 $ 25 $ 543 As of December 31, 2016 (Dollars in thousands) Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets Presented in the Statement of Financial Position Asset Derivatives Interest-rate contracts - pay fixed, receive floating $ 610 $ — $ 610 The Company's interest-rate swaps with counterparties contain credit-risk-related contingent provisions. These provisions provide the counterparty with the right to terminate its derivative positions and require the Company to settle its obligations under the agreements if the Company defaults on certain of its indebtedness. The Company also participates in loans originated by third-party banks, where the originating bank utilizes a back-to-back interest-rate swap structure; however, the Company is not a party to the swap agreements. Under the terms of the loan participations, the Company has accepted contingent liabilities that would only be realized if the swaps were terminated early and there were outstanding losses not covered by the underlying borrowers and the borrowers' pledged collateral. If applicable, the Company's swap-loss exposure would be equal to the percentage of the Company's participation in the underlying loan applied to the originating bank's swap loss. At December 31, 2017 and December 31, 2016 , the Company had two such participation loans and management considers the risk of material swap-loss exposure to be unlikely based on the borrower's financial and collateral strength. See Note 9, "Commitments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk," for additional information on the Company's commitments and contingencies.

Committments, Contingencies and

Committments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk	(9) Commitments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to originate loans, letters of credit, and unadvanced portions of loans and lines of credit. The instruments involve, to varying degrees, elements of credit risk in excess of the amount recognized in the consolidated balance sheets. The contractual amounts of these instruments reflect the extent of involvement the Company has in the particular classes of financial instruments. The Company’s exposure to credit loss in the event of nonperformance by the other party to the financial instrument for loan commitments and letters of credit is represented by the contractual amounts of those instruments. The Company uses the same credit policies in making commitments and conditional obligations as it does for on-balance sheet instruments. Financial instruments with off-balance sheet credit risk at December 31, 2017 and 2016 are as follows: (Dollars in thousands) 2017 2016 Commitments to originate loans $ 13,830 $ 37,753 Commitments to originate residential mortgages loans for sale 2,078 1,946 Commitments to sell residential mortgage loans 2,286 3,115 Letters of credit 21,576 21,497 Unadvanced portions of commercial real estate loans 26,947 56,952 Unadvanced portions of commercial loans and lines 432,731 399,833 Unadvanced portions of construction loans (commercial & residential) 209,916 151,757 Unadvanced portions of home equity lines 94,012 82,884 Unadvanced portions of consumer loans 4,290 3,043 Commitments to originate loans are agreements to lend to a customer provided there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee by the customer. Since some of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s credit worthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the borrower. The Company originates residential mortgage loans intended for sale under agreements to sell such loans on an individual loan basis, and may retain or sell the servicing when selling the loans. Loans sold are subject to standard secondary market underwriting and eligibility representations and warranties over the life of the loan, and are subject to an early payment default period covering the first four payments for certain loan sales. Letters of credit are conditional commitments issued by the Company to guarantee the financial obligation or performance of a customer to a third party. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. If the letter of credit is drawn upon, a loan is created for the customer, generally a commercial loan, with the same criteria associated with similar commercial loans. Unadvanced portions of loans and lines of credit represent credit extended to customers but not yet drawn upon, and are secured or guaranteed under preexisting loan agreements and credit evaluations having taken into consideration the full commitment amount. See Note 8, "Derivatives and Hedging Activities" for information on the Company's interest-rate lock commitments, interest-rate swaps, and participation in loans originated by third-party banks with potential contingent liabilities. There are no material pending legal proceedings to which the Company or its subsidiaries are a party or to which any of its property is subject, other than ordinary and routine litigation incidental to the business of the Company. Management does not believe resolution of any present litigation will have a material adverse effect on the consolidated financial condition or results of operations of the Company.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Shares Authorized and Share Issuance The Company’s authorized capital is divided into common stock and preferred stock. At the Company's annual meeting of shareholders held on May 2, 2017, shareholders voted to amend the Company's Restated Articles of Organization to increase the number of shares of common stock that the Company is authorized to issue from 20,000,000 shares to 40,000,000 shares. The Company is authorized to issue 1,000,000 shares of preferred stock. Holders of common stock are entitled to one vote per share, and are entitled to receive dividends if and when declared by the Board. Dividend and liquidation rights of the common stock may be subject to the rights of any outstanding preferred stock. The Company has a shareholders rights plan, the terms of which were extended in January 2018. Under this extended plan, each share of common stock includes a right to purchase under certain circumstances one one-hundredth of a share of the Company’s Series A Junior Participating Preferred Stock, par value $0.01 per share, at a purchase price of $122.50 per one one-hundredth of a preferred share, subject to adjustment, or, in certain circumstances, to receive cash, property, shares of common stock or other securities of the Company. The rights are not presently exercisable and remain attached to the shares of common stock until the occurrence of certain triggering events that would ordinarily be associated with an unsolicited acquisition or attempted acquisition of 10% or more of the Company’s outstanding shares of common stock. The rights have no voting or dividend privileges, and unless and until they become exercisable, have no dilutive effect on the earnings of the Company. The rights will expire, unless earlier redeemed, exchanged, or otherwise rescinded by the Company, on January 13, 2028 . The Company's stock incentive plans permit the Board to grant, under various terms, stock options (for the purchase of newly issued shares of common stock), restricted stock, restricted stock units and stock appreciation rights to officers and other employees, non-employee directors and consultants. The Company issues stock options and restricted stock awards to officers and other employees and restricted stock awards and stock compensation in lieu of cash fees to non-employee directors. The restricted stock awards allow for the non-forfeitable receipt of dividends, and the voting of all shares, whether or not vested, throughout the vesting periods at the same proportional level as common shares outstanding. The unvested restricted stock awards are the Company's only participating securities and are included in shares outstanding. Unvested participating restricted awards amounted to 117,219 shares and 141,580 shares as of December 31, 2017 and December 31, 2016 , respectively. See Item (r) "Earnings per Share," contained in Note 1, "Summary of Significant Accounting Policies," for additional information regarding unvested participating restricted awards and the Company's earnings per share calculation. Upon vesting, restricted stock awards may be net share-settled to cover payment for employee tax obligations, resulting in shares of common stock being reacquired by the Company. Chapter 156D of the Massachusetts General Laws, a statue known as the Massachusetts Business Corporation Act, which applies to Massachusetts corporations such as the Company, eliminates the concept of "treasury stock" and provides that shares a Massachusetts company reacquires will be treated as authorized but unissued shares. See Note 12, "Stock-Based Compensation," below for additional information regarding the Company's stock incentive plans. The Company's stock incentive plans also allow for newly issued shares of common stock to be issued without restrictions to officers and other employees, non-employee directors and consultants. From time to time, the Company issues shares to community members for consulting on regional advisory councils and grants shares of fully vested stock as employee anniversary awards. These shares vest immediately and the cost, which is deemed to be immaterial, is expensed in the period in which the services are rendered and is based on the market price on the date of grant. In addition to shares issued to employees, non-employee directors, and community members for consulting on regional advisory councils, and shares issued through equity offerings (see "Capital Raised and Capital Adequacy Requirements" below), the Company maintains a dividend reinvestment and direct stock purchase plan ("DRSPP") for stockholders and new investors to reinvest or purchase additional shares of common stock directly from the Company. See "Dividends" below for further information about the DRSPP. Capital Raised and Capital Adequacy Requirements Capital planning by the Company and the Bank considers current needs and anticipated future growth. Historically, the primary sources of capital for the Company and the Bank have been common stock issuances and proceeds from the issuance of subordinated debt. Ongoing sources of capital include the retention of earnings, less dividends paid, proceeds from the exercise of employee stock options and proceeds from purchases of shares pursuant to the Company’s dividend reinvestment plan and direct stock purchase plan (together, the "DRSPP"). The Company believes its current capital is adequate to support ongoing operations. In the second quarter of 2016, the Company completed a combined shareholder subscription rights offering and supplemental community offering (the "Offering"), at an offering price of $21.50 per share, under its $40 million shelf registration statement (Reg No. 333-190017). The Company issued 930,232 shares of common stock and received gross proceeds of $20.0 million ( $19.7 million , net of offering costs). The Company contributed the net proceeds to the Bank to support future asset growth and for general corporate purposes. See Note 14, "Earnings Per Share," for further information regarding the impact of the offering on EPS. Since January 1, 2015, the Company has been subject to increasing capital ratios, with a phase-in period that extends to January 2019, as a result of regulation adopted by the federal bank regulatory agencies known as the "Basel III Rules." Management believes, as of December 31, 2017 , that the Company and the Bank met all capital adequacy requirements to which they were subject. As of December 31, 2017 and December 31, 2016 , the Company met the definition of "well-capitalized" under the applicable Federal Reserve Board regulations and the Bank qualified as "well-capitalized" under the prompt corrective action regulations of Basel III and the FDIC. The Company's and the Bank's actual capital amounts and ratios are presented as of December 31, 2017 and December 31, 2016 in the tables below. Actual Minimum Capital for Capital Adequacy Purposes (1) Minimum Capital To Be Well Capitalized (2) (Dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2017 The Company Total Capital (to risk weighted assets) $ 270,826 11.21 % $ 193,327 8.00 % N/A N/A Tier 1 Capital (to risk weighted assets) 225,738 9.34 % 144,995 6.00 % N/A N/A Tier 1 Capital (to average assets) or Leverage Ratio 225,738 8.22 % 109,838 4.00 % N/A N/A Common equity tier 1 capital (to risk-weighted assets) 225,738 9.34 % 108,747 4.50 % N/A N/A The Bank Total Capital (to risk weighted assets) $ 270,150 11.18 % $ 193,301 8.00 % $ 241,626 10.00 % Tier 1 Capital (to risk weighted assets) 239,910 9.93 % 144,976 6.00 % 193,301 8.00 % Tier 1 Capital (to average assets) or Leverage Ratio 239,910 8.74 % 109,837 4.00 % 137,296 5.00 % Common equity tier 1 capital (to risk-weighted assets) 239,910 9.93 % 108,732 4.50 % 157,057 6.50 % Actual Minimum Capital (1) Minimum Capital To Be Well Capitalized (2) (Dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2016 The Company Total Capital (to risk weighted assets) $ 252,552 11.79 % $ 171,337 8.00 % N/A N/A Tier 1 Capital (to risk weighted assets) 209,887 9.80 % 128,503 6.00 % N/A N/A Tier 1 Capital (to average assets) or Leverage Ratio 209,887 8.34 % 100,628 4.00 % N/A N/A Common equity tier 1 capital (to risk-weighted assets) 209,887 9.80 % 96,377 4.50 % N/A N/A The Bank Total Capital (to risk weighted assets) $ 250,893 11.71 % $ 171,332 8.00 % $ 214,166 10.00 % Tier 1 Capital (to risk weighted assets) 223,062 10.42 % 128,499 6.00 % 171,332 8.00 % Tier 1 Capital (to average assets) or Leverage Ratio 223,062 8.87 % 100,627 4.00 % 125,784 5.00 % Common equity tier 1 capital (to risk-weighted assets) 223,062 10.42 % 96,374 4.50 % 139,208 6.50 % (1) Before application of the capital conservation buffer of 1.25% as of December 31, 2017 and 0.625% as of December 31, 2016 , see discussion below. (2) For the Bank to qualify as “well-capitalized," it must maintain at least the minimum ratios listed. This prompt corrective action framework requirement does not apply to the Company. Under the Basel III Rules, capital ratio requirements for all banking organizations increased and include a "capital conservation buffer," of 2.50% above the regulatory minimum risk-based capital requirements shown above. The capital conservation buffer requirement began to be phased in beginning in January 2016 at 0.625% of risk-weighted assets and will increase by that amount each year until fully implemented in January 2019. If a banking organization dips into its capital conservation buffer it may be restricted in its ability to pay dividends and discretionary bonus payments to its executive officers. Both the Company's and the Bank's actual ratios, as outlined in the table above, would exceed the Basel III risk-based capital requirement with full capital conservation buffer as of December 31, 2017 . For further information on the Basel III requirements see the “Supervision and Regulation” contained in Item 1, “Business” in this Form 10-K. The Basel III minimum capital ratio requirements as applicable to the Company and the Bank in 2019 after the full phase-in period are summarized in the table below: Basel III Minimum for Capital Adequacy Purposes Basel III Additional Capital Conservation Buffer Basel III "Adequate" Ratio with Capital Conservation Buffer Total Capital (to risk weighted assets) 8.00% 2.50% 10.50% Tier 1 Capital (to risk weighted assets) 6.00% 2.50% 8.50% Tier 1 Capital (to average assets) or Leverage Ratio 4.00% —% 4.00% Common equity tier 1 capital (to risk-weighted assets) 4.50% 2.50% 7.00% Failure to meet minimum capital requirements can initiate or result in certain mandatory and possibly additional discretionary supervisory actions by regulators that, if undertaken, could have a material adverse effect on the Company’s consolidated financial statements. Under applicable capital adequacy requirements and the regulatory framework for prompt corrective action applicable to the Bank, the Company must meet specific capital guidelines that involve quantitative measures of the Company’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The Company’s capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Dividends Neither the Company nor the Bank may declare or pay dividends on its stock if the effect thereof would cause stockholders’ equity to be reduced below applicable regulatory capital requirements or if such declaration and payment would otherwise violate regulatory requirements. As the principal asset of the Company, the Bank currently provides the only source of cash for the payment of dividends by the Company. Under Massachusetts law, trust companies such as the Bank may pay dividends only out of "net profits" and only to the extent that such payments will not impair the Bank’s capital stock. Any dividend payment that would exceed the total of the Bank’s net profits for the current year plus its retained net profits of the preceding two years would require the Massachusetts Division of Banks' approval. Applicable provisions of the FDIC Improvement Act also prohibits a bank from paying any dividends on its capital stock if the bank is in default on the payment of any assessment to the FDIC or if the payment of dividends would otherwise cause the bank to become undercapitalized. Any restrictions, regulatory or otherwise, on the ability of the Bank to pay dividends to the Company may restrict the ability of the Company to pay dividends to the holders of its common stock. The statutory term "net profits" essentially equates with the accounting term "net income" and is defined under the Massachusetts banking statutes to mean the remainder of all earnings from current operations plus actual recoveries on loans and investments and other assets after deducting from such total all current operating expenses, actual losses, accrued dividends on any preferred stock and all federal and state taxes. The Company maintains a DRSPP which enables stockholders, at their discretion, to elect to reinvest cash dividends paid on their shares of the Company’s common stock by purchasing additional shares of common stock from the Company at a purchase price equal to fair market value. Under the DRSPP, stockholders and new investors also have the opportunity to purchase shares of the Company's common stock without brokerage fees, subject to monthly minimums and maximums. For the year ended December 31, 2017 , the Company declared and paid $6.2 million in cash dividends. Stockholders utilized the dividend reinvestment portion of the DRSPP to purchase an aggregate of 44,752 shares of the Company's common stock totaling $1.5 million . The direct purchase component of the DRSPP was used by stockholders to purchase 2,014 shares of the Company's common stock totaling $70 thousand during the year ended December 31, 2017 . In 2016 , the Company declared and paid $5.7 million in cash dividends. Stockholders utilized the dividend reinvestment portion of the DRSPP to purchase 53,516 shares of the Company’s common stock totaling $1.4 million . The direct purchase component of the DRSPP was used by stockholders to purchase 1,562 shares of the Company's common stock totaling $38 thousand during the year ended December 31, 2016 . In 2015 , the Company declared and paid $5.2 million in cash dividends. Stockholders utilized the dividend reinvestment portion of the DRSPP to purchase 58,529 shares of the Company’s common stock totaling $1.3 million . The direct purchase component of the DRSPP was used by stockholders to purchase 6,700 shares of the Company's common stock totaling $150 thousand during the year ended December 31, 2015 .

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans 401(k) Defined Contribution Plan The Company has a 401(k) defined contribution employee benefit plan. The 401(k) plan allows eligible employees to contribute a percentage of their earnings to the plan. A portion of the employee contribution, as determined by the Compensation Committee of the Board of Directors, is matched by the Company. In 2017 , 2016 and 2015 , the Company’s percentage match was 60% up to the first 6% contributed by the employee. All eligible employees, at least 18 years of age and completing 1 hour of service, may participate in the 401(k) plan. Effective during the fourth quarter of 2017, vesting for the Company’s 401(k) retirement plan matching contribution is based on years of service with participants becoming 25% vested on the anniversary of their hire date and each subsequent year until they are 100% vesting following four years of service. Unvested amounts not distributable to an employee following termination of employment are used to offset plan expenses and the Company's matching contributions. The Company’s expense for the 401(k) plan match was $965 thousand , $938 thousand and $859 thousand , respectively, for the years ended December 31, 2017 , 2016 , and 2015 . Supplemental Employee Retirement Plan ("SERP") The Company has salary continuation agreements with two of its current executive officers and one former executive officer. These salary continuation agreements provide for predetermined fixed-cash supplemental retirement benefits to be provided for a period of 20 years after each individual reaches a defined “benefit age.” The individuals covered under the SERP have reached the defined benefit age and are receiving payments under the plan. Additionally, the Company has not recognized service costs in the current or prior year as each officer had previously attained their individually defined benefit age and was fully vested under the plan. This non-qualified plan represents a direct liability of the Company, and as such has no specific assets set aside to settle the benefit obligation. The funded status is the aggregate amount accrued, or the "accumulated benefit obligation," which is equal to the present value of the benefits to be provided to the employee or any beneficiary. Because the Company’s benefit obligations provide for predetermined fixed-cash payments, the Company does not have any unrecognized costs to be included as a component of accumulated other comprehensive income. The amounts charged to expense for this plan are included in the table below. The Company anticipates accruing an additional $104 thousand to the SERP for the year ending December 31, 2018 . The following table provides a reconciliation of the changes in the supplemental retirement benefit obligation and the net periodic benefit cost for the years ended December 31: (Dollars in thousands) 2017 2016 2015 Reconciliation of benefit obligation: Benefit obligation at beginning of year $ 2,502 $ 2,654 $ 2,844 Net periodic benefit cost: Interest cost 110 124 133 Actuarial loss (gain) 36 — (47 ) Net periodic benefit costs $ 146 $ 124 $ 86 Benefits paid (276 ) (276 ) (276 ) Benefit obligation at end of year $ 2,372 $ 2,502 $ 2,654 Funded status: Accrued liability as of December 31 $ (2,372 ) $ (2,502 ) $ (2,654 ) Discount rate used for benefit obligation (1) 4.50 % 4.75 % 4.75 % (1) Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss. Benefits expected to be paid in each of the next five years and in the aggregate five years thereafter: (Dollars in thousands) 2018 $ 276 2019 276 2020 276 2021 276 2022 276 2023-2027 1,380 Supplemental Life Insurance The Company has provided supplemental life insurance through split-dollar life insurance arrangements for certain executive and senior officers on whom the Bank owns BOLI. See Item (k) “Bank Owned Life Insurance” in Note 1, “Summary of Significant Accounting Policies,” for further information regarding BOLI. These arrangements provide a death benefit to the officer's designated beneficiaries that extend to postretirement periods for some of the supplemental life insurance plans. The Company has recognized a liability for these future postretirement benefits. These non-qualified plans represent a direct liability of the Company, and as such has no specific assets set aside to settle the benefit obligation. The funded status is the aggregate amount accrued, or the "accumulated postretirement benefit obligation," which is the present value of the post-retirement benefits associated with this arrangement. The following table provides a reconciliation of the changes in the supplemental life insurance plan obligation and the net periodic benefit cost for the years ended December 31: (Dollars in thousands) 2017 2016 2015 Reconciliation of benefit obligation: Benefit obligation at beginning of year $ 1,895 $ 1,792 $ 1,723 Net periodic benefit cost: Service cost (11 ) (9 ) (56 ) Interest cost 91 88 86 Actuarial loss 57 24 39 Total net period cost $ 137 $ 103 $ 69 Benefit obligation at end of year $ 2,032 $ 1,895 $ 1,792 Funded status: Accrued liability as of December 31 $ (2,032 ) $ (1,895 ) $ (1,792 ) Discount rate used for benefit obligation (1) 4.50 % 4.75 % 4.75 % (1) Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss. The amounts charged to expense for the postretirement cost of insurance for split dollar insurance coverage are included in the table above. The Company anticipates accruing an additional $178 thousand to the plan for the year ending December 31, 2018 . See Note 12, "Stock-Based Compensation" below, for additional information regarding employee benefits offered in the form of stock options and stock awards.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company currently has two individual stock incentive plans: the 2009 plan, as amended in 2015, and the 2016 plan. The plans permit the Board of Directors to grant, under various terms, both incentive and non-qualified stock options (for the purchase of newly issued shares of common stock), restricted stock, restricted stock units and stock appreciation rights to officers and other employees, directors and consultants. Option exercises and restricted stock vesting may be net settled to cover option costs and employee tax obligations under the terms of the respective plan. These plans also allow for newly issued shares of common stock to be issued without restrictions to officers and other employees, directors and consultants. As of December 31, 2017 , an aggregate of 465,198 shares remain available for future grants under the plans. The Company's stock-based compensation expense related to these plans includes stock options and stock awards to officers and other employees included in salary and benefits expense, and stock awards and stock compensation in lieu of cash fees to non-employee directors both included in other operating expenses. Total stock-based compensation expense was $1.8 million for the year ended December 31, 2017 , $2.4 million for the year ended December 31, 2016 , and $1.8 million for the year ended December 31, 2015 . The total tax benefit recognized related to the stock-based compensation expense was $716 thousand , $972 thousand and $720 thousand for the years ended 2017 , 2016 and 2015 , respectively. In 2017, with the adoption of ASU 2016-09, related to employee share-based payment accounting, a tax benefit of approximately $922 thousand , associated with employee exercises and vesting of stock compensation, was recorded as a reduction of the Company's income tax expense. Prior to 2017, the related tax benefits were recorded to additional paid-in-capital, and had no impact on the Company's income statements. Those tax benefits amounted to $789 thousand and $217 thousand for the years ended December 31, 2016 and 2015 , respectively. For further information regarding the implementation of this update refer to Note 1, "Summary of Significant Accounting Policies," Item (t), "Recent Accounting Pronouncements" above. Stock Option Awards Options granted generally vest 50% in year two and 50% in year four , on the anniversary date of the awards. Vested options are only exercisable while the employee remains employed with the Bank and for a limited time thereafter. For all awards, if a grantee’s employment or other service relationship, such as service as a director, is terminated for any reason, then any stock options granted that have not vested as of the time of such termination generally must be forfeited, unless the Compensation Committee or the Board of Directors, as the case may be, waives such forfeiture requirement. Under the terms of the plans, stock options may not be granted at less than 100% of the fair market value of the shares on the date of grant and may not have a term of more than ten years. Any shares of common stock reserved for issuance pursuant to options granted under the plans that are returned to the Company unexercised shall remain available for issuance under such plan, while the plan is effective. For participants owning 10% or more of the Company’s outstanding common stock (of which there are currently none), incentive stock options may not be granted at less than 110% of the fair market value of the shares on the date of grant and may not have an expiration term of more than five years. The Company utilizes the Black-Scholes option valuation model in order to determine the per share grant date fair value of option grants. The table below provides a summary of the options granted, including the fair value, the fair value as a percentage of the market value of the stock at the date of grant and the average assumptions used in the model for the years indicated. Stock Option Awards 2017 2016 2015 Options granted 15,009 31,047 27,376 Term in years 10.0 10.0 10.0 Weighted average assumptions used in the fair value model: Expected volatility 40 % 42 % 47 % Expected dividend yield 2.09 % 3.02 % 2.90 % Expected life in years 7.0 7.0 7.0 Risk-free interest rate 2.35 % 1.91 % 1.95 % Weighted average market price on date of grants $ 30.46 $ 21.91 $ 21.03 Per share weighted average fair value $ 11.34 $ 7.91 $ 8.51 Fair value as a percentage of market value at grant date 37 % 36 % 40 % The expected volatility is the anticipated variability in the Company’s share price over the expected life of the option and is based on the Company's historical volatility. The expected dividend yield is the Company’s projected dividends based on historical annualized dividend yield to coincide with volatility divided by its share price at the date of grant. The expected life represents the period of time that the option is expected to be outstanding. The Company utilized the simplified method and under this method, the expected term equals the vesting term plus the contractual term divided by 2. The risk-free interest rate is based on the U.S. Treasury rate in effect at the time of grant for a period equivalent to the expected life of the option. Stock option transactions during the year ended December 31, 2017 are summarized as follows: (Dollars in thousands, except per share data) Options Weighted Average Exercise Price Per Share Weighted Average Remaining Life in Years Aggregate Intrinsic Value Outstanding December 31, 2016 259,779 $ 17.38 4.5 $ 5,243 Granted 15,009 30.46 Exercised 74,339 14.81 Forfeited/Expired 6,231 19.85 Outstanding December 31, 2017 194,218 $ 19.29 5.0 $ 2,866 Vested and Exercisable at December 31, 2017 123,669 $ 17.06 3.4 $ 2,101 The aggregate intrinsic value in the table above represents the difference between the closing price of the Company’s common stock on December 31, 2017 and the exercise price, multiplied by the number of options. If the closing price was less than the exercise price of the option, no intrinsic value was assigned to the grant. At December 31, 2017 , all of the vested and exercisable options were in-the money. The intrinsic value of options vested and exercisable represents the total pretax intrinsic value that would have been received by the option holders had all in-the-money vested option holders exercised their options on December 31, 2017 . The intrinsic value will change based on the fair market value of the Company’s stock. Cash received from option exercises was $355 thousand , $546 thousand and $431 thousand in 2017 , 2016 and 2015 , respectively. The total intrinsic value of options exercised was $1.6 million , $1.0 million and $396 thousand in 2017 , 2016 and 2015 , respectively. Cash paid by the Company for the net settlement of options to cover employee tax obligations was $386 thousand and $158 thousand in 2017 and 2016 , respectively. In 2015 , the amount paid by the Company for the net settlement of options to cover employee tax obligations was immaterial. Stock option activity during the year ended December 31, 2017 for unvested options are summarized as follows: Unvested Options Options Weighted Average Grant Date Fair Value Unvested December 31, 2016 94,034 $ 7.84 Granted 15,009 11.34 Vested 33,693 7.31 Forfeited 4,801 8.30 Unvested December 31, 2017 70,549 $ 8.81 The total fair value of options vested (based on grant date fair value) during the years ended December 31, 2017 , December 31, 2016 and December 31, 2015 was $246 thousand , $237 thousand , and $359 thousand , respectively The Company adopted ASU 2016-09 in January 2017 and elected to record forfeitures as they occur. Prior to the adoption of this standard, accounting guidance required that the stock-based compensation expense recognized in earnings be based on the amount of awards ultimately expected to vest; therefore, a forfeiture assumption had to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differed from those estimates. In 2016 and 2015 , the Company estimated forfeitures based on historical experience for the portion of the grant which had vested and/or grants already vested based on similarities in the type of options and employee group. Compensation expense recognized in association with the stock option awards amounted to $204 thousand , $267 thousand and $318 thousand for the years ended 2017 , 2016 and 2015 , respectively. The total tax benefit recognized related to the stock option expense was $83 thousand , $109 thousand , and $127 thousand for the years ended 2017 , 2016 , and 2015 , respectively. As of December 31, 2017 , there was $339 thousand of unrecognized stock-based compensation expense related to non-vested stock options. That cost is expected to be recognized over the remaining weighted average vesting period of 2.3 years. Stock Awards Restricted stock awards are granted at the market price on the date of the grant. Employee awards generally vest over four years in equal portions beginning on or about the first anniversary date of the award or are performance based awards that vest upon the Company achieving certain predefined performance objectives. Non-employee director awards generally vest over two years in equal portions beginning on or about the first anniversary date of the award. The table below provides a summary of restricted stock awards granted during the years indicated: Restricted Stock Awards (no. of underlying shares) 2017 2016 2015 Two year vesting 6,944 9,060 7,276 Four year vesting 16,253 18,298 17,775 Performance-based vesting 25,623 35,071 30,262 Total restricted stock awards 48,820 62,429 55,313 Weighted average grant date fair value $ 30.46 $ 21.90 $ 21.03 If a grantee’s employment or other service relationship, such as service as a director, is terminated for any reason, then any shares of restricted stock granted that have not vested as of the time of such termination generally must be forfeited, unless the Compensation Committee or the Board of Directors, as the case may be, waives such forfeiture requirement. The restricted stock awards allow for the non-forfeitable receipt of dividends, and the voting of all shares, whether or not vested, throughout the vesting periods at the same proportional level as common shares outstanding. Upon vesting, restricted stock awards may be net share-settled to cover payment for employee tax obligations, resulting in shares of common stock being reacquired by the Company. In 2017 and 2016 , the Company paid $545 thousand and $284 thousand to net settle the vesting of restricted stock awards to cover employee tax obligations. In 2015 , the amount paid by the Company for the net settlement of options to cover employee tax obligations was immaterial. Any shares that are returned to the Company prior to vesting or as payment for employee tax obligations upon vesting shall remain available for issuance under such plan, while the plan is still effective. The following table sets forth a summary of the activity for the Company’s restricted stock awards. (Dollars in thousands, except per share data) Restricted Stock Weighted Average Grant Price Per Share Weighted Average Remaining Life In Years Aggregate Intrinsic Value Unvested December 31, 2016 141,580 $ 20.73 1.4 $ 5,318 Granted 48,820 30.46 Vested/released 69,336 20.07 Forfeited 3,845 23.28 Unvested December 31, 2017 117,219 $ 25.09 1.4 $ 3,991 Stock-based compensation expense recognized in association with the stock awards amounted to $1.3 million for the year ended December 31, 2017 , $1.8 million for the year ended December 31, 2016 , and $1.2 million for the year ended December 31, 2015 . The total tax benefit recognized related to stock award compensation expense was $518 thousand , $746 thousand , and $491 thousand for the years ended 2017 , 2016 , and 2015 , respectively. As of December 31, 2017 , there remained $1.4 million of unrecognized compensation expense related to the restricted stock awards. That cost is expected to be recognized over the remaining weighted average vesting period of 2.1 years. Stock in Lieu of Directors' Fees In addition to restricted stock awards discussed above, the non-employee members of the Company’s Board of Directors may opt to receive newly issued shares of the Company’s common stock in lieu of cash compensation for attendance at Board and Board Committee meetings. Directors must make an irrevocable election to receive shares of common stock in lieu of cash fees prior to December 31st of the preceding year. Directors are granted shares of common stock in lieu of cash fees at a per share price which reflects the market value of the common stock on the first business day of the year. Total directors' fee expense, included in other operating expenses, amounted to $747 thousand , $661 thousand and $424 thousand for the years ended December 31, 2017 , 2016 and 2015 , respectively. Included in the 2017 expense was stock compensation of $281 thousand , which represented 7,326 shares issued to Directors in January 2018 , at a fair market value price of $38.39 per share, which reflected the fair value of the common stock on January 3, 2017 . Included in the 2016 expense was stock compensation of $286 thousand , which represented 12,992 shares issued to Directors in January 2017 , at a fair market value price of $22.04 per share, which reflected the fair value of the common stock on January 4, 2016 . Included in the 2015 expense was stock compensation of $254 thousand , which represented 10,657 shares issued to Directors in January 2016 , at a fair market value price of $23.86 per share, which reflected the fair value of the common stock on January 2, 2015 . The total tax benefit recognized related to the expense of Director stock compensation for attendance was $115 thousand , $117 thousand and $102 thousand , for the years ended 2017 , 2016 and 2015 , respectively. For further information regarding the Company's stock awards, see Note 10, "Stockholders' Equity," above under the caption "Shares authorized and share issuance."

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income tax expense for the years ended December 31, were calculated using the asset and liability method as follows: (Dollars in thousands) 2017 2016 2015 Current tax expense: Federal $ 8,222 $ 8,178 $ 6,808 State 2,271 2,244 1,712 Total current tax expense 10,493 10,422 8,520 Deferred tax (benefit)/ expense: Federal 5,646 (984 ) (284 ) State 89 (277 ) (122 ) Total deferred tax (benefit)/ expense 5,735 (1,261 ) (406 ) Total income tax expense $ 16,228 $ 9,161 $ 8,114 The provision for income taxes differs from the amount computed by applying the statutory U.S. federal income tax rate of 35% for 2017 , 2016 and 2015 to income before taxes as follows: (Dollars in thousands) 2017 2016 2015 Computed income tax expense at statutory rate $ 12,467 $ 9,769 $ 8,492 State income taxes, net of federal tax benefit 1,534 1,279 1,034 Tax-exempt income, net of disallowance (1,665 ) (1,559 ) (1,226 ) Bank-owned life insurance income, net (245 ) (261 ) (251 ) Impact of change in federal statutory rate on deferred tax assets 4,761 — — Tax benefit from stock compensation (922 ) — — Other 298 (67 ) 65 Total income tax expense $ 16,228 $ 9,161 $ 8,114 Effective income tax rate 45.6 % 32.8 % 33.4 % The new federal tax bill enacted in December 2017 caused the Bank to revalue its net deferred tax assets based upon the lower rate at which they will be recovered. The value of the Company’s 2017 net deferred tax assets declined, due to the new lower federal tax rate, with the offset charged to Federal tax expense. This non-cash expense for the Company was approximately $4.8 million . The new federal tax bill will reduce the Bank’s federal tax rate in future periods, beginning in 2018 , to 21% from its previous level of approximately 35% . Also in 2017, with the adoption of ASU 2016-09, related to employee share-based payment accounting, a tax benefit of approximately $922 thousand , associated with employee exercises and vesting of stock compensation, was recorded as a reduction of the Company's tax liability and income tax expense. Prior to 2017, the related tax benefits were recorded to additional paid-in-capital, and had no impact on the Company's income statements. At December 31, the tax effects of each type of income and expense item that give rise to deferred taxes are as follows: (Dollars in thousands) 2017 2016 Deferred tax asset: Allowance for loan losses $ 9,252 $ 12,753 Depreciation 1,831 3,463 Net unrealized loss on investment securities — 444 Other-than-temporary impairment on equity securities — 22 Supplemental employee retirement plans 667 1,018 Non-accrual interest 460 1,145 Stock-based compensation expense 608 1,019 Other 323 390 Total 13,141 20,254 Deferred tax liability: Goodwill 1,590 2,301 Net unrealized gains on investments securities 90 — Deferred origination costs 710 933 Total 2,390 3,234 Net deferred tax asset $ 10,751 $ 17,020 Deferred income taxes are recognized based on the expected future tax consequences of differences between the financial statement and tax basis of assets and liabilities, calculated using currently enacted tax rates. Management records net deferred tax assets to the extent we believe these assets will more likely than not be realized. In making this determination, we consider all available positive and negative evidence, including recent financial operations and projected future taxable income. Management believes based upon positive historical and expected future earnings that it is more likely than not the Company will generate sufficient taxable income to realize the deferred tax asset existing at December 31, 2017 . However, factors beyond management’s control, such as the general state of the economy, can affect future levels of taxable income and there can be no assurances that sufficient taxable income will be generated to fully realize the deferred tax assets in the future. The Company paid total income taxes in 2017 , 2016 , and 2015 of $10.5 million , $10.9 million , and $7.6 million , respectively. The Company did not have any unrecognized tax benefits accrued as income tax liabilities or receivables or as deferred tax items at December 31, 2017 or December 31, 2016 . The Company invests in qualified affordable housing projects as a limited partner. In 2017 , the Company estimated approximately $71 thousand of Federal Low Income Housing tax credits to be recognized. In both 2016 and 2015 , the Company recognized $71 thousand of Federal Low Income Housing tax credits. The Company anticipates that it will receive additional tax credits related to the Federal Low Income Housing Tax Credit program in the amount of $319 thousand which are expected to be realized over the next 5 years.

Earnings per share

Earnings per share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings per share	Earnings per Share The table below presents the increase in average shares outstanding, using the treasury stock method, for the diluted earnings per share calculation for the years ended December 31st: 2017 2016 2015 Basic weighted average common shares outstanding 11,568,430 10,966,333 10,323,016 Dilutive shares 83,333 73,178 66,918 Diluted weighted average common shares outstanding 11,651,763 11,039,511 10,389,934 Basic and diluted weighted average common shares outstanding for the year ended December 31, 2017 include the full impact of the 930,232 shares of common stock issued in the Offering, while the respective weighted averages for the 2016 period was only affected by the Offering from the issue date of June 23, 2016 through period end. There were 14,678 options outstanding that were determined to be anti-dilutive and therefore excluded from the calculation of dilutive shares for the year ended December 31, 2017 . These options, which were not dilutive at that date, may potentially dilute earnings per share in the future. See Note 10, "Stockholders' Equity," under the caption "Shares authorized and share issuance," for information regarding the Company's participating securities and see Item (r) "Earnings per Share," contained in Note 1, "Summary of Significant Accounting Policies," for additional information regarding the earnings per share calculation.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The FASB defines the fair value of an asset or liability to be the price which a seller would receive in an orderly transaction between market participants (an exit price) and also establishes a fair value hierarchy segregating fair value measurements using three levels of inputs: (Level 1) quoted market prices in active markets for identical assets or liabilities; (Level 2) significant other observable inputs, including quoted prices for similar items in active markets, quoted prices for identical or similar items in markets that are not active, inputs such as interest rates and yield curves, volatilities, prepayment speeds, credit risks and default rates which provide a reasonable basis for fair value determination or inputs derived principally from observed market data; and (Level 3) significant unobservable inputs for situations in which there is little, if any, market activity for the asset or liability. Unobservable inputs must reflect reasonable assumptions that market participants would use in pricing the asset or liability, which are developed on the basis of the best information available under the circumstances. The following tables summarize significant assets and liabilities carried at fair value and placement in the fair value hierarchy at the dates specified: December 31, 2017 Fair Value Measurements using: (Dollars in thousands) Fair Value (Level 1) (Level 2) (Level 3) Assets measured on a recurring basis: Debt securities $ 405,206 $ — $ 405,206 $ — FHLB stock 5,215 — — 5,215 Interest-rate swaps 568 — 568 — Assets measured on a non-recurring basis: Impaired loans (collateral dependent) 2,696 — — 2,696 Liabilities measured on a recurring basis: Interest-rate swaps $ 568 $ — $ 568 $ — December 31, 2016 Fair Value Measurements using: (Dollars in thousands) Fair Value (Level 1) (Level 2) (Level 3) Assets measured on a recurring basis: Debt securities $ 362,147 $ — $ 362,147 $ — Equity securities 12,643 12,643 — — FHLB stock 2,094 — — 2,094 Interest-rate swaps 610 — 610 — Assets measured on a non-recurring basis: Impaired loans (collateral dependent) 3,481 — — 3,481 Liabilities measured on a recurring basis: Interest-rate swaps $ 610 $ — $ 610 $ — The Company did not transfer any assets between the fair value measurement levels during the year ended December 31, 2017 or the year ended December 31, 2016 . All of the Company's debt and equity securities that are considered “available-for-sale” are carried at fair value. The debt security category above includes federal agency obligations, commercial and residential federal agency MBS, municipal securities, corporate bonds, and certificates of deposits, as held at those dates. The Company utilizes third-party pricing vendors to provide valuations on its debt securities. Fair values provided by the vendors were generally determined based upon pricing matrices utilizing observable market data inputs for similar or benchmark securities in active markets and/or based on a matrix pricing methodology which employs The Bond Market Association’s standard calculations for cash flow and price/yield analysis, live benchmark bond pricing and terms/condition data available from major pricing sources. Therefore, management regards the inputs and methods used by third-party pricing vendors to be "Level 2 inputs and methods" as defined in the "fair value hierarchy." The Company periodically obtains a second price from an impartial third-party on debt securities to assess the reasonableness of prices provided by the primary independent pricing vendor. The Company’s equity portfolio fair value is measured based on quoted market prices for the shares; therefore these securities are categorized as Level 1 within the fair value hierarchy. As of December 31, 2017 , the Company did not hold any available-for-sale equity securities. The Bank is required to purchase FHLB stock at par value in association with advances from the FHLB; this stock is classified as a restricted investment and carried at cost which management believes approximates fair value; therefore these securities are categorized as Level 3 measures. See Note 1, "Summary of Significant Accounting Policies," Item (e) "Restricted Investments," for further information regarding the Company’s fair value assessment of FHLB capital stock. Impaired loan balances in the table above represent those collateral dependent impaired commercial loans where management has estimated the probable credit loss by comparing the loan’s carrying value against the expected realizable fair value of the collateral (appraised value, or internal analysis less estimated cost to sell, adjusted as necessary for changes in relevant valuation factors subsequent to the measurement date). Certain inputs used in these assessments, and possible subsequent adjustments, are not always observable, and therefore, collateral dependent impaired loans are categorized as Level 3 within the fair value hierarchy. A specific allowance is assigned to the collateral dependent impaired loan for the amount of management’s estimated probable credit loss. The specific allowances assigned to the collateral dependent impaired loans amounted to $872 thousand at December 31, 2017 compared to $1.9 million at December 31, 2016 . The fair values for the interest-rate swap assets and liabilities represent a FASB Level 2 measurement and are based on settlement values adjusted for credit risks and observable market interest rate curves. The settlement values are based on discounted cash flow analysis, a widely accepted valuation technique, reflecting the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. Credit risk adjustments consider factors such as the likelihood of default by the Company and its counterparties, its net exposures and remaining contractual life. The change in value of interest-rate swap assets and liabilities attributable to credit risk was not significant during the reported periods. Refer also to Note 8, “Derivatives and Hedging Activities,” for additional information on the Company's interest-rate swaps. Letters of credit are conditional commitments issued by the Company to guarantee the financial obligation or performance of a customer to a third party. The fair value of these commitments was estimated to be the fees charged to enter into similar agreements, and accordingly these fair value measures are deemed to be FASB Level 2 measurements. In accordance with the FASB, the estimated fair values of these commitments are carried on the consolidated balance sheet as a liability and amortized to income over the life of the letters of credit, which are typically one year. The estimated fair value of these commitments carried on the consolidated balance sheet at December 31, 2017 and December 31, 2016 were deemed immaterial. Interest-rate lock commitments related to the origination of mortgage loans that will be sold are considered derivative instruments. The commitments to sell loans are also considered derivative instruments. The Company generally does not pool mortgage loans for sale, but instead sells the loans on an individual basis. To reduce the net interest rate exposure arising from its loan sale activity, the Company enters into the commitment to sell these loans at essentially the same time that the interest-rate lock commitment is quoted on the origination of the loan. The Company estimates the fair value of these derivatives based on current secondary mortgage market prices. These commitments are accounted for in accordance with FASB guidance. The fair values of the Company’s derivative instruments are deemed to be FASB Level 2 measurements. At December 31, 2017 and December 31, 2016 , the estimated fair value of the Company’s interest-rate lock commitments and commitments to sell these mortgage loans were deemed immaterial. The following table presents additional quantitative information about assets measured at fair value on a recurring and non-recurring basis for which the Company utilized Level 3 inputs (significant unobservable inputs for situations in which there is little, if any, market activity for the asset or liability) to determine fair value as of December 31, 2017 . (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Unobservable Input Value or Range Assets measured on a recurring basis: FHLB stock $5,215 FHLB stated par value N/A N/A Assets measured on a non-recurring basis: Impaired loans (collateral dependent) $2,696 Appraisal of collateral Appraisal adjustments (1) 5% - 50% (1) Appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses. Estimated Fair Values of Assets and Liabilities In addition to disclosures regarding the measurement of assets and liabilities carried at fair value on the consolidated balance sheet, the Company is also required to disclose fair value information about financial instruments for which it is practicable to estimate that value, whether or not recognized on the consolidated balance sheet. The carrying values, estimated fair values and placement in the fair value hierarchy of the Company’s consolidated financial instruments for which fair value is only disclosed but not recognized on the consolidated balance sheet at the dates indicated are summarized as follows: December 31, 2017 Fair value measurement (Dollars in thousands) Carrying Amount Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Financial assets: Loans held for sale $ 208 $ 208 $ — $ 208 $ — Loans, net 2,236,989 2,236,169 — — 2,236,169 Financial liabilities: Certificates of deposit (including brokered) 343,089 341,765 — 341,765 — Borrowed funds 89,000 88,996 — 88,996 — Subordinated debt 14,847 14,208 — — 14,208 December 31, 2016 Fair value measurement (Dollars in thousands) Carrying Amount Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Financial assets: Loans held for sale $ 1,569 $ 1,569 $ — $ 1,569 $ — Loans, net 1,991,387 1,997,887 — — 1,997,887 Financial liabilities: Certificates of deposit (including brokered) 227,257 226,536 — 226,536 — Borrowed funds 10,671 10,670 — 10,670 — Subordinated debt 14,834 14,011 — — 14,011 Excluded from the tables above are certain financial instruments with carrying values that approximated their fair value at the dates indicated, as they were short-term in nature or payable on demand. These include cash and cash equivalents and non-term deposit accounts. The respective carrying values of these instruments would all be considered to be classified within Level 1 of their fair value hierarchy. Also excluded from these tables are the fair values of commitments for unused portions of lines of credit and commitments to originate loans that were short-term, at current market rates and estimated to have no significant change in fair value. When determining fair values noted in the tables above, in cases where quoted fair values are not available, fair values are based upon estimates using various valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. The following methods and assumptions were used by the Company in estimating fair values of its financial instruments: Loans held for sale: Loans held for sale are recorded at the lower of aggregate amortized cost or market value. The fair value is based on comparable market prices for loans with similar rates and terms. Loans: The fair value of loans was determined using discounted cash flow analysis, using interest rates currently being offered by the Company. The incremental credit risk for adversely classified loans was considered in the determination of the fair value of the loans. Financial liabilities: The fair values of certificates of deposit and borrowings were estimated using discounted cash flow analysis using rates offered by the Bank or advance rates offered by the FHLB on December 31, 2017 and December 31, 2016 for similar instruments. The fair value of subordinated debt was estimated using discounted cash flow analysis using a market rate of interest at December 31, 2017 and December 31, 2016 . Limitations: The estimates of fair value of financial instruments were based on information available at December 31, 2017 and December 31, 2016 and are not indicative of the fair market value of those instruments as of the date of this Annual Report on Form 10-K. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. The fair value of the Company's time deposit liabilities do not take into consideration the value of the Company's long-term relationships with depositors, which may have significant value. Because no active market exists for a portion of the Company’s financial instruments, fair value estimates were based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates. Fair value estimates were based on existing on and off-balance sheet financial instruments without an attempt to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments, including premises and equipment and foreclosed real estate, if any. In addition, the tax ramifications related to the realization of the unrealized appreciation and depreciation can have a significant effect on fair value estimates and have not been considered in any of the estimates. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company.

Parent Company Only Financial S

Parent Company Only Financial Statements	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Only Financial Statements	Parent Company Only Financial Statements Balance Sheets December 31, (Dollars in thousands) 2017 2016 Assets Cash $ 345 $ 497 Investment in subsidiaries 245,982 227,960 Other assets 411 1,243 Total assets $ 246,738 $ 229,700 Liabilities and Stockholders’ Equity Liabilities Subordinated debt $ 14,847 $ 14,834 Accrued interest payable 78 78 Other liabilities 3 2 Total liabilities 14,928 14,914 Stockholders' equity: Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued — — Common stock $0.01 par value per share; 40,000,000 shares authorized; 11,609,853 shares issued and outstanding at December 31, 2017 and 11,475,742 shares issued and outstanding at December 31, 2016 116 115 Additional paid-in capital 88,205 85,421 Retained earnings 143,073 130,008 Accumulated other comprehensive income (loss) 416 (758 ) Total stockholders’ equity 231,810 214,786 Total liabilities and stockholders’ equity $ 246,738 $ 229,700 Statements of Income For the years ended December 31, (Dollars in thousands) 2017 2016 2015 Equity in undistributed net income of subsidiaries $ 16,922 $ 19,313 $ 17,277 Dividends distributed by subsidiaries 3,000 150 — Loss distributed by divested subsidiary — — (210 ) Other income — — 17 Total income 19,922 19,463 17,084 Interest expense 925 928 1,071 Other operating expenses 245 194 500 Total operating expenses 1,170 1,122 1,571 Income before income taxes 18,752 18,341 15,513 Benefit from income taxes (641 ) (410 ) (635 ) Net income $ 19,393 $ 18,751 $ 16,148 Parent Company Only Financial Statements Statements of Cash Flows For the years ended December 31, (Dollars in thousands) 2017 2016 2015 Cash flows from operating activities: Net income $ 19,393 $ 18,751 $ 16,148 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (16,922 ) (19,313 ) (17,277 ) Payment from subsidiary bank for stock compensation expense 1,758 2,348 1,791 Changes in: Decrease (increase) in other assets 832 (697 ) (36 ) Decrease in other liabilities 14 9 (482 ) Net cash provided by operating activities 5,075 1,098 144 Cash flows from investing activities: Investment in subsidiary (1) — (19,730 ) 781 Net cash (provided by) used in investing activities — (19,730 ) 781 Cash flows from financing activities: Repayment of subordinated debt (2) — — (10,825 ) Proceeds from the issuance of subordinated debt (2) — — 15,000 Cash dividends paid (6,241 ) (5,684 ) (5,158 ) Proceeds from issuance of common stock, net of expenses 1,590 21,183 1,448 Net settlement for employee tax withholdings on restrict stock and options (931 ) (442 ) — Proceeds from exercise of stock options 355 546 431 Tax benefit from stock-based compensation — 789 217 Net cash (used in) provided by financing activities (5,227 ) 16,392 1,113 Net (decrease) increase in cash and cash equivalents (152 ) (2,240 ) 2,038 Cash and cash equivalents, beginning of year 497 2,737 699 Cash and cash equivalents, end of year $ 345 $ 497 $ 2,737 (1) The outflow in investment in subsidiary in 2016 reflects the Company's investment in the Bank from the Offering. See Note 10 "Stockholders' Equity," above, for further information. (2) See Note 7, "Borrowed Funds and Subordinated Debt," above, for further information regarding changes in the Company's subordinated debt. The Parent Company’s Statements of Comprehensive Income and Statements of Changes in Stockholders’ Equity are identical to the Consolidated Statements of Comprehensive Income and the Consolidated Statements of Changes in Stockholders’ Equity and therefore are not presented here.

Quarterly Results of Operations

Quarterly Results of Operations (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	Quarterly Results of Operations (Unaudited) 2017 (Dollars in thousands, except share data) First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $ 24,364 $ 25,338 $ 27,045 $ 28,285 Interest expense 1,517 1,803 1,911 2,279 Net interest income 22,847 23,535 25,134 26,006 Provision for loan losses 125 280 1,225 (200 ) Net interest income after provision for loan losses 22,722 23,255 23,909 26,206 Non-interest income 3,594 3,710 3,728 3,926 Net gains (losses) on sales of investment securities 540 229 (284 ) 231 Non-interest expense 19,420 18,754 18,833 19,138 Income before income taxes 7,436 8,440 8,520 11,225 Provision for income taxes 1,864 2,845 3,014 8,505 Net income $ 5,572 $ 5,595 $ 5,506 $ 2,720 Basic earnings per share $ 0.48 $ 0.48 $ 0.48 $ 0.23 Diluted earnings per share $ 0.48 $ 0.48 $ 0.47 $ 0.23 2016 (Dollars in thousands, except share data) First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $ 22,465 $ 22,632 $ 23,191 $ 24,027 Interest expense 1,382 1,343 1,374 1,424 Net interest income 21,083 21,289 21,817 22,603 Provision for loan losses 850 267 1,386 490 Net interest income after provision for loan losses 20,233 21,022 20,431 22,113 Non-interest income 3,204 3,519 3,402 3,514 Net gains on sales of investment securities 2 63 546 191 Non-interest expense 16,869 17,542 17,414 18,503 Income before income taxes 6,570 7,062 6,965 7,315 Provision for income taxes 2,257 2,291 2,251 2,362 Net income $ 4,313 $ 4,771 $ 4,714 $ 4,953 Basic earnings per share $ 0.41 $ 0.45 $ 0.41 $ 0.43 Diluted earnings per share $ 0.41 $ 0.45 $ 0.41 $ 0.43

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	The consolidated financial statements of Enterprise Bancorp, Inc. (the "Company," "Enterprise," "we," or "our"), a Massachusetts corporation, include the accounts of the Company and its wholly owned subsidiary, Enterprise Bank and Trust Company commonly referred to as Enterprise Bank (the "Bank"). The Bank is a Massachusetts trust company and state chartered commercial bank organized in 1989. Substantially all of the Company’s operations are conducted through the Bank and its subsidiaries. The Bank’s subsidiaries include Enterprise Insurance Services, LLC and Enterprise Wealth Services, LLC, organized under the laws of the State of Delaware for the purposes of engaging in insurance sales activities and offering non-deposit investment products and services, respectively. In addition, the Bank has the following subsidiaries that are incorporated in the Commonwealth of Massachusetts and classified as security corporations in accordance with applicable Massachusetts General Laws: Enterprise Security Corporation; Enterprise Security Corporation II; and Enterprise Security Corporation III. The security corporations, which hold various types of qualifying securities, are limited to conducting securities investment activities that the Bank itself would be allowed to conduct under applicable laws. At December 31, 2017 , the Company had 24 full service branches serving the Greater Merrimack Valley and North Central regions of Massachusetts and Southern New Hampshire (Southern Hillsborough and Rockingham counties). Through the Bank and its subsidiaries, the Company offers a range of commercial, residential and consumer loan products, deposit products and cash management services, as well as investment advisory and wealth management, trust and insurance services. The services offered through the Bank and its subsidiaries are managed as one strategic unit and represent the Company’s only reportable operating segment. The Federal Deposit Insurance Corporation (the "FDIC") and the Massachusetts Division of Banks (the "Division") have regulatory authority over the Bank. The Bank is also subject to certain regulatory requirements of the Board of Governors of the Federal Reserve System (the "Federal Reserve Board") and, with respect to its New Hampshire branch operations, the New Hampshire Banking Department. The business and operations of the Company are subject to the regulatory oversight of the Federal Reserve Board. The Division also retains supervisory jurisdiction over the Company.
Basis of Accounting	The accompanying audited consolidated financial statements and notes thereto have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") and the instructions for Form 10-K through the rules and interpretive releases of the SEC under federal securities law. In the opinion of management, the accompanying audited consolidated financial statements reflect all necessary adjustments consisting of normal recurring accruals for a fair presentation. All significant intercompany balances and transactions have been eliminated in the accompanying audited consolidated financial statements.
Reclassifications	Certain previous years' amounts in the audited consolidated financial statements, and notes thereto, have been reclassified to conform to the current year's presentation.
Subsequent Events	The Company has evaluated subsequent events and transactions from December 31, 2017 through the date this Annual Report on Form 10-K was filed with the SEC for potential recognition or disclosure as required by GAAP and determined that there were no material subsequent events requiring recognition or disclosure.
Uses of Estimates	Uses of estimates In preparing the financial statements in conformity with GAAP, management is required to exercise judgment in determining many of the methodologies, assumptions and estimates to be utilized. These assumptions and estimates affect the reported values of assets and liabilities as of the balance sheet date and income and expenses for the years then ended. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates should the assumptions and estimates used be incorrect, or change over time due to changes in circumstances. Changes in those estimates resulting from continuing change in the economic environment and other factors will be reflected in the financial statements and results of operations in future periods. The three most significant areas in which management applies critical assumptions and estimates are the estimate of the allowance for loan losses, impairment review of investment securities and the impairment review of goodwill.
Cash and Cash Equivalents	Cash and cash equivalents Cash equivalents are defined as highly liquid investments with original maturities of three months or less, that are readily convertible to known amounts of cash and present insignificant risk of changes in value due to changes in interest rates. The Company's cash and cash equivalents is comprised of cash on hand and cash items due from banks, interest-earning deposits (deposit accounts, excess reserve cash balances, money markets, and money market mutual fund accounts) and federal funds ("fed funds") sold. Balances in cash and cash equivalents will fluctuate due primarily to the timing of net deposit flows, borrowing and loan inflows and outflows, investment purchases and maturities, calls and sales proceeds, and the immediate liquidity needs of the Company.
Investments	Investments Investments that are intended to be held for indefinite periods of time but which may not be held to maturity or on a long-term basis are considered to be "available-for-sale" and are carried at fair value. Net unrealized appreciation and depreciation on investments available-for-sale, net of applicable income taxes, are reflected as a component of accumulated other comprehensive income (loss). Included as available-for-sale are securities that are purchased in connection with the Company’s asset-liability risk management strategy and that may be sold in response to changes in interest rates, resultant prepayment risk and other related factors. In instances where the Company has the positive intent to hold investment securities to maturity, investment securities will be classified as held-to-maturity and carried at amortized cost. As of the balance sheet dates, all of the Company’s investment securities were classified as available-for-sale and carried at fair value. There are inherent risks associated with the Company’s investment activities that could adversely impact the fair market value and the ultimate collectability of the Company’s investments. Management regularly reviews the portfolio for securities with unrealized losses to determine if any of the unrealized losses are other-than-temporarily impaired ("OTTI"). The determination of OTTI involves a high degree of judgment. While management uses available information to measure OTTI at the balance sheet date, future write-downs may be necessary based on extended duration of current unrealized losses, changing market conditions, or circumstances surrounding individual issuers. If an investment is deemed to have an unrealized loss that is OTTI, the Company is required to write-down the investment. For debt securities, OTTI is generally recognized through a charge to earnings as of the balance sheet date, while non-OTTI unrealized losses are recognized in other comprehensive income. Unrealized losses on debt securities are deemed OTTI if 1) the Company intends to sell the security, 2) it is more likely than not that the Company will be required to sell the security before recovery, or 3) a credit loss exists and the Company does not expect to recover the entire amortized cost. For debt securities that have a credit loss, any portion of the loss related to other factors is recorded in other comprehensive income. Once written-down, the previous charge on debt securities may not be recovered through earnings until sale or maturity, if in excess of its new cost basis. Any OTTI charges, depending upon the magnitude of the charges, could have a material adverse effect on the Company’s financial condition and results of operations. At December 31, 2017 the Company did not hold any equity investments. See "Accounting pronouncements not yet adopted by the Company" under "Recent Accounting Pronouncements" in Item (t) below in this Note 1 for treatment of unrealized losses on equities beginning in 2018. See also Note 2, "Investment Securities," for further information on management's OTTI assessment. Investment securities’ discounts are accreted and premiums are amortized over the period of estimated principal repayment using methods that approximate the interest method. Gains or losses on the sale of investment securities are recognized on the trade date on a specific identification basis. See "Accounting pronouncements adopted by the Company" within "Recent Accounting Pronouncements" in Item (t) below in this Note 1 for further information on the Company's amortization of premiums on callable debt securities. (e) Restricted Investments Certain of the Company's derivative agreements contain provisions for collateral to be posted if the derivative exposure exceeds a threshold amount. When the Company has pledged cash as collateral for this purpose, the cash is carried as restricted cash within cash and cash equivalents. See Note 8, "Derivatives and Hedging Activities" for more information about the Company's collateral related to its derivatives. The Bank is also required by the FRB to maintain in reserves certain amounts of vault cash and/or deposits with the FRB. The average daily reserve requirement included in “Cash and Due from Banks” was approximately $7.6 million and $6.8 million , based on the two week computation periods encompassing December 31, 2017 and 2016 , respectively. As a member of the Federal Home Loan Bank of Boston ("FHLB"), the Company is required to purchase certain levels of FHLB capital stock at par value in association with outstanding advances from the FHLB. From time-to-time, the FHLB may initiate the repurchase, at par value, of "excess" levels of its capital stock held by member banks. This stock is classified as a restricted investment and carried at cost, which management believes approximates fair value. FHLB stock represents the only restricted investment held by the Company. Management regularly reviews its holdings of FHLB stock for OTTI. Based on management’s periodic review, the Company has not recorded any OTTI charges on this investment to date. If it was determined that a write-down of FHLB stock was required, impairment would be recognized through a charge to earnings. See Note 2, "Investment Securities," for additional information on management's OTTI review of investments.
Loans Held for Sale	Loans Held for Sale Depending on the current interest rate environment, management projections of future interest rates and the overall asset-liability management program of the Company, management may elect to sell those fixed and adjustable rate residential mortgage loans which are eligible for sale in the secondary market or hold some or all of this residential loan production for the Company's portfolio. Mortgage loans are generally not pooled for sale, but instead sold on an individual basis. Enterprise may retain or sell the servicing when selling the loans. Loans sold are subject to standard secondary market underwriting and eligibility representations and warranties over the life of the loan and are subject to an early payment default period covering the first four payments for certain loan sales. Loans held for sale are carried at the lower of aggregate amortized cost or market value. Market value is based on comparable market prices for loans with similar rates and terms. When loans are sold, a gain or loss is recognized to the extent that the sales proceeds plus unamortized fees and costs exceed, or are less than, the carrying value of the loans. Gains and losses are determined using the specific identification method.
Loans	Loans Loans made by the Company to businesses include commercial mortgage loans, construction and land development loans, secured and unsecured commercial loans and lines of credit, and letters of credit. The Company also originates equipment lease financing for businesses. Loans made to individuals include conventional residential mortgage loans, home equity loans and lines, residential construction loans on owner-occupied primary and secondary residences, and secured and unsecured personal loans and lines of credit. Most loans granted by the Company are collateralized by real estate or equipment and/or are guaranteed by the principals of the borrower. The ability and willingness of the single family residential and consumer borrowers to honor their repayment commitments is generally dependent on the level of overall economic activity and real estate values within the borrowers’ geographic areas. The ability and willingness of commercial real estate, commercial and construction loan borrowers to honor their repayment commitments is generally dependent on the health of the real estate sector in the borrowers’ geographic areas and the general economy, among other factors. Loans are reported at the principal amount outstanding, net of deferred origination fees and costs. The aggregate amount of overdrawn deposit accounts are reclassified as loan balances. Loan origination fees received, offset by direct loan origination costs, are deferred and amortized using the straight line method over three to five years for lines of credit and demand notes or over the life of the related loans using the level-yield method for all other types of loans. When loans are paid off, the unamortized fees and costs are recognized as an adjustment to interest income. From time to time, the Company participates with other banks in the financing of certain commercial projects. In each case in which the Company participates in a loan, the rights and obligations of each participating bank are divided proportionately among the participating banks in an amount equal to their share of ownership and with equal priority among all banks. When the participation qualifies as a sale under GAAP, the balances participated out to other institutions are not carried as assets on the Company's consolidated financial statements. Loans originated by other banks in which the Company is the participating institution are carried in the loan portfolio at the Company's pro rata share of ownership. See also, "Commercial loans" under "Loan categories" in Note 3, 'Loans" for further information about the Company's participation loans.
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses is an estimate of probable credit risk inherent in the loan portfolio as of the specified balance sheet dates. The allowance for loan losses is established through a provision for loan losses, a direct charge to earnings. Loan losses are charged against the allowance when management believes that the collectability of the loan principal is unlikely. Recoveries on loans previously charged-off are credited to the allowance. The Company maintains the allowance at a level that it deems adequate to absorb all reasonably anticipated probable losses from specifically known and other credit risks associated with the portfolio. The Company uses a systematic methodology to measure the amount of estimated loan loss exposure inherent in the portfolio for purposes of establishing a sufficient allowance for loan losses. The methodology uses a two-tiered approach that makes use of specific reserves for loans individually evaluated and deemed impaired and general reserves for larger groups of homogeneous loans, which are collectively evaluated relying on a combination of qualitative and quantitative factors that may affect credit quality of the pool. On a quarterly basis, the Company prepares an estimate of the allowance necessary to cover estimated credit risk inherent in the portfolio as of the specified balance sheet dates. The adequacy of the allowance for loan losses is reviewed and evaluated on a regular basis by an internal management committee and the full Board. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to recognize additions to the allowance based on judgments different from those of management. See Note 4, "Allowance for Loan Losses," for additional accounting policies related to non-accrual, impaired and troubled debt restructured loans and to the allowance for loan losses.
Other Real Estate Owned	Other Real Estate Owned Real estate acquired by the Company through foreclosure proceedings or the acceptance of a deed in lieu of foreclosure is classified as Other Real Estate Owned ("OREO"). When property is acquired, it is generally recorded at the lesser of the loan’s remaining principal balance, net of unamortized deferred fees, or the estimated fair value of the property acquired, less estimated costs to sell, establishing a new cost basis. The estimated fair value is based on market appraisals and the Company’s internal analysis. Any loan balance in excess of the estimated realizable fair value on the date of transfer is charged to the allowance for loan losses on that date. All costs incurred thereafter in maintaining the property, as well as subsequent declines in fair value are charged to non-interest expense.
Premises and Equipment	Premises and Equipment Land is carried at cost. Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation or amortization is computed on a straight-line basis over the lesser of the estimated useful lives of the asset or the respective lease term (with reasonably assured renewal options) for leasehold improvements generally as follows: Bank premises and leasehold improvements 10 to 39 years Computer software and equipment 3 to 5 years Furniture, fixtures and equipment 3 to 10 years
Bank Owned Life Insurance	Bank Owned Life Insurance The Company has purchased bank-owned life insurance ("BOLI') on certain current and former senior and executive officers. The cash surrender value carried on the consolidated balance sheets at December 31, 2017 and December 31, 2016 amounted to $29.5 million and $28.8 million , respectively. There are no associated surrender charges under the outstanding policies.
Impairment of Long-Lived Assets Other than Goodwill	Impairment of Long-Lived Assets Other than Goodwill The Company reviews long-lived assets, including premises and equipment, for impairment on an ongoing basis or whenever events or changes in business circumstances indicate that the remaining useful life may warrant revision or that the carrying amount of the long-lived asset may not be fully recoverable. If impairment is determined to exist, any related impairment loss is recognized through a charge to earnings. Impairment losses on assets disposed of, if any, are based on the estimated proceeds to be received, less cost of disposal.
Goodwill	Goodwill Goodwill carried on the Company’s consolidated financial statements was $5.7 million at both December 31, 2017 and December 31, 2016 . This asset is related to the Company’s acquisition of two branch offices in July 2000. In accordance with GAAP, the Company does not amortize goodwill and instead, at least annually, evaluates whether the carrying value of goodwill has become impaired. Impairment of the goodwill may occur when the estimated fair value of the Company is less than its recorded book value. A determination that goodwill has become impaired results in an immediate write-down of goodwill to its determined value with a resulting charge to operations. The annual impairment test begins with a qualitative assessment of whether it is "more likely than not" that the reporting unit's fair value is less than its carrying amount. The assessment is performed at the reporting unit level. If an entity concludes it is not "more likely than not" that the fair value of a reporting unit is less than its carrying amount, it need not perform a two-step impairment test. In the case of the Company, the services offered through the Bank and subsidiaries are managed as one strategic unit and represent the Company’s only reportable operating segment. Management's qualitative assessment takes into consideration macroeconomic conditions, industry and market considerations, cost or margin factors, financial performance and share price. Based on this assessment, the Company determined that it is not "more likely than not" that the Company's fair value is less than its carrying amount and therefore goodwill was determined not to be impaired at December 31, 2017 . If the Company's qualitative assessment concluded that it is "more likely than not" that the fair value of a reporting unit is less than its carrying amount, it must perform the two-step impairment test to identify potential goodwill impairment and measure the amount of goodwill impairment loss to be recognized, if any. The first step of the goodwill impairment test compares the estimated fair value of the reporting unit with its carrying amount, or the book value of the reporting unit, including goodwill. If the estimated fair value of the reporting unit equals or exceeds its book value, goodwill is considered not impaired, and the second step of the impairment test is unnecessary. The second step, if necessary, measures the amount of goodwill impairment loss to be recognized. The reporting unit must determine fair values for all assets and liabilities, excluding goodwill. The net of the assigned fair value of assets and liabilities is then compared to the book value of the reporting unit, and any excess book value becomes the implied fair value of goodwill. If the carrying amount of the goodwill exceeds the newly calculated implied fair value of that goodwill, an impairment loss is recognized in the amount required to write down the goodwill to the implied fair value.
Investment Assets Under Management	Investment Assets Under Management Investment assets under management, consisting of assets managed through Enterprise Wealth Management and Enterprise Wealth Services and commercial sweep products, totaled $845.0 million and $725.3 million at December 31, 2017 and 2016 , respectively. Fee income is recorded on an accrual basis and recognized over the period in which it is earned. Securities and other property held in a fiduciary or agency capacity are not included in the consolidated balance sheets because they are not assets of the Company.
Derivatives	Derivatives The Company recognizes all derivatives as either assets or liabilities on its consolidated balance sheet and measures those instruments at fair market value. Interest-rate-lock commitments related to the origination of mortgage loans that will be sold are considered derivative instruments. The commitments to sell loans are also considered derivative instruments. The Company generally does not pool mortgage loans for sale, but instead, sells the loans on an individual basis. To reduce the net interest rate exposure arising from its loan sale activity, the Company enters into the commitment to sell these loans at essentially the same time that the interest-rate lock commitment is quoted on the origination of the loan. The Company estimates the fair value of these derivatives based on current secondary mortgage market prices. At December 31, 2017 and 2016 , the estimated fair value of the Company's interest-rate lock commitments and commitments to sell these mortgage loans were deemed immaterial. The Company may use interest-rate-contract swaps as part of its interest-rate risk management strategy. Interest-rate- swap agreements are entered into as hedges against future interest-rate fluctuations on specifically identified assets or liabilities. The Company did not have derivative fair value hedges or derivative cash flow hedges at December 31, 2017 or 2016 . The Company has a "Back-to-Back Swap" program whereby the Bank enters into an interest-rate swap with a qualified commercial banking customer and simultaneously enters into an equal and opposite interest-rate swap with a swap counterparty. The customer interest-rate-swap agreement allows commercial banking customers to convert a floating-rate loan payment to a fixed-rate payment. The transaction structure effectively minimizes the Bank’s net risk exposure resulting from such transactions. Customer-related credit risk is minimized by the cross collateralization of the loan and the interest-rate-swap agreement. Back-to-Back Swaps are not speculative but rather, result from a service the Company provides to certain customers. Back-to-Back Swaps do not meet hedge accounting requirements and therefore changes in the fair value of both the customer swaps and the counterparty swaps, which have an offsetting relationship, are recognized directly in earnings. See Note 8, "Derivatives and Hedging Activities" for more information about the Company's derivatives.
Stock Based Compensation	Stock Based Compensation The Company’s consolidated financial statements include stock-based compensation expense for the portion of stock option awards and stock awards for which the requisite service has been rendered during the period. The compensation expense has been recorded based on the estimated grant-date fair value of the stock option awards, or in the case of stock awards, the market value of the common stock on the date of grant. Prior to the adoption of ASU 2016-09 "Compensation - Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting," in January 2017, forfeitures were estimated and netted against the expense. Upon adoption of this ASU, expense adjustments are made for actual forfeitures as they occur. See "Recent Accounting pronouncements" below in this Note 1, for further information related to the adoption of ASU 2016-09, including the change in recording excess tax benefits and deficiencies. The Company will recognize the remaining estimated compensation expense for the portion of outstanding awards and compensation expense for any future awards, net of actual forfeitures, as the requisite service is rendered (i.e., on a straight-line basis over the remaining vesting period of each award) or as performance objectives are met. Stock awards that do not require future service ("vested awards") will be expensed immediately. Stock-based compensation also includes Director stock compensation for stock awards and stock in lieu of cash fees, both included in other operating expenses, described in more detail in Note 12, "Stock-Based Compensation."
Income Taxes	Income Taxes The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and in the states of Massachusetts and New Hampshire. The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax expense or benefit attributable to differences between the financial statement carrying amounts and the tax basis of assets and liabilities. The deferred tax assets and liabilities are reflected at currently enacted income tax rates applicable to the period in which the deferred tax assets or liabilities are expected to be realized or settled. As changes in tax laws or rates are enacted, deferred tax assets and liabilities will be adjusted accordingly through the provision for income taxes in the period that includes the enactment date. The Company’s policy is to classify interest resulting from underpayment of income taxes as income tax expense in the first period the interest would begin accruing according to the provisions of the relevant tax law. The Company classifies penalties resulting from underpayment of income taxes as income tax expense in the period for which the Company claims or expects to claim an uncertain tax position or in the period in which the Company’s judgment changes regarding an uncertain tax position. The income tax provisions will differ from the expense that would result from applying the federal statutory rate to income before taxes, due primarily to the impact of tax-exempt interest from certain investment securities, loans and BOLI. The Company did not have any unrecognized tax benefits accrued as income tax liabilities or receivables or as deferred tax items at December 31, 2017 or December 31, 2016 . The Company is subject to U.S. federal and state income tax examinations by taxing authorities for the 2014 through 2017 tax years. See Note 13, "Income Taxes," for further information about the Company's income taxes and deferred tax assets, including the impact of the Tax Cuts and Jobs Acts (the "new federal tax bill").
Earnings Per Share	Earnings per Share Basic earnings per share are calculated by dividing net income available to common stockholders by the weighted average number of common shares outstanding (including participating securities) during the year. The Company's only participating securities are unvested restricted stock awards that contain non-forfeitable rights to dividends. Diluted earnings per share reflects the effect on weighted average shares outstanding of the number of additional shares outstanding if dilutive stock options were converted into common stock using the treasury stock method.
Reporting Comprehensive Income	Reporting Comprehensive Income Comprehensive income is defined as all changes to stockholder's equity except investments by and distributions to stockholders. Net income is one component of comprehensive income, with other components referred to in the aggregate as other comprehensive income. The Company’s only other comprehensive income component is the net unrealized holding gains or losses on investments available-for-sale, net of deferred income taxes. Pursuant to GAAP, the Company initially excludes these unrealized holding gains and losses from net income; however, they are later reported as reclassifications out of accumulated other comprehensive income into net income when the securities are sold. When securities are sold, the reclassification of realized gains and losses on available-for-sale securities are included on the Consolidated Statements of Income under the "non-interest income" subheading on the line item "net gains on sales of investment securities" and the related income tax expense is included in the line item "provision for income taxes," both of which are also detailed on the Consolidated Statements of Comprehensive Income under the subheading "reclassification adjustment for net gains included in net income."
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting pronouncements adopted by the Company In March 2016, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU" or "Update") No. 2016-09, "Compensation - Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting. " The new standard was effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The Company adopted ASU No. 2016-09 in the first quarter of 2017. Several aspects of the accounting are simplified including, generally: a) income tax consequences; b) classification of awards as either equity or liabilities; c) accounting for forfeitures; and d) classification on the statement of cash flows. Upon adoption, the most significant impact of this amendment resulted from the prospective application of current excess tax benefits and deficiencies being recognized in income tax expense, which would previously have been recognized in additional paid-in capital, in the reporting period in which they occur. For the year ended December 31, 2017, this reduced the Company's provision for income taxes, increasing earnings by approximately $922 thousand . For the years ended December 31, 2016 and 2015, the Company recognized $789 thousand and $217 thousand , respectively, in additional paid-in-capital in this regard, which, if under the new ASU, would have been recognized as income tax benefit in the income statement. This amount, treated as discrete items in the period in which they occur, will vary from year to year as a function of the volume of share-based payments vested or exercised and the then current market price of the Company's stock in comparison to the compensation cost recognized in the consolidated financial statements. Additionally upon adoption, the Company made a policy election to record forfeitures as they occur rather than make use of an estimate. Using a modified retrospective approach, the Company recorded an immaterial cumulative effect adjustment from retained earnings to additional paid-in-capital. The other provisions did not have a material impact on the Company's consolidated financial statements upon adoption. For further information about the Company's adoption of this ASU see Note 12 "Stock-Based Compensation." In March 2017, the FASB issued ASU No. 2017-08, "Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchases Callable Debt Securities." The amendments shorten the amortization period to the earliest call date for certain callable debt securities held at a premium. The accretion for securities held at a discount is not affected by this statement and remains unchanged. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. A modified retrospective basis is required upon adoption. Early adoption is permitted. The Company early adopted this ASU in the fourth quarter of 2017. This adoption did not have a material impact on the Company's consolidated financial statements, results of operations or disclosures upon adoption. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220)" The ASU eliminates the "stranded tax effects" associated with the new federal tax bill change in the federal corporate income tax rate on the valuation of deferred tax items related to unrealized gains/losses on available for sale securities. These stranded tax effects, the difference between the historical tax rate and the newly enacted tax rate, will be reclassified from accumulated other comprehensive income to retained earnings. The amendment is effective for all organizations for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted for reporting periods in which financial statements had not been issued. The Company chose to early adopt for the year ended December 31, 2017, with a cumulative effect adjustment to retained earnings and accumulated other comprehensive. This adoption did not have a material impact on the Company's consolidated financial statements, results of operations or disclosures upon adoption. Accounting pronouncements not yet adopted by the Company (in order of effective date of implementation) In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers (Topic 606) ". This ASU is intended to create a single source of revenue guidance which is more principles based than current revenue guidance. The guidance affects 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 standards. In August 2015, the FASB issued ASU 2015-14, "Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date" to amend the effective date of ASU 2014-09. The amendments in ASU 2014-09 are effective for annual and interim periods within fiscal years beginning after December 15, 2017. Earlier adoption was permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. The FASB has since issued additional related ASUs amendments intended to clarify certain aspects and improve understanding of the implementation guidance of Topic 606 but do not change the core principles of the guidance in Topic 606. The effective date and transition requirements for the amendments are the same as the effective date and transition requirements of Topic 606. The Company has begun the implementation process and based on the fact that the largest portion of the Company's revenue, interest income and various loan fees, is specifically excluded from the scope of this ASU, and because the Company currently recognizes the majority of the remaining revenue sources in a manner that management believes is consistent with the new ASU, management believes that this new standard will not materially impact the Company's consolidated financial statements, results of operations or disclosures. The foregoing observations are subject to change as management completes the implementation of this ASU in the first quarter of 2018. In January 2016, the FASB issued ASU No. 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities," which updates certain aspects of recognition, measurement, presentation and disclosure of financial instruments. Among other things, ASU No, 2016-01: • Requires 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; • Requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; and • Requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (i.e., securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements. The FASB has since issued an additional related ASU amendment intended to clarify certain aspects and improve understanding of the implementation guidance in ASU No. 2016-01 but does not change the core principles of the original guidance. This ASU is effective for public companies for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. This adoption is not expected to have a material impact on the Company's consolidated financial statements, results of operations or disclosures upon adoption. A s of December 31, 2017, the Company did not hold any equity securities; however the Company intends to invest in equity securities in 2018. The fair value changes that will be recognized in net income will depend on the amount of dollars invested and the magnitude of changes in equity market values. In August 2016, the FASB issued ASU No. 2016-15, "Statement of Cash flows (Topic 230) - Classification of Certain Cash Receipts and Cash Payments." The amendments are intended to reduce diversity in practice related to the presentation of eight specific cash flow issues. For public business entities that are SEC filers, such as the Company, the amendments in this Update are effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Because this amendment primarily impacts the presentation and classification of information, the Company does not expect this ASU to have an impact on the Company's consolidated financial statements and results of operations. The Company is currently in the process of implementing this ASU for the first quarter of 2018. In November 2016, the FASB issued ASU No. 2016-18, "Statement of Cash flows-Restricted Cash (Topic 230)." The amendments in this Update clarify the inclusion of restricted cash in the cash and cash equivalents beginning-of-period and end-of period reconciliation on the consolidated statement of cash flows. For public business entities that are SEC filers, such as the Company, the amendments in this Update are effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Because this amendment primarily impacts the presentation and classification of information, the Company does not expect this ASU to have an impact on the Company's consolidated financial statements and results of operations. The Company is currently in the process of implementing this ASU for the first quarter of 2018. In March 2017, the FASB issued ASU No. 2017-07, "Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost." The amendments in this Update outline the presentation, classification and disclosure requirements for service cost and other components of net benefit costs. For public business entities that are SEC filers, such as the Company, the amendments in this Update are effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. Because this amendment primarily impacts the presentation and classification of information, the Company does not expect this ASU to have an impact on the Company's consolidated financial statements and results of operations. The Company is currently in the process of adopting this ASU for the first quarter of 2018. In May 2017, the FASB issued ASU No. 2017-09, "Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting." The amendments in this Update apply to entities that change the terms of an outstanding share-based payment award. The amendments are intended to reduce diversity in practice as well as cost and complexity when applying guidance in Topic 718 to the modification of the terms and conditions of a share-based payment award. This ASU provides guidance on the three modifications to share-based payment awards and conditions that must be met in order to exempt an entity from modification accounting under Topic 718. The amendments in this Update apply prospectively to award modifications on or after the adoption date, and are effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The Company does not expect that adoption of the ASU will have a material impact on its consolidated financial statements, results of operations or disclosures. The Company is currently in the process of adopting this ASU for the first quarter of 2018. In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)," which supersedes previous leasing guidance in Topic 840, Leases. Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the consolidated financial statements, with certain practical expedients available. The Company is currently evaluating the effects of this ASU on the Company's consolidated financial statements, results of operations and disclosures. Based on the Company's evaluation to date, management believes the more significant implication of this ASU on the Company relates to operating leases of our facilities, mainly branch leases. As of December 31, 2017 , the Company had leases on 17 of its locations, including branches and part of its main campus, and expects that upon adoption of this ASU the balance sheet will reflect both lease liabilities, equal to the present value of lease payments, and right-of-use assets, equal to the lease liability plus payments made to lessors adjusted for prepaid or accrued rent and any initial direct cost incurred. In addition, the Company will recognize lease expense in the income statement on a straight-line basis similar to current operating leases. The straight-line expense will reflect the interest expense on the lease liability (effective interest method) and amortization of the right-of-use asset. Lease expense will be presented as a single line item in the operating expense section of the income statement. Management believes that lease expense under the new standard will generally approximate lease expense under current GAAP. The foregoing observations are subject to change as management completes their evaluation. In June 2016, the FASB issued ASU No. 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments." The amendments in this ASU require a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. Previously, when credit losses were measured under GAAP, an entity generally only considered past events and current conditions in measuring the incurred loss and generally recognition of the full amount of credit losses was delayed until the loss was probable of occurring. The amendments in this ASU eliminate the probable initial recognition threshold in current GAAP and, instead, reflect an entity’s current estimate of all expected credit losses. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. An entity must use judgment in determining the relevant information and estimation methods that are appropriate in its circumstances. The income statement reflects the measurement of credit losses for newly recognized financial assets, as well as the expected increases or decreases of expected credit losses that have taken place during the period. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset(s) to present the net carrying value at the amount expected to be collected on the financial asset. Credit losses on available-for-sale debt securities should be measured in a manner similar to current GAAP. However, the amendments in this Update require that credit losses be presented as an allowance rather than as a write-down. Unlike current GAAP, the ASU provides for reversals of credit losses in future period net income in situations where the estimate of loss declines. An entity will apply the amendments in this Update through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified-retrospective approach). For public business entities that are SEC filers, such as the Company, the amendments in this Update are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption for fiscal years beginning after December 15, 2018 is permitted. The Company has established an implementation committee and an enterprise-wide implementation plan for this ASU, which will consider the impact to operations, financial results, disclosures and controls. At present, the impact of the adoption of ASU No. 2016-13 on the Company's operations, financial results, disclosures and controls is unknown. In January 2017, the FASB issued ASU No. 2017-04, "Intangibles-Goodwill and Other (Topic 350)-Simplifying the Test for Goodwill Impairment. " The main provision in this ASU eliminated Step 2 of the goodwill impairment test and instead requires an entity to perform its annual, or interim, goodwill impairment test by comparing the fair value of the reporting unit with its carrying amount. An impairment charge would be recognized for the amount the carrying value exceeds the reporting unit's fair value as long as the amount recognized doesn't exceed the amount of goodwill allocated to the reporting unit. For public business entities that are SEC filers, such as the Company, the amendments in this Update are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for impairment tests performed on testing dates after January 1, 2017. Goodwill carried on the Company's consolidated financial statements was $5.7 million at both December 31, 2017 and December 31, 2016. This asset is related to the Company's acquisition of two branch offices in July 2000. The Company does not expect the adoption of ASU No. 2017-04 to have a material impact on the Company's consolidated financial statements and results of operations.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Property, Plant and Equipment, Useful Lives	Depreciation or amortization is computed on a straight-line basis over the lesser of the estimated useful lives of the asset or the respective lease term (with reasonably assured renewal options) for leasehold improvements generally as follows: Bank premises and leasehold improvements 10 to 39 years Computer software and equipment 3 to 5 years Furniture, fixtures and equipment 3 to 10 years

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Investment Securities Reconciliation	The amortized cost and fair values of investment securities at December 31, 2017 and 2016 are summarized as follows: 2017 (Dollars in thousands) Amortized cost Unrealized gains Unrealized losses Fair Value Federal agency obligations (1) $ 51,769 $ 30 $ 82 $ 51,717 Residential federal agency MBS (1) 141,054 71 971 140,154 Commercial federal agency MBS (1) 66,777 9 286 66,500 Municipal securities 132,603 2,097 354 134,346 Corporate bonds 11,546 63 67 11,542 Certificates of deposits (2) 950 — 3 947 Total investment securities, at fair value (3) $ 404,699 $ 2,270 $ 1,763 $ 405,206 2016 (Dollars in thousands) Amortized cost Unrealized gains Unrealized losses Fair Value Federal agency obligations (1) $ 74,682 $ 432 $ 45 $ 75,069 Residential federal agency MBS (1) 94,818 96 1,561 93,353 Commercial federal agency MBS (1) 71,993 15 1,730 70,278 Municipal securities 112,401 922 1,520 111,803 Corporate bonds 10,734 51 90 10,695 Certificates of deposits (2) 950 — 1 949 Total debt securities 365,578 1,516 4,947 362,147 Equity investments 10,413 2,532 302 12,643 Total investment securities, at fair value $ 375,991 $ 4,048 $ 5,249 $ 374,790 (1) These categories may include investments issued or guaranteed by government sponsored enterprises such as Fannie Mae ("FNMA"), Freddie Mac ("FHLMC"), Federal Farm Credit Bank ("FFCB"), or one of several Federal Home Loan Banks, as well as, investments guaranteed by Ginnie Mae ("GNMA"), a wholly-owned government entity. (2) Certificates of deposit ("CDs") represent term deposits issued by banks that are subject to FDIC insurance and purchased on the open market. (3) As of December 31, 2017, all investments were debt securities and the Company did not hold any available-for-sale equity securities.
Schedule of Unrealized Loss on Investments	The following tables summarize investments (debt and equity) having temporary impairment, due to the fair market values having declined below the amortized costs of the individual investments, and the period that the investments have been temporarily impaired at December 31, 2017 and 2016 . 2017 Less than 12 months 12 months or longer Total (Dollars in thousands) Fair Value Unrealized Losses Fair value Unrealized Losses Fair Value Unrealized Losses # of holdings Federal agency obligations $ 34,344 $ 82 $ — $ — $ 34,344 $ 82 9 Residential federal agency MBS 109,308 882 2,015 89 111,323 971 30 Commercial federal agency MBS 35,859 205 5,190 81 41,049 286 11 Municipal securities 16,983 129 10,210 225 27,193 354 50 Corporate bonds 2,802 23 2,913 44 5,715 67 33 Certificates of deposits 947 3 — — 947 3 4 Total temporarily impaired investment securities $ 200,243 $ 1,324 $ 20,328 $ 439 $ 220,571 $ 1,763 137 2016 Less than 12 months 12 months or longer Total (Dollars in thousands) Fair Value Unrealized Losses Fair value Unrealized Losses Fair Value Unrealized Losses # of holdings Federal agency obligations $ 13,956 $ 45 $ — $ — $ 13,956 $ 45 3 Residential federal agency MBS 68,138 1,236 8,008 325 76,146 1,561 31 Commercial federal agency MBS 60,060 1,730 — — 60,060 1,730 18 Municipal securities 60,436 1,520 — — 60,436 1,520 107 Corporate bonds 5,729 90 — — 5,729 90 37 Certificates of deposit 949 1 — — 949 1 4 Equity investments 1,185 20 2,743 282 3,928 302 3 Total temporarily impaired investment securities $ 210,453 $ 4,642 $ 10,751 $ 607 $ 221,204 $ 5,249 203
Investments Classified by Contractual Maturity Date	The contractual maturity distribution at December 31, 2017 of total debt securities was as follows: (Dollars in thousands) Amortized Cost Fair Value Due in one year or less $ 19,095 $ 19,159 Due after one, but within five years 82,231 82,255 Due after five, but within ten years 134,395 134,959 Due after ten years 168,978 168,833 Total available-for-sale securities $ 404,699 $ 405,206
Schedule of Realized Gain (Loss) on Sales of Investments	Sales of investments, including pending trades based on trade date, if applicable, for the years ended December 31, 2017 , 2016 , and 2015 are summarized as follows: (Dollars in thousands) 2017 2016 2015 Amortized cost of investments sold (1) $ 145,472 $ 4,299 $ 23,287 Gross realized gains on sales 3,411 803 1,990 Gross realized losses on sales (2,695 ) (1 ) (162 ) Total proceeds from sales of investments $ 146,188 $ 5,101 $ 25,115 (1) Amortized cost of investments sold is determined on a specific identification basis.

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Schedule of Loans by Loan Classification	Major classifications of loans at the periods indicated were as follows: (Dollars in thousands) December 31, 2017 December 31, 2016 Commercial real estate $ 1,201,351 $ 1,038,082 Commercial and industrial 498,802 490,799 Commercial construction 274,905 213,447 Total commercial loans 1,975,058 1,742,328 Residential mortgages 195,492 180,560 Home equity loans and lines 91,706 91,065 Consumer 10,293 10,845 Total retail loans 297,491 282,470 Gross loans 2,272,549 2,024,798 Deferred loan origination fees, net (2,645 ) (2,069 ) Total loans 2,269,904 2,022,729 Allowance for loan losses (32,915 ) (31,342 ) Net loans $ 2,236,989 $ 1,991,387
Schedule of Loans Pledged as Collateral	Loans designated as qualified collateral and pledged to the FHLB for borrowing capacity for the periods indicated are summarized below: (Dollars in thousands) December 31, 2017 December 31, 2016 Commercial real estate $ 224,703 $ 247,664 Residential mortgages 187,524 170,247 Home equity loans and lines 9,405 12,340 Total loans pledged to FHLB $ 421,632 $ 430,251

Allowance For Loan Losses (Tabl

Allowance For Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Financing Receivables by Evaluation Method	The balances of loans as of December 31, 2016 by segment and evaluation method are summarized as follows: (Dollars in thousands) Loans individually evaluated for impairment Loans collectively evaluated for impairment Gross Loans Commercial real estate $ 14,261 $ 1,023,821 $ 1,038,082 Commercial and industrial 13,372 477,427 490,799 Commercial construction 3,364 210,083 213,447 Residential mortgages 289 180,271 180,560 Home equity loans and lines 509 90,556 91,065 Consumer 1 10,844 10,845 Total loans $ 31,796 $ 1,993,002 $ 2,024,798 The balances of loans as of December 31, 2017 by segment and evaluation method are summarized as follows: (Dollars in thousands) Loans individually evaluated for impairment Loans collectively evaluated for impairment Gross Loans Commercial real estate $ 13,739 $ 1,187,612 $ 1,201,351 Commercial and industrial 10,096 488,706 498,802 Commercial construction 1,624 273,281 274,905 Residential mortgages 397 195,095 195,492 Home equity loans and lines 371 91,335 91,706 Consumer 35 10,258 10,293 Total gross loans $ 26,262 $ 2,246,287 $ 2,272,549
Financing Receivable Credit Quality Indicators	The following tables present the Company's credit risk profile for each class of loan in its portfolio by internally assigned adverse risk rating category as of the periods indicated. December 31, 2017 (Dollars in thousands) Adversely Classified Not Adversely Classified Gross Loans Substandard Doubtful Loss Commercial real estate $ 12,895 $ — $ — $ 1,188,456 $ 1,201,351 Commercial and industrial 9,915 48 1 488,838 498,802 Commercial construction 1,624 — — 273,281 274,905 Residential mortgages 1,355 — — 194,137 195,492 Home equity loans and lines 513 — — 91,193 91,706 Consumer 52 10 — 10,231 10,293 Total gross loans $ 26,354 $ 58 $ 1 $ 2,246,136 $ 2,272,549 December 31, 2016 (Dollars in thousands) Adversely Classified Not Adversely Classified Gross Loans Substandard Doubtful Loss Commercial real estate $ 16,003 $ — $ — $ 1,022,079 $ 1,038,082 Commercial and industrial 12,770 99 2 477,928 490,799 Commercial construction 3,364 — — 210,083 213,447 Residential mortgages 1,414 — — 179,146 180,560 Home equity loans and lines 666 — — 90,399 91,065 Consumer 30 — — 10,815 10,845 Total gross loans $ 34,247 $ 99 $ 2 $ 1,990,450 $ 2,024,798
Past Due Financing Receivables	The following tables present an age analysis of past due loans as of the dates indicated: Balance at December 31, 2017 (Dollars in thousands) Past Due 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Total Past Due Loans Current Loans Gross Loans Non-accrual Loans Commercial real estate $ 4,200 $ 69 $ 3,569 $ 7,838 $ 1,193,513 $ 1,201,351 $ 6,751 Commercial and industrial 374 527 327 1,228 497,574 498,802 1,294 Commercial construction 2,526 518 — 3,044 271,861 274,905 193 Residential mortgages 1,931 93 89 2,113 193,379 195,492 262 Home equity loans and lines 491 120 12 623 91,083 91,706 463 Consumer 51 5 45 101 10,192 10,293 69 Total gross loans $ 9,573 $ 1,332 $ 4,042 $ 14,947 $ 2,257,602 $ 2,272,549 $ 9,032 Balance at December 31, 2016 (Dollars in thousands) Past Due 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Total Past Due Loans Current Loans Gross Loans Non-accrual Loans Commercial real estate $ 5,993 $ 923 $ 1,399 $ 8,315 $ 1,029,767 $ 1,038,082 $ 4,876 Commercial and industrial 267 4 1,544 1,815 488,984 490,799 3,174 Commercial construction — — — — 213,447 213,447 519 Residential mortgages 648 — 99 747 179,813 180,560 289 Home equity loans and lines 270 — 269 539 90,526 91,065 616 Consumer 94 13 11 118 10,727 10,845 11 Total gross loans $ 7,272 $ 940 $ 3,322 $ 11,534 $ 2,013,264 $ 2,024,798 $ 9,485
Schedule of Interest Lost on Nonaccrual Loans	The reduction in interest income for the years ended December 31, associated with non-accruing loans is summarized as follows: (Dollars in thousands) 2017 2016 2015 Income in accordance with original loan terms $ 1,906 $ 1,585 $ 1,052 Less income recognized 990 722 426 Reduction in interest income $ 916 $ 863 $ 626
Impaired Financing Receivables	The following tables set forth the recorded investment in impaired loans and the related specific allowance allocated as of the dates indicated: Balance at December 31, 2017 (Dollars in thousands) Unpaid contractual principal balance Total recorded investment in impaired loans Recorded investment with no allowance Recorded investment with allowance Related specific allowance Commercial real estate $ 15,132 $ 13,739 $ 12,850 $ 889 $ 59 Commercial and industrial 10,458 10,096 7,053 3,043 1,284 Commercial construction 1,678 1,624 1,624 — — Residential mortgages 511 397 262 135 5 Home equity loans and lines 543 371 371 — — Consumer 36 35 — 35 35 Total $ 28,358 $ 26,262 $ 22,160 $ 4,102 $ 1,383 Balance at December 31, 2016 (Dollars in thousands) Unpaid contractual principal balance Total recorded investment in impaired loans Recorded investment with no allowance Recorded investment with allowance Related specific allowance Commercial real estate $ 16,010 $ 14,261 $ 12,444 $ 1,817 $ 370 Commercial and industrial 14,291 13,372 9,366 4,006 2,222 Commercial construction 3,408 3,364 3,051 313 28 Residential mortgages 388 289 289 — — Home equity loans and lines 665 509 509 — — Consumer 2 1 — 1 1 Total $ 34,764 $ 31,796 $ 25,659 $ 6,137 $ 2,621 The following table presents the average recorded investment in impaired loans and the related interest recognized during the year ends indicated: December 31, 2017 December 31, 2016 December 31, 2015 (Dollars in thousands) Average recorded investment Interest income (loss) recognized Average recorded investment Interest income (loss) recognized Average recorded investment Interest income recognized Commercial real estate $ 14,473 $ 363 $ 12,988 $ 332 $ 13,827 $ 196 Commercial and industrial 12,272 370 9,790 223 9,372 97 Commercial construction 1,818 92 3,137 150 2,202 83 Residential mortgages 320 2 301 — 449 — Home equity loans and lines 482 (1 ) 356 (4 ) 174 1 Consumer 25 (1 ) 14 — 45 — Total $ 29,390 $ 825 $ 26,586 $ 701 $ 26,069 $ 377
Troubled Debt Restructurings on Financing Receivables	Payment defaults during the years ended December 31, 2017 and December 31, 2016 on loans modified as TDRs within the preceding twelve months are detailed below. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of TDRs that defaulted Post-modification outstanding recorded investment Number of TDRs that defaulted Post-modification outstanding recorded investment Commercial real estate — $ — 1 $ 148 Commercial and industrial 2 20 — — Commercial construction — — — — Residential mortgages — — — — Home equity loans and lines — — — — Consumer — — — — Total 2 $ 20 1 $ 148 Loans modified as TDRs during the year ended December 31, 2017 and December 31, 2016 are detailed below. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of restructurings Pre-modification outstanding recorded investment Post-modification outstanding recorded investment Number of restructurings Pre-modification outstanding recorded investment Post-modification outstanding recorded investment Commercial real estate 3 $ 696 $ 674 8 $ 6,212 $ 7,534 Commercial and industrial 6 386 346 11 5,231 5,244 Commercial construction — — — — — — Residential mortgages 1 136 135 — — — Home equity loans and lines — — — — — — Consumer 1 1 1 — — — Total 11 $ 1,219 $ 1,156 19 $ 11,443 $ 12,778 The following table sets forth the post modification balances of TDRs listed by type of modification for TDRs that occurred during the periods indicated. December 31, 2017 December 31, 2016 (Dollars in thousands) Number of restructurings Amount Number of restructurings Amount Loan advances with adequate collateral — $ — 8 $ 10,533 Extended maturity date 1 175 4 548 Temporary payment reduction and payment re-amortization of remaining principal over extended term 6 790 — — Temporary interest-only payment plan 4 191 7 1,697 Total 11 $ 1,156 19 $ 12,778 Amount of specific reserves included in the allowance for loan losses associated with TDRs listed above $ 155 $ 1,418
Allowance for Credit Losses on Financing Receivables	Changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2017 , are presented below: (Dollars in thousands) Cmml Real Estate Cmml and Industrial Cmml Constr Resid. Mortgage Home Equity Cnsmr Total Beginning Balance, December 31, 2016 $ 14,902 $ 11,204 $ 3,406 $ 960 $ 634 $ 236 $ 31,342 Provision 2,628 (1,737 ) 541 (56 ) (30 ) 84 1,430 Recoveries 193 550 — — 4 8 755 Less: Charge-offs 178 348 — — — 86 612 Ending Balance, December 31, 2017 $ 17,545 $ 9,669 $ 3,947 $ 904 $ 608 $ 242 $ 32,915 Ending allowance balance: Allocated to loans individually evaluated for impairment $ 59 $ 1,284 $ — $ 5 $ — $ 35 $ 1,383 Allocated to loans collectively evaluated for impairment $ 17,486 $ 8,385 $ 3,947 $ 899 $ 608 $ 207 $ 31,532 Changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2016 , are presented below: (Dollars in thousands) Cmml Real Estate Cmml and Industrial Cmml Constr Resid. Mortgage Home Equity Cnsmr Total Beginning Balance, December 31, 2015 $ 13,514 $ 9,758 $ 3,905 $ 1,061 $ 540 $ 230 $ 29,008 Provision 1,696 1,745 (494 ) (101 ) 97 50 2,993 Recoveries 20 681 — — 3 5 709 Less: Charge-offs 328 980 5 — 6 49 1,368 Ending Balance, December 31, 2016 $ 14,902 $ 11,204 $ 3,406 $ 960 $ 634 $ 236 $ 31,342 Ending allowance balance: Allocated to loans individually evaluated for impairment $ 370 $ 2,222 $ 28 $ — $ — $ 1 $ 2,621 Allocated to loans collectively evaluated for impairment $ 14,532 $ 8,982 $ 3,378 $ 960 $ 634 $ 235 $ 28,721 Changes in the allowance for loan losses for the years ended December 31, are summarized as follows: (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 31,342 $ 29,008 $ 27,121 Provision 1,430 2,993 3,267 Recoveries 755 709 409 Less: Charge-offs 612 1,368 1,789 Balance at end of year $ 32,915 $ 31,342 $ 29,008

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and equipment at December 31, are summarized as follows: (Dollars in thousands) 2017 2016 Land $ 5,488 $ 5,201 Bank premises and leasehold improvements 42,525 37,390 Computer software and equipment 9,303 9,250 Furniture, fixtures and equipment 20,347 18,243 Total premises and equipment, before accumulated depreciation 77,663 70,084 Less accumulated depreciation (40,641 ) (36,544 ) Total premises and equipment, net of accumulated depreciation $ 37,022 $ 33,540
Schedule of Future Minimum Rental Payments for Operating Leases	At December 31, 2017 , minimum lease payments for these operating leases were as follows: (Dollars in thousands) Payable in: 2018 $ 1,609 2019 1,392 2020 1,136 2021 1,133 2022 1,131 Thereafter 9,285 Total minimum lease payments $ 15,686

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Schedule of Deposit Liabilities	Deposits at December 31, are summarized as follows: (Dollars in thousands) 2017 2016 Non-interest bearing demand deposits $ 705,846 $ 646,115 Interest-bearing checking 391,111 372,696 Savings 193,385 178,637 Money market 807,931 844,216 Certificates of deposit $250,000 or less 150,445 125,580 Certificates of deposit more than $250,000 45,154 42,315 Total customer deposits 2,293,872 2,209,559 Brokered deposits (1) 147,490 59,362 Total deposits $ 2,441,362 $ 2,268,921 (1) Brokered CDs $250,000 and under.
Schedule of Maturities of Time Deposits	The following table shows the scheduled maturities of certificates of deposit (including brokered deposits with weighted average remaining lives of less than 6 months at December 31, 2017 and approximately 1.5 years as of December 31, 2016 ): (Dollars in thousands) December 31, 2017 December 31, 2016 Due in less than twelve months $ 240,995 $ 136,695 Due in over one year through two years 60,692 38,344 Due in over two years through three years 28,141 32,652 Due in over three years through four years 6,592 8,525 Due in over four years through five years 5,614 5,721 Due in over five years 1,055 5,320 Total certificates of deposit $ 343,089 $ 227,257

Borrowed Funds and Subordinat33

Borrowed Funds and Subordinated Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Borrowed Funds and Debentures	Borrowed funds and subordinated debt outstanding at December 31, for the years indicated are summarized as follows: 2017 2016 2015 (Dollars in thousands) Amount Average Rate Amount Average Rate Amount Average Rate FHLB borrowings $ 89,000 1.54 % $ 10,671 0.80 % $ 40,671 0.51 % Other borrowings — — % — — % 13,000 0.60 % Total borrowed funds $ 89,000 1.54 % $ 10,671 0.80 % $ 53,671 0.53 % Subordinated debt 14,847 6.23 % 14,834 6.26 % 14,822 6.16 % Total borrowed funds and subordinated debt $ 103,847 2.21 % $ 25,505 3.98 % $ 68,493 1.75 %
Schedule of Average Balances and Rates for Borrowed Funds	The following table summarizes the average balance and average cost of borrowed funds for the years indicated. Year ended December 31, 2017 2016 2015 (Dollars in thousands) Average Balance Average Cost Average Balance Average Cost Average Balance Average Cost FHLB advances $ 49,546 1.19 % $ 14,551 0.55 % $ 10,731 0.36 % Other borrowings — — % 107 0.61 % 36 0.61 % Total borrowed funds $ 49,546 1.19 % $ 14,658 0.55 % $ 10,767 0.36 %

Derivatives and Hedging Activ34

Derivatives and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivatives, Fair Value and Classification	The table below presents the fair value and classification of the Company’s derivative financial instruments for the periods presented: As of December 31, 2017 As of December 31, 2016 (Dollars in thousands) Asset Derivatives Liability Derivatives Asset Derivatives Liability Derivatives Interest-rate contracts - pay floating, received fixed $ 25 $ 568 $ — $ 610 Interest-rate contracts - pay fixed, receive floating 543 — 610 — Total interest rate swaps $ 568 $ 568 $ 610 $ 610
Schedule of Derivatives - Offsetting Assets and Liabilities	As of December 31, 2017 (Dollars in thousands) Gross Amounts of Recognized Asset Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets Presented in the Statement of Financial Position Asset Derivatives Interest-rate contracts - pay fixed, receive floating $ 568 $ 25 $ 543 As of December 31, 2016 (Dollars in thousands) Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets Presented in the Statement of Financial Position Asset Derivatives Interest-rate contracts - pay fixed, receive floating $ 610 $ — $ 610

Committments, Contingencies a35

Committments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Financial Instruments with Off-Balance Sheet Risk	Financial instruments with off-balance sheet credit risk at December 31, 2017 and 2016 are as follows: (Dollars in thousands) 2017 2016 Commitments to originate loans $ 13,830 $ 37,753 Commitments to originate residential mortgages loans for sale 2,078 1,946 Commitments to sell residential mortgage loans 2,286 3,115 Letters of credit 21,576 21,497 Unadvanced portions of commercial real estate loans 26,947 56,952 Unadvanced portions of commercial loans and lines 432,731 399,833 Unadvanced portions of construction loans (commercial & residential) 209,916 151,757 Unadvanced portions of home equity lines 94,012 82,884 Unadvanced portions of consumer loans 4,290 3,043

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	Management believes, as of December 31, 2017 , that the Company and the Bank met all capital adequacy requirements to which they were subject. As of December 31, 2017 and December 31, 2016 , the Company met the definition of "well-capitalized" under the applicable Federal Reserve Board regulations and the Bank qualified as "well-capitalized" under the prompt corrective action regulations of Basel III and the FDIC. The Company's and the Bank's actual capital amounts and ratios are presented as of December 31, 2017 and December 31, 2016 in the tables below. Actual Minimum Capital for Capital Adequacy Purposes (1) Minimum Capital To Be Well Capitalized (2) (Dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2017 The Company Total Capital (to risk weighted assets) $ 270,826 11.21 % $ 193,327 8.00 % N/A N/A Tier 1 Capital (to risk weighted assets) 225,738 9.34 % 144,995 6.00 % N/A N/A Tier 1 Capital (to average assets) or Leverage Ratio 225,738 8.22 % 109,838 4.00 % N/A N/A Common equity tier 1 capital (to risk-weighted assets) 225,738 9.34 % 108,747 4.50 % N/A N/A The Bank Total Capital (to risk weighted assets) $ 270,150 11.18 % $ 193,301 8.00 % $ 241,626 10.00 % Tier 1 Capital (to risk weighted assets) 239,910 9.93 % 144,976 6.00 % 193,301 8.00 % Tier 1 Capital (to average assets) or Leverage Ratio 239,910 8.74 % 109,837 4.00 % 137,296 5.00 % Common equity tier 1 capital (to risk-weighted assets) 239,910 9.93 % 108,732 4.50 % 157,057 6.50 % Actual Minimum Capital (1) Minimum Capital To Be Well Capitalized (2) (Dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2016 The Company Total Capital (to risk weighted assets) $ 252,552 11.79 % $ 171,337 8.00 % N/A N/A Tier 1 Capital (to risk weighted assets) 209,887 9.80 % 128,503 6.00 % N/A N/A Tier 1 Capital (to average assets) or Leverage Ratio 209,887 8.34 % 100,628 4.00 % N/A N/A Common equity tier 1 capital (to risk-weighted assets) 209,887 9.80 % 96,377 4.50 % N/A N/A The Bank Total Capital (to risk weighted assets) $ 250,893 11.71 % $ 171,332 8.00 % $ 214,166 10.00 % Tier 1 Capital (to risk weighted assets) 223,062 10.42 % 128,499 6.00 % 171,332 8.00 % Tier 1 Capital (to average assets) or Leverage Ratio 223,062 8.87 % 100,627 4.00 % 125,784 5.00 % Common equity tier 1 capital (to risk-weighted assets) 223,062 10.42 % 96,374 4.50 % 139,208 6.50 % (1) Before application of the capital conservation buffer of 1.25% as of December 31, 2017 and 0.625% as of December 31, 2016 , see discussion below. (2) For the Bank to qualify as “well-capitalized," it must maintain at least the minimum ratios listed. This prompt corrective action framework requirement does not apply to the Company.
Schedule of Basel III Minimum Requirements at Full Phase In [Table Text Block]	The Basel III minimum capital ratio requirements as applicable to the Company and the Bank in 2019 after the full phase-in period are summarized in the table below: Basel III Minimum for Capital Adequacy Purposes Basel III Additional Capital Conservation Buffer Basel III "Adequate" Ratio with Capital Conservation Buffer Total Capital (to risk weighted assets) 8.00% 2.50% 10.50% Tier 1 Capital (to risk weighted assets) 6.00% 2.50% 8.50% Tier 1 Capital (to average assets) or Leverage Ratio 4.00% —% 4.00% Common equity tier 1 capital (to risk-weighted assets) 4.50% 2.50% 7.00%

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Schedule of Changes in Projected Benefit Obligations	The following table provides a reconciliation of the changes in the supplemental retirement benefit obligation and the net periodic benefit cost for the years ended December 31: (Dollars in thousands) 2017 2016 2015 Reconciliation of benefit obligation: Benefit obligation at beginning of year $ 2,502 $ 2,654 $ 2,844 Net periodic benefit cost: Interest cost 110 124 133 Actuarial loss (gain) 36 — (47 ) Net periodic benefit costs $ 146 $ 124 $ 86 Benefits paid (276 ) (276 ) (276 ) Benefit obligation at end of year $ 2,372 $ 2,502 $ 2,654 Funded status: Accrued liability as of December 31 $ (2,372 ) $ (2,502 ) $ (2,654 ) Discount rate used for benefit obligation (1) 4.50 % 4.75 % 4.75 % (1) Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss.
Schedule of Expected Benefit Payments	Benefits expected to be paid in each of the next five years and in the aggregate five years thereafter: (Dollars in thousands) 2018 $ 276 2019 276 2020 276 2021 276 2022 276 2023-2027 1,380
Supplemental Life Insurance Benefit
Defined Benefit Plan Disclosure [Line Items]
Schedule of Changes in Projected Benefit Obligations	The following table provides a reconciliation of the changes in the supplemental life insurance plan obligation and the net periodic benefit cost for the years ended December 31: (Dollars in thousands) 2017 2016 2015 Reconciliation of benefit obligation: Benefit obligation at beginning of year $ 1,895 $ 1,792 $ 1,723 Net periodic benefit cost: Service cost (11 ) (9 ) (56 ) Interest cost 91 88 86 Actuarial loss 57 24 39 Total net period cost $ 137 $ 103 $ 69 Benefit obligation at end of year $ 2,032 $ 1,895 $ 1,792 Funded status: Accrued liability as of December 31 $ (2,032 ) $ (1,895 ) $ (1,792 ) Discount rate used for benefit obligation (1) 4.50 % 4.75 % 4.75 % (1) Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The table below provides a summary of the options granted, including the fair value, the fair value as a percentage of the market value of the stock at the date of grant and the average assumptions used in the model for the years indicated. Stock Option Awards 2017 2016 2015 Options granted 15,009 31,047 27,376 Term in years 10.0 10.0 10.0 Weighted average assumptions used in the fair value model: Expected volatility 40 % 42 % 47 % Expected dividend yield 2.09 % 3.02 % 2.90 % Expected life in years 7.0 7.0 7.0 Risk-free interest rate 2.35 % 1.91 % 1.95 % Weighted average market price on date of grants $ 30.46 $ 21.91 $ 21.03 Per share weighted average fair value $ 11.34 $ 7.91 $ 8.51 Fair value as a percentage of market value at grant date 37 % 36 % 40 %
Schedule of Share-based Compensation, Stock Options, Activity	Stock option transactions during the year ended December 31, 2017 are summarized as follows: (Dollars in thousands, except per share data) Options Weighted Average Exercise Price Per Share Weighted Average Remaining Life in Years Aggregate Intrinsic Value Outstanding December 31, 2016 259,779 $ 17.38 4.5 $ 5,243 Granted 15,009 30.46 Exercised 74,339 14.81 Forfeited/Expired 6,231 19.85 Outstanding December 31, 2017 194,218 $ 19.29 5.0 $ 2,866 Vested and Exercisable at December 31, 2017 123,669 $ 17.06 3.4 $ 2,101
Schedule of Unvested Options	Stock option activity during the year ended December 31, 2017 for unvested options are summarized as follows: Unvested Options Options Weighted Average Grant Date Fair Value Unvested December 31, 2016 94,034 $ 7.84 Granted 15,009 11.34 Vested 33,693 7.31 Forfeited 4,801 8.30 Unvested December 31, 2017 70,549 $ 8.81
Schedule of Restricted Stock Awards Granted	The table below provides a summary of restricted stock awards granted during the years indicated: Restricted Stock Awards (no. of underlying shares) 2017 2016 2015 Two year vesting 6,944 9,060 7,276 Four year vesting 16,253 18,298 17,775 Performance-based vesting 25,623 35,071 30,262 Total restricted stock awards 48,820 62,429 55,313 Weighted average grant date fair value $ 30.46 $ 21.90 $ 21.03
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity	The following table sets forth a summary of the activity for the Company’s restricted stock awards. (Dollars in thousands, except per share data) Restricted Stock Weighted Average Grant Price Per Share Weighted Average Remaining Life In Years Aggregate Intrinsic Value Unvested December 31, 2016 141,580 $ 20.73 1.4 $ 5,318 Granted 48,820 30.46 Vested/released 69,336 20.07 Forfeited 3,845 23.28 Unvested December 31, 2017 117,219 $ 25.09 1.4 $ 3,991

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The components of income tax expense for the years ended December 31, were calculated using the asset and liability method as follows: (Dollars in thousands) 2017 2016 2015 Current tax expense: Federal $ 8,222 $ 8,178 $ 6,808 State 2,271 2,244 1,712 Total current tax expense 10,493 10,422 8,520 Deferred tax (benefit)/ expense: Federal 5,646 (984 ) (284 ) State 89 (277 ) (122 ) Total deferred tax (benefit)/ expense 5,735 (1,261 ) (406 ) Total income tax expense $ 16,228 $ 9,161 $ 8,114
Schedule of Effective Income Tax Rate Reconciliation	The provision for income taxes differs from the amount computed by applying the statutory U.S. federal income tax rate of 35% for 2017 , 2016 and 2015 to income before taxes as follows: (Dollars in thousands) 2017 2016 2015 Computed income tax expense at statutory rate $ 12,467 $ 9,769 $ 8,492 State income taxes, net of federal tax benefit 1,534 1,279 1,034 Tax-exempt income, net of disallowance (1,665 ) (1,559 ) (1,226 ) Bank-owned life insurance income, net (245 ) (261 ) (251 ) Impact of change in federal statutory rate on deferred tax assets 4,761 — — Tax benefit from stock compensation (922 ) — — Other 298 (67 ) 65 Total income tax expense $ 16,228 $ 9,161 $ 8,114 Effective income tax rate 45.6 % 32.8 % 33.4 %
Schedule of Deferred Tax Assets and Liabilities	At December 31, the tax effects of each type of income and expense item that give rise to deferred taxes are as follows: (Dollars in thousands) 2017 2016 Deferred tax asset: Allowance for loan losses $ 9,252 $ 12,753 Depreciation 1,831 3,463 Net unrealized loss on investment securities — 444 Other-than-temporary impairment on equity securities — 22 Supplemental employee retirement plans 667 1,018 Non-accrual interest 460 1,145 Stock-based compensation expense 608 1,019 Other 323 390 Total 13,141 20,254 Deferred tax liability: Goodwill 1,590 2,301 Net unrealized gains on investments securities 90 — Deferred origination costs 710 933 Total 2,390 3,234 Net deferred tax asset $ 10,751 $ 17,020

Earnings per share (Tables)

Earnings per share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares	The table below presents the increase in average shares outstanding, using the treasury stock method, for the diluted earnings per share calculation for the years ended December 31st: 2017 2016 2015 Basic weighted average common shares outstanding 11,568,430 10,966,333 10,323,016 Dilutive shares 83,333 73,178 66,918 Diluted weighted average common shares outstanding 11,651,763 11,039,511 10,389,934

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis	The following tables summarize significant assets and liabilities carried at fair value and placement in the fair value hierarchy at the dates specified: December 31, 2017 Fair Value Measurements using: (Dollars in thousands) Fair Value (Level 1) (Level 2) (Level 3) Assets measured on a recurring basis: Debt securities $ 405,206 $ — $ 405,206 $ — FHLB stock 5,215 — — 5,215 Interest-rate swaps 568 — 568 — Assets measured on a non-recurring basis: Impaired loans (collateral dependent) 2,696 — — 2,696 Liabilities measured on a recurring basis: Interest-rate swaps $ 568 $ — $ 568 $ — December 31, 2016 Fair Value Measurements using: (Dollars in thousands) Fair Value (Level 1) (Level 2) (Level 3) Assets measured on a recurring basis: Debt securities $ 362,147 $ — $ 362,147 $ — Equity securities 12,643 12,643 — — FHLB stock 2,094 — — 2,094 Interest-rate swaps 610 — 610 — Assets measured on a non-recurring basis: Impaired loans (collateral dependent) 3,481 — — 3,481 Liabilities measured on a recurring basis: Interest-rate swaps $ 610 $ — $ 610 $ —
Quantitative Information About Significant Unobservable Inputs for Fair Value Measurements	The following table presents additional quantitative information about assets measured at fair value on a recurring and non-recurring basis for which the Company utilized Level 3 inputs (significant unobservable inputs for situations in which there is little, if any, market activity for the asset or liability) to determine fair value as of December 31, 2017 . (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Unobservable Input Value or Range Assets measured on a recurring basis: FHLB stock $5,215 FHLB stated par value N/A N/A Assets measured on a non-recurring basis: Impaired loans (collateral dependent) $2,696 Appraisal of collateral Appraisal adjustments (1) 5% - 50% (1) Appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses.
Fair Value, by Balance Sheet Grouping	The carrying values, estimated fair values and placement in the fair value hierarchy of the Company’s consolidated financial instruments for which fair value is only disclosed but not recognized on the consolidated balance sheet at the dates indicated are summarized as follows: December 31, 2017 Fair value measurement (Dollars in thousands) Carrying Amount Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Financial assets: Loans held for sale $ 208 $ 208 $ — $ 208 $ — Loans, net 2,236,989 2,236,169 — — 2,236,169 Financial liabilities: Certificates of deposit (including brokered) 343,089 341,765 — 341,765 — Borrowed funds 89,000 88,996 — 88,996 — Subordinated debt 14,847 14,208 — — 14,208 December 31, 2016 Fair value measurement (Dollars in thousands) Carrying Amount Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Financial assets: Loans held for sale $ 1,569 $ 1,569 $ — $ 1,569 $ — Loans, net 1,991,387 1,997,887 — — 1,997,887 Financial liabilities: Certificates of deposit (including brokered) 227,257 226,536 — 226,536 — Borrowed funds 10,671 10,670 — 10,670 — Subordinated debt 14,834 14,011 — — 14,011

Parent Company Only Financial42

Parent Company Only Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule of Condensed Balance Sheet	Balance Sheets December 31, (Dollars in thousands) 2017 2016 Assets Cash $ 345 $ 497 Investment in subsidiaries 245,982 227,960 Other assets 411 1,243 Total assets $ 246,738 $ 229,700 Liabilities and Stockholders’ Equity Liabilities Subordinated debt $ 14,847 $ 14,834 Accrued interest payable 78 78 Other liabilities 3 2 Total liabilities 14,928 14,914 Stockholders' equity: Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued — — Common stock $0.01 par value per share; 40,000,000 shares authorized; 11,609,853 shares issued and outstanding at December 31, 2017 and 11,475,742 shares issued and outstanding at December 31, 2016 116 115 Additional paid-in capital 88,205 85,421 Retained earnings 143,073 130,008 Accumulated other comprehensive income (loss) 416 (758 ) Total stockholders’ equity 231,810 214,786 Total liabilities and stockholders’ equity $ 246,738 $ 229,700
Schedule of Condensed Income Statement	Statements of Income For the years ended December 31, (Dollars in thousands) 2017 2016 2015 Equity in undistributed net income of subsidiaries $ 16,922 $ 19,313 $ 17,277 Dividends distributed by subsidiaries 3,000 150 — Loss distributed by divested subsidiary — — (210 ) Other income — — 17 Total income 19,922 19,463 17,084 Interest expense 925 928 1,071 Other operating expenses 245 194 500 Total operating expenses 1,170 1,122 1,571 Income before income taxes 18,752 18,341 15,513 Benefit from income taxes (641 ) (410 ) (635 ) Net income $ 19,393 $ 18,751 $ 16,148
Schedule of Condensed Cash Flow Statement	Parent Company Only Financial Statements Statements of Cash Flows For the years ended December 31, (Dollars in thousands) 2017 2016 2015 Cash flows from operating activities: Net income $ 19,393 $ 18,751 $ 16,148 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (16,922 ) (19,313 ) (17,277 ) Payment from subsidiary bank for stock compensation expense 1,758 2,348 1,791 Changes in: Decrease (increase) in other assets 832 (697 ) (36 ) Decrease in other liabilities 14 9 (482 ) Net cash provided by operating activities 5,075 1,098 144 Cash flows from investing activities: Investment in subsidiary (1) — (19,730 ) 781 Net cash (provided by) used in investing activities — (19,730 ) 781 Cash flows from financing activities: Repayment of subordinated debt (2) — — (10,825 ) Proceeds from the issuance of subordinated debt (2) — — 15,000 Cash dividends paid (6,241 ) (5,684 ) (5,158 ) Proceeds from issuance of common stock, net of expenses 1,590 21,183 1,448 Net settlement for employee tax withholdings on restrict stock and options (931 ) (442 ) — Proceeds from exercise of stock options 355 546 431 Tax benefit from stock-based compensation — 789 217 Net cash (used in) provided by financing activities (5,227 ) 16,392 1,113 Net (decrease) increase in cash and cash equivalents (152 ) (2,240 ) 2,038 Cash and cash equivalents, beginning of year 497 2,737 699 Cash and cash equivalents, end of year $ 345 $ 497 $ 2,737 (1) The outflow in investment in subsidiary in 2016 reflects the Company's investment in the Bank from the Offering. See Note 10 "Stockholders' Equity," above, for further information. (2) See Note 7, "Borrowed Funds and Subordinated Debt," above, for further information regarding changes in the Company's subordinated debt.

Quarterly Results of Operatio43

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	2017 (Dollars in thousands, except share data) First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $ 24,364 $ 25,338 $ 27,045 $ 28,285 Interest expense 1,517 1,803 1,911 2,279 Net interest income 22,847 23,535 25,134 26,006 Provision for loan losses 125 280 1,225 (200 ) Net interest income after provision for loan losses 22,722 23,255 23,909 26,206 Non-interest income 3,594 3,710 3,728 3,926 Net gains (losses) on sales of investment securities 540 229 (284 ) 231 Non-interest expense 19,420 18,754 18,833 19,138 Income before income taxes 7,436 8,440 8,520 11,225 Provision for income taxes 1,864 2,845 3,014 8,505 Net income $ 5,572 $ 5,595 $ 5,506 $ 2,720 Basic earnings per share $ 0.48 $ 0.48 $ 0.48 $ 0.23 Diluted earnings per share $ 0.48 $ 0.48 $ 0.47 $ 0.23 2016 (Dollars in thousands, except share data) First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $ 22,465 $ 22,632 $ 23,191 $ 24,027 Interest expense 1,382 1,343 1,374 1,424 Net interest income 21,083 21,289 21,817 22,603 Provision for loan losses 850 267 1,386 490 Net interest income after provision for loan losses 20,233 21,022 20,431 22,113 Non-interest income 3,204 3,519 3,402 3,514 Net gains on sales of investment securities 2 63 546 191 Non-interest expense 16,869 17,542 17,414 18,503 Income before income taxes 6,570 7,062 6,965 7,315 Provision for income taxes 2,257 2,291 2,251 2,362 Net income $ 4,313 $ 4,771 $ 4,714 $ 4,953 Basic earnings per share $ 0.41 $ 0.45 $ 0.41 $ 0.43 Diluted earnings per share $ 0.41 $ 0.45 $ 0.41 $ 0.43

Summary of Significant Accoun44

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)propertybranchespaymentsegment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jul. 31, 2000branches
Summary of Significant Accounting Policies [Line Items]
Number of branches | branches	24
Reportable operating segments | segment	1
Federal Reserve Bank Average Daily Reserve Requirement included in Cash and Due from Banks	$ 7,600	$ 6,800
Bank-owned life insurance	29,466	28,765
Goodwill	5,656	5,656
Number of offices related to the goodwill in acquisition | branches				2
Investment assets under management	845,000	725,300
Income tax benefit for stock compensation in income statement	$ 922	0	$ 0
Tax benefit from stock compensation		$ 789	$ 217
Number of operating leases | property	17
Bank premises and leasehold improvements | Minimum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	10 years
Bank premises and leasehold improvements | Maximum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	39 years
Computer software and equipment | Minimum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Computer software and equipment | Maximum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	5 years
Furniture, fixtures and equipment | Minimum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Furniture, fixtures and equipment | Maximum
Summary of Significant Accounting Policies [Line Items]
Estimated useful lives	10 years
Residential
Summary of Significant Accounting Policies [Line Items]
Early payment default period | payment	4
Lines of Credit and Demand Notes | Minimum
Summary of Significant Accounting Policies [Line Items]
Period that loan deferred income is amortized	3 years
Lines of Credit and Demand Notes | Maximum
Summary of Significant Accounting Policies [Line Items]
Period that loan deferred income is amortized	5 years
Income Tax Expense | Accounting Standards Update 2016-09
Summary of Significant Accounting Policies [Line Items]
Income tax benefit for stock compensation in income statement	$ 922

Investments (Details)

Investments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Investment securities at fair value		$ 405,206		$ 374,790
Securities pledged as collateral		383,100		361,200
Debt Securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost				365,578
Unrealized gains				1,516
Unrealized losses				4,947
Investment securities at fair value				362,147
Federal agency obligations
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost	[1]	51,769		74,682
Unrealized gains	[1]	30		432
Unrealized losses	[1]	82		45
Investment securities at fair value	[1]	51,717		75,069
Residential federal agency MBS
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost	[1]	141,054		94,818
Unrealized gains	[1]	71		96
Unrealized losses	[1]	971		1,561
Investment securities at fair value	[1]	140,154		93,353
Commercial federal agency MBS
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost	[1]	66,777		71,993
Unrealized gains	[1]	9		15
Unrealized losses	[1]	286		1,730
Investment securities at fair value	[1]	66,500		70,278
Collateralized mortgage obligations
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Investment securities at fair value		171,700		107,000
Municipal securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost		132,603		112,401
Unrealized gains		2,097		922
Unrealized losses		354		1,520
Investment securities at fair value		134,346		111,803
Tax exempt interest earned on municipal securities		4,000		3,600	$ 2,900
Average balance tax exempt securities		111,600		100,000
Corporate bonds
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost		11,546		10,734
Unrealized gains		63		51
Unrealized losses		67		90
Investment securities at fair value		11,542		10,695
Certificates of Deposit
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost	[2]	950		950
Unrealized gains	[2]	0		0
Unrealized losses	[2]	3		1
Investment securities at fair value	[2]	947		949
Equity investments
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost				10,413
Unrealized gains				2,532
Unrealized losses				302
Investment securities at fair value				12,643
Available for sale securities, at fair value
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Amortized cost		404,699	[3]	375,991
Unrealized gains		2,270	[3]	4,048
Unrealized losses		1,763	[3]	5,249
Investment securities at fair value		$ 405,206	[3]	$ 374,790
[1]	These categories may include investments issued or guaranteed by government sponsored enterprises such as Fannie Mae ("FNMA"), Freddie Mac ("FHLMC"), Federal Farm Credit Bank ("FFCB"), or one of several Federal Home Loan Banks, as well as, investments guaranteed by Ginnie Mae ("GNMA"), a wholly-owned government entity.
[2]	Certificates of deposit ("CDs") represent term deposits issued by banks that are subject to FDIC insurance and purchased on the open market.
[3]	As of December 31, 2017, all investments were debt securities and the Company did not hold any available-for-sale equity securities.

Investments - Continuous Loss P

Investments - Continuous Loss Position (Details) $ in Thousands	Dec. 31, 2017USD ($)investments	Dec. 31, 2016USD ($)investments
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 200,243	$ 210,453
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	1,324	4,642
Investments Temporarily Impaired, 12 months or longer, Fair Value	20,328	10,751
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	439	607
Investments Temporarily Impaired, Fair Value	220,571	221,204
Investments Temporarily Impaired, Unrealized Losses	$ 1,763	$ 5,249
Number of securities in loss position | investments	137	203
Federal agency obligations
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 34,344	$ 13,956
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	82	45
Investments Temporarily Impaired, 12 months or longer, Fair Value	0	0
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	0	0
Investments Temporarily Impaired, Fair Value	34,344	13,956
Investments Temporarily Impaired, Unrealized Losses	$ 82	$ 45
Number of securities in loss position | investments	9	3
Residential federal agency MBS
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 109,308	$ 68,138
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	882	1,236
Investments Temporarily Impaired, 12 months or longer, Fair Value	2,015	8,008
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	89	325
Investments Temporarily Impaired, Fair Value	111,323	76,146
Investments Temporarily Impaired, Unrealized Losses	$ 971	$ 1,561
Number of securities in loss position | investments	30	31
Commercial federal agency MBS
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 35,859	$ 60,060
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	205	1,730
Investments Temporarily Impaired, 12 months or longer, Fair Value	5,190	0
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	81	0
Investments Temporarily Impaired, Fair Value	41,049	60,060
Investments Temporarily Impaired, Unrealized Losses	$ 286	$ 1,730
Number of securities in loss position | investments	11	18
Municipal securities
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 16,983	$ 60,436
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	129	1,520
Investments Temporarily Impaired, 12 months or longer, Fair Value	10,210	0
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	225	0
Investments Temporarily Impaired, Fair Value	27,193	60,436
Investments Temporarily Impaired, Unrealized Losses	$ 354	$ 1,520
Number of securities in loss position | investments	50	107
Corporate bonds
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 2,802	$ 5,729
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	23	90
Investments Temporarily Impaired, 12 months or longer, Fair Value	2,913	0
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	44	0
Investments Temporarily Impaired, Fair Value	5,715	5,729
Investments Temporarily Impaired, Unrealized Losses	$ 67	$ 90
Number of securities in loss position | investments	33	37
Certificates of Deposit
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value	$ 947	$ 949
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses	3	1
Investments Temporarily Impaired, 12 months or longer, Fair Value	0	0
Investments Temporarily Impaired,12 months or longer, Unrealized Losses	0	0
Investments Temporarily Impaired, Fair Value	947	949
Investments Temporarily Impaired, Unrealized Losses	$ 3	$ 1
Number of securities in loss position | investments	4	4
Equity investments
Schedule of Investment Securities [Line Items]
Investments Temporarily Impaired, Less than 12 months, Fair Value		$ 1,185
Investments Temporarily Impaired, Less than 12 months, Unrealized Losses		20
Investments Temporarily Impaired, 12 months or longer, Fair Value		2,743
Investments Temporarily Impaired,12 months or longer, Unrealized Losses		282
Investments Temporarily Impaired, Fair Value		3,928
Investments Temporarily Impaired, Unrealized Losses		$ 302
Number of securities in loss position | investments		3

Investments - Maturities (Detai

Investments - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Schedule of Investment Securities [Line Items]
Investment securities at fair value	$ 405,206		$ 374,790
Callable debt securities, amortized cost	74,500
Callable debt securities, fair value	75,700
Available for sale securities, at fair value
Schedule of Investment Securities [Line Items]
Amortized Cost, Within One Year	19,095
Fair Value, Within One Year	19,159
Amortized Cost Basis, After One, But Within Five Years	82,231
Fair Value, After One, But Within Five Years	82,255
Amortized Cost, After Five, But Within Ten Years	134,395
Fair Value, After Five, But Within Ten Years	134,959
Amortized Cost Basis, After Ten Years	168,978
Fair Value, After Ten Years	168,833
Amortized cost	404,699	[1]	375,991
Investment securities at fair value	$ 405,206	[1]	$ 374,790
[1]	As of December 31, 2017, all investments were debt securities and the Company did not hold any available-for-sale equity securities.

Investments - Sales (Details)

Investments - Sales (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Amortized cost of investments sold, including pending trades	[1]	$ 145,472	$ 4,299	$ 23,287
Gross realized gains on sales		3,411	803	1,990
Gross realized losses on sales		(2,695)	(1)	(162)
Proceeds from sale of investment securities, Including pending trades		$ 146,188	$ 5,101	$ 25,115
[1]	Amortized cost of investments sold is determined on a specific identification basis.

Loans - Balance by Class of Loa

Loans - Balance by Class of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Loans by Loan Classification [Line Items]
Gross loans	$ 2,272,549	$ 2,024,798
Deferred loan origination fees, net	(2,645)	(2,069)
Total loans	2,269,904	2,022,729
Allowance for loan losses	(32,915)	(31,342)	$ (29,008)	$ (27,121)
Net loans	2,236,989	1,991,387
Commercial
Schedule of Loans by Loan Classification [Line Items]
Gross loans	1,975,058	1,742,328
Commercial real estate
Schedule of Loans by Loan Classification [Line Items]
Gross loans	1,201,351	1,038,082
Allowance for loan losses	(17,545)	(14,902)	(13,514)
Commercial and industrial
Schedule of Loans by Loan Classification [Line Items]
Gross loans	498,802	490,799
Allowance for loan losses	(9,669)	(11,204)	(9,758)
Commercial construction
Schedule of Loans by Loan Classification [Line Items]
Gross loans	274,905	213,447
Allowance for loan losses	(3,947)	(3,406)	(3,905)
Retail
Schedule of Loans by Loan Classification [Line Items]
Gross loans	297,491	282,470
Residential
Schedule of Loans by Loan Classification [Line Items]
Gross loans	195,492	180,560
Allowance for loan losses	(904)	(960)	(1,061)
Home Equity
Schedule of Loans by Loan Classification [Line Items]
Gross loans	91,706	91,065
Allowance for loan losses	(608)	(634)	(540)
Consumer
Schedule of Loans by Loan Classification [Line Items]
Gross loans	10,293	10,845
Allowance for loan losses	$ (242)	$ (236)	$ (230)

Loans - Loan Categories Narrati

Loans - Loan Categories Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)payment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Schedule of Loans by Loan Classification [Line Items]
Outstanding loan balances to related parties	$ 33.9	$ 18.6
Unadvanced lines of credit available to related parties	16.8	9.8
New loans and net increases to loan balances to related parties during period	30.2	2.3
Principal paydowns on related party loans	7.9	1.9
Commercial
Schedule of Loans by Loan Classification [Line Items]
Participation loans amount	91.6	85.2
Participations loans sold that are still serviced amount	70.7	62.3
Tax exempt interest income on qualified commercial loans	2.1	2.1	$ 1.6
Average tax exempt loan balances	$ 64.4	63.9
Commercial real estate | Minimum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	15 years
Commercial real estate | Maximum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	25 years
Commercial and industrial | Minimum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	1 year
Commercial and industrial | Maximum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	7 years
Commercial construction | Minimum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	1 year
Commercial construction | Maximum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	3 years
Residential
Schedule of Loans by Loan Classification [Line Items]
Early payment default period | payment	4
Amount of loans serviced for others	$ 18.4	$ 18.7
Residential | Maximum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	30 years
Home Equity | Maximum
Schedule of Loans by Loan Classification [Line Items]
Loan-to-value ratio	80.00%
Home equity loans | Minimum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	3 years
Home equity loans | Maximum
Schedule of Loans by Loan Classification [Line Items]
Repayment period, term of loan	15 years
Home equity lines of credit
Schedule of Loans by Loan Classification [Line Items]
Term of interest only payments	10 years
Term of principal and interest payments after Interest only term	15 years
Multi-family owner occupied residential property | Minimum
Schedule of Loans by Loan Classification [Line Items]
Loan-to-value ratio	75.00%
Single family owner occupied residential property | Maximum
Schedule of Loans by Loan Classification [Line Items]
Loan-to-value ratio	97.00%

Loans - Loans Serving as Collat

Loans - Loans Serving as Collateral (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans pledged to the FHLB for borrowing capacity	$ 421,632	$ 430,251
Commercial real estate
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans pledged to the FHLB for borrowing capacity	224,703	247,664
Residential
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans pledged to the FHLB for borrowing capacity	187,524	170,247
Home Equity
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans pledged to the FHLB for borrowing capacity	$ 9,405	$ 12,340

Allowance For Loan Losses - Eva

Allowance For Loan Losses - Evaluation Method (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	$ 26,262	$ 31,796
Loans collectively evaluated for impairment	2,246,287	1,993,002
Gross loans	2,272,549	2,024,798
Commercial real estate
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	13,739	14,261
Loans collectively evaluated for impairment	1,187,612	1,023,821
Gross loans	1,201,351	1,038,082
Commercial and industrial
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	10,096	13,372
Loans collectively evaluated for impairment	488,706	477,427
Gross loans	498,802	490,799
Commercial construction
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	1,624	3,364
Loans collectively evaluated for impairment	273,281	210,083
Gross loans	274,905	213,447
Residential
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	397	289
Loans collectively evaluated for impairment	195,095	180,271
Gross loans	195,492	180,560
Home Equity
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	371	509
Loans collectively evaluated for impairment	91,335	90,556
Gross loans	91,706	91,065
Consumer
Schedule of Financing Receivable by Evaluation Method [Line Items]
Loans individually evaluated for impairment	35	1
Loans collectively evaluated for impairment	10,258	10,844
Gross loans	$ 10,293	$ 10,845

Allowance For Loan Losses - Adv

Allowance For Loan Losses - Adversely Classified Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Gross loans	$ 2,272,549	$ 2,024,798
Adversely classified loans to total loans	1.16%	1.70%
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Gross loans	$ 1,201,351	$ 1,038,082
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Gross loans	498,802	490,799
Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Gross loans	274,905	213,447
Residential
Financing Receivable, Recorded Investment [Line Items]
Gross loans	195,492	180,560
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Gross loans	91,706	91,065
Consumer
Financing Receivable, Recorded Investment [Line Items]
Gross loans	10,293	10,845
Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross loans	26,354	34,247
Substandard | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Gross loans	12,895	16,003
Substandard | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Gross loans	9,915	12,770
Substandard | Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Gross loans	1,624	3,364
Substandard | Residential
Financing Receivable, Recorded Investment [Line Items]
Gross loans	1,355	1,414
Substandard | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Gross loans	513	666
Substandard | Consumer
Financing Receivable, Recorded Investment [Line Items]
Gross loans	52	30
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Gross loans	58	99
Doubtful | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Doubtful | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Gross loans	48	99
Doubtful | Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Doubtful | Residential
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Doubtful | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Doubtful | Consumer
Financing Receivable, Recorded Investment [Line Items]
Gross loans	10	0
Loss
Financing Receivable, Recorded Investment [Line Items]
Gross loans	1	2
Loss | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Loss | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Gross loans	1	2
Loss | Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Loss | Residential
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Loss | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Loss | Consumer
Financing Receivable, Recorded Investment [Line Items]
Gross loans	0	0
Not Adversely Classified
Financing Receivable, Recorded Investment [Line Items]
Gross loans	2,246,136	1,990,450
Not Adversely Classified | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Gross loans	1,188,456	1,022,079
Not Adversely Classified | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Gross loans	488,838	477,928
Not Adversely Classified | Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Gross loans	273,281	210,083
Not Adversely Classified | Residential
Financing Receivable, Recorded Investment [Line Items]
Gross loans	194,137	179,146
Not Adversely Classified | Home Equity
Financing Receivable, Recorded Investment [Line Items]
Gross loans	91,193	90,399
Not Adversely Classified | Consumer
Financing Receivable, Recorded Investment [Line Items]
Gross loans	$ 10,231	$ 10,815

Allowance For Loan Losses - Pas

Allowance For Loan Losses - Past Due and Non-Accrual Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Aging of Financing Receivables [Line Items]
Number of days a loan must be paid current before accrual of interest is resumed	180 days
Total Past Due Loans	$ 14,947	$ 11,534
Current Loans	2,257,602	2,013,264
Gross loans	2,272,549	2,024,798
Non-accrual loans	$ 9,032	$ 9,485
The ratio of non-accrual loans to total loans	0.40%	0.47%
Additional funding commitments for loans on non-accrual	$ 25
Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	7,838	$ 8,315
Current Loans	1,193,513	1,029,767
Gross loans	1,201,351	1,038,082
Non-accrual loans	6,751	4,876
Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	1,228	1,815
Current Loans	497,574	488,984
Gross loans	498,802	490,799
Non-accrual loans	1,294	3,174
Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	3,044	0
Current Loans	271,861	213,447
Gross loans	274,905	213,447
Non-accrual loans	193	519
Residential
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	2,113	747
Current Loans	193,379	179,813
Gross loans	195,492	180,560
Non-accrual loans	262	289
Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	623	539
Current Loans	91,083	90,526
Gross loans	91,706	91,065
Non-accrual loans	463	616
Consumer
Schedule of Aging of Financing Receivables [Line Items]
Total Past Due Loans	101	118
Current Loans	10,192	10,727
Gross loans	10,293	10,845
Non-accrual loans	69	11
Loans 30-59 Days Past Due
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	9,573	7,272
Loans 30-59 Days Past Due | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	4,200	5,993
Loans 30-59 Days Past Due | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	374	267
Loans 30-59 Days Past Due | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	2,526	0
Loans 30-59 Days Past Due | Residential
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	1,931	648
Loans 30-59 Days Past Due | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	491	270
Loans 30-59 Days Past Due | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	51	94
Loans 60-89 Days Past Due
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	1,332	940
Loans 60-89 Days Past Due | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	69	923
Loans 60-89 Days Past Due | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	527	4
Loans 60-89 Days Past Due | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	518	0
Loans 60-89 Days Past Due | Residential
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	93	0
Loans 60-89 Days Past Due | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	120	0
Loans 60-89 Days Past Due | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	5	13
\Loans equal to or greater than 90 days past due
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	4,042	3,322
\Loans equal to or greater than 90 days past due | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	3,569	1,399
\Loans equal to or greater than 90 days past due | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	327	1,544
\Loans equal to or greater than 90 days past due | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	0	0
\Loans equal to or greater than 90 days past due | Residential
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	89	99
\Loans equal to or greater than 90 days past due | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	12	269
\Loans equal to or greater than 90 days past due | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	45	11
Not Adversely Classified
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	2,246,136	1,990,450
Non-accrual loans not adversely classified	21	220
Not Adversely Classified | Commercial real estate
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	1,188,456	1,022,079
Not Adversely Classified | Commercial and industrial
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	488,838	477,928
Not Adversely Classified | Commercial construction
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	273,281	210,083
Not Adversely Classified | Residential
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	194,137	179,146
Not Adversely Classified | Home Equity
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	91,193	90,399
Not Adversely Classified | Consumer
Schedule of Aging of Financing Receivables [Line Items]
Gross loans	$ 10,231	$ 10,815

Allowance For Loan Losses - Int

Allowance For Loan Losses - Interest Income Lost on Nonaccrual Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Income in accordance with original loan terms	$ 1,906	$ 1,585	$ 1,052
Less income recognized	990	722	426
Reduction in interest income	$ 916	$ 863	$ 626

Allowance For Loan Losses - Imp

Allowance For Loan Losses - Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Total accruing impaired loans	$ 17,400	$ 22,400
Impaired non-accrual loans	8,900	9,400
Interest income that was not recognized on loans that were deem impaired	890	858	$ 688
Additional funding commitments on impaired loans	416
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	28,358	34,764
Total recorded investment in impaired loans	26,262	31,796
Recorded investment with no allowance	22,160	25,659
Recorded investment with allowance	4,102	6,137
Related allowance	1,383	2,621
Average recorded investment	29,390	26,586	26,069
Interest income recognized	825	701	377
Commercial real estate
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	15,132	16,010
Total recorded investment in impaired loans	13,739	14,261
Recorded investment with no allowance	12,850	12,444
Recorded investment with allowance	889	1,817
Related allowance	59	370
Average recorded investment	14,473	12,988	13,827
Interest income recognized	363	332	196
Commercial and industrial
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	10,458	14,291
Total recorded investment in impaired loans	10,096	13,372
Recorded investment with no allowance	7,053	9,366
Recorded investment with allowance	3,043	4,006
Related allowance	1,284	2,222
Average recorded investment	12,272	9,790	9,372
Interest income recognized	370	223	97
Commercial construction
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	1,678	3,408
Total recorded investment in impaired loans	1,624	3,364
Recorded investment with no allowance	1,624	3,051
Recorded investment with allowance	0	313
Related allowance	0	28
Average recorded investment	1,818	3,137	2,202
Interest income recognized	92	150	83
Residential
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	511	388
Total recorded investment in impaired loans	397	289
Recorded investment with no allowance	262	289
Recorded investment with allowance	135	0
Related allowance	5	0
Average recorded investment	320	301	449
Interest income recognized	2	0	0
Home Equity
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	543	665
Total recorded investment in impaired loans	371	509
Recorded investment with no allowance	371	509
Recorded investment with allowance	0	0
Related allowance	0	0
Average recorded investment	482	356	174
Interest income recognized	(1)	(4)	1
Consumer
Impaired Financing Receivable, Recorded Investment [Abstract]
Unpaid contractual principal balance	36	2
Total recorded investment in impaired loans	35	1
Recorded investment with no allowance	0	0
Recorded investment with allowance	35	1
Related allowance	35	1
Average recorded investment	25	14	45
Interest income recognized	$ (1)	$ 0	$ 0

Allowance For Loan Losses - Tro

Allowance For Loan Losses - Troubled Debt Restructures (Details)	12 Months Ended
	Dec. 31, 2017USD ($)restructuring	Dec. 31, 2016USD ($)restructuring
Financing Receivable, Modifications [Line Items]
Total Troubled Debt Restructure (TDR) loans	$ 20,300,000	$ 27,000,000
TDR loans on accrual status	17,400,000	22,400,000
TDR loans included in non-performing loans	2,900,000	$ 4,600,000
Additional funding commitment on TDRs	$ 391,000
Number of restructurings | restructuring	11	19
Pre-modification outstanding recorded investment	$ 1,219,000	$ 11,443,000
Post-modification recorded investment	$ 1,156,000	$ 12,778,000
Number of TDRs that defaulted | restructuring	2	1
Post-modification outstanding recorded investment, TDRs that defaulted	$ 20,000	$ 148,000
Charge-offs associated with TDRs	0	0
Specific reserves allocated to TDRs	$ 155,000	$ 1,418,000
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	3	8
Pre-modification outstanding recorded investment	$ 696,000	$ 6,212,000
Post-modification recorded investment	$ 674,000	$ 7,534,000
Number of TDRs that defaulted | restructuring	0	1
Post-modification outstanding recorded investment, TDRs that defaulted	$ 0	$ 148,000
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	6	11
Pre-modification outstanding recorded investment	$ 386,000	$ 5,231,000
Post-modification recorded investment	$ 346,000	$ 5,244,000
Number of TDRs that defaulted | restructuring	2	0
Post-modification outstanding recorded investment, TDRs that defaulted	$ 20,000	$ 0
Commercial construction
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0
Post-modification recorded investment	$ 0	$ 0
Number of TDRs that defaulted | restructuring	0	0
Post-modification outstanding recorded investment, TDRs that defaulted	$ 0	$ 0
Residential
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	1	0
Pre-modification outstanding recorded investment	$ 136,000	$ 0
Post-modification recorded investment	$ 135,000	$ 0
Number of TDRs that defaulted | restructuring	0	0
Post-modification outstanding recorded investment, TDRs that defaulted	$ 0	$ 0
Home Equity
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0
Post-modification recorded investment	$ 0	$ 0
Number of TDRs that defaulted | restructuring	0	0
Post-modification outstanding recorded investment, TDRs that defaulted	$ 0	$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	1	0
Pre-modification outstanding recorded investment	$ 1,000	$ 0
Post-modification recorded investment	$ 1,000	$ 0
Number of TDRs that defaulted | restructuring	0	0
Post-modification outstanding recorded investment, TDRs that defaulted	$ 0	$ 0
Loan Advances With Adequate Collateral
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	0	8
Post-modification recorded investment	$ 0	$ 10,533,000
Extended Maturity
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	1	4
Post-modification recorded investment	$ 175,000	$ 548,000
Temporary payment reduction and payment re-amortization of remaining principal over extended term
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	6	0
Post-modification recorded investment	$ 790,000	$ 0
Temporary interest only plan
Financing Receivable, Modifications [Line Items]
Number of restructurings | restructuring	4	7
Post-modification recorded investment	$ 191,000	$ 1,697,000

Allowance For Loan Losses - Oth

Allowance For Loan Losses - Other Real Estate Owned (Details)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)property	Dec. 31, 2015USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of OREO	$ 0	$ 0
Net gains on sales of OREO	0	0	$ 154,000
Consumer Mortgage Loans in Process of Foreclosure, Amount	$ 101,000	$ 200,000
Other real estate owned
Accounts, Notes, Loans and Financing Receivable [Line Items]
Oreo Additions	0	0
OREO fair value adjustment	$ 0	$ 0	$ 0

Allowance For Loan Losses - All

Allowance For Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses to total loans ratio	1.45%				1.55%				1.45%	1.55%
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				$ 31,342				$ 29,008	$ 31,342	$ 29,008	$ 27,121
Provision for loan losses	$ (200)	$ 1,225	$ 280	125	$ 490	$ 1,386	$ 267	850	1,430	2,993	3,267
Recoveries									755	709	409
Less: Charge offs									612	1,368	1,789
Ending Balance	32,915				31,342				32,915	31,342	29,008
Allocated to loans individually evaluated for impairment	1,383				2,621				1,383	2,621
Allocated to loans collectively evaluated for impairment	31,532				28,721				31,532	28,721
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				14,902				13,514	14,902	13,514
Provision for loan losses									2,628	1,696
Recoveries									193	20
Less: Charge offs									178	328
Ending Balance	17,545				14,902				17,545	14,902	13,514
Allocated to loans individually evaluated for impairment	59				370				59	370
Allocated to loans collectively evaluated for impairment	17,486				14,532				17,486	14,532
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				11,204				9,758	11,204	9,758
Provision for loan losses									(1,737)	1,745
Recoveries									550	681
Less: Charge offs									348	980
Ending Balance	9,669				11,204				9,669	11,204	9,758
Allocated to loans individually evaluated for impairment	1,284				2,222				1,284	2,222
Allocated to loans collectively evaluated for impairment	8,385				8,982				8,385	8,982
Commercial construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				3,406				3,905	3,406	3,905
Provision for loan losses									541	(494)
Recoveries									0	0
Less: Charge offs									0	5
Ending Balance	3,947				3,406				3,947	3,406	3,905
Allocated to loans individually evaluated for impairment	0				28				0	28
Allocated to loans collectively evaluated for impairment	3,947				3,378				3,947	3,378
Residential
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				960				1,061	960	1,061
Provision for loan losses									(56)	(101)
Recoveries									0	0
Less: Charge offs									0	0
Ending Balance	904				960				904	960	1,061
Allocated to loans individually evaluated for impairment	5				0				5	0
Allocated to loans collectively evaluated for impairment	899				960				899	960
Home Equity
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				634				540	634	540
Provision for loan losses									(30)	97
Recoveries									4	3
Less: Charge offs									0	6
Ending Balance	608				634				608	634	540
Allocated to loans individually evaluated for impairment	0				0				0	0
Allocated to loans collectively evaluated for impairment	608				634				608	634
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				$ 236				$ 230	236	230
Provision for loan losses									84	50
Recoveries									8	5
Less: Charge offs									86	49
Ending Balance	242				236				242	236	$ 230
Allocated to loans individually evaluated for impairment	35				1				35	1
Allocated to loans collectively evaluated for impairment	$ 207				$ 235				$ 207	$ 235

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Gross premises and equipment	$ 77,663	$ 70,084
Less accumulated depreciation	(40,641)	(36,544)
Total premises and equipment, net of accumulated depreciation	37,022	33,540
Depreciation expense	4,700	4,400	$ 4,300
Land
Property, Plant and Equipment [Line Items]
Gross premises and equipment	5,488	5,201
Bank premises and leasehold improvements
Property, Plant and Equipment [Line Items]
Gross premises and equipment	42,525	37,390
Computer software and equipment
Property, Plant and Equipment [Line Items]
Gross premises and equipment	9,303	9,250
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Gross premises and equipment	$ 20,347	$ 18,243

Premises and Equipment - Operat

Premises and Equipment - Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
2,018	$ 1,609
2,019	1,392
2,020	1,136
2,021	1,133
2,022	1,131
Thereafter	9,285
Total minimum lease payments	15,686
Operating Leases, Rent Expense	1,400	$ 1,300	$ 1,200
Rental income	$ 133	$ 159	$ 153

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Non-interest bearing demand deposits		$ 705,846	$ 646,115
Interest bearing checking		391,111	372,696
Savings		193,385	178,637
Money market		807,931	844,216
Certificates of deposit, $250,000 or less		150,445	125,580
Certificates of deposit more than $250,000		45,154	42,315
Total customer deposits		2,293,872	2,209,559
Brokered deposits	[1]	147,490	59,362
Deposits		2,441,362	2,268,921
Reciprocal deposits		249,600	281,600
Overdrawn deposits reclassified as loans		$ 359	$ 558
[1]	Brokered CDs $250,000 and under.

Deposits - Maturities (Details)

Deposits - Maturities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Weighted average remaining life, brokered deposits	6 months	1 year 6 months
Due in less than twelve months	$ 240,995	$ 136,695
Due in over one year through two years	60,692	38,344
Due in over two years through three years,	28,141	32,652
Due in over three years through four years	6,592	8,525
Due in over four years through five years	5,614	5,721
Due in over five years	1,055	5,320
Total certificates of deposit	$ 343,089	$ 227,257

Borrowed Funds and Subordinat64

Borrowed Funds and Subordinated Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Federal Home Loan Bank Borrowings	$ 89,000	$ 10,671	$ 40,671
Other Borrowings	$ 0	$ 0	$ 13,000
Other Borrowings, Weighted Average interest Rate	0.00%	0.00%	0.60%
Borrowed Funds	$ 89,000	$ 10,671	$ 53,671
Borrowed Funds, Weighted Average Interest Rate	1.54%	0.80%	0.53%
Subordinated debt	$ 14,847	$ 14,834	$ 14,822
Subordinated Debt, Weighted Average Interest Rate	6.23%	6.26%	6.16%
Total borrowed funds and subordinated debt, amount	$ 103,847	$ 25,505	$ 68,493
Total borrowed funds and subordinated debt, Average Rate	2.21%	3.98%	1.75%
Weighted Average
Debt Instrument [Line Items]
Federal Home Loan Bank Borrowings,Weighted Average Interest Rate	1.54%	0.80%	0.51%

Borrowed Funds and Subordinat65

Borrowed Funds and Subordinated Debt - Textual (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
FHLB overnight borrowings		$ 39,000,000
FHLB overnight borrowings, weighted average rate		1.59%
Short-term FHLB borrowings, maturing in January 2018		$ 50,000,000
Short-term FHLB borrowings, maturing January 2018, weighted average rate		1.50%
Maximum FHLB and other borrowings outstanding at any month end		$ 149,300,000	$ 43,700,000	$ 53,700,000
Junior subordinated debt, Amount				10,800,000
Subordinated debt		$ 14,847,000	$ 14,834,000	$ 14,822,000
Fixed-to Floating Rate Subordinated Notes
Debt Instrument [Line Items]
Subordinated debt, rate		6.00%
Subordinated debt	$ 15,000,000
Original debt issuance costs	$ 190,000
Line of credit | FHLB
Debt Instrument [Line Items]
Remaining borrowing capacity at FHLB		$ 415,000,000
Line of credit | Federal Reserve Bank of Boston
Debt Instrument [Line Items]
Remaining borrowing capacity at FRB		$ 120,000,000
London Interbank Offered Rate (LIBOR) [Member] | Fixed-to Floating Rate Subordinated Notes
Debt Instrument [Line Items]
Fixed to Floating Rate Conversion Date		Jan. 31, 2025
Spread over LIBOR fixed to floating rate note, rate		3.90%

Borrowed Funds and Subordinat66

Borrowed Funds and Subordinated Debt - Average Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
FHLB advances, Average Balance	$ 49,546	$ 14,551	$ 10,731
FHLB advances, Average Rate	1.19%	0.55%	0.36%
Other borrowings, Average Balance	$ 0	$ 107	$ 36
Other borrowings, Average Rate	0.00%	0.61%	0.61%
Total borrowed funds, Average Balance	$ 49,546	$ 14,658	$ 10,767
Total borrowed funds, Average Rate	1.19%	0.55%	0.36%

Derivatives and Hedging Activ67

Derivatives and Hedging Activities (Details)	12 Months Ended
	Dec. 31, 2017USD ($)instrumentloan	Dec. 31, 2016USD ($)instrumentloan	Dec. 31, 2015USD ($)
Derivative [Line Items]
Number of Participation Loans with Swap Contingent Liabilities | loan	2	2
Interest Rate Swap
Derivative [Line Items]
Gain (Loss) on Interest Rate Swaps	$ 0	$ 0	$ 0
Number of Interest Rate Swaps | instrument	6	4
Aggregate notional value of interest-rate swaps	$ 29,400,000	$ 26,700,000
Fair Value of Interest-Rate Swap Assets	568,000	610,000
Fair Value of Interest-Rate Swap Liabilities	568,000	610,000
Counterparty Credit Risk Exposure on Interest Rate Swaps	543,000	610,000
Collateral Received for Interest-rate Swaps	480,000	0
Receive Fixed Pay Variable | Interest Rate Swap
Derivative [Line Items]
Fair Value of Interest-Rate Swap Assets	25,000	0
Fair Value of Interest-Rate Swap Liabilities	568,000	610,000
Pay Fixed Receive Variable | Interest Rate Swap
Derivative [Line Items]
Fair Value of Interest-Rate Swap Assets	543,000	610,000
Fair Value of Interest-Rate Swap Liabilities	0	0
Gross Amount Interest Rate Swap Asset Recognized	568,000	610,000
Gross Amount Interest-Rate offset in Statement of Financial Position	$ 25,000	$ 0

Committments, Contingencies a68

Committments, Contingencies and Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)payment	Dec. 31, 2016USD ($)
Other Commitments [Line Items]
Commitments to Originate Loans	$ 13,830	$ 37,753
Commitments to Sell Residential Mortgage Loans	2,286	3,115
Letters of Credit	21,576	21,497
Residential
Other Commitments [Line Items]
Commitments to Originate Loans for Sale	$ 2,078	1,946
Early payment default period | payment	4
Commercial real estate
Other Commitments [Line Items]
Financial instruments with off-balance sheet credit risk	$ 26,947	56,952
Commercial and industrial
Other Commitments [Line Items]
Financial instruments with off-balance sheet credit risk	432,731	399,833
Commercial and residential construction
Other Commitments [Line Items]
Financial instruments with off-balance sheet credit risk	209,916	151,757
Home Equity
Other Commitments [Line Items]
Financial instruments with off-balance sheet credit risk	94,012	82,884
Consumer Loan
Other Commitments [Line Items]
Financial instruments with off-balance sheet credit risk	$ 4,290	$ 3,043

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($)	Jun. 23, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2019	Jan. 31, 2018	May 01, 2017	Jan. 31, 2016
Class of Stock [Line Items]
Common stock, shares authorized			40,000,000					20,000,000
Preferred stock, shares authorized			1,000,000	1,000,000
Preferred stock, par value			$ 0.01	$ 0.01
Unvested participating restricted stock awards			117,219	141,580
Shareholder subscription rights and community offering, price per share		$ 21.50
Maximum amount that was available to be raised under shelf registration		$ 40,000,000
Shares issued in shareholder subscription rights and community offering	930,232
Gross proceeds from shareholder subscription rights and community offering		20,000,000
Net proceeds from shareholder subscription rights offering and community offering		$ 19,700,000
Capital Conservation Buffer on Regulatory Risk-Based Requirements, Phase-in			1.25%	0.625%					0.625%
Common stock dividend paid			$ 6,241,000	$ 5,684,000	$ 5,158,000
Common stock issued under dividend reinvestment plan, value			1,494,000	1,381,000	1,277,000
Common stock issued under direct stock purchase plan, value			70,000	38,000	150,000
Retained Earnings
Class of Stock [Line Items]
Common stock dividend paid			$ 6,241,000	$ 5,684,000	$ 5,158,000
Common Stock
Class of Stock [Line Items]
Common stock issued under dividend reinvestment plan, shares			44,752	53,516	58,529
Common stock issued under dividend reinvestment plan, value			$ 0	$ 1,000	$ 1,000
Common stock issued under direct stock purchase plan, shares			2,014	1,562	6,700
Common Stock
Class of Stock [Line Items]
Votes Per Share, Number			1
Basel III Minimum Requirements Forecast [Member]
Class of Stock [Line Items]
Basel III Additional Capital Conservation Buffer at full phase-in (percent)						2.50%
Subsequent Event | Series A Junior Participating Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value							$ 0.01
Amount of a share allowed to be purchased under right to purchase							0.01
Price per one one-hundredth of a share							$ 122.50
Minimum acquisition percentage to trigger the exercise of the right to purchase							10.00%

Stockholders' Equity - Regulato

Stockholders' Equity - Regulatory Capital Requirements (Details) - USD ($) $ in Thousands		Dec. 31, 2017		Dec. 31, 2016	Jan. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Conservation Buffer on Regulatory Risk-Based Requirements, Phase-in		1.25%		0.625%	0.625%
Total Capital, Actual, Amount		$ 270,826		$ 252,552
Total Capital (to risk weighted assets), Actual, Ratio		11.21%		11.79%
Total Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 193,327		$ 171,337
Total Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		8.00%	[1]	8.00%
Tier 1 Risk Based Capital, Actual, Amount		$ 225,738		$ 209,887
Tier 1 Risk Based Capital (to risk weighted assets), Actual, Ratio		9.34%		9.80%
Tier 1 Risk Based Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 144,995		$ 128,503
Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		6.00%	[1]	6.00%
Tier 1 Leverage Capital, Actual, Amount		$ 225,738		$ 209,887
Tier 1 Leverage Capital (to average assets), Actual, Ratio		8.22%		8.34%
Tier 1 Leverage Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 109,838		$ 100,628
Tier 1 Leverage Capital (to average assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.00%	[1]	4.00%
Common Equity Tier 1 Risk Based Capital, Actual, Amount		$ 225,738		$ 209,887
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Actual, Ratio		9.34%		9.80%
Common Equity Tier 1 Risk Based Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 108,747		$ 96,377
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.50%	[1]	4.50%
The Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual, Amount		$ 270,150		$ 250,893
Total Capital (to risk weighted assets), Actual, Ratio		11.18%		11.71%
Total Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 193,301		$ 171,332
Total Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		8.00%	[1]	8.00%
Total Capital, Minimum Capital To Be Well Capitalized, Amount		$ 241,626		$ 214,166
Total Capital (to risk weighted assets), Minimum Capital To Be Well Capitalized, Ratio	[2]	10.00%		10.00%
Tier 1 Risk Based Capital, Actual, Amount		$ 239,910		$ 223,062
Tier 1 Risk Based Capital (to risk weighted assets), Actual, Ratio		9.93%		10.42%
Tier 1 Risk Based Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 144,976		$ 128,499
Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		6.00%	[1]	6.00%
Tier 1 Risk Based Capital, Minimum Capital To Be Well Capitalized, Amount		$ 193,301		$ 171,332
Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital To Be Well Capitalized, Ratio	[2]	8.00%		8.00%
Tier 1 Leverage Capital, Actual, Amount		$ 239,910		$ 223,062
Tier 1 Leverage Capital (to average assets), Actual, Ratio		8.74%		8.87%
Tier 1 Leverage Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 109,837		$ 100,627
Tier 1 Leverage Capital (to average assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.00%	[1]	4.00%
Tier 1 Leverage Capital, Minimum Capital To Be Well Capitalized, Amount		$ 137,296		$ 125,784
Tier 1 Leverage Capital (to average assets), Minimum Capital To Be Well Capitalized, Ratio	[2]	5.00%		5.00%
Common Equity Tier 1 Risk Based Capital, Actual, Amount		$ 239,910		$ 223,062
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Actual, Ratio		9.93%		10.42%
Common Equity Tier 1 Risk Based Capital, Minimum Capital for Capital Adequacy Purposes, Amount		$ 108,732		$ 96,374
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.50%	[1]	4.50%
Common Equity Tier 1 Risk Based Capital, Minimum Capital To Be Well Capitalized, Amount		$ 157,057		$ 139,208
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital To Be Well Capitalized, Ratio	[2]	6.50%		6.50%
[1]	Before application of the capital conservation buffer of 1.25% as of December 31, 2017 and 0.625% as of December 31, 2016, see discussion below.
[2]	For the Bank to qualify as “well-capitalized," it must maintain at least the minimum ratios listed. This prompt corrective action framework requirement does not apply to the Company.

Stockholders' Equity - Basel II

Stockholders' Equity - Basel III Minimum Capital Adequacy Requirements after Full Phase In (Details)	Dec. 31, 2019	Dec. 31, 2017	[1]	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		8.00%		8.00%
Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		6.00%		6.00%
Tier 1 Leverage Capital (to average assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.00%		4.00%
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio		4.50%		4.50%
Basel III Minimum Requirements Forecast [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio	10.50%
Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio	8.50%
Tier 1 Leverage Capital (to average assets), Minimum Capital for Capital Adequacy Purposes, Ratio	4.00%
Common Equity Tier 1 Risk Based Capital (to risk weighted assets), Minimum Capital for Capital Adequacy Purposes, Ratio	7.00%
Basel III Additional Capital Conservation Buffer at full phase-in (percent)	2.50%
[1]	Before application of the capital conservation buffer of 1.25% as of December 31, 2017 and 0.625% as of December 31, 2016, see discussion below.

Employee Benefit Plans - Define

Employee Benefit Plans - Defined Contribution Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Company's percent match on 401(K) defined contribution plan	60.00%	60.00%	60.00%
Maximum percentage of employee contribution matched by the Company	6.00%	6.00%	6.00%
Minimum age to be eligible for 401(k) plan	18 years
Number of minimum hours required to work for 401(k) plan eligibility	1 hour
Employer's matching contribution, annual vesting percentage for 401(k) plan	25.00%
Number of years to be fully vested for 401(k) plan	4 years
Expense for the 401(k) plan match	$ 965	$ 938	$ 859

Employee Benefit Plans - Supple

Employee Benefit Plans - Supplemental Retirement Plan (SERP) (Details) - Supplemental Employee Retirement Plan $ in Thousands		12 Months Ended
		Dec. 31, 2017USD ($)officer	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of active executive officers under plan | officer		2
Number of former executive officers under plan | officer		1
Term of SERP benefits		20 years
Accrual for benefit obligation for following year		$ 104
Benefit obligation at beginning of year		2,502	$ 2,654	$ 2,844
Interest cost		110	124	133
Actuarial loss(gain)		36	0	(47)
Net periodic benefit cost(benefit)		146	124	86
Benefits paid		(276)	(276)	(276)
Benefit obligation at end of year		2,372	2,502	2,654
Accrued liability at end of year		$ (2,372)	$ (2,502)	$ (2,654)
Discount rate used for benefit obligation	[1]	4.50%	4.75%	4.75%
[1]	Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss.

Employee Benefit Plans - Expect

Employee Benefit Plans - Expected Future Benefit Payments for SERP (Details) $ in Thousands	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
2,018	$ 276
2,019	276
2,020	276
2,021	276
2,022	276
2023-2027	$ 1,380

Employee Benefit Plans - Supp75

Employee Benefit Plans - Supplemental Life Insurance (Details) - Supplemental Life Insurance Benefit - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefit Plan Disclosures [Line Items]
Benefit obligation at beginning of year		$ 1,895	$ 1,792	$ 1,723
Service cost		(11)	(9)	(56)
Interest cost		91	88	86
Actuarial loss(gain)		57	24	39
Net periodic benefit cost(benefit)		137	103	69
Benefit obligation at end of year		2,032	1,895	1,792
Accrued liability at end of year		$ (2,032)	$ (1,895)	$ (1,792)
Discount rate used for benefit obligation	[1]	4.50%	4.75%	4.75%
Accrual for benefit obligation for following year		$ 178
[1]	Management utilizes the Moody’s 20 year AA corporate bond rates to establish the reasonableness of the discount rate used. The Company reviews and periodically updates the discount rate to reflect changes in bond market rates. The impact of the discount rate change is reflected as the actuarial gain or loss.

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options, Stock Awards, and Stock in Lieu of Directors' Fees (Details) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Jan. 31, 2018shares	Jan. 31, 2017shares	Jan. 31, 2016shares	Dec. 31, 2017USD ($)plansshares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jan. 03, 2017$ / shares	Jan. 04, 2016$ / shares	Jan. 02, 2015$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of individual stock incentive plans | plans				2
Shares remain available for future grants under the 2009 plan | shares				465,198
Stock-based compensation expense				$ 1,753	$ 2,380	$ 1,803
Tax benefit recognized related to stock-based compensation expense				716	972	720
Income tax benefit for stock compensation in income statement				$ 922	0	0
Tax benefit from stock compensation					789	217
Price as a percentage of fair market value that stock options may not be granted below				100.00%
Percentage of ownership of common stock by participants that if greater causes greater grant price				10.00%
Price as a percentage of fair market value that stock options may not be granted below for anyone who owns more than 10% common stock				110.00%
Expiration period of options granted for those who own more than 10% common stock				5 years
Proceeds from stock option exercises				$ 355	546	431
Total intrinsic value of options exercised				1,600	1,000	396
Cash paid by the Company to net settle employee taxes on restricted stock and options				931	442	0
Fair value of options vested				246	237	359
Directors fee expense				747	661	424
Number of shares issued in lieu of cash to directors | shares		12,992	10,657
Fair market share price | $ / shares							$ 38.39	$ 22.04	$ 23.86
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued in lieu of cash to directors | shares	7,326
Non-Employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax benefit recognized related to stock-based compensation expense				115	117	102
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				204	267	318
Tax benefit recognized related to stock-based compensation expense				$ 83	$ 109	$ 127
Term in years				10 years	10 years	10 years
Cash paid by the Company to net settle employee taxes on restricted stock and options				$ 386	$ 158
Unrecognized stock-based compensation expense				$ 339
Remaining vesting period unrecognized compensation expense is to be recognized				2 years 3 months 18 days
Restricted Stock and Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 1,300	1,800	$ 1,200
Tax benefit recognized related to stock-based compensation expense				518	746	491
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash paid by the Company to net settle employee taxes on restricted stock and options				545	284
Unrecognized stock-based compensation expense				$ 1,400
Remaining vesting period unrecognized compensation expense is to be recognized				2 years 1 month 6 days
Restricted Stock | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Restricted Stock | Non-Employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				2 years
Common stock in lieu of cash | Non-Employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 281	286	254
Two year vesting | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting percentage				50.00%
Four year vesting | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting percentage				50.00%
Accounting Standards Update 2016-09 | Income Tax Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit for stock compensation in income statement				$ 922
Additional Paid-in Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax benefit from stock compensation					$ 789	$ 217

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Options Granted (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	15,009	31,047	27,376
Options granted, per share weighted average fair value	$ 11.34
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term in years	10 years	10 years	10 years
Expected volatility	40.00%	42.00%	47.00%
Market price on date of grant	$ 30.46	$ 21.91	$ 21.03
Options granted, per share weighted average fair value	$ 11.34	$ 7.91	$ 8.51
Weighted Average | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	2.09%	3.02%	2.90%
Expected life in years	7 years	7 years	7 years
Risk-free interest rate	2.35%	1.91%	1.95%
Fair Value as a percentage of market value at grant date	37.00%	36.00%	40.00%

Stock-Based Compensation - St78

Stock-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding Options, beginning balance	259,779
Stock options granted	15,009	31,047	27,376
Exercised, Options	74,339
Forfeited/Expired, Options	6,231
Outstanding Options, ending balance	194,218	259,779
Outstanding Options, Weighted Average Exercise Price, beginning balance	$ 17.38
Granted, Weighted Average Exercise Price	30.46
Exercised, Weighted Average Exercise Price	14.81
Forfeited/Expired, Weighted Average Exercise Price	19.85
Outstanding Options, Weighted Average Exercise Price, ending balance	$ 19.29	$ 17.38
Outstanding Options, Weighted Average Remaining Life	5 years	4 years 6 months
Options Outstanding, Aggregate Intrinsic Value, beginning balance	$ 5,243
Options Outstanding, Aggregate Intrinsic Value, ending balance	$ 2,866	$ 5,243
Vested and Exercisable, ending balance, Options	123,669
Vested and Exercisable, ending balance, Weighted Average Exercise Price	$ 17.06
Vested and Exercisable, ending balance, Weighted Average Remaining Life	3 years 4 months 24 days
Vested and Exercisable, ending balance, Aggregate Intrinsic Value	$ 2,101

Stock-Based Compensation - Su79

Stock-Based Compensation - Summary of Unvested Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of Unvested Options [Abstract]
Unvested, options, beginning balance	94,034
Stock options granted	15,009	31,047	27,376
Options vested, number of shares	33,693
Unvested options forfeited, Number of Shares	4,801
Unvested, options, ending balance	70,549	94,034
Unvested options, beginning balance, weighted average grant date fair value	$ 7.84
Options granted, per share weighted average fair value	11.34
Options, vested, weighted average grant date fair value	7.31
Unvested Options forfeited, weighted average grant date fair value	8.30
Unvested options, ending balance, weighted average grant date fair value	$ 8.81	$ 7.84

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Grants (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards in the period	48,820	62,429	55,313
Weighted Average Grant Date Fair Value, Stock Awards	$ 30.46	$ 21.90	$ 21.03
Non-Employee Director | Two year vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards in the period	6,944	9,060	7,276
Employee | Four year vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards in the period	16,253	18,298	17,775
Employee | Performance-based vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards in the period	25,623	35,071	30,262

Stock-Based Compensation - Re81

Stock-Based Compensation - Restricted Stock Award Activity and Weighted Average Price (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance, Restricted Stock	141,580
Unvested, ending balance, Restricted Stock	117,219	141,580
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance, Restricted Stock	141,580
Stock awards in the period	48,820	62,429	55,313
Vested/released, Restricted Stock	69,336
Forfeited, Restricted Stock	3,845
Unvested, ending balance, Restricted Stock	117,219	141,580
Unvested, beginning balance, Weighted Average Grant Price Per Share	$ 20.73
Weighted Average Grant Date Fair Value, Stock Awards	30.46	$ 21.90	$ 21.03
Vested/released, Weighted Average Grant Price Per Share	20.07
Forfeited, Weighted Average Grant Price Per Share	23.28
Unvested, ending balance, Weighted Average Grant Price Per Share	$ 25.09	$ 20.73
Unvested, Weighted Average Remaining Life In Years	1 year 4 months 24 days	1 year 4 months 24 days
Unvested, Aggregate Intrinsic Value	$ 3,991,000	$ 5,318,000

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Federal									$ 8,222	$ 8,178	$ 6,808
State									2,271	2,244	1,712
Total current tax expense									10,493	10,422	8,520
Deferred tax expense (benefit):
Federal									5,646	(984)	(284)
State									89	(277)	(122)
Total deferred tax expense/ (benefit)									5,735	(1,261)	(406)
Total income tax expense	$ 8,505	$ 3,014	$ 2,845	$ 1,864	$ 2,362	$ 2,251	$ 2,291	$ 2,257	$ 16,228	$ 9,161	$ 8,114

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate									35.00%	35.00%	35.00%
Computed income tax expense at statutory rate									$ 12,467	$ 9,769	$ 8,492
State income taxes, net of federal tax benefit									1,534	1,279	1,034
Tax exempt income, net of disallowance									(1,665)	(1,559)	(1,226)
Bank Owned Life Insurance, net									(245)	(261)	(251)
Impact in tax expense of change in federal statutory rate on deferred tax assets									4,761	0	0
Income tax benefit for stock compensation in income statement									(922)	0	0
Other									298	(67)	65
Total income tax expense	$ 8,505	$ 3,014	$ 2,845	$ 1,864	$ 2,362	$ 2,251	$ 2,291	$ 2,257	$ 16,228	$ 9,161	$ 8,114
Effective income tax rate									45.60%	32.80%	33.40%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Income Taxes [Line Items]
Impact in tax expense of change in federal statutory rate on deferred tax assets		$ 4,761	$ 0	$ 0
Federal statutory tax rate		35.00%	35.00%	35.00%
Income tax benefit for stock compensation in income statement		$ 922	$ 0	$ 0
Total income taxes paid, net		10,459	10,868	7,594
New federal tax rate forecast
Schedule of Income Taxes [Line Items]
Federal statutory tax rate	21.00%
Accounting Standards Update 2016-09 | Income Tax Expense
Schedule of Income Taxes [Line Items]
Income tax benefit for stock compensation in income statement		922
Federal Low Income Housing Tax Credit
Schedule of Income Taxes [Line Items]
Tax credit carryforward recognized during period		71	$ 71	$ 71
Anticipated additional tax credits		$ 319
Number of years tax credit to be recognized over		5 years

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Asset and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of Deferred Tax Assets [Abstract]
Allowance for loan losses	$ 9,252	$ 12,753
Depreciation	1,831	3,463
Net unrealized loss on investment securities	0	444
Other-than-temporary impairment on equity securities	0	22
Supplemental employee retirement plans	667	1,018
Non-accrual interest	460	1,145
Stock-based compensation expense	608	1,019
Other	323	390
Total	13,141	20,254
Components of Deferred Tax Liabilities [Abstract]
Goodwill	1,590	2,301
Net unrealized gains on investments securities	90	0
Deferred origination costs	710	933
Total	2,390	3,234
Net deferred tax asset	$ 10,751	$ 17,020

Earnings per share (Details)

Earnings per share (Details) - shares	Jun. 23, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic weighted average common shares outstanding		11,568,430	10,966,333	10,323,016
Dilutive shares		83,333	73,178	66,918
Diluted weighted average common shares outstanding		11,651,763	11,039,511	10,389,934
Shares issued in shareholder subscription rights and community offering	930,232
Antidilutive Shares Excluded from EPS		14,678

Fair Value Measurements - Recur

Fair Value Measurements - Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific allowance for collateral dependent impaired loans	$ 872	$ 1,900
Letter of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortization period of estimated fair value on letters of credit	1 year
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities	$ 0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets		12,643
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | FHLB Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities	568	610
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	405,206	362,147
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets		0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | FHLB Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	568	610
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets		0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | FHLB Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	5,215	2,094
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	0	0
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent), Fair Value	0	0
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent), Fair Value	0	0
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent), Fair Value	2,696	3,481
Fair Value | Fair Value, Measurements, Recurring | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities	568	610
Fair Value | Fair Value, Measurements, Recurring | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	405,206	362,147
Fair Value | Fair Value, Measurements, Recurring | Equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets		12,643
Fair Value | Fair Value, Measurements, Recurring | FHLB Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	5,215	2,094
Fair Value | Fair Value, Measurements, Recurring | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets	568	610
Fair Value | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (collateral dependent), Fair Value	$ 2,696	$ 3,481

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative (Details) - Fair Value, Inputs, Level 3 - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring | FHLB Stock
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of assets		$ 5,215	$ 2,094
Fair Value, Measurements, Recurring | FHLB Stock | FHLB Stated Par Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of assets		5,215
Fair Value, Measurements, Nonrecurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans (collateral dependent), Fair Value		2,696	$ 3,481
Fair Value, Measurements, Nonrecurring | Impaired loans (collateral dependent) | Appraisal of collateral
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans (collateral dependent), Fair Value	[1]	$ 2,696
Fair Value, Measurements, Nonrecurring | Impaired loans (collateral dependent) | Appraisal of collateral | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input Value or Range		5.00%
Fair Value, Measurements, Nonrecurring | Impaired loans (collateral dependent) | Appraisal of collateral | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input Value or Range		50.00%
[1]	Appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses.

Fair Value Measurements - Balan

Fair Value Measurements - Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying Amount
Financial assets:
Loans held for sale	$ 208	$ 1,569
Loans, net	2,236,989	1,991,387
Financial liabilities:
Borrowed funds	89,000	10,671
Subordinated debt	14,847	14,834
Carrying Amount | Certificates of Deposit
Financial liabilities:
Certificates of deposit	343,089	227,257
Fair Value
Financial assets:
Loans held for sale	208	1,569
Loans, net	2,236,169	1,997,887
Financial liabilities:
Borrowed funds	88,996	10,670
Subordinated debt	14,208	14,011
Fair Value | Certificates of Deposit
Financial liabilities:
Certificates of deposit	341,765	226,536
Fair Value, Inputs, Level 1
Financial assets:
Loans held for sale	0	0
Loans, net	0	0
Financial liabilities:
Borrowed funds	0	0
Subordinated debt	0	0
Fair Value, Inputs, Level 1 | Certificates of Deposit
Financial liabilities:
Certificates of deposit	0	0
Fair Value, Inputs, Level 2
Financial assets:
Loans held for sale	208	1,569
Loans, net	0	0
Financial liabilities:
Borrowed funds	88,996	10,670
Subordinated debt	0	0
Fair Value, Inputs, Level 2 | Certificates of Deposit
Financial liabilities:
Certificates of deposit	341,765	226,536
Fair Value, Inputs, Level 3
Financial assets:
Loans held for sale	0	0
Loans, net	2,236,169	1,997,887
Financial liabilities:
Borrowed funds	0	0
Subordinated debt	14,208	14,011
Fair Value, Inputs, Level 3 | Certificates of Deposit
Financial liabilities:
Certificates of deposit	$ 0	$ 0

Parent Company Only Financial90

Parent Company Only Financial Statements - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash	$ 54,806	$ 50,475	$ 51,495	$ 40,146
Total assets	2,817,564	2,526,269
Liabilities
Subordinated debt	14,847	14,834	14,822
Accrued interest payable	478	263
Other liabilities	40,067	16,794
Total liabilities	2,585,754	2,311,483
Stockholders' Equity
Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued	0	0
Common stock $0.01 par value per share; 40,000,000 shares authorized; 11,609,853 shares issued and outstanding at December 31, 2017 and 11,475,742 shares issued and outstanding at December 31, 2016	116	115
Additional paid-in capital	88,205	85,421
Retained earnings	143,073	130,008
Accumulated other comprehensive income (loss)	416	(758)
Total stockholders’ equity	231,810	214,786	180,327	166,950
Total liabilities and stockholders’ equity	2,817,564	2,526,269
Parent
Assets
Cash	345	497	$ 2,737	$ 699
Investment in subsidiaries	245,982	227,960
Other assets	411	1,243
Total assets	246,738	229,700
Liabilities
Subordinated debt	14,847	14,834
Accrued interest payable	78	78
Other liabilities	3	2
Total liabilities	14,928	14,914
Stockholders' Equity
Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued	0	0
Common stock $0.01 par value per share; 40,000,000 shares authorized; 11,609,853 shares issued and outstanding at December 31, 2017 and 11,475,742 shares issued and outstanding at December 31, 2016	116	115
Additional paid-in capital	88,205	85,421
Retained earnings	143,073	130,008
Accumulated other comprehensive income (loss)	416	(758)
Total stockholders’ equity	231,810	214,786
Total liabilities and stockholders’ equity	$ 246,738	$ 229,700

Parent Company Only Financial91

Parent Company Only Financial Statements - Balance Sheet (Additional) (Details) - $ / shares	Dec. 31, 2017	May 01, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Common stock, par value	$ 0.01		$ 0.01
Common stock, shares authorized	40,000,000	20,000,000
Common stock, shares issued	11,609,853		11,475,742
Common stock, shares outstanding	11,609,853		11,475,742
Preferred stock, par value	$ 0.01		$ 0.01
Preferred stock, shares authorized	1,000,000		1,000,000
Preferred stock, shares issued	0		0
Parent
Condensed Financial Statements, Captions [Line Items]
Common stock, par value	$ 0.01		$ 0.01
Common stock, shares authorized	40,000,000
Common stock, shares issued	11,609,853		11,475,742
Common stock, shares outstanding	11,609,853		11,475,742
Preferred stock, par value	$ 0.01		$ 0.01
Preferred stock, shares authorized	1,000,000		1,000,000
Preferred stock, shares issued	0		0

Parent Company Only Financial92

Parent Company Only Financial Statements - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Other income									$ 2,637	$ 2,393	$ 2,465
Interest expense	$ 2,279	$ 1,911	$ 1,803	$ 1,517	$ 1,424	$ 1,374	$ 1,343	$ 1,382	7,510	5,523	5,177
Income before income taxes	11,225	8,520	8,440	7,436	7,315	6,965	7,062	6,570	35,621	27,912	24,262
Provision for (benefit from) income tax	8,505	3,014	2,845	1,864	2,362	2,251	2,291	2,257	16,228	9,161	8,114
Net income	$ 2,720	$ 5,506	$ 5,595	$ 5,572	$ 4,953	$ 4,714	$ 4,771	$ 4,313	19,393	18,751	16,148
Parent
Condensed Financial Statements, Captions [Line Items]
Equity in undistributed net income of subsidiaries									16,922	19,313	17,277
Dividend distributed by subsidiaries									3,000	150	0
Loss distributed by divested subsidiary									0	0	(210)
Other income									0	0	17
Total income									19,922	19,463	17,084
Interest expense									925	928	1,071
Other operating expenses									245	194	500
Total operating expenses									1,170	1,122	1,571
Income before income taxes									18,752	18,341	15,513
Provision for (benefit from) income tax									(641)	(410)	(635)
Net income									$ 19,393	$ 18,751	$ 16,148

Parent Company Only Financial93

Parent Company Only Financial Statements - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 2,720	$ 5,506	$ 5,595	$ 5,572	$ 4,953	$ 4,714	$ 4,771	$ 4,313	$ 19,393	$ 18,751		$ 16,148
Changes in:
Net cash provided by operating activities									37,931	27,323		25,723
Cash flows from investing activities:
Net cash used in investing activities									(279,143)	(252,508)		(259,860)
Cash flows from financing activities:
Repayment of subordinated debt									0	0		(10,825)
Proceeds from the issuance of subordinated debt									0	0		15,000
Cash dividends paid									(6,241)	(5,684)		(5,158)
Proceeds from issuance of common stock, net of expenses									1,590	21,183		1,448
Net settlement for employee taxes on restricted stock and options									(931)	(442)		0
Proceeds from stock option exercises									355	546		431
Tax benefit from stock-based compensation									0	789		217
Net cash provided by financing activities									245,543	224,165		245,486
Net (decrease) increase in cash and cash equivalents									4,331	(1,020)		11,349
Cash and cash equivalents, beginning of year				50,475				51,495	50,475	51,495		40,146
Cash and cash equivalents, end of year	54,806				50,475				54,806	50,475		51,495
Parent
Cash flows from operating activities:
Net income									19,393	18,751		16,148
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries									(16,922)	(19,313)		(17,277)
Payment from subsidiary bank for stock compensation expense									1,758	2,348		1,791
Changes in:
Decrease (increase) in other assets									832	(697)		(36)
Decrease in other liabilities									14	9		(482)
Net cash provided by operating activities									5,075	1,098		144
Cash flows from investing activities:
Investment in subsidiary									0	(19,730)	[1]	781
Net cash used in investing activities									0	(19,730)		781
Cash flows from financing activities:
Repayment of subordinated debt									0	0		(10,825)	[2]
Proceeds from the issuance of subordinated debt									0	0		15,000	[2]
Cash dividends paid									(6,241)	(5,684)		(5,158)
Proceeds from issuance of common stock, net of expenses									1,590	21,183		1,448
Net settlement for employee taxes on restricted stock and options									(931)	(442)		0
Proceeds from stock option exercises									355	546		431
Tax benefit from stock-based compensation									0	789		217
Net cash provided by financing activities									(5,227)	16,392		1,113
Net (decrease) increase in cash and cash equivalents									(152)	(2,240)		2,038
Cash and cash equivalents, beginning of year				$ 497				$ 2,737	497	2,737		699
Cash and cash equivalents, end of year	$ 345				$ 497				$ 345	$ 497		$ 2,737
[1]	The outflow in investment in subsidiary in 2016 reflects the Company's investment in the Bank from the Offering. See Note 10 "Stockholders' Equity," above, for further information.
[2]	See Note 7, "Borrowed Funds and Subordinated Debt," above, for further information regarding changes in the Company's subordinated debt.

Quarterly Results of Operatio94

Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 28,285	$ 27,045	$ 25,338	$ 24,364	$ 24,027	$ 23,191	$ 22,632	$ 22,465	$ 105,032	$ 92,315	$ 83,471
Interest expense	2,279	1,911	1,803	1,517	1,424	1,374	1,343	1,382	7,510	5,523	5,177
Net interest income	26,006	25,134	23,535	22,847	22,603	21,817	21,289	21,083	97,522	86,792	78,294
Provision for loan losses	(200)	1,225	280	125	490	1,386	267	850	1,430	2,993	3,267
Net interest income after provision for loan losses	26,206	23,909	23,255	22,722	22,113	20,431	21,022	20,233	96,092	83,799	75,027
Non-interest income	3,926	3,728	3,710	3,594	3,514	3,402	3,519	3,204
Net gains on sales of investment securities	231	(284)	229	540	191	546	63	2	716	802	1,828
Non-interest expense	19,138	18,833	18,754	19,420	18,503	17,414	17,542	16,869	76,145	70,328	65,732
Income before income taxes	11,225	8,520	8,440	7,436	7,315	6,965	7,062	6,570	35,621	27,912	24,262
Provision for income taxes	8,505	3,014	2,845	1,864	2,362	2,251	2,291	2,257	16,228	9,161	8,114
Net income	$ 2,720	$ 5,506	$ 5,595	$ 5,572	$ 4,953	$ 4,714	$ 4,771	$ 4,313	$ 19,393	$ 18,751	$ 16,148
Basic earnings per share	$ 0.23	$ 0.48	$ 0.48	$ 0.48	$ 0.43	$ 0.41	$ 0.45	$ 0.41	$ 1.68	$ 1.71	$ 1.56
Diluted earnings per share	$ 0.23	$ 0.47	$ 0.48	$ 0.48	$ 0.43	$ 0.41	$ 0.45	$ 0.41	$ 1.66	$ 1.70	$ 1.55