The First Bancorp, Inc. (FNLC) 10-K 14 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Mar. 01, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	First Bancorp, Inc /ME/
Entity Central Index Key	765,207
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 272,996
Entity Common Stock, Shares Outstanding		10,846,398
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 19,207	$ 17,366
Interest-bearing deposits in other banks	860	293
Securities available for sale	300,172	300,416
Securities to be held to maturity (fair value of $259,655,000 at December 31, 2017, and $225,537,000 at December 31, 2016)	256,567	226,828
Restricted equity securities, at cost	10,358	11,930
Loans held for sale	386	782
Loans	1,164,139	1,071,526
Less allowance for loan losses	10,729	10,138
Net loans	1,153,410	1,061,388
Accrued interest receivable	5,867	5,532
Premises and equipment, net	22,502	22,202
Other real estate owned	1,012	375
Goodwill	29,805	29,805
Other assets	42,784	35,958
Total assets	1,842,930	1,712,875
Liabilities
Demand deposits	181,970	140,482
NOW deposits	281,405	282,971
Money market deposits	163,898	125,544
Savings deposits	232,605	217,340
Certificates of deposit	559,001	476,620
Total deposits	1,418,879	1,242,957
Borrowed funds – short term	113,638	158,774
Borrowed funds – long term	115,120	120,127
Other liabilities	13,972	18,496
Total liabilities	1,661,609	1,540,354
Commitments and contingent liabilities
Shareholders' equity
Common stock, one cent par value per share	108	108
Additional paid-in capital	61,747	60,723
Retained earnings	121,144	111,693
Accumulated other comprehensive income (loss)
Net unrealized loss on securities available for sale	(2,901)	(935)
Net unrealized loss on securities transferred from available for sale to held to maturity	(174)	(129)
Net unrealized gain on cash flow hedging derivative instruments	1,544	1,163
Net unrecognized loss on postretirement benefit costs	(147)	(102)
Total shareholders' equity	181,321	172,521
Total liabilities and shareholders' equity	$ 1,842,930	$ 1,712,875
Common stock
Number of shares authorized (in shares)	18,000,000	18,000,000
Number of shares issued (in shares)	10,829,918	10,793,946
Number of shares outstanding (in shares)	10,829,918	10,793,946
Book value per common share (usd per share)	$ 16.74	$ 15.98
Tangible book value per common share (usd per share)	$ 13.97	$ 13.20

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Securities to be held to maturity, fair value	$ 259,655	$ 225,537
Common stock, par value (usd per share)	$ 0.01	$ 0.01

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest and dividend income
Interest and fees on loans (includes tax-exempt income of $798,000 in 2017, $670,000 in 2016, and $578,000 in 2015)	$ 45,373	$ 39,996	$ 36,620
Interest on deposits with other banks	52	22	19
Interest and dividends on investments (includes tax-exempt income of $6,501,000 in 2017, $5,168,000 in 2016, and $5,157,000 in 2015)	15,407	13,741	14,171
Total interest and dividend income	60,832	53,759	50,810
Interest expense
Interest on deposits	9,479	6,028	5,285
Interest on borrowed funds	4,050	4,784	4,589
Total interest expense	13,529	10,812	9,874
Net interest income	47,303	42,947	40,936
Provision for loan losses	2,000	1,600	1,550
Net interest income after provision for loan losses	45,303	41,347	39,386
Non-interest income
Fiduciary and investment management income	2,680	2,411	2,258
Service charges on deposit accounts	2,081	2,237	2,384
Net securities gains	471	673	1,399
Mortgage origination and servicing income	1,853	2,192	1,558
Other operating income	5,463	4,986	4,631
Total non-interest income	12,548	12,499	12,230
Non-interest expense
Salaries and employee benefits	16,601	15,215	15,080
Occupancy expense	2,400	2,313	2,312
Furniture and equipment expense	3,681	3,305	3,171
FDIC insurance premiums	1,008	789	890
Amortization of identified intangibles	43	43	58
Other operating expense	7,918	7,718	8,385
Total non-interest expense	31,651	29,383	29,896
Income before income taxes	26,200	24,463	21,720
Applicable tax expense	6,612	6,454	5,514
Net income	$ 19,588	$ 18,009	$ 16,206
Basic earnings per common share (in usd per share)	$ 1.82	$ 1.68	$ 1.52
Diluted earnings per common share (in usd per share)	$ 1.81	$ 1.66	$ 1.51
Other comprehensive income (loss), net of tax
Net unrealized loss on securities available for sale	$ (1,452)	$ (2,058)	$ (1,399)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of amortization	(14)	(17)	(64)
Net unrealized gain on cash flow hedging derivative instruments	107	1,163	0
Net unrecognized gain (loss) on postretirement benefits	(19)	54	(31)
Other comprehensive loss	(1,378)	(858)	(1,494)
Comprehensive income	$ 18,210	$ 17,151	$ 14,712

Consolidated Statements of Inc5

Consolidated Statements of Income and Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Interest and fees on loans (tax-exempt income)	$ 798	$ 670	$ 578
Interest and dividends on investments (tax-exempt income)	$ 6,501	$ 5,168	$ 5,157

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common stock and additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Warrants	WarrantsRetained earnings
Balance at Dec. 31, 2014	$ 161,554	$ 59,389	$ 99,816	$ 2,349
Balance (in shares) at Dec. 31, 2014		10,724,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,206		16,206
Net unrealized gain (loss) on securities available for sale, net of tax	(1,399)			(1,399)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(64)			(64)
Unrecognized gain (loss) for post-retirement benefits, net of tax	(31)			(31)
Comprehensive income (loss)	14,712		16,206	(1,494)
Cash dividends declared	(9,349)		(9,349)
Equity compensation expense	296	$ 296
Payment for repurchase of common stock and warrants	(180)	$ (180)
Payment for repurchase of common stock (in shares)		(10,138)
Issuance of restricted stock (in shares)		14,179
Proceeds from sale of common stock	465	$ 465
Proceeds from sale of common stock (in shares)		25,455
Balance at Dec. 31, 2015	167,498	$ 59,970	106,673	855
Balance (in shares) at Dec. 31, 2015		10,753,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,503
Net unrealized gain (loss) on securities available for sale, net of tax	1,852
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(11)
Balance at Mar. 31, 2016	171,544
Balance at Dec. 31, 2015	167,498	$ 59,970	106,673	855
Balance (in shares) at Dec. 31, 2015		10,753,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,009		18,009
Net unrealized gain (loss) on securities available for sale, net of tax	(2,058)			(2,058)
Net unrealized gain on cash flow hedging derivate instruments, net of tax	1,163			1,163
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(17)			(17)
Unrecognized gain (loss) for post-retirement benefits, net of tax	54			54
Comprehensive income (loss)	17,151		18,009	(858)
Cash dividends declared	(11,110)		(11,110)
Equity compensation expense	298	$ 298
Payment for repurchase of common stock and warrants	(129)		(129)		$ (1,750)	$ (1,750)
Payment for repurchase of common stock (in shares)		(7,156)
Tax benefit from vesting of restricted stock	32	$ 32
Issuance of restricted stock (in shares)		21,847
Proceeds from sale of common stock	531	$ 531
Proceeds from sale of common stock (in shares)		25,400
Balance at Dec. 31, 2016	$ 172,521	$ 60,831	111,693	(3)
Balance (in shares) at Dec. 31, 2016	10,793,946	10,793,946
Balance at Mar. 31, 2016	$ 171,544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,624
Net unrealized gain (loss) on securities available for sale, net of tax	1,025
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(10)
Balance at Jun. 30, 2016	174,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,562
Net unrealized gain (loss) on securities available for sale, net of tax	(1,292)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	9
Balance at Sep. 30, 2016	175,994
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,320
Net unrealized gain (loss) on securities available for sale, net of tax	(3,643)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(5)
Balance at Dec. 31, 2016	$ 172,521	$ 60,831	111,693	(3)
Balance (in shares) at Dec. 31, 2016	10,793,946	10,793,946
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 4,637
Net unrealized gain (loss) on securities available for sale, net of tax	1
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(4)
Balance at Mar. 31, 2017	174,910
Balance at Dec. 31, 2016	$ 172,521	$ 60,831	111,693	(3)
Balance (in shares) at Dec. 31, 2016	10,793,946	10,793,946
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 19,588		19,588
Net unrealized gain (loss) on securities available for sale, net of tax	(1,452)			(1,452)
Net unrealized gain on cash flow hedging derivative instruments, net of tax	107			107
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(14)			(14)
Unrecognized gain (loss) for post-retirement benefits, net of tax	(19)			(19)
Comprehensive income (loss)	18,210		19,588	(1,378)
Cash dividends declared	(10,280)		(10,280)
Equity compensation expense	392	$ 392
Payment for repurchase of common stock and warrants	(154)		(154)
Payment for repurchase of common stock (in shares)		(5,562)
Reclassification adjustment for effect of enacted tax law changes			297	(297)
Issuance of restricted stock (in shares)		18,850
Proceeds from sale of common stock	632	$ 632
Proceeds from sale of common stock (in shares)		22,684
Balance at Dec. 31, 2017	$ 181,321	$ 61,855	121,144	(1,678)
Balance (in shares) at Dec. 31, 2017	10,829,918	10,829,918
Balance at Mar. 31, 2017	$ 174,910
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,883
Net unrealized gain (loss) on securities available for sale, net of tax	349
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(4)
Balance at Jun. 30, 2017	177,537
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,982
Net unrealized gain (loss) on securities available for sale, net of tax	(240)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(3)
Balance at Sep. 30, 2017	179,882
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,086
Net unrealized gain (loss) on securities available for sale, net of tax	(1,562)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(3)
Balance at Dec. 31, 2017	$ 181,321	$ 61,855	$ 121,144	$ (1,678)
Balance (in shares) at Dec. 31, 2017	10,829,918	10,829,918

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends declared, per share (USD per share)	$ 0.95	$ 1.03	$ 0.87

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Net income	$ 19,588	$ 18,009	$ 16,206
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,864	1,745	1,720
Change in deferred taxes	2,083	(139)	332
Provision for loan losses	2,000	1,600	1,550
Loans originated for resale	(39,039)	(54,257)	(31,306)
Proceeds from sales and transfers of loans	40,172	55,035	31,671
Net gain on sales of loans	(737)	(1,211)	(714)
Net gain on sale or call of securities	(471)	(673)	(1,399)
Net amortization of investment premiums	3,390	2,810	783
Net (gain) loss on sale of other real estate owned	(84)	(177)	5
Provision for losses on other real estate owned	17	132	311
Equity compensation expense	392	298	296
Tax benefit from vesting of restricted stock	0	32	0
Net increase in other assets and accrued interest	(4,742)	(2,460)	(455)
Net increase (decrease) in other liabilities	(2,020)	665	1,418
Net gain on disposal of premises and equipment	(108)	0	0
Amortization of investments in limited partnerships	178	194	266
Net acquisition amortization	43	43	58
Net cash provided by operating activities	22,526	21,646	20,742
Cash flows from investing activities
(Increase) decrease in interest-bearing deposits in other banks	(567)	3,720	(454)
Proceeds from sales of securities available for sale	15,587	10,309	35,468
Proceeds from maturities, payments, calls of securities available for sale	157,013	79,223	36,588
Proceeds from maturities, payments, calls of securities held to maturity	14,770	88,899	45,688
Proceeds from sales of other real estate owned	607	1,786	3,260
Purchases of securities available for sale	(177,706)	(172,343)	(111,616)
Purchases of securities to be held to maturity	(44,334)	(75,573)	(9,644)
Investment in bank-owned life insurance	0	0	(10,000)
Purchase of Federal Home Loan Bank Stock	0	0	(345)
Redemption of restricted equity securities	1,572	2,327	0
Net increase in loans	(95,199)	(84,850)	(74,375)
Capital expenditures	(2,529)	(2,131)	(927)
Proceeds from sale of premises and equipment	473	0	10
Net cash used in investing activities	(130,313)	(148,633)	(86,347)
Cash flows from financing activities
Net increase in demand, savings, and money market accounts	88,372	94,130	94,889
Net increase (decrease) in certificates of deposit	82,381	105,638	(76,519)
Advances on long-term borrowings	50,000	35,000	55,000
Repayment on long-term borrowings	(70,000)	(30,000)	(40,000)
Net increase (decrease) in short-term borrowings	(30,143)	(63,556)	42,541
Payment to repurchase common stock	(154)	(129)	(180)
Proceeds from sale of common stock	632	531	465
Repurchase of warrants	0	(1,750)	0
Dividends paid	(11,460)	(9,810)	(9,349)
Net cash provided by financing activities	109,628	130,054	66,847
Net increase in cash and cash equivalents	1,841	3,067	1,242
Cash and cash equivalents at beginning of year	17,366	14,299	13,057
Cash and cash equivalents at end of year	19,207	17,366	14,299
Interest paid	13,366	10,767	9,960
Income taxes paid	5,730	6,367	4,235
Non-cash transactions:
Net transfer from loans to other real estate owned	$ 1,177	$ 584	$ 1,323

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 Principles of Consolidation The consolidated financial statements include the accounts of the Company and the Bank. All intercompany accounts and transactions have been eliminated in consolidation. Subsequent Events Events occurring subsequent to December 31, 2017 , have been evaluated as to their potential impact to the financial statements. Use of Estimates in Preparation of Financial Statements In preparing the financial statements in accordance with accounting principles generally accepted in the United States of America ("GAAP"), Management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the balance sheet and revenues and expenses for the reporting period. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant change in the near-term relate to the determination of the allowance for loan losses, goodwill, the valuation of mortgage servicing rights, and other-than-temporary impairment of securities. Investment Securities Investment securities are classified as available for sale or held to maturity when purchased. There are no trading account securities. Securities available for sale consist primarily of debt securities which Management intends to hold for indefinite periods of time. They may be used as part of the Bank's funds management strategy, and may be sold in response to changes in interest rates or prepayment risk, changes in liquidity needs, or for other reasons. They are accounted for at fair value, with unrealized gains or losses adjusted through shareholders' equity, net of related income taxes. The cost basis is adjusted for the amortization of premiums and accretion of discounts, computed using the effective interest method over the securities' contractual lives. Securities to be held to maturity consist primarily of debt securities which Management has acquired solely for long-term investment purposes, rather than for purposes of trading or future sale. For securities to be held to maturity, Management has the intent and the Bank has the ability to hold such securities until their respective maturity dates. Such securities are carried at cost adjusted for the amortization of premiums and accretion of discounts, computed using the effective interest method over the securities' contractual lives. Investment securities transactions are accounted for on a settlement date basis; reported amounts would not be materially different from those accounted for on a trade date basis. Gains and losses on the sales of investment securities are determined using the amortized cost of the specifically identified security. For declines in the fair value of individual debt securities available for sale below their cost that are deemed to be other than temporary, where the Bank does not intend to sell the security and it is more likely than not that the Bank will not be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in the fair value of the debt security related to 1) credit loss is recognized in earnings and 2) other factors is recognized in other comprehensive income or loss. Credit loss is deemed to exist if the present value of expected future cash flows using the effective rate at acquisition is less than the amortized cost basis of the debt security. For individual debt securities where the Bank intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost, the other-than-temporary impairment is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date. Derivative Financial Instruments Designated as Hedges The Company recognizes all derivatives in the consolidated balance sheets at fair value. On the date the Bank enters into the derivative contract, the Company designates the derivative as a hedge of either a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), a hedge of the fair value of a recognized asset or liability or of an unrecognized firm commitment (“fair value hedge”), or a held for trading instrument (“trading instrument”). The Bank formally documents relationships between hedging instruments and hedged items, as well as its risk management objectives and strategy for undertaking various hedge transactions. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are effective in offsetting changes in cash flows or fair values of hedged items. Changes in fair value of a derivative that is effective and that qualifies as a cash flow hedge are recorded in other comprehensive income (loss) and are reclassified into earnings when the forecasted transaction or related cash flows affect earnings. Changes in fair value of a derivative that qualifies as a fair value hedge and the change in fair value of the hedged item are both recorded in earnings and offset each other when the transaction is effective. Those derivatives that are classified as trading instruments are recorded at fair value with changes in fair value recorded in earnings. The Company discontinues hedge accounting when it determines that the derivative is no longer effective in offsetting changes in the cash flows of the hedged item, that it is unlikely that the forecasted transaction will occur, or that the designation of the derivative as a hedging instrument is no longer appropriate. Loans Held for Sale Loans held for sale consist of residential real estate mortgage loans and are carried at the lower of aggregate cost or fair value, as determined by current investor yield requirements. Loans Loans are generally reported at their outstanding principal balances, adjusted for chargeoffs, the allowance for loan losses and any deferred fees or costs to originate loans. Loan commitments are recorded when funded. Loan Fees and Costs Loan origination fees and certain direct loan origination costs are deferred and recognized in interest income as an adjustment to the loan yield over the life of the related loans. The unamortized net deferred fees and costs are included on the balance sheets with the related loan balances, and the amortization is included with the related interest income. Allowance for Loan Losses Loans considered to be uncollectible are charged against the allowance for loan losses. The allowance for loan losses is maintained at a level determined by Management to be appropriate to absorb probable losses. This allowance is increased by provisions charged to operating expenses and recoveries on loans previously charged off. Arriving at an appropriate level of allowance for loan losses necessarily involves a high degree of judgment. In determining the appropriate level of allowance for loan losses, Management takes into consideration several factors, including reviews of individual non-performing loans and performing loans listed on the watch report requiring periodic evaluation, loan portfolio size by category, recent loss experience, delinquency trends and current economic conditions. For all loan classes, loans over 30 days past due are considered delinquent. Impaired loans include restructured loans and loans placed on non-accrual status when, based on current information and events, it is probable that the Bank will be unable to collect all amounts due according to the contractual terms of the loan agreement. These loans are measured at the present value of expected future cash flows discounted at the loan's effective interest rate or at the fair value of the collateral if the loan is collateral dependent. Management takes into consideration impaired loans in addition to the above mentioned factors in determining the appropriate level of allowance for loan losses. Troubled Debt Restructured A troubled debt restructured ("TDR") constitutes a restructuring of debt if the Bank, for economic or legal reasons related to the borrower's financial difficulties, grants a concession to the borrower that it would not otherwise consider. To determine whether or not a loan should be classified as a TDR, Management evaluates a loan to first determine if the borrower demonstrates financial difficulty. Common indicators of this include past due status with bank obligations, substandard credit bureau reports, or an inability to refinance with another lender. If the borrower is experiencing financial difficulty and concessions are granted, such as maturity date extension, interest rate adjustments to below market pricing, or a deferral of payments, the loan will generally be classified as a TDR. Accrual of Interest Income and Expense Interest on loans and investment securities is taken into income using methods which relate the income earned to the balances of loans and investment securities outstanding. Interest expense on liabilities is derived by applying applicable interest rates to principal amounts outstanding. For all classes of loans, recording of interest income on problem loans, which includes impaired loans, ceases when collectibility of principal and interest within a reasonable period of time becomes doubtful. Cash payments received on non-accrual loans, which includes impaired loans, are applied to reduce the loan's principal balance until the remaining principal balance is deemed collectible, after which interest is recognized when collected. As a general rule, a loan may be restored to accrual status when payments are current for a substantial period of time, generally six months, and repayment of the remaining contractual amounts is expected or when it otherwise becomes well secured and in the process of collection. Premises and Equipment Premises, furniture and equipment are stated at cost, less accumulated depreciation. Depreciation expense is computed by straight-line methods over the asset's estimated useful life. Other Real Estate Owned ("OREO") Real estate acquired by foreclosure or deed in lieu of foreclosure is transferred to OREO and recorded at fair value, less estimated costs to sell, based on appraised value at the date actually or constructively received. Loan losses arising from the acquisition of such property are charged against the allowance for loan losses. Subsequent provisions to reduce the carrying value of a property are recorded to the allowance for OREO losses and a charge to operations on a property specific basis. Goodwill and Identified Intangible Assets Intangible assets include the excess of the purchase price over the fair value of net assets acquired (goodwill) from the acquisition of FNB Bankshares in 2005 as well as the core deposit intangible related to the same acquisition. The core deposit intangible is amortized on a straight-line basis over ten years . There was no annual amortization expense for 2017 or 2016 as the expense is now fully amortized. For 2015 the annual amortization expense was $15,000 . Intangible assets also include the goodwill and core deposit intangible from the 2012 acquisition of a bank branch in Rockland, Maine and a bank building in Bangor, Maine. The core deposit intangible will be amortized on a straight-line basis over ten years . Annual amortization expense for each of 2017 , 2016 and 2015 was $43,000 , and the amortization expense for each year until fully amortized (presently expected to be 2022) will be $43,000 . The straight-line basis is used because the Company does not expect significant run off in the core deposits acquired. The Company annually evaluates goodwill, and periodically evaluates other intangible assets, for impairment. At December 31, 2017 , the Company determined goodwill and other intangible assets were not impaired. Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between financial statement carrying amounts of assets and liabilities and their respective tax bases, and for tax credits that are available to offset future taxable income. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period the change is enacted. On December 22, 2017 the Tax Cuts and Jobs Act of 2017 ("TCJA") was enacted. One facet of TCJA reduced the federal corporate income tax rate from 35% to 21% effective January 1, 2018. As a result of this legislation, the Company evaluated its deferred tax assets and deferred tax liabilities. The effect of the new corporate income tax rate reduced the value of our net tax deferred assets by $134,000 , and a charge to earnings was recorded for this amount in the fourth quarter of 2017. Loan Servicing Servicing rights are recognized when they are acquired through sale of loans. Capitalized servicing rights are reported in other assets and are amortized into non-interest income in proportion to, and over the period of, the estimated future net servicing income of the underlying financial assets. Servicing rights are evaluated for impairment based upon the fair value of the rights as compared to amortized cost. Impairment is determined by stratifying rights by predominant characteristics, such as interest rates and terms. Impairment is recognized through a valuation allowance for an individual stratum, to the extent that fair value is less than the capitalized amount for the stratum. Post-Retirement Benefits The cost of providing post-retirement benefits is accrued during the active service period of the employee or director. Earnings Per Share Basic earnings per share data are based on the weighted average number of common shares outstanding during each year. Diluted earnings per share gives effect to restricted stock granted and stock options and warrants outstanding, determined by the treasury stock method. Comprehensive Income (Loss) Comprehensive income (loss) includes net income and other comprehensive income (loss), which is comprised of the change in unrealized gains and losses on securities available for sale, net of tax, change in unrealized losses on securities transferred from available for sale to held to maturity, net of amortization, change in unrealized gain on cash flow hedging derivative instruments, net of tax, and unrecognized gains and losses related to post-retirement benefit costs, net of tax. Segments The First Bancorp, Inc., through the branches of its subsidiary, First National Bank, provides a broad range of financial services to individuals and companies in coastal Maine. These services include demand, time, and savings deposits; lending; ATM processing; and investment management and trust services. Operations are managed and financial performance is evaluated on a corporate-wide basis. Accordingly, all of the Company's banking operations are considered by Management to be aggregated in one reportable operating segment.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents For the purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand, amounts due from banks and federal funds sold. At December 31, 2017 , the Company had a contractual clearing balance of $500,000 and a reserve balance requirement of $2,654,000 at the Federal Reserve Bank, which are satisfied by both cash on hand at branches and balances held at the Federal Reserve Bank of Boston. The Company maintains a portion of its cash in bank deposit accounts which, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant risk with respect to these accounts.

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities The following tables summarize the amortized cost and estimated fair value of investment securities at December 31, 2017 and 2016 : Amortized Unrealized Unrealized Fair Value As of December 31, 2017 Cost Gains Losses (Estimated) Securities available for sale Mortgage-backed securities $ 293,689,000 $ 722,000 $ (4,422,000 ) $ 289,989,000 State and political subdivisions 6,860,000 16,000 (107,000 ) 6,769,000 Other equity securities 3,296,000 121,000 (3,000 ) 3,414,000 $ 303,845,000 $ 859,000 $ (4,532,000 ) $ 300,172,000 Securities to be held to maturity U.S. Government-sponsored agencies $ 11,155,000 $ — $ (180,000 ) $ 10,975,000 Mortgage-backed securities 23,284,000 568,000 (128,000 ) 23,724,000 State and political subdivisions 217,828,000 3,931,000 (1,103,000 ) 220,656,000 Corporate securities 4,300,000 — — 4,300,000 $ 256,567,000 $ 4,499,000 $ (1,411,000 ) $ 259,655,000 Restricted equity securities Federal Home Loan Bank Stock $ 9,321,000 $ — $ — $ 9,321,000 Federal Reserve Bank Stock 1,037,000 — — 1,037,000 $ 10,358,000 $ — $ — $ 10,358,000 Amortized Unrealized Unrealized Fair Value As of December 31, 2016 Cost Gains Losses (Estimated) Securities available for sale Mortgage-backed securities $ 282,397,000 $ 1,334,000 $ (3,127,000 ) $ 280,604,000 State and political subdivisions 16,183,000 475,000 (176,000 ) 16,482,000 Other equity securities 3,274,000 63,000 (7,000 ) 3,330,000 $ 301,854,000 $ 1,872,000 $ (3,310,000 ) $ 300,416,000 Securities to be held to maturity U.S. Government-sponsored agencies $ 11,943,000 $ 35,000 $ (233,000 ) $ 11,745,000 Mortgage-backed securities 31,201,000 967,000 (147,000 ) 32,021,000 State and political subdivisions 179,384,000 1,971,000 (3,884,000 ) 177,471,000 Corporate securities 4,300,000 — — 4,300,000 $ 226,828,000 $ 2,973,000 $ (4,264,000 ) $ 225,537,000 Restricted equity securities Federal Home Loan Bank Stock $ 10,893,000 $ — $ — $ 10,893,000 Federal Reserve Bank Stock 1,037,000 — — 1,037,000 $ 11,930,000 $ — $ — $ 11,930,000 The following table summarizes the contractual maturities of investment securities at December 31, 2017 : Securities available for sale Securities to be held to maturity Amortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated) Due in 1 year or less $ 111,000 $ 112,000 $ 635,000 $ 637,000 Due in 1 to 5 years 841,000 842,000 18,059,000 18,164,000 Due in 5 to 10 years 29,003,000 29,177,000 37,182,000 37,719,000 Due after 10 years 270,594,000 266,627,000 200,691,000 203,135,000 Equity securities 3,296,000 3,414,000 — — $ 303,845,000 $ 300,172,000 $ 256,567,000 $ 259,655,000 The following table summarizes the contractual maturities of investment securities at December 31, 2016 : Securities available for sale Securities to be held to maturity Amortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated) Due in 1 year or less $ 253,000 $ 253,000 $ 906,000 $ 913,000 Due in 1 to 5 years 2,251,000 2,298,000 13,451,000 13,714,000 Due in 5 to 10 years 21,043,000 21,505,000 41,588,000 42,448,000 Due after 10 years 275,033,000 273,030,000 170,883,000 168,462,000 Equity securities 3,274,000 3,330,000 — — $ 301,854,000 $ 300,416,000 $ 226,828,000 $ 225,537,000 At December 31, 2017 , securities with a fair value of $231,516,000 were pledged to secure borrowings from the Federal Home Loan Bank of Boston, public deposits, repurchase agreements, and for other purposes as required by law. This compares to securities with a fair value of $222,328,000 as of December 31, 2016 pledged for the same purposes. Gains and losses on the sale of securities available for sale are computed by subtracting the amortized cost at the time of sale from the security's selling price, net of accrued interest to be received. The following table shows securities gains and losses for 2017 , 2016 and 2015 : 2017 2016 2015 Proceeds from sales of securities $ 15,587,000 $ 10,309,000 $ 35,468,000 Gross realized gains 471,000 673,000 1,399,000 Gross realized losses — — — Net gain $ 471,000 $ 673,000 $ 1,399,000 Related income taxes $ 165,000 $ 236,000 $ 490,000 Management reviews securities with unrealized losses for other than temporary impairment. As of December 31, 2017 , there were 241 securities with unrealized losses held in the Company's portfolio. These securities were temporarily impaired as a result of changes in interest rates reducing their fair value, of which 157 had been temporarily impaired for 12 months or more. At the present time, there have been no material changes in the credit quality of these securities resulting in other than temporary impairment, and in Management's opinion, no additional write-down for other-than-temporary impairment is warranted. Information regarding securities temporarily impaired as of December 31, 2017 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized As of December 31, 2017 Value Losses Value Losses Value Losses U.S. Government-sponsored agencies $ 7,161,000 $ (94,000 ) $ 3,814,000 $ (86,000 ) $ 10,975,000 $ (180,000 ) Mortgage-backed securities 132,025,000 (1,857,000 ) 101,707,000 (2,693,000 ) 233,732,000 (4,550,000 ) State and political subdivisions 9,425,000 (149,000 ) 38,864,000 (1,061,000 ) 48,289,000 (1,210,000 ) Other equity securities — — 9,000 (3,000 ) 9,000 (3,000 ) $ 148,611,000 $ (2,100,000 ) $ 144,394,000 $ (3,843,000 ) $ 293,005,000 $ (5,943,000 ) As of December 31, 2016 , there were 299 securities with unrealized losses held in the Company's portfolio. These securities were temporarily impaired as a result of changes in interest rates reducing their fair value, of which 15 had been temporarily impaired for 12 months or more. Information regarding securities temporarily impaired as of December 31, 2016 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized As of December 31, 2016 Value Losses Value Losses Value Losses U.S. Government-sponsored agencies $ 6,642,000 $ (233,000 ) $ — $ — $ 6,642,000 $ (233,000 ) Mortgage-backed securities 197,528,000 (3,090,000 ) 2,905,000 (184,000 ) 200,433,000 (3,274,000 ) State and political subdivisions 72,348,000 (4,060,000 ) — — 72,348,000 (4,060,000 ) Other equity securities — — 128,000 (7,000 ) 128,000 (7,000 ) $ 276,518,000 $ (7,383,000 ) $ 3,033,000 $ (191,000 ) $ 279,551,000 $ (7,574,000 ) During the third quarter of 2014, the Company transferred securities with a total amortized cost of $89,780,000 and a corresponding fair value of $89,757,000 from available for sale to held to maturity. The net unrealized loss, net of taxes, on these securities at the date of the transfer was $15,000 . The net unrealized holding loss at the time of transfer continues to be reported in accumulated other comprehensive income (loss), net of tax and is amortized over the remaining lives of the securities as an adjustment of the yield. The amortization of the net unrealized loss reported in accumulated other comprehensive income (loss) will offset the effect on interest income of the discount for the transferred securities. The remaining unamortized balance of the net unrealized losses for the securities transferred from available for sale to held to maturity was $174,000 at December 31, 2017 . These securities were transferred as a part of the Company's overall investment and balance sheet strategies. The Bank is a member of the Federal Home Loan Bank ("FHLB") of Boston, a cooperatively owned wholesale bank for housing and finance in the six New England States. As a requirement of membership in the FHLB, the Bank must own a minimum required amount of FHLB stock, calculated periodically based primarily on its level of borrowings from the FHLB. The Bank uses the FHLB for much of its wholesale funding needs. As of December 31, 2017 and 2016 , the Bank's investment in FHLB stock totaled $9,321,000 and $10,893,000 , respectively. FHLB stock is a restricted equity security and therefore is reported at cost, which equals par value. The Company periodically evaluates its investment in FHLB stock for impairment based on, among other factors, the capital adequacy of the FHLB and its overall financial condition. No impairment losses have been recorded through December 31, 2017 . The Bank will continue to monitor its investment in FHLB stock.

Mortgage Servicing Rights

Mortgage Servicing Rights	12 Months Ended
	Dec. 31, 2017
Transfers and Servicing [Abstract]
Mortgage Servicing Rights	Mortgage Servicing Rights At December 31, 2017 and 2016 , the Bank serviced loans for others totaling $260,258,000 and $250,083,000 , respectively. Net gains from the sale of loans totaled $737,000 in 2017 , $1,211,000 in 2016 , and $714,000 in 2015 . In 2017 , mortgage servicing rights of $567,000 were capitalized and amortization for the year totaled $362,000 . At December 31, 2017 , mortgage servicing rights had a fair value of $2,321,000 . In 2016 , mortgage servicing rights of $554,000 were capitalized and amortization for the year totaled $459,000 . At December 31, 2016 , mortgage servicing rights had a fair value of $1,696,000 . Financial Accounting Standards Board ("FASB") Accounting Standards Codification (the "Codification" or "ASC") Topic 860, "Transfers and Servicing", requires all separately recognized servicing assets and servicing liabilities to be initially measured at fair value, if practicable. Servicing assets and servicing liabilities are reported using the amortization method or the fair value measurement method. In evaluating the carrying values of mortgage servicing rights, the Company obtains third party valuations based on loan level data including note rate, type and term of the underlying loans. The model utilizes several assumptions, the most significant of which are loan prepayments, calculated using a three -month moving average of weekly prepayment data published by the Public Securities Association (PSA) and modeled against the serviced loan portfolio, and the discount rate to discount future cash flows. As of December 31, 2017 , the prepayment assumption using the PSA model was 167 , which translates into an anticipated annual prepayment rate of 10.00% . The discount rate is 9.50% . Other assumptions include delinquency rates, foreclosure rates, servicing cost inflation, and annual unit loan cost. All assumptions are adjusted periodically to reflect current circumstances. Amortization of mortgage servicing rights, as well as write-offs due to prepayments of the related mortgage loans, are recorded as a charge against mortgage servicing fee income. Mortgage servicing rights are included in other assets and detailed in the following table: As of December 31, 2017 2016 Mortgage servicing rights $ 5,428,000 $ 5,901,000 Accumulated amortization (4,160,000 ) (4,680,000 ) Impairment reserve — (108,000 ) $ 1,268,000 $ 1,113,000

Loans

Loans	12 Months Ended
	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Abstract]
Loans	Loans The following table shows the composition of the Company's loan portfolio as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 Commercial Real estate $ 323,809,000 27.8 % $ 302,506,000 28.2 % Construction 38,056,000 3.3 % 25,406,000 2.4 % Other 181,528,000 15.6 % 150,769,000 14.1 % Municipal 33,391,000 2.9 % 27,056,000 2.5 % Residential Term 432,661,000 37.1 % 411,469,000 38.4 % Construction 17,868,000 1.5 % 18,303,000 1.7 % Home equity line of credit 111,302,000 9.6 % 110,907,000 10.4 % Consumer 25,524,000 2.2 % 25,110,000 2.3 % Total loans $ 1,164,139,000 100.0 % $ 1,071,526,000 100.0 % Loan balances include net deferred loan costs of $5,748,000 in 2017 and $4,921,000 in 2016 . Pursuant to collateral agreements, qualifying first mortgage loans, which were valued at $239,805,000 and $257,122,000 at December 31, 2017 and 2016 , respectively, were used to collateralize borrowings from the Federal Home Loan Bank of Boston. In addition, commercial, construction and home equity loans totaling $290,247,000 at December 31, 2017 and $261,463,000 at December 31, 2016 , were used to collateralize a standby line of credit at the Federal Reserve Bank of Boston that is currently unused. At December 31, 2017 and 2016 , non-accrual loans were $14,736,000 and $7,774,000 , respectively. For the years ended December 31, 2017 , 2016 and 2015 , interest income which would have been recognized on these loans, if interest had been accrued, was $496,000 , $288,000 , and $369,000 , respectively. Loans more than 90 days past due accruing interest totaled $445,000 at December 31, 2017 and $777,000 at December 31, 2016 . The Company continues to accrue interest on these loans because it believes collection of principal and interest is reasonably assured. Loans to directors, officers and employees totaled $34,715,000 at December 31, 2017 and $34,889,000 at December 31, 2016 . A summary of loans to directors and executive officers is as follows: For the years ended December 31, 2017 2016 Balance at beginning of year $ 23,293,000 $ 20,401,000 New loans 867,000 6,278,000 Repayments (1,863,000 ) (3,386,000 ) Balance at end of year $ 22,297,000 $ 23,293,000 Information on the past-due status of loans as of December 31, 2017 , is presented in the following table: 30-59 Days Past Due 60-89 Days Past Due 90+ Days Past Due All Past Due Current Total 90+ Days & Accruing Commercial Real estate $ 574,000 $ 80,000 $ 220,000 $ 874,000 $ 322,935,000 $ 323,809,000 $ — Construction — — — — 38,056,000 38,056,000 — Other 542,000 6,663,000 574,000 7,779,000 173,749,000 181,528,000 — Municipal — — — — 33,391,000 33,391,000 — Residential Term 1,031,000 4,372,000 2,256,000 7,659,000 425,002,000 432,661,000 436,000 Construction 101,000 370,000 — 471,000 17,397,000 17,868,000 — Home equity line of credit 537,000 445,000 725,000 1,707,000 109,595,000 111,302,000 — Consumer 159,000 18,000 9,000 186,000 25,338,000 25,524,000 9,000 Total $ 2,944,000 $ 11,948,000 $ 3,784,000 $ 18,676,000 $ 1,145,463,000 $ 1,164,139,000 $ 445,000 Information on the past-due status of loans as of December 31, 2016 , is presented in the following table: 30-59 Days Past Due 60-89 Days Past Due 90+ Days Past Due All Past Due Current Total 90+ Days & Accruing Commercial Real estate $ 1,039,000 $ 22,000 $ 2,415,000 $ 3,476,000 $ 299,030,000 $ 302,506,000 $ 753,000 Construction — — — — 25,406,000 25,406,000 — Other 202,000 33,000 796,000 1,031,000 149,738,000 150,769,000 20,000 Municipal — — — — 27,056,000 27,056,000 — Residential Term 631,000 3,970,000 1,802,000 6,403,000 405,066,000 411,469,000 — Construction — — — — 18,303,000 18,303,000 — Home equity line of credit 704,000 157,000 703,000 1,564,000 109,343,000 110,907,000 — Consumer 135,000 45,000 4,000 184,000 24,926,000 25,110,000 4,000 Total $ 2,711,000 $ 4,227,000 $ 5,720,000 $ 12,658,000 $ 1,058,868,000 $ 1,071,526,000 $ 777,000 For all classes, loans are placed on non-accrual status when, based on current information and events, it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the loan agreement or when principal and interest is 90 days or more past due unless the loan is both well secured and in the process of collection (in which case the loan may continue to accrue interest in spite of its past due status). A loan is "well secured" if it is secured (1) by collateral in the form of liens on or pledges of real or personal property, including securities, that have a realizable value sufficient to discharge the debt (including accrued interest) in full, or (2) by the guarantee of a financially responsible party. A loan is "in the process of collection" if collection of the loan is proceeding in due course either (1) through legal action, including judgment enforcement procedures, or, (2) in appropriate circumstances, through collection efforts not involving legal action which are reasonably expected to result in repayment of the debt or in its restoration to a current status in the near future. Information on nonaccrual loans as of December 31, 2017 and 2016 is presented in the following table: As of December 31, 2017 2016 Commercial Real estate $ 752,000 $ 1,907,000 Construction — — Other 9,357,000 964,000 Municipal — — Residential Term 3,778,000 4,060,000 Construction — — Home equity line of credit 833,000 843,000 Consumer 16,000 — Total $ 14,736,000 $ 7,774,000 Information regarding impaired loans is as follows: For the years ended December 31, 2017 2016 2015 Average investment in impaired loans $ 29,108,000 $ 28,217,000 $ 32,698,000 Interest income recognized on impaired loans, all on cash basis 784,000 1,104,000 1,220,000 As of December 31, 2017 2016 Balance of impaired loans $ 31,392,000 $ 27,583,000 Less portion for which no allowance for loan losses is allocated (18,023,000 ) (19,716,000 ) Portion of impaired loan balance for which an allowance for loan losses is allocated $ 13,369,000 $ 7,867,000 Portion of allowance for loan losses allocated to the impaired loan balance $ 1,812,000 $ 974,000 Impaired loans include restructured loans and loans placed on non-accrual. These loans are measured at the present value of expected future cash flows discounted at the loan's effective interest rate or at the fair value of the collateral if the loan is collateral dependent. If the measure of an impaired loan is lower than the recorded investment in the loan and estimated selling costs, a specific reserve is established for the difference, or, in certain situations, if the measure of an impaired loan is lower than the recorded investment in the loan and estimated selling costs, the difference is written off. A breakdown of impaired loans by category as of December 31, 2017 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 3,791,000 $ 3,996,000 $ — $ 5,124,000 $ 164,000 Construction 741,000 741,000 — 62,000 38,000 Other 2,591,000 2,671,000 — 1,908,000 36,000 Municipal — — — — — Residential Term 9,769,000 10,909,000 — 10,770,000 297,000 Construction — — — — — Home equity line of credit 1,115,000 1,429,000 — 1,351,000 18,000 Consumer 16,000 29,000 — 12,000 — $ 18,023,000 $ 19,775,000 $ — $ 19,227,000 $ 553,000 With an Allowance Recorded Commercial Real estate $ 3,999,000 $ 4,116,000 $ 224,000 $ 4,460,000 $ 152,000 Construction — — — 699,000 — Other 7,327,000 7,371,000 1,309,000 2,584,000 — Municipal — — — — — Residential Term 1,979,000 2,144,000 255,000 2,106,000 79,000 Construction — — — — — Home equity line of credit 64,000 67,000 24,000 32,000 — Consumer — — — — — $ 13,369,000 $ 13,698,000 $ 1,812,000 $ 9,881,000 $ 231,000 Total Commercial Real estate $ 7,790,000 $ 8,112,000 $ 224,000 $ 9,584,000 $ 316,000 Construction 741,000 741,000 — 761,000 38,000 Other 9,918,000 10,042,000 1,309,000 4,492,000 36,000 Municipal — — — — — Residential Term 11,748,000 13,053,000 255,000 12,876,000 376,000 Construction — — — — — Home equity line of credit 1,179,000 1,496,000 24,000 1,383,000 18,000 Consumer 16,000 29,000 — 12,000 — $ 31,392,000 $ 33,473,000 $ 1,812,000 $ 29,108,000 $ 784,000 Substantially all interest income recognized on impaired loans for all classes of financing receivables was recognized on a cash basis as received. A breakdown of impaired loans by category as of December 31, 2016 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 5,201,000 $ 5,614,000 $ — $ 6,252,000 $ 220,000 Construction — — — 32,000 — Other 1,671,000 1,852,000 — 1,074,000 86,000 Municipal — — — — — Residential Term 11,483,000 12,654,000 — 11,025,000 442,000 Construction — — — — — Home equity line of credit 1,361,000 1,733,000 — 1,213,000 33,000 Consumer — — — 9,000 — $ 19,716,000 $ 21,853,000 $ — $ 19,605,000 $ 781,000 With an Allowance Recorded Commercial Real estate $ 4,820,000 $ 4,925,000 $ 505,000 $ 4,153,000 $ 186,000 Construction 763,000 763,000 100,000 816,000 36,000 Other 72,000 72,000 39,000 317,000 — Municipal — — — — — Residential Term 2,186,000 2,328,000 304,000 3,209,000 101,000 Construction — — — — — Home equity line of credit 26,000 28,000 26,000 69,000 — Consumer — — — 48,000 — $ 7,867,000 $ 8,116,000 $ 974,000 $ 8,612,000 $ 323,000 Total Commercial Real estate $ 10,021,000 $ 10,539,000 $ 505,000 $ 10,405,000 $ 406,000 Construction 763,000 763,000 100,000 848,000 36,000 Other 1,743,000 1,924,000 39,000 1,391,000 86,000 Municipal — — — — — Residential Term 13,669,000 14,982,000 304,000 14,234,000 543,000 Construction — — — — — Home equity line of credit 1,387,000 1,761,000 26,000 1,282,000 33,000 Consumer — — — 57,000 — $ 27,583,000 $ 29,969,000 $ 974,000 $ 28,217,000 $ 1,104,000 A breakdown of impaired loans by category as of December 31, 2015 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 7,173,000 $ 7,496,000 $ — $ 8,990,000 $ 301,000 Construction 30,000 30,000 — 3,000 1,000 Other 1,163,000 1,210,000 — 1,893,000 76,000 Municipal — — — — — Residential Term 11,122,000 12,157,000 — 10,480,000 415,000 Construction — — — — — Home equity line of credit 1,401,000 2,054,000 — 1,400,000 43,000 Consumer — — — 42,000 3,000 $ 20,889,000 $ 22,947,000 $ — $ 22,808,000 $ 839,000 With an Allowance Recorded Commercial Real estate $ 3,544,000 $ 3,627,000 $ 89,000 $ 3,066,000 $ 149,000 Construction 996,000 996,000 302,000 1,153,000 44,000 Other 71,000 77,000 8,000 256,000 5,000 Municipal — — — — — Residential Term 3,966,000 4,193,000 326,000 5,228,000 180,000 Construction — — — — — Home equity line of credit 65,000 66,000 29,000 187,000 3,000 Consumer — — — — — $ 8,642,000 $ 8,959,000 $ 754,000 $ 9,890,000 $ 381,000 Total Commercial Real estate $ 10,717,000 $ 11,123,000 $ 89,000 $ 12,056,000 $ 450,000 Construction 1,026,000 1,026,000 302,000 1,156,000 45,000 Other 1,234,000 1,287,000 8,000 2,149,000 81,000 Municipal — — — — — Residential Term 15,088,000 16,350,000 326,000 15,708,000 595,000 Construction — — — — — Home equity line of credit 1,466,000 2,120,000 29,000 1,587,000 46,000 Consumer — — — 42,000 3,000 $ 29,531,000 $ 31,906,000 $ 754,000 $ 32,698,000 $ 1,220,000 Troubled Debt Restructured A TDR constitutes a restructuring of debt if the Company, for economic or legal reasons related to the borrower's financial difficulties, grants a concession to the borrower that it would not otherwise consider. To determine whether or not a loan should be classified as a TDR, Management evaluates a loan based upon the following criteria: • The borrower demonstrates financial difficulty; common indicators include past due status with bank obligations, substandard credit bureau reports, or an inability to refinance with another lender, and • The Company has granted a concession; common concession types include maturity date extension, interest rate adjustments to below market pricing, and deferment of payments. As of December 31, 2017 , the Company had 62 loans with a value of $17,801,000 that have been classified as TDRs. This compares to 71 loans with a value of $21,526,000 classified as TDRs as of December 31, 2016 . The impairment carried as a specific reserve in the allowance for loan losses is calculated by present valuing the cashflow modification on the loan, or, for collateral-dependent loans, using the fair value of the collateral less costs to sell. The following table shows TDRs by class and the specific reserve as of December 31, 2017 : Number of Loans Balance Specific Reserves Commercial Real estate 8 $ 7,038,000 $ 90,000 Construction 1 741,000 — Other 4 561,000 — Municipal — — — Residential Term 46 8,948,000 233,000 Construction — — — Home equity line of credit 3 513,000 — Consumer — — — 62 $ 17,801,000 $ 323,000 The following table shows TDRs by class and the specific reserve as of December 31, 2016 : Number of Loans Balance Specific Reserves Commercial Real estate 10 $ 8,937,000 $ 375,000 Construction 1 763,000 100,000 Other 5 779,000 — Municipal — — — Residential Term 52 10,503,000 261,000 Construction — — — Home equity line of credit 3 544,000 — Consumer — — — 71 $ 21,526,000 $ 736,000 As of December 31, 2017 , 12 of the loans classified as TDRs with a total balance of $1,407,000 were more than 30 days past due. None of these loans had been placed on TDR status in the previous 12 months. The following table shows past-due TDRs by class and the associated specific reserves included in the allowance for loan losses as of December 31, 2017 : Number of Loans Balance Specific Reserves Commercial Real estate — $ — $ — Construction — — — Other — — — Municipal — — — Residential Term 11 1,240,000 44,000 Construction — — — Home equity line of credit 1 167,000 — Consumer — — — 12 $ 1,407,000 $ 44,000 As of December 31, 2016 , 12 of the loans classified as TDRs with a total balance of $2,303,000 were more than 30 days past due. None of these loans had been placed on TDR status in the previous 12 months. The following table shows past-due TDRs by class and the associated specific reserves included in the allowance for loan losses as of December 31, 2016 : Number of Loans Balance Specific Reserves Commercial Real estate 1 $ 822,000 $ 264,000 Construction — — — Other — — — Municipal — — — Residential Term 10 1,314,000 26,000 Construction — — — Home equity line of credit 1 167,000 — Consumer — — — 12 $ 2,303,000 $ 290,000 For the years ended December 31, 2017 and 2016 , no loans were placed on TDR status. As of December 31, 2017 , Management is aware of four loans classified as TDRs that are involved in bankruptcy with an outstanding balance of $688,000 . As of December 31, 2017 , there were nine loans with an outstanding balance of $1,145,000 that were classified as TDRs and were on non-accrual status, three of which, with an outstanding balance of $458,000 , were in the process of foreclosure. Residential Mortgage Loans in Process of Foreclosure As of December 31, 2017 , there were 12 mortgage loans collateralized by residential real estate in the process of foreclosure with a total balance of $1,777,000 ; this compares to 15 mortgage loans collateralized by residential real estate in the process of foreclosure with a total balance of $2,058,000 as of December 31, 2016 .

Allowance for Loan Losses

Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for Loan Losses	Allowance for Loan Losses The Company provides for loan losses through the establishment of an allowance for loan losses which represents an estimated reserve for existing losses in the loan portfolio. A systematic methodology is used for determining the allowance that includes a quarterly review process, risk rating changes, and adjustments to the allowance. The loan portfolio is classified in eight classes and credit risk is evaluated separately in each class. The loan portfolio is classified in eight classes and credit risk is evaluated separately in each class. Major risk characteristics relevant to each portfolio segment are as follows: Commercial Real Estate - Commercial real estate loans are impacted by factors such as competitive market forces, vacancy rates, cap rates, net operating incomes, lease renewals and overall economic demand. In addition, loans in the recreational and tourism sector can be affected by weather conditions, such as unseasonably low winter snowfalls. Commercial real estate lending also carries a higher degree of environmental risk than other real estate lending. Commercial Construction - Commercial construction loans are impacted by factors similar to those for commercial real estate loans in addition to risks related to contractor financial capacity and ability to complete a project within acceptable time frames and within budget. Commercial Other - A weakened economy, soft consumer spending, and the rising cost of labor or raw materials are examples of issues that can impact the credit quality in this segment. Municipal Loans - The overall health of the economy, including unemployment rates and housing prices, has an impact on the credit quality of this segment. Residential Real Estate Term - The overall health of the economy, including unemployment rates and housing prices, has an impact on the credit quality of this segment. Residential Real Estate Construction - The overall health of the economy, including unemployment rates and housing prices, has an impact on the credit quality of this segment. Residential construction loans are impacted by factors similar to those for residential real estate term loans in addition to risks related to contractor financial capacity and ability to complete a project within acceptable time frames and within budget. Home Equity Line of Credit - The overall health of the economy, including unemployment rates and housing prices, has an impact on the credit quality of this segment. Consumer - The overall health of the economy, including unemployment rates, has an impact on the credit quality of this segment. The appropriate level of the allowance is evaluated continually based on a review of significant loans, with a particular emphasis on nonaccruing, past due, and other loans that may require special attention. Other factors include general conditions in local and national economies; loan portfolio composition and asset quality indicators; and internal factors such as changes in underwriting policies, credit administration practices, experience, ability and depth of lending management, among others. The allowance consists of four elements: (1) specific reserves for loans evaluated individually for impairment; (2) general reserves for each portfolio segment based on historical loan loss experience, (3) qualitative reserves judgmentally adjusted for local and national economic conditions, concentrations, portfolio composition, volume and severity of delinquencies and nonaccrual loans, trends of criticized and classified loans, changes in credit policies and underwriting standards, credit administration practices, and other factors as applicable for each portfolio segment; and (4) unallocated reserves. All outstanding loans are considered in evaluating the appropriateness of the allowance. The following table summarizes the composition of the allowance for loan losses, by class of financing receivable and allowance, as of December 31, 2017 and 2016 : As of December 31, 2017 2016 Allowance for Loans Evaluated Individually for Impairment Commercial Real estate $ 224,000 $ 505,000 Construction — 100,000 Other 1,309,000 39,000 Municipal — — Residential Term 255,000 304,000 Construction — — Home equity line of credit 24,000 26,000 Consumer — — Total $ 1,812,000 $ 974,000 Allowance for Loans Evaluated Collectively for Impairment Commercial Real estate $ 3,648,000 $ 3,483,000 Construction 434,000 296,000 Other 2,049,000 1,741,000 Municipal 20,000 18,000 Residential Term 875,000 984,000 Construction 36,000 44,000 Home equity line of credit 668,000 781,000 Consumer 545,000 559,000 Unallocated 642,000 1,258,000 Total $ 8,917,000 $ 9,164,000 Total Allowance for Loan Losses Commercial Real estate $ 3,872,000 $ 3,988,000 Construction 434,000 396,000 Other 3,358,000 1,780,000 Municipal 20,000 18,000 Residential Term 1,130,000 1,288,000 Construction 36,000 44,000 Home equity line of credit 692,000 807,000 Consumer 545,000 559,000 Unallocated 642,000 1,258,000 Total $ 10,729,000 $ 10,138,000 The allowance consists of four elements: (1) specific reserves for loans evaluated individually for impairment; (2) general reserves for each portfolio segment based on historical loan loss experience; (3) qualitative reserves judgmentally adjusted for local and national economic conditions, concentrations, portfolio composition, volume and severity of delinquencies and nonaccrual loans, trends of criticized and classified loans, changes in credit policies, and underwriting standards, credit administration practices, and other factors as applicable for each portfolio segment; and (4) unallocated reserves. All outstanding loans are considered in evaluating the appropriateness of the allowance. A breakdown of the allowance for loan losses as of December 31, 2017 and 2016 , by class of financing receivable and allowance element, is presented in the following tables: As of December 31, 2017 Specific Reserves on Loans Evaluated Individually for Impairment General Reserves on Loans Based on Historical Loss Experience Reserves for Qualitative Factors Unallocated Reserves Total Reserves Commercial Real estate $ 224,000 $ 1,285,000 $ 2,363,000 $ — $ 3,872,000 Construction — 153,000 281,000 — 434,000 Other 1,309,000 723,000 1,326,000 — 3,358,000 Municipal — — 20,000 — 20,000 Residential Term 255,000 311,000 564,000 — 1,130,000 Construction — 13,000 23,000 — 36,000 Home equity line of credit 24,000 297,000 371,000 — 692,000 Consumer — 251,000 294,000 — 545,000 Unallocated — — — 642,000 642,000 $ 1,812,000 $ 3,033,000 $ 5,242,000 $ 642,000 $ 10,729,000 As of December 31, 2016 Specific Reserves on Loans Evaluated Individually for Impairment General Reserves on Loans Based on Historical Loss Experience Reserves for Qualitative Factors Unallocated Reserves Total Reserves Commercial Real estate $ 505,000 $ 1,471,000 $ 2,012,000 $ — $ 3,988,000 Construction 100,000 125,000 171,000 — 396,000 Other 39,000 735,000 1,006,000 — 1,780,000 Municipal — — 18,000 — 18,000 Residential Term 304,000 563,000 421,000 — 1,288,000 Construction — 25,000 19,000 — 44,000 Home equity line of credit 26,000 444,000 337,000 — 807,000 Consumer — 328,000 231,000 — 559,000 Unallocated — — — 1,258,000 1,258,000 $ 974,000 $ 3,691,000 $ 4,215,000 $ 1,258,000 $ 10,138,000 Qualitative adjustment factors are taken into consideration when determining reserve estimates. These adjustment factors are based upon our evaluation of various current conditions, including those listed below. • General economic conditions. • Credit quality trends with emphasis on loan delinquencies, nonaccrual levels and classified loans. • Recent loss experience in particular segments of the portfolio. • Loan volumes and concentrations, including changes in mix. • Other factors, including changes in quality of the loan origination; loan policy changes; changes in credit risk management processes; Bank regulatory and external loan review examination results. The qualitative portion of the allowance for loan losses was 0.45% of related loans as of December 31, 2017 , compared to 0.39% of related loans as of December 31, 2016 . The qualitative portion increased $1,027,000 between December 31, 2016 and December 31, 2017 due to loan growth, slippage in certain economic factors, and an increase in nonaccrual loans. The unallocated component totaled $642,000 at December 31, 2017 , or 6.0% of the total reserve. This compares to $1,258,000 or 12.4% as of December 31, 2016 . The change results from reduced imprecision owing to additional information related to certain loan relationships having been obtained and analyzed. The allowance for loan losses as a percent of total loans stood at 0.92% as of December 31, 2017 , compared to 0.95% of total loans as of December 31, 2016 . Commercial loans are comprised of three major classes; commercial real estate loans, commercial construction loans and other commercial loans. Commercial real estate loans consist of mortgage loans to finance investments in real property such as multi-family residential, commercial/retail, office, industrial, hotels, educational and other specific or mixed use properties. Commercial real estate loans are typically written with amortizing payment structures. Collateral values are determined based on appraisals and evaluations in accordance with established policy and regulatory guidelines. Commercial real estate loans typically have a loan-to-value ratio of up to 80% based upon current valuation information at the time the loan is made. Commercial real estate loans are primarily paid by the cash flow generated from the real property, such as operating leases, rents, or other operating cash flows from the borrower. Commercial construction loans consist of loans to finance construction in a mix of owner- and non-owner occupied commercial real estate properties. Commercial construction loans typically have maturities of less than two years . Payment structures during the construction period are typically on an interest only basis, although principal payments may be established depending on the type of construction project being financed. During the construction phase, commercial construction loans are primarily paid by cash flow generated from the construction project or other operating cash flows from the borrower or guarantors, if applicable. At the end of the construction period, loan repayment typically comes from a third party source in the event that the Bank will not be providing permanent term financing. Collateral valuation and loan-to-value guidelines follow those for commercial real estate loans. Other commercial loans consist of revolving and term loan obligations extended to business and corporate enterprises for the purpose of financing working capital and or capital investment. Collateral generally consists of pledges of business assets including, but not limited to, accounts receivable, inventory, plant and equipment, and/or real estate, if applicable. Commercial loans are primarily paid by the operating cash flow of the borrower. Commercial loans may be secured or unsecured. Municipal loans are comprised of loans to municipalities in Maine for capitalized expenditures, construction projects or tax-anticipation notes. All municipal loans are considered general obligations of the municipality and are collateralized by the taxing ability of the municipality for repayment of debt. Residential loans are comprised of two classes: term loans and construction loans. Residential term loans consist of residential real estate loans held in the Bank's loan portfolio made to borrowers who demonstrate the ability to make scheduled payments with full consideration to underwriting factors. Borrower qualifications include favorable credit history combined with supportive income requirements and loan-to-value ratios within established policy and regulatory guidelines. Collateral values are determined based on appraisals and evaluations in accordance with established policy and regulatory guidelines. Residential loans typically have a loan-to-value ratio of up to 80% based on appraisal information at the time the loan is made. Collateral consists of mortgage liens on one- to four-family residential properties. Loans are offered with fixed or adjustable rates with amortization terms of up to thirty years . Residential construction loans typically consist of loans for the purpose of constructing single family residences to be owned and occupied by the borrower. Borrower qualifications include favorable credit history combined with supportive income requirements and loan-to-value ratios within established policy and regulatory guidelines. Residential construction loans normally have construction terms of one year or less and payment during the construction term is typically on an interest only basis from sources including interest reserves, borrower liquidity and/or income. Residential construction loans will typically convert to permanent financing from the Bank or have another financing commitment in place from an acceptable mortgage lender. Collateral valuation and loan-to-value guidelines are consistent with those for residential term loans. Home equity lines of credit are made to qualified individuals and are secured by senior or junior mortgage liens on owner-occupied one- to four-family homes, condominiums, or vacation homes. The home equity line of credit typically has a variable interest rate and is billed as interest-only payments during the draw period. At the end of the draw period, the home equity line of credit is billed as a percentage of the principal balance plus all accrued interest. Loan maturities are normally 300 months . Borrower qualifications include favorable credit history combined with supportive income requirements and combined loan-to- value ratios usually not exceeding 80% inclusive of priority liens. Collateral valuation guidelines follow those for residential real estate loans. Consumer loan products including personal lines of credit and amortizing loans made to qualified individuals for various purposes such as auto, recreational vehicles, debt consolidation, personal expenses or overdraft protection. Borrower qualifications include favorable credit history combined with supportive income and collateral requirements within established policy guidelines. Consumer loans may be secured or unsecured. Construction, land and land development loans, both commercial and residential, comprise a small portion of the portfolio, and at 34.4% of capital are below the regulatory guidance of 100.0% of capital at December 31, 2017. Construction loans and non- owner-occupied commercial real estate loans are at 129.2% of total capital at December 31, 2017 , below the regulatory limit of 300.0% of capital. The process of establishing the allowance with respect to the commercial loan portfolio begins when a Loan Officer or Senior Officer (or designate) initially assigns each loan a risk rating, using established credit criteria, which is reviewed and updated if necessary at least annually or when conditions may warrant a change in the assigned risk rating. Approximately 50% of the outstanding loans and commitments are subject to review and validation annually by an independent consulting firm. Additionally, commercial loan relationships with exposure greater than or equal to $500,000 and lines of credit greater than $250,000 are subject to review annually by the Bank's internal credit review function. The methodology employs Management's judgment as to the level of losses on existing loans based on internal review of the loan portfolio, including an analysis of a borrower's current financial position, and the consideration of current and anticipated economic conditions and their potential effects on specific borrowers and or lines of business. The risk rating system has eight levels, defined as follows: 1 Strong Credits rated "1" are characterized by borrowers fully responsible for the credit with excellent capacity to pay principal and interest. Loans rated "1" may be secured with acceptable forms of liquid collateral. 2 Above Average Credits rated "2" are characterized by borrowers that have better than average liquidity, capitalization, earnings and/or cash flow with a consistent record of solid financial performance. 3 Satisfactory Credits rated "3" are characterized by borrowers with favorable liquidity, profitability and financial condition with adequate cash flow to pay debt service. 4 Average Credits rated "4" are characterized by borrowers that present risk more than 1, 2 and 3 rated loans and merit an ordinary level of ongoing monitoring. Financial condition is on par or somewhat below industry averages while cash flow is generally adequate to meet debt service requirements. 5 Watch Credits rated "5" are characterized by borrowers that warrant greater monitoring due to financial condition or unresolved and identified risk factors. 6 Other Assets Especially Mentioned (OAEM) Loans in this category are currently supported but are potentially weak and constitute an undue and unwarranted credit risk, but not to the point of justifying a classification of substandard. OAEM have potential weaknesses which may, if not checked or corrected, weaken the asset or inadequately protect the Bank's credit position at some future date. 7 Substandard Loans in this category are inadequately supported by the current paying capacity of the borrower or of the collateral, if any. These loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. Substandard loans are characterized by the distinct possibility that the Bank may sustain some loss if deficiencies are not corrected. 8 Doubtful Loans classified "Doubtful" have the same weaknesses as those classified substandard with the added characteristic that the weaknesses make collection or liquidation in full, based on currently existing facts, conditions, and values, highly questionable and improbable. The possibility of loss is high, but because of certain important and reasonably specific pending factors which may work to the advantage and strengthening of the asset, its classification as an estimated loss is deferred until its more exact status may be determined. The following table summarizes the risk ratings for the Company's commercial construction, commercial real estate, commercial other and municipal loans as of December 31, 2017 : Commercial Real Estate Commercial Construction Commercial Other Municipal Loans All Risk- Rated Loans 1 Strong $ — $ — $ 1,586,000 $ — $ 1,586,000 2 Above average 12,534,000 40,000 5,776,000 32,673,000 51,023,000 3 Satisfactory 73,899,000 2,856,000 38,151,000 718,000 115,624,000 4 Average 173,956,000 22,446,000 84,360,000 — 280,762,000 5 Watch 41,652,000 12,714,000 33,934,000 — 88,300,000 6 OAEM 3,442,000 — 2,765,000 — 6,207,000 7 Substandard 18,203,000 — 14,956,000 — 33,159,000 8 Doubtful 123,000 — — — 123,000 Total $ 323,809,000 $ 38,056,000 $ 181,528,000 $ 33,391,000 $ 576,784,000 The following table summarizes the risk ratings for the Company's commercial construction, commercial real estate, commercial other and municipal loans as of December 31, 2016 : Commercial Real Estate Commercial Construction Commercial Other Municipal Loans All Risk- Rated Loans 1 Strong $ 2,000 $ — $ 850,000 $ — $ 852,000 2 Above average 13,981,000 49,000 8,934,000 25,527,000 48,491,000 3 Satisfactory 81,286,000 1,345,000 48,212,000 1,529,000 132,372,000 4 Average 139,421,000 16,506,000 65,146,000 — 221,073,000 5 Watch 43,181,000 7,349,000 16,864,000 — 67,394,000 6 OAEM 4,569,000 — 1,587,000 — 6,156,000 7 Substandard 20,066,000 157,000 9,176,000 — 29,399,000 8 Doubtful — — — — — Total $ 302,506,000 $ 25,406,000 $ 150,769,000 $ 27,056,000 $ 505,737,000 Commercial loans are generally charged off when all or a portion of the principal amount is determined to be uncollectible. This determination is based on circumstances specific to a borrower including repayment ability, analysis of collateral and other factors as applicable. Residential loans are comprised of two classes: term loans, which include traditional amortizing home mortgages, and construction loans, which include loans for owner-occupied residential construction. Residential loans typically have a 75% to 80% loan to value based upon current appraisal information at the time the loan is made. Home equity loans and lines of credit are typically written to the same underwriting standards. Consumer loans are primarily amortizing loans to individuals collateralized by automobiles, pleasure craft and recreation vehicles, typically with a maximum loan to value of 80% to 90% of the purchase price of the collateral. Consumer loans also include a small amount of unsecured short-term time notes to individuals. Residential loans, consumer loans and home equity lines of credit are segregated into homogeneous pools with similar risk characteristics. Trends and current conditions are analyzed and historical loss experience is adjusted accordingly. Quantitative and qualitative adjustment factors for these segments are consistent with those for the commercial and municipal classes. Certain loans in the residential, home equity lines of credit and consumer classes identified as having the potential for further deterioration are analyzed individually to confirm impairment status, and to determine the need for a specific reserve; however, there is no formal rating system used for these classes. Consumer loans greater than 120 days past due are generally charged off. Residential loans 90 days or more past due are placed on non-accrual status unless the loans are both well secured and in the process of collection. One-to four-family residential real estate loans and home equity loans are written down or charged-off no later than 180 days past due, or for residential real estate secured loans having a borrower in bankruptcy, within 60 days of receipt of notification of filing from the bankruptcy court, whichever is sooner. This is subject to completion of a current assessment of the value of the collateral with any outstanding loan balance in excess of the fair value of the property, less costs to sell, written down or charged-off. There were no changes to the Company's accounting policies or methodology used to estimate the allowance for loan losses during the year ended December 31, 2017 . The following tables present allowance for loan losses activity by class, allowance for loan loss balances by class and related loan balances by class for the years ended December 31, 2017 , 2016 and 2015 : For the year ended December 31, 2017 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,988,000 $ 396,000 $ 1,780,000 $ 18,000 $ 1,288,000 $ 44,000 $ 807,000 $ 559,000 $ 1,258,000 $ 10,138,000 Chargeoffs 587,000 — 212,000 — 456,000 — 28,000 335,000 — 1,618,000 Recoveries — — 49,000 — 40,000 — 11,000 109,000 — 209,000 Provision (credit) 471,000 38,000 1,741,000 2,000 258,000 (8,000 ) (98,000 ) 212,000 (616,000 ) 2,000,000 Ending balance $ 3,872,000 $ 434,000 $ 3,358,000 $ 20,000 $ 1,130,000 $ 36,000 $ 692,000 $ 545,000 $ 642,000 $ 10,729,000 Ending balance specifically evaluated for impairment $ 224,000 $ — $ 1,309,000 $ — $ 255,000 $ — $ 24,000 $ — $ — $ 1,812,000 Ending balance collectively evaluated for impairment $ 3,648,000 $ 434,000 $ 2,049,000 $ 20,000 $ 875,000 $ 36,000 $ 668,000 $ 545,000 $ 642,000 $ 8,917,000 Related loan balances: Ending balance $ 323,809,000 $ 38,056,000 $ 181,528,000 $ 33,391,000 $ 432,661,000 $ 17,868,000 $ 111,302,000 $ 25,524,000 $ — $ 1,164,139,000 Ending balance specifically evaluated for impairment $ 7,790,000 $ 741,000 $ 9,918,000 $ — $ 11,748,000 $ — $ 1,179,000 $ 16,000 $ — $ 31,392,000 Ending balance collectively evaluated for impairment $ 316,019,000 $ 37,315,000 $ 171,610,000 $ 33,391,000 $ 420,913,000 $ 17,868,000 $ 110,123,000 $ 25,508,000 $ — $ 1,132,747,000 For the year ended December 31, 2016 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,120,000 $ 580,000 $ 1,452,000 $ 17,000 $ 1,391,000 $ 24,000 $ 893,000 $ 566,000 $ 1,873,000 $ 9,916,000 Chargeoffs 294,000 75,000 376,000 — 379,000 — 147,000 450,000 — 1,721,000 Recoveries — 8,000 129,000 — 93,000 — 5,000 108,000 — 343,000 Provision (credit) 1,162,000 (117,000 ) 575,000 1,000 183,000 20,000 56,000 335,000 (615,000 ) 1,600,000 Ending balance $ 3,988,000 $ 396,000 $ 1,780,000 $ 18,000 $ 1,288,000 $ 44,000 $ 807,000 $ 559,000 $ 1,258,000 $ 10,138,000 Ending balance specifically evaluated for impairment $ 505,000 $ 100,000 $ 39,000 $ — $ 304,000 $ — $ 26,000 $ — $ — $ 974,000 Ending balance collectively evaluated for impairment $ 3,483,000 $ 296,000 $ 1,741,000 $ 18,000 $ 984,000 $ 44,000 $ 781,000 $ 559,000 $ 1,258,000 $ 9,164,000 Related loan balances: Ending balance $ 302,506,000 $ 25,406,000 $ 150,769,000 $ 27,056,000 $ 411,469,000 $ 18,303,000 $ 110,907,000 $ 25,110,000 $ — $ 1,071,526,000 Ending balance specifically evaluated for impairment $ 10,021,000 $ 763,000 $ 1,743,000 $ — $ 13,669,000 $ — $ 1,387,000 $ — $ — $ 27,583,000 Ending balance collectively evaluated for impairment $ 292,485,000 $ 24,643,000 $ 149,026,000 $ 27,056,000 $ 397,800,000 $ 18,303,000 $ 109,520,000 $ 25,110,000 $ — $ 1,043,943,000 For the year ended December 31, 2015 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,532,000 $ 823,000 $ 1,505,000 $ 15,000 $ 1,185,000 $ 20,000 $ 1,060,000 $ 542,000 $ 1,662,000 $ 10,344,000 Chargeoffs 280,000 9,000 732,000 — 420,000 — 582,000 350,000 — 2,373,000 Recoveries 2,000 1,000 88,000 — 152,000 — 31,000 121,000 — 395,000 Provision (credit) (134,000 ) (235,000 ) 591,000 2,000 474,000 4,000 384,000 253,000 211,000 1,550,000 Ending balance $ 3,120,000 $ 580,000 $ 1,452,000 $ 17,000 $ 1,391,000 $ 24,000 $ 893,000 $ 566,000 $ 1,873,000 $ 9,916,000 Ending balance specifically evaluated for impairment $ 89,000 $ 302,000 $ 8,000 $ — $ 326,000 $ — $ 29,000 $ — $ — $ 754,000 Ending balance collectively evaluated for impairment $ 3,031,000 $ 278,000 $ 1,444,000 $ 17,000 $ 1,065,000 $ 24,000 $ 864,000 $ 566,000 $ 1,873,000 $ 9,162,000 Related loan balances: Ending balance $ 269,462,000 $ 24,881,000 $ 128,341,000 $ 19,751,000 $ 403,030,000 $ 8,451,000 $ 110,202,000 $ 24,520,000 $ — $ 988,638,000 Ending balance specifically evaluated for impairment $ 10,717,000 $ 1,026,000 $ 1,234,000 $ — $ 15,088,000 $ — $ 1,466,000 $ — $ — $ 29,531,000 Ending balance collectively evaluated for impairment $ 258,745,000 $ 23,855,000 $ 127,107,000 $ 19,751,000 $ 387,942,000 $ 8,451,000 $ 108,736,000 $ 24,520,000 $ — $ 959,107,000

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 are carried at cost and consist of the following: As of December 31, 2017 2016 Land $ 4,639,000 $ 4,742,000 Land improvements 1,052,000 1,041,000 Buildings 22,254,000 21,601,000 Equipment 13,147,000 12,032,000 41,092,000 39,416,000 Less accumulated depreciation 18,590,000 17,214,000 $ 22,502,000 $ 22,202,000 Future minimum receipts under lease agreements at December 31, 2017 for each of the next five years and in the aggregate are: 2018 $192,000 2019 141,000 2020 101,000 2021 97,000 2022 94,000 Thereafter 9,000 $634,000

Other Real Estate Owned

Other Real Estate Owned	12 Months Ended
	Dec. 31, 2017
Real Estate Owned, Disclosure of Detailed Components [Abstract]
Other Real Estate Owned	Other Real Estate Owned The following summarizes other real estate owned: As of December 31, 2017 2016 Real estate acquired in settlement of loans $ 1,012,000 $ 375,000 Changes in the allowance for losses from other real estate owned were as follows: For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ 205,000 $ 162,000 $ 654,000 Losses charged to allowance (169,000 ) (89,000 ) (803,000 ) Provision charged to operating expenses 17,000 132,000 311,000 Balance at end of year $ 53,000 $ 205,000 $ 162,000

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The current and deferred components of income tax expense (benefit) were as follows: For the years ended December 31, 2017 2016 2015 Federal income tax Current $ 4,184,000 $ 6,276,000 $ 4,895,000 Deferred 2,083,000 (139,000 ) 332,000 6,267,000 6,137,000 5,227,000 State franchise tax 345,000 317,000 287,000 $ 6,612,000 $ 6,454,000 $ 5,514,000 The actual tax expense differs from the expected tax expense (computed by applying the applicable U.S. Federal corporate income tax rate to income before income taxes) as follows: For the years ended December 31, 2017 2016 2015 Expected tax expense $ 9,170,000 $ 8,562,000 $ 7,602,000 Non-taxable income (2,625,000 ) (2,176,000 ) (2,086,000 ) State franchise tax, net of federal tax benefit 224,000 206,000 187,000 Equity compensation (83,000 ) — — Tax credits, net of amortization (88,000 ) (105,000 ) (185,000 ) Change in federal tax rate 134,000 — — Other (120,000 ) (33,000 ) (4,000 ) $ 6,612,000 $ 6,454,000 $ 5,514,000 Deferred tax assets and liabilities are recognized at the expected future tax rate. On December 22, 2017, the federal tax rate decreased from 35% to 21% effective January 1, 2018. Accordingly, deferred tax assets and liabilities were revalued at December 31, 2017 to reflect the 21% tax rate. Deferred tax assets and liabilities are classified in other assets and other liabilities in the consolidated balance sheets. No valuation allowance is deemed necessary for the deferred tax asset. Items that give rise to the deferred income tax assets and liabilities and the tax effect of each at December 31, 2017 and 2016 are as follows: 2017 2016 Allowance for loan losses $ 2,253,000 $ 3,548,000 OREO 11,000 72,000 Accrued pension and post-retirement 1,036,000 1,730,000 Goodwill — 2,000 Unrealized loss on securities transferred from available for sale to held to maturity 46,000 70,000 Unrealized loss on securities available for sale 772,000 503,000 Restricted stock grants 173,000 237,000 Core deposit intangible 15,000 20,000 Investment in flow through entities 22,000 29,000 Other assets 28,000 48,000 Total deferred tax asset 4,356,000 6,259,000 Net deferred loan costs (1,313,000 ) (1,895,000 ) Depreciation (1,306,000 ) (1,808,000 ) Goodwill (39,000 ) — Mortgage servicing rights (266,000 ) (390,000 ) Unrealized gain on derivative instruments (410,000 ) (626,000 ) Prepaid expense (821,000 ) — Total deferred tax liability (4,155,000 ) (4,719,000 ) Net deferred tax asset $ 201,000 $ 1,540,000 At December 31, 2017 and 2016, the Company held investments in two limited partnerships with related low income housing tax credits. The investments are carried at cost and amortized on the effective yield method as they were entered into prior to 2015. The tax credits from the investments are estimated at $204,000 and $231,000 for the years ended December 31, 2017 and 2016 , respectively, and are recorded as a reduction of income tax expense. Amortization of the investment in the limited partnership totaled $178,000 and $194,000 for the years ended December 31, 2017 and 2016 , respectively, and is recognized as a component of income tax expense in the consolidated statements of income. The carrying value of these investments was $1,408,000 and $1,503,000 at December 31, 2017 and 2016 , respectively, and is recorded in securities available for sale. The Company's total exposure to the limited partnerships was $1,408,000 and $1,503,000 at December 31, 2017 and 2016 , respectively, which is comprised of the Company's equity investment in the limited partnerships. FASB ASC Topic 740, "Income Taxes," defines the criteria that an individual tax position must satisfy for some or all of the benefits of that position to be recognized in a company's financial statements. Topic 740 prescribes a recognition threshold of more-likely-than-not, and a measurement attribute for all tax positions taken or expected to be taken on a tax return, in order for those tax positions to be recognized in the financial statements. The Company is currently open to audit under the statute of limitations by the Internal Revenue Service for the years ended December 31, 2014 through 2017 .

Certificates of Deposit

Certificates of Deposit	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Certificates of Deposit	Certificates of Deposit The following table represents the breakdown of certificates of deposit at December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 Certificates of deposit < $100,000 $ 284,066,000 $ 195,115,000 Certificates $100,000 to $250,000 232,759,000 240,904,000 Certificates $250,000 and over 42,176,000 40,601,000 $ 559,001,000 $ 476,620,000 At December 31, 2017 , the scheduled maturities of certificates of deposit are as follows: Year of Maturity Less than $100,000 $100,000 and Greater All Certificates of Deposit 2018 $ 215,571,000 $ 177,745,000 $ 393,316,000 2019 26,401,000 27,164,000 53,565,000 2020 17,516,000 33,710,000 51,226,000 2021 13,137,000 17,060,000 30,197,000 2022 11,411,000 19,256,000 30,667,000 2023 and thereafter 30,000 — 30,000 $ 284,066,000 $ 274,935,000 $ 559,001,000 Interest on certificates of deposit of $100,000 or more was $2,105,000 , $1,970,000 , and $2,431,000 in 2017 , 2016 and 2015 , respectively.

Borrowed Funds

Borrowed Funds	12 Months Ended
	Dec. 31, 2017
Borrowed Funds [Abstract]
Borrowed Funds	Borrowed Funds Borrowed funds consist of advances from the FHLB and securities sold under agreements to repurchase with municipal and commercial customers. Pursuant to collateral agreements, FHLB advances are collateralized by all stock in FHLB, qualifying first mortgage loans, U.S. Government and Agency securities not pledged to others, and funds on deposit with FHLB. All FHLB advances as of December 31, 2017 had fixed rates of interest until their respective maturity dates. Securities sold under agreements to repurchase include U.S. agencies securities and other securities. Repurchase agreements have maturity dates ranging from one to 365 days. The Bank also has in place $44,000,000 in credit lines with correspondent banks and a credit facility of $168,000,000 with the Federal Reserve Bank of Boston using commercial and home equity loans as collateral which are currently not in use. Borrowed funds at December 31, 2017 and 2016 have the following range of interest rates and maturity dates: As of December 31, 2017 Federal Home Loan Bank Advances 2018 1.59% - 3.25% $ 43,074,000 2020 1.60% - 1.97% 55,000,000 2021 1.55% 10,000,000 2023 and thereafter 0.00% - 0.99% 50,120,000 158,194,000 Repurchase agreements Municipal and commercial customers 0.15% - 2.48% 70,564,000 $ 228,758,000 As of December 31, 2016 Federal Home Loan Bank Advances 2017 0.99% - 3.69% $ 74,600,000 2018 2.25% - 3.25% 30,000,000 2020 1.60% - 1.97% 55,000,000 2021 1.55% 10,000,000 2022 and thereafter 0.00% - 0.59% 25,127,000 194,727,000 Repurchase agreements Municipal and commercial customers 0.15% - 1.93% 84,174,000 $ 278,901,000

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits, Description [Abstract]
Employee Benefit Plans	Employee Benefit Plans 401(k) Plan The Bank has a defined contribution plan available to substantially all employees who have completed three months of service. Employees may contribute up to Internal Revenue Service determined limits and the Bank may provide a match to employee contributions not to exceed 3.0% of compensation depending on contribution level. Subject to a vote of the Board of Directors, the Bank may also make a profit-sharing contribution to the Plan. Such contribution equaled 2.0% of each eligible employee's compensation in 2017 , 2016 , and 2015 . The expense related to the 401(k) plan was $554,000 , $435,000 , and $462,000 in 2017 , 2016 , and 2015 , respectively. Deferred Compensation and Supplemental Retirement Plan The Bank also provides unfunded supplemental retirement benefits for certain officers, payable in installments over 20 years upon retirement or death. The agreements consist of individual contracts with differing characteristics that, when taken together, do not constitute a post-retirement plan. The costs for these benefits are recognized over the service periods of the participating officers in accordance with FASB ASC Topic 712, "Compensation – Nonretirement Postemployment Benefits". The expense of these supplemental plans was $219,000 in 2017 , $215,000 in 2016 , and $312,000 in 2015 . As of December 31, 2017 and 2016 , the accrued liability of these plans was $3,060,000 and $3,073,000 , respectively, and is recorded in other liabilities. Post-Retirement Benefit Plans The Bank sponsors two post-retirement benefit plans. One plan currently provides a subsidy for health insurance premiums to certain retired employees and a future subsidy for seven active employees who were age 50 and over in 1996. These subsidies are based on years of service and range between $40 and $1,200 per month per person. The Bank also provides health insurance for retired directors. The other plan provides life insurance coverage to certain retired employees. None of these plans are pre-funded. The Company utilizes FASB ASC Topic 712 to recognize the overfunded or underfunded status of a defined benefit post-retirement plan as an asset or liability in its balance sheet and to recognize changes in the funded status in the year in which the changes occur through comprehensive income (loss). The following table sets forth the accumulated post-retirement benefit obligation and funded status: At December 31, 2017 2016 2015 Change in benefit obligations Benefit obligation at beginning of year: $ 1,870,000 $ 1,967,000 $ 1,928,000 Interest cost 77,000 81,000 80,000 Benefits paid (113,000 ) (109,000 ) (102,000 ) Actuarial (gain) loss 40,000 (69,000 ) 61,000 Benefit obligation at end of year: $ 1,874,000 $ 1,870,000 $ 1,967,000 Funded status Benefit obligation at end of year $ (1,874,000 ) $ (1,870,000 ) $ (1,967,000 ) Unamortized loss 186,000 156,000 240,000 Accrued benefit cost $ (1,688,000 ) $ (1,714,000 ) $ (1,727,000 ) Weighted average discount rate as of December 31 4.25 % 4.25 % 4.25 % The following table sets forth the net periodic benefit cost: For the years ended December 31, 2017 2016 2015 Components of net periodic benefit cost Interest cost $ 77,000 $ 81,000 $ 80,000 Amortization of loss — 4,000 — Other settlement expense 11,000 11,000 12,000 Net periodic benefit cost $ 88,000 $ 96,000 $ 92,000 Weighted average discount rate for net periodic cost 4.25 % 4.25 % 4.25 % The measurement date for benefit obligations was as of year-end for all years presented. The estimated amount of benefits to be paid in 2018 is $128,000 . For years ending 2019 through 2022 , the estimated amount of benefits to be paid is $128,000 , $127,000 , $126,000 and $124,000 , respectively, and the total estimated amount of benefits to be paid for years ended 2023 through 2027 is $636,000 . Plan expense for 2018 is estimated to be $77,000 . In accordance with FASB ASC Topic 715, "Compensation – Retirement Benefits", amounts not yet reflected in net periodic benefit cost and included in accumulated other comprehensive income (loss) are as follows: At December 31, 2017 2016 Portion to Be Recognized in Income in 2018 Unamortized net actuarial loss $ (186,000 ) $ (156,000 ) $ (185,000 ) Deferred tax benefit at 35% 65,000 54,000 65,000 Reclassification adjustment for effect of enacted tax law changes (26,000 ) — — Net unrecognized post-retirement benefits included in accumulated other comprehensive income (loss) $ (147,000 ) $ (102,000 ) $ (120,000 )

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following table summarizes activity in the unrealized gain or loss on available for sale securities included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ (935,000 ) $ 1,123,000 $ 2,522,000 Unrealized losses arising during the year (1,763,000 ) (2,493,000 ) (754,000 ) Reclassification of realized gains during the year (471,000 ) (673,000 ) (1,399,000 ) Related deferred taxes 782,000 1,108,000 754,000 Reclassification adjustment for effect of enacted tax law changes (514,000 ) — — Net change (1,966,000 ) (2,058,000 ) (1,399,000 ) Balance at end of year $ (2,901,000 ) $ (935,000 ) $ 1,123,000 The reclassification of realized gains is included in the net securities gains line of the consolidated statements of income and comprehensive income and the tax effect is included in the income tax expense line of the same statement. The following table summarizes activity in the unrealized loss on securities transferred from available for sale to held to maturity included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ (129,000 ) $ (112,000 ) $ (48,000 ) Amortization of net unrealized losses (22,000 ) (26,000 ) (98,000 ) Related deferred taxes 8,000 9,000 34,000 Reclassification adjustment for effect of enacted tax law changes (31,000 ) — — Net change (45,000 ) (17,000 ) (64,000 ) Balance at end of year $ (174,000 ) $ (129,000 ) $ (112,000 ) The following table represents the effect of the Company's derivative financial instruments included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ 1,163,000 $ — $ — Unrealized gains on cash flow hedging derivatives arising during the year 165,000 1,790,000 — Related deferred taxes (58,000 ) (627,000 ) — Reclassification adjustment for effect of enacted tax law changes 274,000 — — Net change 381,000 1,163,000 — Balance at end of year $ 1,544,000 $ 1,163,000 $ — The following table summarizes activity in the unrealized gain or loss on postretirement benefits included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 : For the years ended December 31, 2017 2016 2015 Unrecognized postretirement benefits at beginning of year $ (102,000 ) $ (156,000 ) $ (125,000 ) Change in unamortized net actuarial loss (30,000 ) 84,000 (48,000 ) Related deferred taxes 11,000 (30,000 ) 17,000 Reclassification adjustment for effect of enacted tax law changes (26,000 ) $ — $ — Net change (45,000 ) $ 54,000 $ (31,000 ) Unrecognized postretirement benefits at end of year $ (147,000 ) $ (102,000 ) $ (156,000 ) The reclassification of accumulated losses is a component of net periodic benefit cost (see Note 12) and the income tax effect is included in the income tax expense line of the consolidated statements of income and comprehensive income.

Financial Derivative Instrument

Financial Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Derivative Instruments	Financial Derivative Instruments As part of its overall asset and liability management strategy, the Company periodically uses derivative instruments to mitigate significant unplanned fluctuations in earnings and cash flows caused by interest rate volatility. The Company’s interest rate risk management strategy involves modifying the re-pricing characteristics of certain assets or liabilities so that changes in interest rates do not have a significant effect on net interest income. The Company recognizes its derivative instruments in the consolidated balance sheet at fair value. On the date the derivative instrument is entered into, the Company designates whether the derivative is part of a hedging relationship (i.e., cash flow or fair value hedge). The Company formally documents relationships between hedging instruments and hedged items, as well as its risk management objective and strategy for undertaking hedge transactions. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives used in hedging transactions are highly effective in offsetting the changes in cash flows or fair values of hedged items. Changes in fair value of derivative instruments that are highly effective and qualify as cash flow hedges are recorded in other comprehensive income or loss. Any ineffective portion is recorded in earnings. The Company discontinues hedge accounting when it is determined that the derivative is no longer highly effective in offsetting changes of the hedged risk on the hedged item, or management determines that the designation of the derivative as a hedging instrument is no longer appropriate. In 2016, interest rate swaps were contracted to limit the Company’s exposure to rising interest rates on short-term liabilities indexed to one-month London Inter-bank Offered Rates (LIBOR). The interest rate swaps were designated as cash flow hedges. No new derivate instruments were added in 2017. The details of the interest rate swap agreements are as follows: As of December 31, 2017 2016 Notional Amount Effective Date Maturity Date Variable Index Received Fixed Rate Paid Fair Value (1) Fair Value (1) $ 30,000,000 June 28, 2016 June 28, 2021 1-Month USD LIBOR 0.94 % $ 1,154,000 $ 1,049,000 $ 20,000,000 June 27, 2016 June 27, 2021 1-Month USD LIBOR 0.89 % $ 801,000 741,000 $ 50,000,000 $ 1,955,000 $ 1,790,000 (1) Presented within other assets in the consolidated balance sheet. The Company would reclassify unrealized gains or losses accounted for within accumulated other comprehensive income (loss) into earnings if the interest rate swaps were to become ineffective or the swaps were to terminate. In the next 12 months, the Company does not believe it will be required to reclassify any unrealized gains or losses accounted for within accumulated other comprehensive income (loss) into earnings as a result of ineffectiveness or swap termination. Amounts paid or received under the swaps are reported in interest expense in the statement of income, and in interest paid in the statement of cash flows.

Preferred and Common Stock

Preferred and Common Stock	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Preferred and Common Stock	Preferred and Common Stock Preferred Stock On January 9, 2009, the Company issued $25,000,000 in Fixed Rate Cumulative Perpetual Preferred Stock, Series A, to the U.S. Treasury under the Capital Purchase Program ("the CPP Shares"). The CPP Shares qualified as Tier 1 capital on the Company's books for regulatory purposes and ranked senior to the Company's common stock and senior or at an equal level in the Company's capital structure to any other shares of preferred stock the Company may issue in the future. In three separate transactions in 2012 and 2013, the Company repurchased all of the CPP Shares from the Treasury. Incident to such issuance of the CPP Shares, the Company issued to the U.S. Treasury warrants (the "Warrants") to purchase up to 225,904 shares of the Company's common stock at a price per share of $16.60 (subject to adjustment). The Warrants (and any shares of common stock issuable pursuant to the Warrants) are freely transferable by Treasury to third parties. The warrants have a term of 10 years and could be exercised by Treasury or a subsequent holder at any time or from time to time during their term. To the extent they had not previously been exercised, the Warrants will expire after ten years. The Warrants were unchanged as a result of the CPP Shares repurchase transactions. In May 2015, the Treasury sold all of the Warrants to private parties. In accordance with the contractual terms of the Warrants, the number of shares issuable upon exercise of the Warrants and the strike price were adjusted at the time of the sale. As a result of this transaction, the number of shares issuable under the Warrants was adjusted to 226,819 with a strike price of $16.53 per share. In November 2016, the Company repurchased all of the outstanding Warrants for an aggregate purchase price of $1,750,000 . Common Stock In 2016, the Company reserved 250,000 shares of its common stock to be made available to directors and employees who elect to participate in the stock purchase or savings and investment plans. As of December 31, 2017 , 27,273 shares had been issued pursuant to these plans, leaving 222,727 shares available for future use. The issuance price is based on the market price of the stock at issuance date. Prior to 2016, the Company had reserved 700,000 shares of its common stock to be made available to directors and employees who elect to participate in the stock purchase or savings investment plans. Sales of stock to directors and employees amounted to 12,762 shares in 2017 , and 14,511 shares in 2016 , and 13,787 shares in 2015 . In 2001, the Company established a dividend reinvestment plan to allow shareholders to use their cash dividends for the automatic purchase of shares in the Company. When the plan was established, 600,000 shares were registered with the Securities and Exchange Commission, and as of December 31, 2017 , 257,759 shares have been issued, leaving 342,241 shares usable for future issuance. Participation in this plan is optional and at the individual discretion of each shareholder. Shares are purchased for the plan from the Company at a price per share equal to the average of the daily bid and asked prices reported on the NASDAQ System for the five trading days immediately preceding, but not including, the dividend payment date. Sales of stock under the dividend reinvestment plan amounted to 9,922 shares in 2017 , 10,889 shares in 2016 , and 11,668 shares in 2015 . Issuance of common stock for these plans totaled $632,000 , $531,000 and $465,000 for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Stock Options and Stock-Based C

Stock Options and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Options and Stock-Based Compensation	Stock Options and Stock-Based Compensation At the 2010 Annual Meeting, shareholders approved the 2010 Equity Incentive Plan (the "2010 Plan"). This reserves 400,000 shares of common stock for issuance in connection with stock options, restricted stock awards and other equity based awards to attract and retain the best available personnel, provide additional incentive to officers, employees and non-employee Directors and promote the success of our business. Such grants and awards have been and will be structured in a manner that does not encourage the recipients to expose the Company to undue or inappropriate risk. Options issued under the 2010 Plan will qualify for treatment as incentive stock options for purposes of Section 422 of the Internal Revenue Code. Other compensation under the 2010 Plan will qualify as performance-based for purposes of Section 162(m) of the Internal Revenue Code, and will satisfy NASDAQ guidelines relating to equity compensation. As of December 31, 2017 , 127,560 shares of restricted stock had been granted under the 2010 Plan, of which 71,086 shares remain restricted as of December 31, 2017 as detailed in the following table: Year Granted Vesting Term (In Years) Shares Remaining Term (In Years) 2013 5.0 14,776 0.3 2014 5.0 10,422 1.3 2015 5.0 12,023 2.3 2016 5.0 15,015 3.3 2017 1.0 3,976 0.4 2017 3.0 4,902 2.3 2017 5.0 9,972 4.3 71,086 2.0 The compensation cost related to these restricted stock grants was $1,428,000 and will be recognized over the vesting terms of each grant. In 2017 , $392,000 of expense was recognized for these restricted shares, leaving $601,000 in unrecognized expense as of December 31, 2017 . In 2016 , $298,000 of expense was recognized for restricted shares, leaving $457,000 in unrecognized expense as of December 31, 2016 . The Company established a shareholder-approved stock option plan in 1995 (the "1995 Plan"), under which the Company granted options to employees for 600,000 shares of common stock. Only incentive stock options were granted under the 1995 Plan. The exercise price of each option grant was determined by the Options Committee of the Board of Directors, and in no instance was less than the fair market value on the date of the grant. An option's maximum term was ten years from the date of grant, with 50% of the options granted vesting two years from the date of grant and the remaining 50% vesting five years from the date of grant. As of January 16, 2005, all options under the 1995 Plan had been granted, and as of January 16, 2015, all options under the 1995 Plan had been exercised or expired.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table provides detail for basic earnings per share (EPS) and diluted (EPS) for the years ended December 31, 2017 , 2016 and 2015 : Income (Numerator) Shares (Denominator) Per-Share Amount For the year ended December 31, 2017 Net income as reported $ 19,588,000 Basic EPS: Income available to common shareholders 19,588,000 10,747,306 $ 1.82 Effect of dilutive securities: restricted stock 71,712 Diluted EPS: Income available to common shareholders plus assumed conversions $ 19,588,000 10,819,018 $ 1.81 For the year ended December 31, 2016 Net income as reported $ 18,009,000 Basic EPS: Income available to common shareholders 18,009,000 10,713,290 $ 1.68 Effect of dilutive securities: restricted stock and warrants 116,512 Diluted EPS: Income available to common shareholders plus assumed conversions $ 18,009,000 10,829,802 $ 1.66 For the year ended December 31, 2015 Net income as reported $ 16,206,000 Basic EPS: Income available to common shareholders 16,206,000 10,674,755 $ 1.52 Effect of dilutive securities: restricted stock and warrants 90,114 Diluted EPS: Income available to common shareholders plus assumed conversions $ 16,206,000 10,764,869 $ 1.51 All EPS calculations have been made using the weighted average number of shares outstanding during the period. The dilutive securities are restricted stock granted to certain key members of Management and warrants granted to the U.S. Treasury under the Capital Purchase Program. The dilutive number of shares has been calculated using the treasury method, assuming that all granted stock and warrants were vested and exercised at the end of each period. The following table presents the number of options and warrants outstanding as of December 31, 2015 and the amount for which the average price at year end is above or below the strike price: Outstanding In-the-Money Out-of-the-Money As of December 31, 2015 Warrants issued to private parties 226,819 226,819 — Total dilutive securities 226,819 226,819 —

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2017
Regulatory Capital Requirements [Abstract]
Regulatory Capital Requirements	Regulatory Capital Requirements The ability of the Company to pay cash dividends to its shareholders depends primarily on receipt of dividends from its subsidiary, the Bank. The Bank may pay dividends to its parent out of so much of its net income as the Bank's directors deem appropriate, subject to the limitation that the total of all dividends declared by the Bank in any calendar year may not exceed the total of its net income of that year combined with its retained net income of the preceding two years and subject to minimum regulatory capital requirements. The amount available for dividends in 2018 will be 2018 earnings plus retained earnings of $15,846,000 from 2017 and 2016 . The payment of dividends by the Company is also affected by various regulatory requirements and policies, such as the requirements to maintain adequate capital. In addition, if, in the opinion of the applicable regulatory authority, a bank under its jurisdiction is engaged in or is about to engage in an unsafe or unsound practice (which, depending on the financial condition of the bank, could include the payment of dividends), that authority may require, after notice and hearing, that such bank cease and desist from that practice. The Federal Reserve Bank and the Comptroller of the Currency have each indicated that paying dividends that deplete a bank's capital base to an inadequate level would be an unsafe and unsound banking practice. The Federal Reserve Bank, the Comptroller of the Currency and the Federal Deposit Insurance Corporation have issued policy statements which provide that bank holding companies and insured banks should generally only pay dividends out of current operating earnings. In addition to the effect on the payment of dividends, failure to meet minimum capital requirements can also result in mandatory and discretionary actions by regulators that, if undertaken, could have an impact on the Company's operations. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Bank must meet specific capital guidelines that involve quantitative measurements of the Bank's assets, liabilities, and certain off-balance-sheet items as calculated under regulatory accounting practices. The Bank's capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Financial institution regulators have established guidelines for minimum capital ratios for banks and bank holding companies. The net unrealized gain or loss on securities available for sale is generally not included in computing regulatory capital. During the first quarter of 2015, the Company adopted the new Basel III regulatory capital framework as approved by the federal banking agencies. The adoption of this new framework modified the calculation of the various capital ratios, added a new ratio, common equity tier 1, and revised the adequately and well capitalized thresholds. Additionally, under the new rule, in order to avoid limitations on capital distributions, including dividend payments, the Company must hold a capital conservation buffer above the adequately capitalized risk-based capital ratios. The capital conservation buffer is being phased in from 0.0% for 2015 to 2.50% by 2019. As of December 31, 2017 , the Company's capital conservation buffer was 7.24% , and met both the 2017 minimum requirement of 2.25% and the fully phased-in 2019 minimum requirement. As of December 31, 2017 , the most recent notification from the Office of the Comptroller of the Currency classified the Bank as well-capitalized under the regulatory framework for prompt corrective action. To be categorized as well-capitalized, the Bank must maintain minimum total risk-based, Tier 1 risk-based, common equity Tier 1 risk-based and Tier 1 leverage ratios as set forth in the table. There are no conditions or events since this notification that Management believes have changed the institution's category. The actual and minimum capital amounts and ratios for the Bank are presented in the following table: Actual For capital adequacy purposes To be well-capitalized under prompt corrective action provisions As of December 31, 2017 Tier 2 capital to $ 162,355,000 $ 86,063,000 $ 107,579,000 risk-weighted assets 15.09 % 8.00 % 10.00 % Tier 1 capital to $ 151,526,000 $ 64,548,000 $ 86,063,000 risk-weighted assets 14.09 % 6.00 % 8.00 % Common equity Tier 1 capital to $ 151,526,000 $ 48,411,000 $ 69,926,000 risk-weighted assets 14.09 % 4.50 % 6.50 % Tier 1 capital to $ 151,526,000 $ 71,386,000 $ 89,233,000 average assets 8.49 % 4.00 % 5.00 % As of December 31, 2016 Tier 2 capital to $ 151,487,000 $ 77,928,000 $ 97,410,000 risk-weighted assets 15.55 % 8.00 % 10.00 % Tier 1 capital to $ 141,249,000 $ 58,446,000 $ 77,928,000 risk-weighted assets 14.50 % 6.00 % 8.00 % Common equity Tier 1 capital to $ 141,249,000 $ 43,835,000 $ 63,317,000 risk-weighted assets 14.50 % 4.50 % 6.50 % Tier 1 capital to $ 141,249,000 $ 65,437,000 $ 81,797,000 average assets 8.63 % 4.00 % 5.00 % The actual and minimum capital amounts and ratios for the Company, on a consolidated basis, are presented in the following table: Actual For capital adequacy purposes To be well-capitalized under prompt corrective action provisions As of December 31, 2017 Tier 2 capital to $ 163,943,000 $ 86,070,000 n/a risk-weighted assets 15.24 % 8.00 % n/a Tier 1 capital to $ 153,114,000 $ 64,553,000 n/a risk-weighted assets 14.23 % 6.00 % n/a Common equity Tier 1 capital to $ 153,114,000 $ 48,415,000 n/a risk-weighted assets 14.23 % 4.50 % n/a Tier 1 capital to $ 153,114,000 $ 71,435,000 n/a average assets 8.57 % 4.00 % n/a As of December 31, 2016 Tier 2 capital to $ 152,802,000 $ 77,928,000 n/a risk-weighted assets 15.69 % 8.00 % n/a Tier 1 capital to $ 142,564,000 $ 58,446,000 n/a risk-weighted assets 14.64 % 6.00 % n/a Common equity Tier 1 capital to $ 142,564,000 $ 43,835,000 n/a risk-weighted assets 14.64 % 4.50 % n/a Tier 1 capital to $ 142,564,000 $ 65,470,000 n/a average assets 8.71 % 4.00 % n/a

Off-Balance-Sheet Financial Ins

Off-Balance-Sheet Financial Instruments and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Off-Balance-Sheet Financial Instruments and Concentrations of Credit Risk	Off-Balance-Sheet Financial Instruments and Concentrations of Credit Risk The Bank 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, commitments for unused lines of credit, and standby letters of credit. The instruments involve, to varying degrees, elements of credit risk in excess of the amount recognized in the consolidated balance sheets. The contract amounts of those instruments reflect the extent of involvement the Bank has in particular classes of financial instruments. Commitments for unused lines of credit are agreements to lend to a customer provided there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Bank evaluates each customer's creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Bank upon extension of credit, is based on Management's credit evaluation of the borrower. The Bank did not incur any losses on its commitments in 2017 , 2016 or 2015 . Standby letters of credit are conditional commitments issued by the Bank to guarantee a customer's performance to a third party, with the customer being obligated to repay (with interest) any amounts paid out by the Bank under the letter of credit. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loans to customers. The Bank's exposure to credit loss in the event of nonperformance by the other party to the financial instrument for loan commitments and standby letters of credit is represented by the contractual amount of those instruments. The Bank uses the same credit policies in making commitments and conditional obligations as it does for on-balance sheet instruments. At December 31, 2017 and 2016 , the Bank had the following off-balance-sheet financial instruments, whose contract amounts represent credit risk: As of December 31, 2017 2016 Unused lines, collateralized by residential real estate $ 76,887,000 $ 76,646,000 Other unused commitments 62,771,000 57,738,000 Standby letters of credit 3,497,000 4,198,000 Commitments to extend credit 8,724,000 10,684,000 Total $ 151,879,000 $ 149,266,000 The Bank grants residential, commercial and consumer loans to customers principally located in the Mid-Coast and Down East regions of Maine. Collateral on these loans typically consists of residential or commercial real estate, or personal property. Although the loan portfolio is diversified, a substantial portion of borrowers' ability to honor their contracts is dependent on the economic conditions in the area, especially in the real estate sector. Derivative Financial Instruments Designated as Hedges As part of its overall asset and liability management strategy, the Company periodically uses derivative instruments to minimize significant unplanned fluctuations in earnings and cash flows caused by interest rate volatility. The Company's interest rate risk management strategy involves modifying the re-pricing characteristics of certain assets and/or liabilities so that change in interest rates does not have a significant adverse effect on net interest income. Derivative instruments that Management periodically uses as part of its interest rate risk management strategy may include interest rate swap agreements, interest rate floor agreements, and interest rate cap agreements. At December 31, 2017 , the Company had two outstanding, off-balance sheet, derivative instruments. These derivative instruments were interest rate swap agreements, with notional principal amounts totaling $50,000,000 and an unrealized gain of $1,544,000 , net of tax. The notional amounts of the financial derivative instruments do not represent exposure to credit loss. The Company is exposed to credit loss only to the extent the counter-party defaults in its responsibility to pay interest under the terms of the agreements. The credit risk in derivative instruments is mitigated by entering into transactions with highly-rated counterparties that Management believes to be creditworthy and by limiting the amount of exposure to each counter-party. At December 31, 2017 , the Company’s derivative instrument counterparties were credit rated “A” by the major credit rating agencies. The interest rate swap agreements were entered into by the Company to limit its exposure to rising interest rates and were designated as cash flow hedges.

Fair Value Disclosures

Fair Value Disclosures	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Disclosures Certain assets and liabilities are recorded at fair value to provide additional insight into the Company's quality of earnings. Some of these assets and liabilities are measured on a recurring basis while others are measured on a nonrecurring basis, with the determination based upon applicable existing accounting pronouncements. For example, securities available for sale are recorded at fair value on a recurring basis. Other assets, such as mortgage servicing rights, loans held for sale, and impaired loans, are recorded at fair value on a nonrecurring basis using the lower of cost or market methodology to determine impairment of individual assets. The Company groups assets and liabilities which are recorded at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. A financial instrument's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement (with level 1 considered highest and level 3 considered lowest). A brief description of each level follows. Level 1 – Valuation is based upon quoted prices for identical instruments in active markets. Level 2 – Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 3 – Valuation is generated from model-based techniques that use at least one significant assumption not observable in the market. These unobservable assumptions reflect estimates that market participants would use in pricing the asset or liability. Valuation includes use of discounted cash flow models and similar techniques. The fair value methods and assumptions for the Company's financial instruments and other assets measured at fair value are set forth below. Cash, Cash Equivalents and Interest-Bearing Deposits in Other Banks The carrying values of cash equivalents, due from banks and federal funds sold approximate their relative fair values. As such, the Company classifies these financial instruments as Level 1. Investment Securities The fair values of investment securities are estimated by independent providers using a market approach with observable inputs, including matrix pricing and recent transactions. In obtaining such valuation information from third parties, the Company has evaluated their valuation methodologies used to develop the fair values in order to determine whether the valuations are representative of an exit price in the Company's principal markets. The Company's principal markets for its securities portfolios are the secondary institutional markets, with an exit price that is predominantly reflective of bid level pricing in those markets. Fair values are calculated based on the value of one unit without regard to any premium or discount that may result from concentrations of ownership of a financial instrument, possible tax ramifications, or estimated transaction costs. If these considerations had been incorporated into the fair value estimates, the aggregate fair value could have been changed. The carrying values of restricted equity securities approximate fair values. As such, the Company classifies investment securities as Level 2. Loans Held for Sale Loans held for sale are recorded at the lower of carrying value or market value. The fair value of mortgage loans held for sale is based on what secondary markets are currently offering for portfolios with similar characteristics. As such, the Company classifies mortgage loans held for sale as Level 2. Loans Fair values are estimated for portfolios of loans with similar financial characteristics. The fair values of performing loans are calculated by discounting scheduled cash flows through the estimated maturity using estimated market discount rates that reflect the credit and interest risk inherent in the loan. The estimates of maturity are based on the Company's historical experience with repayments for each loan classification, modified, as required, by an estimate of the effect of current economic and lending conditions, and the effects of estimated prepayments. Assumptions regarding credit risk, cash flows, and discount rates are judgmentally determined using available market information and specific borrower information. Management has made estimates of fair value using discount rates that it believes to be reasonable. However, because there is no market for many of these financial instruments, Management has no basis to determine whether the fair value presented above would be indicative of the value negotiated in an actual sale. As such, the Company classifies loans as Level 3, except for certain collateral-dependent impaired loans. Fair values of impaired loans are based on estimated cash flows and are discounted using a rate commensurate with the risk associated with the estimated cash flows, or if collateral dependent, discounted to the appraised value of the collateral as determined by reference to sale prices of similar properties, less costs to sell. As such, the Company classifies collateral dependent impaired loans for which a specific reserve results in a fair value measure as Level 2. All other impaired loans are classified as Level 3. Other Real Estate Owned Real estate acquired through foreclosure is initially recorded at fair value. The fair value of other real estate owned is based on property appraisals and an analysis of sales prices of similar properties currently available. As such, the Company records other real estate owned as nonrecurring Level 2. Mortgage Servicing Rights Mortgage servicing rights represent the value associated with servicing residential mortgage loans. Servicing assets and servicing liabilities are reported using the amortization method and compared to fair value for impairment. In evaluating the fair values of mortgage servicing rights, the Company obtains third party valuations based on loan level data including note rate, type and term of the underlying loans. As such, the Company classifies mortgage servicing rights as Level 2. Accrued Interest Receivable The fair value estimate of this financial instrument approximates the carrying value as this financial instrument has a short maturity. It is the Company's policy to stop accruing interest on loans for which it is probable that the interest is not collectible. Therefore, this financial instrument has been adjusted for estimated credit loss. As such, the Company classifies accrued interest receivable as Level 2. Deposits The fair value of deposits is based on the discounted value of contractual cash flows. The discount rate is estimated using the rates currently offered for deposits of similar remaining maturities. As such, the Company classifies deposits as Level 2. The fair value estimates do not include the benefit that results from the low-cost funding provided by the deposits compared to the cost of borrowing funds in the market. If that value were considered, the fair value of the Company's net assets could increase. Borrowed Funds The fair value of borrowed funds is based on the discounted value of contractual cash flows. The discount rate is estimated using the rates currently available for borrowings of similar remaining maturities. As such, the Company classifies borrowed funds as Level 2. Accrued Interest Payable The fair value estimate approximates the carrying amount as this financial instrument has a short maturity. As such, the Company classifies accrued interest payable as Level 2. Derivatives The fair value of interest rate swaps is determined using inputs that are observable in the market place obtained from third parties including yield curves, publicly available volatilities, and floating indexes and, accordingly, are classified as Level 2 inputs. The credit value adjustments associated with derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. As of December 31, 2017 and 2016 , the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives due to collateral postings. Off-Balance-Sheet Instruments Off-balance-sheet instruments include loan commitments. Fair values for loan commitments have not been presented as the future revenue derived from such financial instruments is not significant. Limitations Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These values 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. Because no market exists for a significant portion of the Company's financial instruments, fair value estimates are based on Management's 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 are based on existing on- and off-balance-sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. Other significant assets and liabilities that are not considered financial instruments include the deferred tax asset, premises and equipment, and other real estate owned. In addition, tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in any of the estimates. Assets and Liabilities Recorded at Fair Value on a Recurring Basis The following tables present the balances of assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2017 and 2016 . At December 31, 2017 Level 1 Level 2 Level 3 Total Securities available for sale Mortgage-backed securities $ — $ 289,989,000 $ — $ 289,989,000 State and political subdivisions — 6,769,000 — 6,769,000 Other equity securities — 3,414,000 — 3,414,000 Total securities available for sale $ — $ 300,172,000 $ — $ 300,172,000 Interest rate swap agreements $ — $ 1,955,000 $ — $ 1,955,000 Total assets $ — $ 302,127,000 $ — $ 302,127,000 At December 31, 2016 Level 1 Level 2 Level 3 Total Securities available for sale Mortgage-backed securities $ — $ 280,604,000 $ — $ 280,604,000 State and political subdivisions — 16,482,000 — 16,482,000 Other equity securities — 3,330,000 — 3,330,000 Total securities available for sale $ — $ 300,416,000 $ — $ 300,416,000 Interest rate swap agreements $ — $ 1,790,000 $ — $ 1,790,000 Total assets $ — $ 302,206,000 $ — $ 302,206,000 Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis The following tables present assets measured at fair value on a nonrecurring basis that have had a fair value adjustment since their initial recognition. Other real estate owned is presented net of an allowance for losses of $53,000 and $205,000 at December 31, 2017 and 2016 , respectively. Only collateral-dependent impaired loans with a related specific allowance for loan losses or a partial charge off are included in impaired loans for purposes of fair value disclosures. Impaired loans below are presented net of specific allowances of $1,531,000 and $478,000 at December 31, 2017 and 2016 , respectively. At December 31, 2017 Level 1 Level 2 Level 3 Total Other real estate owned $ — $ 1,012,000 $ — $ 1,012,000 Impaired loans — 6,521,000 — 6,521,000 Total assets $ — $ 7,533,000 $ — $ 7,533,000 At December 31, 2016 Level 1 Level 2 Level 3 Total Other real estate owned $ — $ 375,000 $ — $ 375,000 Impaired loans — 827,000 — 827,000 Total assets $ — $ 1,202,000 $ — $ 1,202,000 Fair Value of Financial Instruments FASB ASC Topic 825, "Financial Instruments," requires disclosures of fair value information about financial instruments, whether or not recognized in the balance sheet, if the fair values can be reasonably determined. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company's various financial instruments. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques using observable inputs when available. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument. FASB ASC Topic 825 excludes certain financial instruments and all nonfinancial instruments from its disclosure requirements. Accordingly, the aggregate fair value amounts presented may not necessarily represent the underlying fair value of the Company. The carrying amounts and estimated fair values for financial instruments as of December 31, 2017 were as follows: Carrying Estimated As of December 31, 2017 value fair value Level 1 Level 2 Level 3 Financial assets Cash and cash equivalents $ 19,207,000 $ 19,207,000 $ 19,207,000 $ — $ — Interest-bearing deposits in other banks 860,000 860,000 860,000 — — Securities available for sale 300,172,000 300,172,000 — 300,172,000 — Securities to be held to maturity 256,567,000 259,655,000 — 259,655,000 — Restricted equity securities 10,358,000 10,358,000 — 10,358,000 — Loans held for sale 386,000 386,000 — 386,000 — Loans (net of allowance for loan losses) Commercial Real estate 319,691,000 311,321,000 — 72,000 311,249,000 Construction 37,594,000 36,610,000 — — 36,610,000 Other 177,956,000 175,455,000 — 6,018,000 169,437,000 Municipal 33,370,000 33,280,000 — — 33,280,000 Residential Term 431,459,000 431,028,000 — 391,000 430,637,000 Construction 17,830,000 17,613,000 — — 17,613,000 Home equity line of credit 110,566,000 109,012,000 — 40,000 108,972,000 Consumer 24,944,000 24,408,000 — — 24,408,000 Total loans 1,153,410,000 1,138,727,000 — 6,521,000 1,132,206,000 Mortgage servicing rights 1,268,000 2,321,000 — 2,321,000 — Interest rate swap agreements 1,955,000 1,955,000 — 1,955,000 — Accrued interest receivable 5,867,000 5,867,000 — 5,867,000 — Financial liabilities Demand deposits $ 181,970,000 $ 174,481,000 $ — $ 174,481,000 $ — NOW deposits 281,405,000 261,702,000 — 261,702,000 — Money market deposits 163,898,000 153,497,000 — 153,497,000 — Savings deposits 232,605,000 203,799,000 — 203,799,000 — Local certificates of deposit 223,074,000 220,734,000 — 220,734,000 — National certificates of deposit 335,927,000 335,775,000 — 335,775,000 — Total deposits 1,418,879,000 1,349,988,000 — 1,349,988,000 — Repurchase agreements 70,564,000 67,976,000 — 67,976,000 — Federal Home Loan Bank advances 158,194,000 156,396,000 — 156,396,000 — Total borrowed funds 228,758,000 224,372,000 — 224,372,000 — Accrued interest payable 642,000 642,000 — 642,000 — The carrying amounts and estimated fair values for financial instruments as of December 31, 2016 were as follows: Carrying Estimated As of December 31, 2016 value fair value Level 1 Level 2 Level 3 Financial assets Cash and cash equivalents $ 17,366,000 $ 17,366,000 $ 17,366,000 $ — $ — Interest-bearing deposits in other banks 293,000 293,000 293,000 — — Securities available for sale 300,416,000 300,416,000 — 300,416,000 — Securities to be held to maturity 226,828,000 225,537,000 — 225,537,000 — Restricted equity securities 11,930,000 11,930,000 — 11,930,000 — Loans held for sale 782,000 782,000 — 782,000 — Loans (net of allowance for loan losses) Commercial Real estate 297,952,000 293,103,000 — 558,000 292,545,000 Construction 24,954,000 24,548,000 — — 24,548,000 Other 148,737,000 147,394,000 — 33,000 147,361,000 Municipal 27,035,000 27,446,000 — — 27,446,000 Residential Term 409,999,000 410,327,000 — 236,000 410,091,000 Construction 18,253,000 18,125,000 — — 18,125,000 Home equity line of credit 109,986,000 108,740,000 — — 108,740,000 Consumer 24,472,000 24,131,000 — — 24,131,000 Total loans 1,061,388,000 1,053,814,000 — 827,000 1,052,987,000 Mortgage servicing rights 1,113,000 1,696,000 — 1,696,000 — Interest rate swap agreements 1,790,000 1,790,000 — 1,790,000 — Accrued interest receivable 5,532,000 5,532,000 — 5,532,000 — Financial liabilities Demand deposits $ 140,482,000 $ 133,342,000 $ — $ 133,342,000 $ — NOW deposits 282,971,000 259,418,000 — 259,418,000 — Money market deposits 125,544,000 115,087,000 — 115,087,000 — Savings deposits 217,340,000 188,260,000 — 188,260,000 — Local certificates of deposit 210,316,000 209,370,000 — 209,370,000 — National certificates of deposit 266,304,000 266,372,000 — 266,372,000 — Total deposits 1,242,957,000 1,171,849,000 — 1,171,849,000 — Repurchase agreements 84,174,000 79,827,000 — 79,827,000 — Federal Home Loan Bank advances 194,727,000 193,733,000 — 193,733,000 — Total borrowed funds 278,901,000 273,560,000 — 273,560,000 — Accrued interest payable 479,000 479,000 — 479,000 —

Other Operating Income and Expe

Other Operating Income and Expense	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other Operating Income and Expense	Other Operating Income and Expense Other operating income and other operating expense include the following items greater than 1% of revenues. For the years ended December 31, 2017 2016 2015 Other operating income ATM and debit card income $ 3,378,000 $ 3,024,000 $ 2,714,000 Other operating expense Advertising and marketing expense $ 1,208,000 $ 1,099,000 $ 1,178,000 Accounting and auditing expenses 818,000 690,000 797,000 ATM and interchange expense 886,000 853,000 814,000

Legal Contingencies

Legal Contingencies	12 Months Ended
	Dec. 31, 2017
Loss Contingency [Abstract]
Legal Contingencies	Legal Contingencies Various legal claims also arise from time to time in the normal course of business which, in the opinion of Management, will have no material effect on the Company's consolidated financial statements.

Reclassifications

Reclassifications	12 Months Ended
	Dec. 31, 2017
Prior Period Adjustment [Abstract]
Reclassifications	Reclassifications Certain items from prior years were reclassified in the financial statements to conform with the current year presentation. These do not have a material impact on the balance sheet or statement of income presentations.

Condensed Financial Information

Condensed Financial Information of Parent	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of Parent	Condensed Financial Information of Parent Condensed financial information for The First Bancorp, Inc. exclusive of its subsidiary is as follows: Balance Sheets As of December 31, 2017 2016 Assets Cash and cash equivalents $ 958,000 $ 613,000 Dividends receivable 2,500,000 3,800,000 Investments 441,000 432,000 Investment in subsidiary 152,174,000 143,611,000 Premises and equipment 3,000 4,000 Goodwill 27,559,000 27,559,000 Other assets 312,000 300,000 Total assets $ 183,947,000 $ 176,319,000 Liabilities and shareholders' equity Dividends payable $ 2,599,000 $ 3,778,000 Other liabilities 27,000 20,000 Total liabilities 2,626,000 3,798,000 Shareholders' equity Common stock 108,000 108,000 Additional paid-in capital 61,747,000 60,723,000 Retained earnings 119,373,000 111,653,000 Accumulated other comprehensive income Net unrealized gain on available for sale securities, net of tax 93,000 37,000 Total accumulated other comprehensive income 93,000 37,000 Total shareholders' equity 181,321,000 172,521,000 Total liabilities and shareholders' equity $ 183,947,000 $ 176,319,000 Statements of Income For the years ended December 31, 2017 2016 2015 Interest and dividends on investments $ 15,000 $ 22,000 $ 18,000 Net securities losses (3,000 ) (6,000 ) — Total income 12,000 16,000 18,000 Occupancy expense 5,000 9,000 12,000 Other operating expense 588,000 528,000 488,000 Total expense 593,000 537,000 500,000 Loss before income taxes and Bank earnings (581,000 ) (521,000 ) (482,000 ) Applicable income taxes (187,000 ) (186,000 ) (172,000 ) Loss before Bank earnings (394,000 ) (335,000 ) (310,000 ) Equity in earnings of Bank Remitted 11,180,000 11,300,000 10,000,000 Unremitted 8,802,000 7,044,000 6,516,000 Net income $ 19,588,000 $ 18,009,000 $ 16,206,000 Statements of Cash Flows For the years ended December 31, 2017 2016 2015 Cash flows from operating activities: Net income $ 19,588,000 $ 18,009,000 $ 16,206,000 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation 5,000 8,000 12,000 Equity compensation expense 392,000 298,000 296,000 Loss on sale of investments 3,000 6,000 — Tax benefit from vesting of restricted stock — 32,000 — (Increase) decrease in other assets 27,000 136,000 (135,000 ) (Increase) decrease in dividends receivable 1,300,000 (1,300,000 ) (50,000 ) Increase (decrease) in dividends payable (1,179,000 ) 112,000 — Increase (decrease) in other liabilities (3,000 ) (4,000 ) 160,000 Unremitted earnings of Bank (8,802,000 ) (7,044,000 ) (6,516,000 ) Net cash provided by operating activities 11,331,000 10,253,000 9,973,000 Cash flows from investing activities: Proceeds from sales/maturities of investments — 87,000 — Capital expenditures (4,000 ) — — Net cash provided by (used in) investing activities (4,000 ) 87,000 — Cash flows from financing activities: Purchase of common stock (154,000 ) (129,000 ) (180,000 ) Proceeds from sale of common stock 632,000 531,000 465,000 Repurchase of warrants — (1,750,000 ) — Dividends paid (11,460,000 ) (9,810,000 ) (9,349,000 ) Net cash used in financing activities (10,982,000 ) (11,158,000 ) (9,064,000 ) Net increase (decrease) in cash and cash equivalents 345,000 (818,000 ) 909,000 Cash and cash equivalents at beginning of year 613,000 1,431,000 522,000 Cash and cash equivalents at end of year $ 958,000 $ 613,000 $ 1,431,000

New Accounting Pronouncements

New Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements The FASB issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, in 2014 to replace the current plethora of industry-specific rules with a broad, principles-based framework for recognizing and measuring revenue. Due to the complexity of the new pronouncement and the anticipated effort required by entities in many industries to implement ASU No. 2014-09, FASB delayed the effective date. Public business entities, certain not-for-profit entities, and certain employee benefit plans should apply the guidance to annual reporting periods beginning after December 15, 2017, and all other entities should apply the guidance to annual reporting periods beginning after December 15, 2018. FASB formed a Transition Resource Group to assist it in identifying implementation issues that may require further clarification or amendment to ASU No. 2014-09. As a result of that group’s deliberations, FASB has issued the following amendments, which will be effective concurrently with ASU No. 2014-09: ASU No. 2016-08, Principal versus Agent Considerations, which clarifies whether an entity should record the gross amount of revenue or only its ultimate share when a third party is also involved in providing goods or services to a customer; ASU No. 2016-10, Identifying Performance Obligations and Licensing, which clarifies and simplifies the process for determining whether performance obligations to a customer should be segregated and accounted for individually, and clarifies how the new revenue rules apply to licenses of intellectual property; and ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients, which clarifies and simplifies the process of assessing collectability of consideration under a contract, presentation of sales taxes, accounting for noncash consideration received, and certain transitional issues. Since the guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other U.S. GAAP, the Company does not expect the new guidance to have a material impact on revenue most closely associated with financial instruments, including interest income and expense. The Company is currently performing an overall assessment of revenue streams and reviewing contracts potentially affected by the ASU including trust and asset management fees, deposit related fees, interchange fees, and merchant income, to determine the potential impact the new guidance is expected to have on the Company’s Consolidated Financial Statements. In addition, the Company continues to follow certain implementation issues relevant to the banking industry which are still pending resolution. The Company plans to adopt ASU No. 2014-09 on January 1, 2018 utilizing the modified retrospective approach. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. The ASU was issued to enhance the reporting model for financial instruments to provide users of financial statements with more decision-useful information. This ASU changes how entities account for equity investments that do not result in consolidation and are not accounted for under the equity method of accounting. The ASU also changes certain disclosure requirements and other aspects of U.S. GAAP, including a requirement for public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Management does not expect the ASU to have a material effect on the Company's consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The ASU was issued to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2018. Management is reviewing the guidance in the ASU to determine whether it will have a material effect on the Company’s consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting. This ASU includes provisions intended to simplify various aspects related to how share-based payments are accounted for and presented in the financial statements. Some of the key provisions of this new ASU include: (1) companies will no longer record excess tax benefits and certain tax deficiencies in additional paid-in capital (APIC). Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement, and APIC pools will be eliminated. The guidance also eliminates the requirement that excess tax benefits be realized before companies can recognize them. In addition, the guidance requires companies to present excess tax benefits as an operating activity on the statement of cash flows rather than as a financing activity; (2) increase the amount an employer can withhold to cover income taxes on awards and still qualify for the exception to liability classification for shares used to satisfy the employer’s statutory income tax withholding obligation. The new guidance will also require an employer to classify the cash paid to a tax authority when shares are withheld to satisfy its statutory income tax withholding obligation as a financing activity on its statement of cash flows (current guidance did not specify how these cash flows should be classified); and (3) permit companies to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated on the date the award is granted, or recognized when they occur. ASU No. 2016-09 is effective for interim and annual reporting periods beginning after December 15, 2016. The adoption of the ASU did not have a material effect on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Under the new guidance, which will replace the existing incurred loss model for recognizing credit losses, banks and other lending institutions will be required to recognize the full amount of expected credit losses. The new guidance, which is referred to as the current expected credit loss model, requires that expected credit losses for financial assets held at the reporting date that are accounted for at amortized cost be measured and recognized based on historical experience and current and reasonably supportable forecasted conditions to reflect the full amount of expected credit losses. A modified version of these requirements also applies to debt securities classified as available for sale. The ASU is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, including interim periods within such years. The Company is currently evaluating the impact of the adoption of the ASU on its consolidated financial statements, and anticipates it may have a material impact. The Bank has formed an implementation committee for ASU 2016-13. To date, committee members have participated in educational seminars on the new standards, begun the process of identifying the historical data sets that will be necessary to implement the new standard, and chose a third-party vendor who provides software solutions for ASU 2016-13 modeling and calculation. In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. The ASU was issued to reduce the cost and complexity of the goodwill impairment test. To simplify the subsequent measurement of goodwill, step two of the goodwill impairment test was eliminated. Instead, a Company will recognize an impairment of goodwill should the carrying value of a reporting unit exceed its fair value (i.e. step one). The ASU will be effective for the Company on January 1, 2020 and will be applied prospectively. The Company does not expect the implementation to have a material effect on the Company's consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-08, Premium Amortization on Purchased Callable Debt Securities. This ASU shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. Today, entities generally amortize the premium over the contractual life of the security. The new guidance does not change the accounting for purchased callable debt securities held at a discount; the discount continues to be accreted to maturity. The ASU is effective for interim and annual reporting periods beginning after December 15, 2018; early adoption is permitted. The guidance calls for a modified retrospective transition approach under which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company's current practice aligns with the ASU therefore Management believes there will be no impact on the Company's consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. The ASU was issued to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a shared-based payment award. The ASU include guidance on determining which changes to the terms and conditions of share-based payment awards require and entity to apply modification accounting under Topic 718. The ASU is effective for the annual period, and interim periods within the annual periods, beginning after December 15, 2017. Early adoption is permitted, including adoption in any interim period. The ASU should be applied prospectively to an award modified on or after the adoption date. Management does not expect the ASU to have a material effect on the Company's consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815). The amendments in this ASU improve the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements. In addition, this ASU makes certain targeted improvements to simplify the application of the hedge accounting guidance in current US GAAP. The amendments in this ASU are effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal year. Early application is permitted in any interim period after issuance of the ASU. Management is reviewing the guidance in this ASU to determine whether it will have a material effect on the Company's consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Loss). This ASU was issued to allow a reclassification from accumulated other comprehensive income (loss) to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. Consequently, the amendments eliminate the stranded tax effects resulting from the Tax Cuts and Jobs Act and will improve the usefulness of information reported to financial statement users. However, because the amendments only relate to the reclassification of the income tax effects of the Tax Cuts and Jobs Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not affected. The ASU is effective for fiscal years beginning after December 15, 2018, with early adoption permitted for financial statements which have not yet been issued. The Company adopted the ASU for the December 31, 2017 consolidated financial statements, which resulted in a reclassification adjustment on the Consolidated Statements of Changes in Shareholders' Equity of $297,000 from accumulated other comprehensive income (loss) to retained earnings. Refer to Note 9, Income Taxes, for additional information.

Quarterly Information

Quarterly Information	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Information	Quarterly Information The following tables provide unaudited financial information by quarter for each of the past two years: Dollars in thousands except per share data 2016Q1 2016Q2 2016Q3 2016Q4 2017Q1 2017Q2 2017Q3 2017Q4 Balance Sheets Cash and cash equivalents $ 14,533 $ 20,838 $ 23,456 $ 17,366 $ 17,600 $ 23,718 $ 22,375 $ 19,207 Interest-bearing deposits in other banks 6,372 7,568 15,098 293 3,272 291 584 860 Investments 453,336 457,599 471,063 527,244 553,453 552,269 541,678 556,739 Restricted equity securities 13,875 14,441 14,048 11,930 13,363 12,311 10,798 10,358 Net loans and loans held for sale 994,947 1,029,568 1,019,922 1,062,170 1,080,347 1,110,919 1,110,508 1,153,796 Other assets 91,618 91,440 91,501 93,872 95,793 96,143 95,758 101,970 Total assets $ 1,574,681 $ 1,621,454 $ 1,635,088 $ 1,712,875 $ 1,763,828 $ 1,795,651 $ 1,781,701 $ 1,842,930 Deposits $ 1,109,441 $ 1,145,709 $ 1,173,749 $ 1,242,957 $ 1,346,483 $ 1,319,259 $ 1,350,049 $ 1,418,879 Borrowed funds 276,531 283,095 268,098 278,901 226,467 282,277 234,328 228,758 Other liabilities 17,165 17,862 17,247 18,496 15,968 16,578 17,442 13,972 Shareholders' equity 171,544 174,788 175,994 172,521 174,910 177,537 179,882 181,321 Total liabilities & equity $ 1,574,681 $ 1,621,454 $ 1,635,088 $ 1,712,875 $ 1,763,828 $ 1,795,651 $ 1,781,701 $ 1,842,930 Income and Comprehensive Income Statements Interest income $ 13,276 $ 13,600 $ 13,283 $ 13,600 $ 14,491 $ 15,002 $ 15,517 $ 15,822 Interest expense 2,547 2,649 2,754 2,862 3,015 3,337 3,563 3,614 Net interest income 10,729 10,951 10,529 10,738 11,476 11,665 11,954 12,208 Provision for loan losses 375 375 375 475 500 500 750 250 Net interest income after provision for loan losses 10,354 10,576 10,154 10,263 10,976 11,165 11,204 11,958 Non-interest income 2,964 3,006 3,469 3,060 2,843 3,002 3,493 3,210 Non-interest expense 7,200 7,245 7,405 7,533 7,698 7,640 8,013 8,300 Income before taxes 6,118 6,337 6,218 5,790 6,121 6,527 6,684 6,868 Income taxes 1,615 1,713 1,656 1,470 1,484 1,644 1,702 1,782 Net income $ 4,503 $ 4,624 $ 4,562 $ 4,320 $ 4,637 $ 4,883 $ 4,982 $ 5,086 Basic earnings per share $ 0.42 $ 0.43 $ 0.43 $ 0.40 $ 0.43 $ 0.45 $ 0.46 $ 0.48 Diluted earnings per share $ 0.42 $ 0.43 $ 0.42 $ 0.39 $ 0.43 $ 0.45 $ 0.46 $ 0.47 Other comprehensive income (loss), net of tax Net unrealized gain (loss) on securities available for sale $ 1,852 $ 1,025 $ (1,292 ) $ (3,643 ) $ 1 $ 349 $ (240 ) $ (1,562 ) Net unrealized gain (loss) on securities transfered from available for sale to held to maturity (11 ) (10 ) 9 (5 ) (4 ) (4 ) (3 ) (3 ) Net unrealized gain (loss) on cash flow hedging derivative instruments — (135 ) 193 1,105 63 (171 ) (20 ) 235 Unrecognized gain (loss) on postretirement benefit costs — — — 54 — — — (19 ) Other comprehensive income (loss) $ 1,841 $ 880 $ (1,090 ) $ (2,489 ) $ 60 $ 174 $ (263 ) $ (1,349 ) Comprehensive income $ 6,344 $ 5,504 $ 3,472 $ 1,831 $ 4,697 $ 5,057 $ 4,719 $ 3,737

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and the Bank. All intercompany accounts and transactions have been eliminated in consolidation.
Subsequent Events	Subsequent Events Events occurring subsequent to December 31, 2017 , have been evaluated as to their potential impact to the financial statements.
Use of Estimates in Preparation of Financial Statements	Use of Estimates in Preparation of Financial Statements In preparing the financial statements in accordance with accounting principles generally accepted in the United States of America ("GAAP"), Management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the balance sheet and revenues and expenses for the reporting period. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant change in the near-term relate to the determination of the allowance for loan losses, goodwill, the valuation of mortgage servicing rights, and other-than-temporary impairment of securities.
Investment Securities	Investment Securities Investment securities are classified as available for sale or held to maturity when purchased. There are no trading account securities. Securities available for sale consist primarily of debt securities which Management intends to hold for indefinite periods of time. They may be used as part of the Bank's funds management strategy, and may be sold in response to changes in interest rates or prepayment risk, changes in liquidity needs, or for other reasons. They are accounted for at fair value, with unrealized gains or losses adjusted through shareholders' equity, net of related income taxes. The cost basis is adjusted for the amortization of premiums and accretion of discounts, computed using the effective interest method over the securities' contractual lives. Securities to be held to maturity consist primarily of debt securities which Management has acquired solely for long-term investment purposes, rather than for purposes of trading or future sale. For securities to be held to maturity, Management has the intent and the Bank has the ability to hold such securities until their respective maturity dates. Such securities are carried at cost adjusted for the amortization of premiums and accretion of discounts, computed using the effective interest method over the securities' contractual lives. Investment securities transactions are accounted for on a settlement date basis; reported amounts would not be materially different from those accounted for on a trade date basis. Gains and losses on the sales of investment securities are determined using the amortized cost of the specifically identified security. For declines in the fair value of individual debt securities available for sale below their cost that are deemed to be other than temporary, where the Bank does not intend to sell the security and it is more likely than not that the Bank will not be required to sell the security before recovery of its amortized cost basis, the other-than-temporary decline in the fair value of the debt security related to 1) credit loss is recognized in earnings and 2) other factors is recognized in other comprehensive income or loss. Credit loss is deemed to exist if the present value of expected future cash flows using the effective rate at acquisition is less than the amortized cost basis of the debt security. For individual debt securities where the Bank intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost, the other-than-temporary impairment is recognized in earnings equal to the entire difference between the security's cost basis and its fair value at the balance sheet date.
Derivative Financial Instruments Designated as Hedges	Derivative Financial Instruments Designated as Hedges The Company recognizes all derivatives in the consolidated balance sheets at fair value. On the date the Bank enters into the derivative contract, the Company designates the derivative as a hedge of either a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), a hedge of the fair value of a recognized asset or liability or of an unrecognized firm commitment (“fair value hedge”), or a held for trading instrument (“trading instrument”). The Bank formally documents relationships between hedging instruments and hedged items, as well as its risk management objectives and strategy for undertaking various hedge transactions. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are effective in offsetting changes in cash flows or fair values of hedged items. Changes in fair value of a derivative that is effective and that qualifies as a cash flow hedge are recorded in other comprehensive income (loss) and are reclassified into earnings when the forecasted transaction or related cash flows affect earnings. Changes in fair value of a derivative that qualifies as a fair value hedge and the change in fair value of the hedged item are both recorded in earnings and offset each other when the transaction is effective. Those derivatives that are classified as trading instruments are recorded at fair value with changes in fair value recorded in earnings. The Company discontinues hedge accounting when it determines that the derivative is no longer effective in offsetting changes in the cash flows of the hedged item, that it is unlikely that the forecasted transaction will occur, or that the designation of the derivative as a hedging instrument is no longer appropriate.
Loans Held for Sale	Loans Held for Sale Loans held for sale consist of residential real estate mortgage loans and are carried at the lower of aggregate cost or fair value, as determined by current investor yield requirements.
Loans	Loans Loans are generally reported at their outstanding principal balances, adjusted for chargeoffs, the allowance for loan losses and any deferred fees or costs to originate loans. Loan commitments are recorded when funded.
Loan Fees and Costs	Loan Fees and Costs Loan origination fees and certain direct loan origination costs are deferred and recognized in interest income as an adjustment to the loan yield over the life of the related loans. The unamortized net deferred fees and costs are included on the balance sheets with the related loan balances, and the amortization is included with the related interest income.
Allowance for Loan Losses	Allowance for Loan Losses Loans considered to be uncollectible are charged against the allowance for loan losses. The allowance for loan losses is maintained at a level determined by Management to be appropriate to absorb probable losses. This allowance is increased by provisions charged to operating expenses and recoveries on loans previously charged off. Arriving at an appropriate level of allowance for loan losses necessarily involves a high degree of judgment. In determining the appropriate level of allowance for loan losses, Management takes into consideration several factors, including reviews of individual non-performing loans and performing loans listed on the watch report requiring periodic evaluation, loan portfolio size by category, recent loss experience, delinquency trends and current economic conditions. For all loan classes, loans over 30 days past due are considered delinquent. Impaired loans include restructured loans and loans placed on non-accrual status when, based on current information and events, it is probable that the Bank will be unable to collect all amounts due according to the contractual terms of the loan agreement. These loans are measured at the present value of expected future cash flows discounted at the loan's effective interest rate or at the fair value of the collateral if the loan is collateral dependent. Management takes into consideration impaired loans in addition to the above mentioned factors in determining the appropriate level of allowance for loan losses.
Troubled Debt Restructured	Troubled Debt Restructured A troubled debt restructured ("TDR") constitutes a restructuring of debt if the Bank, for economic or legal reasons related to the borrower's financial difficulties, grants a concession to the borrower that it would not otherwise consider. To determine whether or not a loan should be classified as a TDR, Management evaluates a loan to first determine if the borrower demonstrates financial difficulty. Common indicators of this include past due status with bank obligations, substandard credit bureau reports, or an inability to refinance with another lender. If the borrower is experiencing financial difficulty and concessions are granted, such as maturity date extension, interest rate adjustments to below market pricing, or a deferral of payments, the loan will generally be classified as a TDR.
Accrual of Interest Income and Expense	Accrual of Interest Income and Expense Interest on loans and investment securities is taken into income using methods which relate the income earned to the balances of loans and investment securities outstanding. Interest expense on liabilities is derived by applying applicable interest rates to principal amounts outstanding. For all classes of loans, recording of interest income on problem loans, which includes impaired loans, ceases when collectibility of principal and interest within a reasonable period of time becomes doubtful. Cash payments received on non-accrual loans, which includes impaired loans, are applied to reduce the loan's principal balance until the remaining principal balance is deemed collectible, after which interest is recognized when collected. As a general rule, a loan may be restored to accrual status when payments are current for a substantial period of time, generally six months, and repayment of the remaining contractual amounts is expected or when it otherwise becomes well secured and in the process of collection.
Premises and Equipment	Premises and Equipment Premises, furniture and equipment are stated at cost, less accumulated depreciation. Depreciation expense is computed by straight-line methods over the asset's estimated useful life.
Other Real Estate Owned (OREO)	Other Real Estate Owned ("OREO") Real estate acquired by foreclosure or deed in lieu of foreclosure is transferred to OREO and recorded at fair value, less estimated costs to sell, based on appraised value at the date actually or constructively received. Loan losses arising from the acquisition of such property are charged against the allowance for loan losses. Subsequent provisions to reduce the carrying value of a property are recorded to the allowance for OREO losses and a charge to operations on a property specific basis.
Goodwill and Identified Intangible Assets	Goodwill and Identified Intangible Assets Intangible assets include the excess of the purchase price over the fair value of net assets acquired (goodwill) from the acquisition of FNB Bankshares in 2005 as well as the core deposit intangible related to the same acquisition. The core deposit intangible is amortized on a straight-line basis over ten years . There was no annual amortization expense for 2017 or 2016 as the expense is now fully amortized. For 2015 the annual amortization expense was $15,000 . Intangible assets also include the goodwill and core deposit intangible from the 2012 acquisition of a bank branch in Rockland, Maine and a bank building in Bangor, Maine. The core deposit intangible will be amortized on a straight-line basis over ten years . Annual amortization expense for each of 2017 , 2016 and 2015 was $43,000 , and the amortization expense for each year until fully amortized (presently expected to be 2022) will be $43,000 . The straight-line basis is used because the Company does not expect significant run off in the core deposits acquired. The Company annually evaluates goodwill, and periodically evaluates other intangible assets, for impairment. At December 31, 2017 , the Company determined goodwill and other intangible assets were not impaired.
Income Taxes	Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between financial statement carrying amounts of assets and liabilities and their respective tax bases, and for tax credits that are available to offset future taxable income. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period the change is enacted
Loan Servicing	Loan Servicing Servicing rights are recognized when they are acquired through sale of loans. Capitalized servicing rights are reported in other assets and are amortized into non-interest income in proportion to, and over the period of, the estimated future net servicing income of the underlying financial assets. Servicing rights are evaluated for impairment based upon the fair value of the rights as compared to amortized cost. Impairment is determined by stratifying rights by predominant characteristics, such as interest rates and terms. Impairment is recognized through a valuation allowance for an individual stratum, to the extent that fair value is less than the capitalized amount for the stratum.
Post-Retirement Benefits	Post-Retirement Benefits The cost of providing post-retirement benefits is accrued during the active service period of the employee or director.
Earnings Per Share	Earnings Per Share Basic earnings per share data are based on the weighted average number of common shares outstanding during each year. Diluted earnings per share gives effect to restricted stock granted and stock options and warrants outstanding, determined by the treasury stock method.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes net income and other comprehensive income (loss), which is comprised of the change in unrealized gains and losses on securities available for sale, net of tax, change in unrealized losses on securities transferred from available for sale to held to maturity, net of amortization, change in unrealized gain on cash flow hedging derivative instruments, net of tax, and unrecognized gains and losses related to post-retirement benefit costs, net of tax.
Segments	Segments The First Bancorp, Inc., through the branches of its subsidiary, First National Bank, provides a broad range of financial services to individuals and companies in coastal Maine. These services include demand, time, and savings deposits; lending; ATM processing; and investment management and trust services. Operations are managed and financial performance is evaluated on a corporate-wide basis. Accordingly, all of the Company's banking operations are considered by Management to be aggregated in one reportable operating segment.
Reclassifications	Reclassifications Certain items from prior years were reclassified in the financial statements to conform with the current year presentation. These do not have a material impact on the balance sheet or statement of income presentations.
Fair Value Measurement	Certain assets and liabilities are recorded at fair value to provide additional insight into the Company's quality of earnings. Some of these assets and liabilities are measured on a recurring basis while others are measured on a nonrecurring basis, with the determination based upon applicable existing accounting pronouncements. For example, securities available for sale are recorded at fair value on a recurring basis. Other assets, such as mortgage servicing rights, loans held for sale, and impaired loans, are recorded at fair value on a nonrecurring basis using the lower of cost or market methodology to determine impairment of individual assets. The Company groups assets and liabilities which are recorded at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. A financial instrument's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement (with level 1 considered highest and level 3 considered lowest). A brief description of each level follows. Level 1 – Valuation is based upon quoted prices for identical instruments in active markets. Level 2 – Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 3 – Valuation is generated from model-based techniques that use at least one significant assumption not observable in the market. These unobservable assumptions reflect estimates that market participants would use in pricing the asset or liability. Valuation includes use of discounted cash flow models and similar techniques.
Fair Value of Financial Instruments	The fair value methods and assumptions for the Company's financial instruments and other assets measured at fair value are set forth below. Cash, Cash Equivalents and Interest-Bearing Deposits in Other Banks The carrying values of cash equivalents, due from banks and federal funds sold approximate their relative fair values. As such, the Company classifies these financial instruments as Level 1. Investment Securities The fair values of investment securities are estimated by independent providers using a market approach with observable inputs, including matrix pricing and recent transactions. In obtaining such valuation information from third parties, the Company has evaluated their valuation methodologies used to develop the fair values in order to determine whether the valuations are representative of an exit price in the Company's principal markets. The Company's principal markets for its securities portfolios are the secondary institutional markets, with an exit price that is predominantly reflective of bid level pricing in those markets. Fair values are calculated based on the value of one unit without regard to any premium or discount that may result from concentrations of ownership of a financial instrument, possible tax ramifications, or estimated transaction costs. If these considerations had been incorporated into the fair value estimates, the aggregate fair value could have been changed. The carrying values of restricted equity securities approximate fair values. As such, the Company classifies investment securities as Level 2. Loans Held for Sale Loans held for sale are recorded at the lower of carrying value or market value. The fair value of mortgage loans held for sale is based on what secondary markets are currently offering for portfolios with similar characteristics. As such, the Company classifies mortgage loans held for sale as Level 2. Loans Fair values are estimated for portfolios of loans with similar financial characteristics. The fair values of performing loans are calculated by discounting scheduled cash flows through the estimated maturity using estimated market discount rates that reflect the credit and interest risk inherent in the loan. The estimates of maturity are based on the Company's historical experience with repayments for each loan classification, modified, as required, by an estimate of the effect of current economic and lending conditions, and the effects of estimated prepayments. Assumptions regarding credit risk, cash flows, and discount rates are judgmentally determined using available market information and specific borrower information. Management has made estimates of fair value using discount rates that it believes to be reasonable. However, because there is no market for many of these financial instruments, Management has no basis to determine whether the fair value presented above would be indicative of the value negotiated in an actual sale. As such, the Company classifies loans as Level 3, except for certain collateral-dependent impaired loans. Fair values of impaired loans are based on estimated cash flows and are discounted using a rate commensurate with the risk associated with the estimated cash flows, or if collateral dependent, discounted to the appraised value of the collateral as determined by reference to sale prices of similar properties, less costs to sell. As such, the Company classifies collateral dependent impaired loans for which a specific reserve results in a fair value measure as Level 2. All other impaired loans are classified as Level 3. Other Real Estate Owned Real estate acquired through foreclosure is initially recorded at fair value. The fair value of other real estate owned is based on property appraisals and an analysis of sales prices of similar properties currently available. As such, the Company records other real estate owned as nonrecurring Level 2. Mortgage Servicing Rights Mortgage servicing rights represent the value associated with servicing residential mortgage loans. Servicing assets and servicing liabilities are reported using the amortization method and compared to fair value for impairment. In evaluating the fair values of mortgage servicing rights, the Company obtains third party valuations based on loan level data including note rate, type and term of the underlying loans. As such, the Company classifies mortgage servicing rights as Level 2. Accrued Interest Receivable The fair value estimate of this financial instrument approximates the carrying value as this financial instrument has a short maturity. It is the Company's policy to stop accruing interest on loans for which it is probable that the interest is not collectible. Therefore, this financial instrument has been adjusted for estimated credit loss. As such, the Company classifies accrued interest receivable as Level 2. Deposits The fair value of deposits is based on the discounted value of contractual cash flows. The discount rate is estimated using the rates currently offered for deposits of similar remaining maturities. As such, the Company classifies deposits as Level 2. The fair value estimates do not include the benefit that results from the low-cost funding provided by the deposits compared to the cost of borrowing funds in the market. If that value were considered, the fair value of the Company's net assets could increase. Borrowed Funds The fair value of borrowed funds is based on the discounted value of contractual cash flows. The discount rate is estimated using the rates currently available for borrowings of similar remaining maturities. As such, the Company classifies borrowed funds as Level 2. Accrued Interest Payable The fair value estimate approximates the carrying amount as this financial instrument has a short maturity. As such, the Company classifies accrued interest payable as Level 2. Derivatives The fair value of interest rate swaps is determined using inputs that are observable in the market place obtained from third parties including yield curves, publicly available volatilities, and floating indexes and, accordingly, are classified as Level 2 inputs. The credit value adjustments associated with derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. As of December 31, 2017 and 2016 , the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives due to collateral postings. Off-Balance-Sheet Instruments Off-balance-sheet instruments include loan commitments. Fair values for loan commitments have not been presented as the future revenue derived from such financial instruments is not significant. Limitations Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These values 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. Because no market exists for a significant portion of the Company's financial instruments, fair value estimates are based on Management's 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 are based on existing on- and off-balance-sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. Other significant assets and liabilities that are not considered financial instruments include the deferred tax asset, premises and equipment, and other real estate owned. In addition, tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in any of the estimates.
New Accounting Pronouncements	New Accounting Pronouncements The FASB issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, in 2014 to replace the current plethora of industry-specific rules with a broad, principles-based framework for recognizing and measuring revenue. Due to the complexity of the new pronouncement and the anticipated effort required by entities in many industries to implement ASU No. 2014-09, FASB delayed the effective date. Public business entities, certain not-for-profit entities, and certain employee benefit plans should apply the guidance to annual reporting periods beginning after December 15, 2017, and all other entities should apply the guidance to annual reporting periods beginning after December 15, 2018. FASB formed a Transition Resource Group to assist it in identifying implementation issues that may require further clarification or amendment to ASU No. 2014-09. As a result of that group’s deliberations, FASB has issued the following amendments, which will be effective concurrently with ASU No. 2014-09: ASU No. 2016-08, Principal versus Agent Considerations, which clarifies whether an entity should record the gross amount of revenue or only its ultimate share when a third party is also involved in providing goods or services to a customer; ASU No. 2016-10, Identifying Performance Obligations and Licensing, which clarifies and simplifies the process for determining whether performance obligations to a customer should be segregated and accounted for individually, and clarifies how the new revenue rules apply to licenses of intellectual property; and ASU No. 2016-12, Narrow-Scope Improvements and Practical Expedients, which clarifies and simplifies the process of assessing collectability of consideration under a contract, presentation of sales taxes, accounting for noncash consideration received, and certain transitional issues. Since the guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other U.S. GAAP, the Company does not expect the new guidance to have a material impact on revenue most closely associated with financial instruments, including interest income and expense. The Company is currently performing an overall assessment of revenue streams and reviewing contracts potentially affected by the ASU including trust and asset management fees, deposit related fees, interchange fees, and merchant income, to determine the potential impact the new guidance is expected to have on the Company’s Consolidated Financial Statements. In addition, the Company continues to follow certain implementation issues relevant to the banking industry which are still pending resolution. The Company plans to adopt ASU No. 2014-09 on January 1, 2018 utilizing the modified retrospective approach. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. The ASU was issued to enhance the reporting model for financial instruments to provide users of financial statements with more decision-useful information. This ASU changes how entities account for equity investments that do not result in consolidation and are not accounted for under the equity method of accounting. The ASU also changes certain disclosure requirements and other aspects of U.S. GAAP, including a requirement for public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Management does not expect the ASU to have a material effect on the Company's consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The ASU was issued to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2018. Management is reviewing the guidance in the ASU to determine whether it will have a material effect on the Company’s consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting. This ASU includes provisions intended to simplify various aspects related to how share-based payments are accounted for and presented in the financial statements. Some of the key provisions of this new ASU include: (1) companies will no longer record excess tax benefits and certain tax deficiencies in additional paid-in capital (APIC). Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement, and APIC pools will be eliminated. The guidance also eliminates the requirement that excess tax benefits be realized before companies can recognize them. In addition, the guidance requires companies to present excess tax benefits as an operating activity on the statement of cash flows rather than as a financing activity; (2) increase the amount an employer can withhold to cover income taxes on awards and still qualify for the exception to liability classification for shares used to satisfy the employer’s statutory income tax withholding obligation. The new guidance will also require an employer to classify the cash paid to a tax authority when shares are withheld to satisfy its statutory income tax withholding obligation as a financing activity on its statement of cash flows (current guidance did not specify how these cash flows should be classified); and (3) permit companies to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated on the date the award is granted, or recognized when they occur. ASU No. 2016-09 is effective for interim and annual reporting periods beginning after December 15, 2016. The adoption of the ASU did not have a material effect on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Under the new guidance, which will replace the existing incurred loss model for recognizing credit losses, banks and other lending institutions will be required to recognize the full amount of expected credit losses. The new guidance, which is referred to as the current expected credit loss model, requires that expected credit losses for financial assets held at the reporting date that are accounted for at amortized cost be measured and recognized based on historical experience and current and reasonably supportable forecasted conditions to reflect the full amount of expected credit losses. A modified version of these requirements also applies to debt securities classified as available for sale. The ASU is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, including interim periods within such years. The Company is currently evaluating the impact of the adoption of the ASU on its consolidated financial statements, and anticipates it may have a material impact. The Bank has formed an implementation committee for ASU 2016-13. To date, committee members have participated in educational seminars on the new standards, begun the process of identifying the historical data sets that will be necessary to implement the new standard, and chose a third-party vendor who provides software solutions for ASU 2016-13 modeling and calculation. In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. The ASU was issued to reduce the cost and complexity of the goodwill impairment test. To simplify the subsequent measurement of goodwill, step two of the goodwill impairment test was eliminated. Instead, a Company will recognize an impairment of goodwill should the carrying value of a reporting unit exceed its fair value (i.e. step one). The ASU will be effective for the Company on January 1, 2020 and will be applied prospectively. The Company does not expect the implementation to have a material effect on the Company's consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-08, Premium Amortization on Purchased Callable Debt Securities. This ASU shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. Today, entities generally amortize the premium over the contractual life of the security. The new guidance does not change the accounting for purchased callable debt securities held at a discount; the discount continues to be accreted to maturity. The ASU is effective for interim and annual reporting periods beginning after December 15, 2018; early adoption is permitted. The guidance calls for a modified retrospective transition approach under which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company's current practice aligns with the ASU therefore Management believes there will be no impact on the Company's consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. The ASU was issued to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a shared-based payment award. The ASU include guidance on determining which changes to the terms and conditions of share-based payment awards require and entity to apply modification accounting under Topic 718. The ASU is effective for the annual period, and interim periods within the annual periods, beginning after December 15, 2017. Early adoption is permitted, including adoption in any interim period. The ASU should be applied prospectively to an award modified on or after the adoption date. Management does not expect the ASU to have a material effect on the Company's consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815). The amendments in this ASU improve the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements. In addition, this ASU makes certain targeted improvements to simplify the application of the hedge accounting guidance in current US GAAP. The amendments in this ASU are effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal year. Early application is permitted in any interim period after issuance of the ASU. Management is reviewing the guidance in this ASU to determine whether it will have a material effect on the Company's consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Loss). This ASU was issued to allow a reclassification from accumulated other comprehensive income (loss) to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. Consequently, the amendments eliminate the stranded tax effects resulting from the Tax Cuts and Jobs Act and will improve the usefulness of information reported to financial statement users. However, because the amendments only relate to the reclassification of the income tax effects of the Tax Cuts and Jobs Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not affected. The ASU is effective for fiscal years beginning after December 15, 2018, with early adoption permitted for financial statements which have not yet been issued. The Company adopted the ASU for the December 31, 2017 consolidated financial statements, which resulted in a reclassification adjustment on the Consolidated Statements of Changes in Shareholders' Equity of $297,000 from accumulated other comprehensive income (loss) to retained earnings. Refer to Note 9, Income Taxes, for additional information.
Financial Derivative Instruments	As part of its overall asset and liability management strategy, the Company periodically uses derivative instruments to mitigate significant unplanned fluctuations in earnings and cash flows caused by interest rate volatility. The Company’s interest rate risk management strategy involves modifying the re-pricing characteristics of certain assets or liabilities so that changes in interest rates do not have a significant effect on net interest income. The Company recognizes its derivative instruments in the consolidated balance sheet at fair value. On the date the derivative instrument is entered into, the Company designates whether the derivative is part of a hedging relationship (i.e., cash flow or fair value hedge). The Company formally documents relationships between hedging instruments and hedged items, as well as its risk management objective and strategy for undertaking hedge transactions. The Company also assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives used in hedging transactions are highly effective in offsetting the changes in cash flows or fair values of hedged items. Changes in fair value of derivative instruments that are highly effective and qualify as cash flow hedges are recorded in other comprehensive income or loss. Any ineffective portion is recorded in earnings. The Company discontinues hedge accounting when it is determined that the derivative is no longer highly effective in offsetting changes of the hedged risk on the hedged item, or management determines that the designation of the derivative as a hedging instrument is no longer appropriate. In 2016, interest rate swaps were contracted to limit the Company’s exposure to rising interest rates on short-term liabilities indexed to one-month London Inter-bank Offered Rates (LIBOR). The interest rate swaps were designated as cash flow hedges.

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Available For Sale, Held-to-Maturity, and Restricted Equity Securities	The following tables summarize the amortized cost and estimated fair value of investment securities at December 31, 2017 and 2016 : Amortized Unrealized Unrealized Fair Value As of December 31, 2017 Cost Gains Losses (Estimated) Securities available for sale Mortgage-backed securities $ 293,689,000 $ 722,000 $ (4,422,000 ) $ 289,989,000 State and political subdivisions 6,860,000 16,000 (107,000 ) 6,769,000 Other equity securities 3,296,000 121,000 (3,000 ) 3,414,000 $ 303,845,000 $ 859,000 $ (4,532,000 ) $ 300,172,000 Securities to be held to maturity U.S. Government-sponsored agencies $ 11,155,000 $ — $ (180,000 ) $ 10,975,000 Mortgage-backed securities 23,284,000 568,000 (128,000 ) 23,724,000 State and political subdivisions 217,828,000 3,931,000 (1,103,000 ) 220,656,000 Corporate securities 4,300,000 — — 4,300,000 $ 256,567,000 $ 4,499,000 $ (1,411,000 ) $ 259,655,000 Restricted equity securities Federal Home Loan Bank Stock $ 9,321,000 $ — $ — $ 9,321,000 Federal Reserve Bank Stock 1,037,000 — — 1,037,000 $ 10,358,000 $ — $ — $ 10,358,000 Amortized Unrealized Unrealized Fair Value As of December 31, 2016 Cost Gains Losses (Estimated) Securities available for sale Mortgage-backed securities $ 282,397,000 $ 1,334,000 $ (3,127,000 ) $ 280,604,000 State and political subdivisions 16,183,000 475,000 (176,000 ) 16,482,000 Other equity securities 3,274,000 63,000 (7,000 ) 3,330,000 $ 301,854,000 $ 1,872,000 $ (3,310,000 ) $ 300,416,000 Securities to be held to maturity U.S. Government-sponsored agencies $ 11,943,000 $ 35,000 $ (233,000 ) $ 11,745,000 Mortgage-backed securities 31,201,000 967,000 (147,000 ) 32,021,000 State and political subdivisions 179,384,000 1,971,000 (3,884,000 ) 177,471,000 Corporate securities 4,300,000 — — 4,300,000 $ 226,828,000 $ 2,973,000 $ (4,264,000 ) $ 225,537,000 Restricted equity securities Federal Home Loan Bank Stock $ 10,893,000 $ — $ — $ 10,893,000 Federal Reserve Bank Stock 1,037,000 — — 1,037,000 $ 11,930,000 $ — $ — $ 11,930,000
Contractual Maturities of Investment Securities	The following table summarizes the contractual maturities of investment securities at December 31, 2017 : Securities available for sale Securities to be held to maturity Amortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated) Due in 1 year or less $ 111,000 $ 112,000 $ 635,000 $ 637,000 Due in 1 to 5 years 841,000 842,000 18,059,000 18,164,000 Due in 5 to 10 years 29,003,000 29,177,000 37,182,000 37,719,000 Due after 10 years 270,594,000 266,627,000 200,691,000 203,135,000 Equity securities 3,296,000 3,414,000 — — $ 303,845,000 $ 300,172,000 $ 256,567,000 $ 259,655,000 The following table summarizes the contractual maturities of investment securities at December 31, 2016 : Securities available for sale Securities to be held to maturity Amortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated) Due in 1 year or less $ 253,000 $ 253,000 $ 906,000 $ 913,000 Due in 1 to 5 years 2,251,000 2,298,000 13,451,000 13,714,000 Due in 5 to 10 years 21,043,000 21,505,000 41,588,000 42,448,000 Due after 10 years 275,033,000 273,030,000 170,883,000 168,462,000 Equity securities 3,274,000 3,330,000 — — $ 301,854,000 $ 300,416,000 $ 226,828,000 $ 225,537,000
Schedule of Securities Gains and Losses	The following table shows securities gains and losses for 2017 , 2016 and 2015 : 2017 2016 2015 Proceeds from sales of securities $ 15,587,000 $ 10,309,000 $ 35,468,000 Gross realized gains 471,000 673,000 1,399,000 Gross realized losses — — — Net gain $ 471,000 $ 673,000 $ 1,399,000 Related income taxes $ 165,000 $ 236,000 $ 490,000
Schedule of Temporary Impairment Losses	Information regarding securities temporarily impaired as of December 31, 2017 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized As of December 31, 2017 Value Losses Value Losses Value Losses U.S. Government-sponsored agencies $ 7,161,000 $ (94,000 ) $ 3,814,000 $ (86,000 ) $ 10,975,000 $ (180,000 ) Mortgage-backed securities 132,025,000 (1,857,000 ) 101,707,000 (2,693,000 ) 233,732,000 (4,550,000 ) State and political subdivisions 9,425,000 (149,000 ) 38,864,000 (1,061,000 ) 48,289,000 (1,210,000 ) Other equity securities — — 9,000 (3,000 ) 9,000 (3,000 ) $ 148,611,000 $ (2,100,000 ) $ 144,394,000 $ (3,843,000 ) $ 293,005,000 $ (5,943,000 ) As of December 31, 2016 , there were 299 securities with unrealized losses held in the Company's portfolio. These securities were temporarily impaired as a result of changes in interest rates reducing their fair value, of which 15 had been temporarily impaired for 12 months or more. Information regarding securities temporarily impaired as of December 31, 2016 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized As of December 31, 2016 Value Losses Value Losses Value Losses U.S. Government-sponsored agencies $ 6,642,000 $ (233,000 ) $ — $ — $ 6,642,000 $ (233,000 ) Mortgage-backed securities 197,528,000 (3,090,000 ) 2,905,000 (184,000 ) 200,433,000 (3,274,000 ) State and political subdivisions 72,348,000 (4,060,000 ) — — 72,348,000 (4,060,000 ) Other equity securities — — 128,000 (7,000 ) 128,000 (7,000 ) $ 276,518,000 $ (7,383,000 ) $ 3,033,000 $ (191,000 ) $ 279,551,000 $ (7,574,000 )

Mortgage Servicing Rights (Tabl

Mortgage Servicing Rights (Tables)	12 Months Ended
	Dec. 31, 2017
Transfers and Servicing [Abstract]
Reconciliation of Mortgage Servicing Assets	Mortgage servicing rights are included in other assets and detailed in the following table: As of December 31, 2017 2016 Mortgage servicing rights $ 5,428,000 $ 5,901,000 Accumulated amortization (4,160,000 ) (4,680,000 ) Impairment reserve — (108,000 ) $ 1,268,000 $ 1,113,000

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Abstract]
Composition of Loan Portfolio	The following table shows the composition of the Company's loan portfolio as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 Commercial Real estate $ 323,809,000 27.8 % $ 302,506,000 28.2 % Construction 38,056,000 3.3 % 25,406,000 2.4 % Other 181,528,000 15.6 % 150,769,000 14.1 % Municipal 33,391,000 2.9 % 27,056,000 2.5 % Residential Term 432,661,000 37.1 % 411,469,000 38.4 % Construction 17,868,000 1.5 % 18,303,000 1.7 % Home equity line of credit 111,302,000 9.6 % 110,907,000 10.4 % Consumer 25,524,000 2.2 % 25,110,000 2.3 % Total loans $ 1,164,139,000 100.0 % $ 1,071,526,000 100.0 %
Loans to Directors, Officers and Employees which exceed $60,000	A summary of loans to directors and executive officers is as follows: For the years ended December 31, 2017 2016 Balance at beginning of year $ 23,293,000 $ 20,401,000 New loans 867,000 6,278,000 Repayments (1,863,000 ) (3,386,000 ) Balance at end of year $ 22,297,000 $ 23,293,000
Past Due Loans Aging	Information on the past-due status of loans as of December 31, 2017 , is presented in the following table: 30-59 Days Past Due 60-89 Days Past Due 90+ Days Past Due All Past Due Current Total 90+ Days & Accruing Commercial Real estate $ 574,000 $ 80,000 $ 220,000 $ 874,000 $ 322,935,000 $ 323,809,000 $ — Construction — — — — 38,056,000 38,056,000 — Other 542,000 6,663,000 574,000 7,779,000 173,749,000 181,528,000 — Municipal — — — — 33,391,000 33,391,000 — Residential Term 1,031,000 4,372,000 2,256,000 7,659,000 425,002,000 432,661,000 436,000 Construction 101,000 370,000 — 471,000 17,397,000 17,868,000 — Home equity line of credit 537,000 445,000 725,000 1,707,000 109,595,000 111,302,000 — Consumer 159,000 18,000 9,000 186,000 25,338,000 25,524,000 9,000 Total $ 2,944,000 $ 11,948,000 $ 3,784,000 $ 18,676,000 $ 1,145,463,000 $ 1,164,139,000 $ 445,000 Information on the past-due status of loans as of December 31, 2016 , is presented in the following table: 30-59 Days Past Due 60-89 Days Past Due 90+ Days Past Due All Past Due Current Total 90+ Days & Accruing Commercial Real estate $ 1,039,000 $ 22,000 $ 2,415,000 $ 3,476,000 $ 299,030,000 $ 302,506,000 $ 753,000 Construction — — — — 25,406,000 25,406,000 — Other 202,000 33,000 796,000 1,031,000 149,738,000 150,769,000 20,000 Municipal — — — — 27,056,000 27,056,000 — Residential Term 631,000 3,970,000 1,802,000 6,403,000 405,066,000 411,469,000 — Construction — — — — 18,303,000 18,303,000 — Home equity line of credit 704,000 157,000 703,000 1,564,000 109,343,000 110,907,000 — Consumer 135,000 45,000 4,000 184,000 24,926,000 25,110,000 4,000 Total $ 2,711,000 $ 4,227,000 $ 5,720,000 $ 12,658,000 $ 1,058,868,000 $ 1,071,526,000 $ 777,000
Nonaccrual Loans	Information on nonaccrual loans as of December 31, 2017 and 2016 is presented in the following table: As of December 31, 2017 2016 Commercial Real estate $ 752,000 $ 1,907,000 Construction — — Other 9,357,000 964,000 Municipal — — Residential Term 3,778,000 4,060,000 Construction — — Home equity line of credit 833,000 843,000 Consumer 16,000 — Total $ 14,736,000 $ 7,774,000
Impaired Loans	Information regarding impaired loans is as follows: For the years ended December 31, 2017 2016 2015 Average investment in impaired loans $ 29,108,000 $ 28,217,000 $ 32,698,000 Interest income recognized on impaired loans, all on cash basis 784,000 1,104,000 1,220,000 As of December 31, 2017 2016 Balance of impaired loans $ 31,392,000 $ 27,583,000 Less portion for which no allowance for loan losses is allocated (18,023,000 ) (19,716,000 ) Portion of impaired loan balance for which an allowance for loan losses is allocated $ 13,369,000 $ 7,867,000 Portion of allowance for loan losses allocated to the impaired loan balance $ 1,812,000 $ 974,000
Impaired Loans by class of financing receivable	A breakdown of impaired loans by category as of December 31, 2017 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 3,791,000 $ 3,996,000 $ — $ 5,124,000 $ 164,000 Construction 741,000 741,000 — 62,000 38,000 Other 2,591,000 2,671,000 — 1,908,000 36,000 Municipal — — — — — Residential Term 9,769,000 10,909,000 — 10,770,000 297,000 Construction — — — — — Home equity line of credit 1,115,000 1,429,000 — 1,351,000 18,000 Consumer 16,000 29,000 — 12,000 — $ 18,023,000 $ 19,775,000 $ — $ 19,227,000 $ 553,000 With an Allowance Recorded Commercial Real estate $ 3,999,000 $ 4,116,000 $ 224,000 $ 4,460,000 $ 152,000 Construction — — — 699,000 — Other 7,327,000 7,371,000 1,309,000 2,584,000 — Municipal — — — — — Residential Term 1,979,000 2,144,000 255,000 2,106,000 79,000 Construction — — — — — Home equity line of credit 64,000 67,000 24,000 32,000 — Consumer — — — — — $ 13,369,000 $ 13,698,000 $ 1,812,000 $ 9,881,000 $ 231,000 Total Commercial Real estate $ 7,790,000 $ 8,112,000 $ 224,000 $ 9,584,000 $ 316,000 Construction 741,000 741,000 — 761,000 38,000 Other 9,918,000 10,042,000 1,309,000 4,492,000 36,000 Municipal — — — — — Residential Term 11,748,000 13,053,000 255,000 12,876,000 376,000 Construction — — — — — Home equity line of credit 1,179,000 1,496,000 24,000 1,383,000 18,000 Consumer 16,000 29,000 — 12,000 — $ 31,392,000 $ 33,473,000 $ 1,812,000 $ 29,108,000 $ 784,000 Substantially all interest income recognized on impaired loans for all classes of financing receivables was recognized on a cash basis as received. A breakdown of impaired loans by category as of December 31, 2016 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 5,201,000 $ 5,614,000 $ — $ 6,252,000 $ 220,000 Construction — — — 32,000 — Other 1,671,000 1,852,000 — 1,074,000 86,000 Municipal — — — — — Residential Term 11,483,000 12,654,000 — 11,025,000 442,000 Construction — — — — — Home equity line of credit 1,361,000 1,733,000 — 1,213,000 33,000 Consumer — — — 9,000 — $ 19,716,000 $ 21,853,000 $ — $ 19,605,000 $ 781,000 With an Allowance Recorded Commercial Real estate $ 4,820,000 $ 4,925,000 $ 505,000 $ 4,153,000 $ 186,000 Construction 763,000 763,000 100,000 816,000 36,000 Other 72,000 72,000 39,000 317,000 — Municipal — — — — — Residential Term 2,186,000 2,328,000 304,000 3,209,000 101,000 Construction — — — — — Home equity line of credit 26,000 28,000 26,000 69,000 — Consumer — — — 48,000 — $ 7,867,000 $ 8,116,000 $ 974,000 $ 8,612,000 $ 323,000 Total Commercial Real estate $ 10,021,000 $ 10,539,000 $ 505,000 $ 10,405,000 $ 406,000 Construction 763,000 763,000 100,000 848,000 36,000 Other 1,743,000 1,924,000 39,000 1,391,000 86,000 Municipal — — — — — Residential Term 13,669,000 14,982,000 304,000 14,234,000 543,000 Construction — — — — — Home equity line of credit 1,387,000 1,761,000 26,000 1,282,000 33,000 Consumer — — — 57,000 — $ 27,583,000 $ 29,969,000 $ 974,000 $ 28,217,000 $ 1,104,000 A breakdown of impaired loans by category as of December 31, 2015 , is presented in the following table: Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Recognized Interest Income With No Related Allowance Commercial Real estate $ 7,173,000 $ 7,496,000 $ — $ 8,990,000 $ 301,000 Construction 30,000 30,000 — 3,000 1,000 Other 1,163,000 1,210,000 — 1,893,000 76,000 Municipal — — — — — Residential Term 11,122,000 12,157,000 — 10,480,000 415,000 Construction — — — — — Home equity line of credit 1,401,000 2,054,000 — 1,400,000 43,000 Consumer — — — 42,000 3,000 $ 20,889,000 $ 22,947,000 $ — $ 22,808,000 $ 839,000 With an Allowance Recorded Commercial Real estate $ 3,544,000 $ 3,627,000 $ 89,000 $ 3,066,000 $ 149,000 Construction 996,000 996,000 302,000 1,153,000 44,000 Other 71,000 77,000 8,000 256,000 5,000 Municipal — — — — — Residential Term 3,966,000 4,193,000 326,000 5,228,000 180,000 Construction — — — — — Home equity line of credit 65,000 66,000 29,000 187,000 3,000 Consumer — — — — — $ 8,642,000 $ 8,959,000 $ 754,000 $ 9,890,000 $ 381,000 Total Commercial Real estate $ 10,717,000 $ 11,123,000 $ 89,000 $ 12,056,000 $ 450,000 Construction 1,026,000 1,026,000 302,000 1,156,000 45,000 Other 1,234,000 1,287,000 8,000 2,149,000 81,000 Municipal — — — — — Residential Term 15,088,000 16,350,000 326,000 15,708,000 595,000 Construction — — — — — Home equity line of credit 1,466,000 2,120,000 29,000 1,587,000 46,000 Consumer — — — 42,000 3,000 $ 29,531,000 $ 31,906,000 $ 754,000 $ 32,698,000 $ 1,220,000
Troubled Debt Restructurings on Financing Receivables	The following table shows TDRs by class and the specific reserve as of December 31, 2017 : Number of Loans Balance Specific Reserves Commercial Real estate 8 $ 7,038,000 $ 90,000 Construction 1 741,000 — Other 4 561,000 — Municipal — — — Residential Term 46 8,948,000 233,000 Construction — — — Home equity line of credit 3 513,000 — Consumer — — — 62 $ 17,801,000 $ 323,000 The following table shows TDRs by class and the specific reserve as of December 31, 2016 : Number of Loans Balance Specific Reserves Commercial Real estate 10 $ 8,937,000 $ 375,000 Construction 1 763,000 100,000 Other 5 779,000 — Municipal — — — Residential Term 52 10,503,000 261,000 Construction — — — Home equity line of credit 3 544,000 — Consumer — — — 71 $ 21,526,000 $ 736,000 As of December 31, 2017 , 12 of the loans classified as TDRs with a total balance of $1,407,000 were more than 30 days past due. None of these loans had been placed on TDR status in the previous 12 months. The following table shows past-due TDRs by class and the associated specific reserves included in the allowance for loan losses as of December 31, 2017 : Number of Loans Balance Specific Reserves Commercial Real estate — $ — $ — Construction — — — Other — — — Municipal — — — Residential Term 11 1,240,000 44,000 Construction — — — Home equity line of credit 1 167,000 — Consumer — — — 12 $ 1,407,000 $ 44,000 As of December 31, 2016 , 12 of the loans classified as TDRs with a total balance of $2,303,000 were more than 30 days past due. None of these loans had been placed on TDR status in the previous 12 months. The following table shows past-due TDRs by class and the associated specific reserves included in the allowance for loan losses as of December 31, 2016 : Number of Loans Balance Specific Reserves Commercial Real estate 1 $ 822,000 $ 264,000 Construction — — — Other — — — Municipal — — — Residential Term 10 1,314,000 26,000 Construction — — — Home equity line of credit 1 167,000 — Consumer — — — 12 $ 2,303,000 $ 290,000

Allowance for Loan Losses (Tabl

Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for loan losses by class of financing receivable and allowance	The following table summarizes the composition of the allowance for loan losses, by class of financing receivable and allowance, as of December 31, 2017 and 2016 : As of December 31, 2017 2016 Allowance for Loans Evaluated Individually for Impairment Commercial Real estate $ 224,000 $ 505,000 Construction — 100,000 Other 1,309,000 39,000 Municipal — — Residential Term 255,000 304,000 Construction — — Home equity line of credit 24,000 26,000 Consumer — — Total $ 1,812,000 $ 974,000 Allowance for Loans Evaluated Collectively for Impairment Commercial Real estate $ 3,648,000 $ 3,483,000 Construction 434,000 296,000 Other 2,049,000 1,741,000 Municipal 20,000 18,000 Residential Term 875,000 984,000 Construction 36,000 44,000 Home equity line of credit 668,000 781,000 Consumer 545,000 559,000 Unallocated 642,000 1,258,000 Total $ 8,917,000 $ 9,164,000 Total Allowance for Loan Losses Commercial Real estate $ 3,872,000 $ 3,988,000 Construction 434,000 396,000 Other 3,358,000 1,780,000 Municipal 20,000 18,000 Residential Term 1,130,000 1,288,000 Construction 36,000 44,000 Home equity line of credit 692,000 807,000 Consumer 545,000 559,000 Unallocated 642,000 1,258,000 Total $ 10,729,000 $ 10,138,000
Loan losses by loan segment and allowance element	A breakdown of the allowance for loan losses as of December 31, 2017 and 2016 , by class of financing receivable and allowance element, is presented in the following tables: As of December 31, 2017 Specific Reserves on Loans Evaluated Individually for Impairment General Reserves on Loans Based on Historical Loss Experience Reserves for Qualitative Factors Unallocated Reserves Total Reserves Commercial Real estate $ 224,000 $ 1,285,000 $ 2,363,000 $ — $ 3,872,000 Construction — 153,000 281,000 — 434,000 Other 1,309,000 723,000 1,326,000 — 3,358,000 Municipal — — 20,000 — 20,000 Residential Term 255,000 311,000 564,000 — 1,130,000 Construction — 13,000 23,000 — 36,000 Home equity line of credit 24,000 297,000 371,000 — 692,000 Consumer — 251,000 294,000 — 545,000 Unallocated — — — 642,000 642,000 $ 1,812,000 $ 3,033,000 $ 5,242,000 $ 642,000 $ 10,729,000 As of December 31, 2016 Specific Reserves on Loans Evaluated Individually for Impairment General Reserves on Loans Based on Historical Loss Experience Reserves for Qualitative Factors Unallocated Reserves Total Reserves Commercial Real estate $ 505,000 $ 1,471,000 $ 2,012,000 $ — $ 3,988,000 Construction 100,000 125,000 171,000 — 396,000 Other 39,000 735,000 1,006,000 — 1,780,000 Municipal — — 18,000 — 18,000 Residential Term 304,000 563,000 421,000 — 1,288,000 Construction — 25,000 19,000 — 44,000 Home equity line of credit 26,000 444,000 337,000 — 807,000 Consumer — 328,000 231,000 — 559,000 Unallocated — — — 1,258,000 1,258,000 $ 974,000 $ 3,691,000 $ 4,215,000 $ 1,258,000 $ 10,138,000
Summary of risk ratings for loans	The following table summarizes the risk ratings for the Company's commercial construction, commercial real estate, commercial other and municipal loans as of December 31, 2017 : Commercial Real Estate Commercial Construction Commercial Other Municipal Loans All Risk- Rated Loans 1 Strong $ — $ — $ 1,586,000 $ — $ 1,586,000 2 Above average 12,534,000 40,000 5,776,000 32,673,000 51,023,000 3 Satisfactory 73,899,000 2,856,000 38,151,000 718,000 115,624,000 4 Average 173,956,000 22,446,000 84,360,000 — 280,762,000 5 Watch 41,652,000 12,714,000 33,934,000 — 88,300,000 6 OAEM 3,442,000 — 2,765,000 — 6,207,000 7 Substandard 18,203,000 — 14,956,000 — 33,159,000 8 Doubtful 123,000 — — — 123,000 Total $ 323,809,000 $ 38,056,000 $ 181,528,000 $ 33,391,000 $ 576,784,000 The following table summarizes the risk ratings for the Company's commercial construction, commercial real estate, commercial other and municipal loans as of December 31, 2016 : Commercial Real Estate Commercial Construction Commercial Other Municipal Loans All Risk- Rated Loans 1 Strong $ 2,000 $ — $ 850,000 $ — $ 852,000 2 Above average 13,981,000 49,000 8,934,000 25,527,000 48,491,000 3 Satisfactory 81,286,000 1,345,000 48,212,000 1,529,000 132,372,000 4 Average 139,421,000 16,506,000 65,146,000 — 221,073,000 5 Watch 43,181,000 7,349,000 16,864,000 — 67,394,000 6 OAEM 4,569,000 — 1,587,000 — 6,156,000 7 Substandard 20,066,000 157,000 9,176,000 — 29,399,000 8 Doubtful — — — — — Total $ 302,506,000 $ 25,406,000 $ 150,769,000 $ 27,056,000 $ 505,737,000
Allowance for loan losses transactions	The following tables present allowance for loan losses activity by class, allowance for loan loss balances by class and related loan balances by class for the years ended December 31, 2017 , 2016 and 2015 : For the year ended December 31, 2017 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,988,000 $ 396,000 $ 1,780,000 $ 18,000 $ 1,288,000 $ 44,000 $ 807,000 $ 559,000 $ 1,258,000 $ 10,138,000 Chargeoffs 587,000 — 212,000 — 456,000 — 28,000 335,000 — 1,618,000 Recoveries — — 49,000 — 40,000 — 11,000 109,000 — 209,000 Provision (credit) 471,000 38,000 1,741,000 2,000 258,000 (8,000 ) (98,000 ) 212,000 (616,000 ) 2,000,000 Ending balance $ 3,872,000 $ 434,000 $ 3,358,000 $ 20,000 $ 1,130,000 $ 36,000 $ 692,000 $ 545,000 $ 642,000 $ 10,729,000 Ending balance specifically evaluated for impairment $ 224,000 $ — $ 1,309,000 $ — $ 255,000 $ — $ 24,000 $ — $ — $ 1,812,000 Ending balance collectively evaluated for impairment $ 3,648,000 $ 434,000 $ 2,049,000 $ 20,000 $ 875,000 $ 36,000 $ 668,000 $ 545,000 $ 642,000 $ 8,917,000 Related loan balances: Ending balance $ 323,809,000 $ 38,056,000 $ 181,528,000 $ 33,391,000 $ 432,661,000 $ 17,868,000 $ 111,302,000 $ 25,524,000 $ — $ 1,164,139,000 Ending balance specifically evaluated for impairment $ 7,790,000 $ 741,000 $ 9,918,000 $ — $ 11,748,000 $ — $ 1,179,000 $ 16,000 $ — $ 31,392,000 Ending balance collectively evaluated for impairment $ 316,019,000 $ 37,315,000 $ 171,610,000 $ 33,391,000 $ 420,913,000 $ 17,868,000 $ 110,123,000 $ 25,508,000 $ — $ 1,132,747,000 For the year ended December 31, 2016 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,120,000 $ 580,000 $ 1,452,000 $ 17,000 $ 1,391,000 $ 24,000 $ 893,000 $ 566,000 $ 1,873,000 $ 9,916,000 Chargeoffs 294,000 75,000 376,000 — 379,000 — 147,000 450,000 — 1,721,000 Recoveries — 8,000 129,000 — 93,000 — 5,000 108,000 — 343,000 Provision (credit) 1,162,000 (117,000 ) 575,000 1,000 183,000 20,000 56,000 335,000 (615,000 ) 1,600,000 Ending balance $ 3,988,000 $ 396,000 $ 1,780,000 $ 18,000 $ 1,288,000 $ 44,000 $ 807,000 $ 559,000 $ 1,258,000 $ 10,138,000 Ending balance specifically evaluated for impairment $ 505,000 $ 100,000 $ 39,000 $ — $ 304,000 $ — $ 26,000 $ — $ — $ 974,000 Ending balance collectively evaluated for impairment $ 3,483,000 $ 296,000 $ 1,741,000 $ 18,000 $ 984,000 $ 44,000 $ 781,000 $ 559,000 $ 1,258,000 $ 9,164,000 Related loan balances: Ending balance $ 302,506,000 $ 25,406,000 $ 150,769,000 $ 27,056,000 $ 411,469,000 $ 18,303,000 $ 110,907,000 $ 25,110,000 $ — $ 1,071,526,000 Ending balance specifically evaluated for impairment $ 10,021,000 $ 763,000 $ 1,743,000 $ — $ 13,669,000 $ — $ 1,387,000 $ — $ — $ 27,583,000 Ending balance collectively evaluated for impairment $ 292,485,000 $ 24,643,000 $ 149,026,000 $ 27,056,000 $ 397,800,000 $ 18,303,000 $ 109,520,000 $ 25,110,000 $ — $ 1,043,943,000 For the year ended December 31, 2015 Commercial Residential Home Equity Line of Credit Real Estate Construction Other Municipal Term Construction Consumer Unallocated Total Allowance for loan losses: Beginning balance $ 3,532,000 $ 823,000 $ 1,505,000 $ 15,000 $ 1,185,000 $ 20,000 $ 1,060,000 $ 542,000 $ 1,662,000 $ 10,344,000 Chargeoffs 280,000 9,000 732,000 — 420,000 — 582,000 350,000 — 2,373,000 Recoveries 2,000 1,000 88,000 — 152,000 — 31,000 121,000 — 395,000 Provision (credit) (134,000 ) (235,000 ) 591,000 2,000 474,000 4,000 384,000 253,000 211,000 1,550,000 Ending balance $ 3,120,000 $ 580,000 $ 1,452,000 $ 17,000 $ 1,391,000 $ 24,000 $ 893,000 $ 566,000 $ 1,873,000 $ 9,916,000 Ending balance specifically evaluated for impairment $ 89,000 $ 302,000 $ 8,000 $ — $ 326,000 $ — $ 29,000 $ — $ — $ 754,000 Ending balance collectively evaluated for impairment $ 3,031,000 $ 278,000 $ 1,444,000 $ 17,000 $ 1,065,000 $ 24,000 $ 864,000 $ 566,000 $ 1,873,000 $ 9,162,000 Related loan balances: Ending balance $ 269,462,000 $ 24,881,000 $ 128,341,000 $ 19,751,000 $ 403,030,000 $ 8,451,000 $ 110,202,000 $ 24,520,000 $ — $ 988,638,000 Ending balance specifically evaluated for impairment $ 10,717,000 $ 1,026,000 $ 1,234,000 $ — $ 15,088,000 $ — $ 1,466,000 $ — $ — $ 29,531,000 Ending balance collectively evaluated for impairment $ 258,745,000 $ 23,855,000 $ 127,107,000 $ 19,751,000 $ 387,942,000 $ 8,451,000 $ 108,736,000 $ 24,520,000 $ — $ 959,107,000

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 are carried at cost and consist of the following: As of December 31, 2017 2016 Land $ 4,639,000 $ 4,742,000 Land improvements 1,052,000 1,041,000 Buildings 22,254,000 21,601,000 Equipment 13,147,000 12,032,000 41,092,000 39,416,000 Less accumulated depreciation 18,590,000 17,214,000 $ 22,502,000 $ 22,202,000
Schedule of Anticipated Rental Revenue	Future minimum receipts under lease agreements at December 31, 2017 for each of the next five years and in the aggregate are: 2018 $192,000 2019 141,000 2020 101,000 2021 97,000 2022 94,000 Thereafter 9,000 $634,000

Other Real Estate Owned (Tables

Other Real Estate Owned (Tables)	12 Months Ended
	Dec. 31, 2017
Real Estate Owned, Disclosure of Detailed Components [Abstract]
Other Real Estate Owned	The following summarizes other real estate owned: As of December 31, 2017 2016 Real estate acquired in settlement of loans $ 1,012,000 $ 375,000
Change in Allowance for Losses from Other Real Estate Owned	Changes in the allowance for losses from other real estate owned were as follows: For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ 205,000 $ 162,000 $ 654,000 Losses charged to allowance (169,000 ) (89,000 ) (803,000 ) Provision charged to operating expenses 17,000 132,000 311,000 Balance at end of year $ 53,000 $ 205,000 $ 162,000

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current and Deferred Components of Income Tax Expense	The current and deferred components of income tax expense (benefit) were as follows: For the years ended December 31, 2017 2016 2015 Federal income tax Current $ 4,184,000 $ 6,276,000 $ 4,895,000 Deferred 2,083,000 (139,000 ) 332,000 6,267,000 6,137,000 5,227,000 State franchise tax 345,000 317,000 287,000 $ 6,612,000 $ 6,454,000 $ 5,514,000
Actual Tax Expense from Expected Tax Expense	The actual tax expense differs from the expected tax expense (computed by applying the applicable U.S. Federal corporate income tax rate to income before income taxes) as follows: For the years ended December 31, 2017 2016 2015 Expected tax expense $ 9,170,000 $ 8,562,000 $ 7,602,000 Non-taxable income (2,625,000 ) (2,176,000 ) (2,086,000 ) State franchise tax, net of federal tax benefit 224,000 206,000 187,000 Equity compensation (83,000 ) — — Tax credits, net of amortization (88,000 ) (105,000 ) (185,000 ) Change in federal tax rate 134,000 — — Other (120,000 ) (33,000 ) (4,000 ) $ 6,612,000 $ 6,454,000 $ 5,514,000
Components of Deferred Tax Assets and Liabilities	Items that give rise to the deferred income tax assets and liabilities and the tax effect of each at December 31, 2017 and 2016 are as follows: 2017 2016 Allowance for loan losses $ 2,253,000 $ 3,548,000 OREO 11,000 72,000 Accrued pension and post-retirement 1,036,000 1,730,000 Goodwill — 2,000 Unrealized loss on securities transferred from available for sale to held to maturity 46,000 70,000 Unrealized loss on securities available for sale 772,000 503,000 Restricted stock grants 173,000 237,000 Core deposit intangible 15,000 20,000 Investment in flow through entities 22,000 29,000 Other assets 28,000 48,000 Total deferred tax asset 4,356,000 6,259,000 Net deferred loan costs (1,313,000 ) (1,895,000 ) Depreciation (1,306,000 ) (1,808,000 ) Goodwill (39,000 ) — Mortgage servicing rights (266,000 ) (390,000 ) Unrealized gain on derivative instruments (410,000 ) (626,000 ) Prepaid expense (821,000 ) — Total deferred tax liability (4,155,000 ) (4,719,000 ) Net deferred tax asset $ 201,000 $ 1,540,000

Certificates of Deposit (Tables

Certificates of Deposit (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Certificates of deposit	The following table represents the breakdown of certificates of deposit at December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 Certificates of deposit < $100,000 $ 284,066,000 $ 195,115,000 Certificates $100,000 to $250,000 232,759,000 240,904,000 Certificates $250,000 and over 42,176,000 40,601,000 $ 559,001,000 $ 476,620,000
Maturities of certificates of deposit	At December 31, 2017 , the scheduled maturities of certificates of deposit are as follows: Year of Maturity Less than $100,000 $100,000 and Greater All Certificates of Deposit 2018 $ 215,571,000 $ 177,745,000 $ 393,316,000 2019 26,401,000 27,164,000 53,565,000 2020 17,516,000 33,710,000 51,226,000 2021 13,137,000 17,060,000 30,197,000 2022 11,411,000 19,256,000 30,667,000 2023 and thereafter 30,000 — 30,000 $ 284,066,000 $ 274,935,000 $ 559,001,000

Borrowed Funds (Tables)

Borrowed Funds (Tables)	12 Months Ended
	Dec. 31, 2017
Borrowed Funds [Abstract]
Range of Interest Rates and Maturity Dates of Borrowed Funds	Borrowed funds at December 31, 2017 and 2016 have the following range of interest rates and maturity dates: As of December 31, 2017 Federal Home Loan Bank Advances 2018 1.59% - 3.25% $ 43,074,000 2020 1.60% - 1.97% 55,000,000 2021 1.55% 10,000,000 2023 and thereafter 0.00% - 0.99% 50,120,000 158,194,000 Repurchase agreements Municipal and commercial customers 0.15% - 2.48% 70,564,000 $ 228,758,000 As of December 31, 2016 Federal Home Loan Bank Advances 2017 0.99% - 3.69% $ 74,600,000 2018 2.25% - 3.25% 30,000,000 2020 1.60% - 1.97% 55,000,000 2021 1.55% 10,000,000 2022 and thereafter 0.00% - 0.59% 25,127,000 194,727,000 Repurchase agreements Municipal and commercial customers 0.15% - 1.93% 84,174,000 $ 278,901,000

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits, Description [Abstract]
Accumulated post-retirement benefit obligation and funded status	The following table sets forth the accumulated post-retirement benefit obligation and funded status: At December 31, 2017 2016 2015 Change in benefit obligations Benefit obligation at beginning of year: $ 1,870,000 $ 1,967,000 $ 1,928,000 Interest cost 77,000 81,000 80,000 Benefits paid (113,000 ) (109,000 ) (102,000 ) Actuarial (gain) loss 40,000 (69,000 ) 61,000 Benefit obligation at end of year: $ 1,874,000 $ 1,870,000 $ 1,967,000 Funded status Benefit obligation at end of year $ (1,874,000 ) $ (1,870,000 ) $ (1,967,000 ) Unamortized loss 186,000 156,000 240,000 Accrued benefit cost $ (1,688,000 ) $ (1,714,000 ) $ (1,727,000 ) Weighted average discount rate as of December 31 4.25 % 4.25 % 4.25 %
Schedule of net benefit costs	The following table sets forth the net periodic benefit cost: For the years ended December 31, 2017 2016 2015 Components of net periodic benefit cost Interest cost $ 77,000 $ 81,000 $ 80,000 Amortization of loss — 4,000 — Other settlement expense 11,000 11,000 12,000 Net periodic benefit cost $ 88,000 $ 96,000 $ 92,000 Weighted average discount rate for net periodic cost 4.25 % 4.25 % 4.25 %
Schedule of net periodic benefit cost not yet recognized	In accordance with FASB ASC Topic 715, "Compensation – Retirement Benefits", amounts not yet reflected in net periodic benefit cost and included in accumulated other comprehensive income (loss) are as follows: At December 31, 2017 2016 Portion to Be Recognized in Income in 2018 Unamortized net actuarial loss $ (186,000 ) $ (156,000 ) $ (185,000 ) Deferred tax benefit at 35% 65,000 54,000 65,000 Reclassification adjustment for effect of enacted tax law changes (26,000 ) — — Net unrecognized post-retirement benefits included in accumulated other comprehensive income (loss) $ (147,000 ) $ (102,000 ) $ (120,000 )

Other Comprehensive Income (L46

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes activity in the unrealized gain or loss on available for sale securities included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ (935,000 ) $ 1,123,000 $ 2,522,000 Unrealized losses arising during the year (1,763,000 ) (2,493,000 ) (754,000 ) Reclassification of realized gains during the year (471,000 ) (673,000 ) (1,399,000 ) Related deferred taxes 782,000 1,108,000 754,000 Reclassification adjustment for effect of enacted tax law changes (514,000 ) — — Net change (1,966,000 ) (2,058,000 ) (1,399,000 ) Balance at end of year $ (2,901,000 ) $ (935,000 ) $ 1,123,000 The reclassification of realized gains is included in the net securities gains line of the consolidated statements of income and comprehensive income and the tax effect is included in the income tax expense line of the same statement. The following table summarizes activity in the unrealized loss on securities transferred from available for sale to held to maturity included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ (129,000 ) $ (112,000 ) $ (48,000 ) Amortization of net unrealized losses (22,000 ) (26,000 ) (98,000 ) Related deferred taxes 8,000 9,000 34,000 Reclassification adjustment for effect of enacted tax law changes (31,000 ) — — Net change (45,000 ) (17,000 ) (64,000 ) Balance at end of year $ (174,000 ) $ (129,000 ) $ (112,000 ) The following table represents the effect of the Company's derivative financial instruments included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 . For the years ended December 31, 2017 2016 2015 Balance at beginning of year $ 1,163,000 $ — $ — Unrealized gains on cash flow hedging derivatives arising during the year 165,000 1,790,000 — Related deferred taxes (58,000 ) (627,000 ) — Reclassification adjustment for effect of enacted tax law changes 274,000 — — Net change 381,000 1,163,000 — Balance at end of year $ 1,544,000 $ 1,163,000 $ — The following table summarizes activity in the unrealized gain or loss on postretirement benefits included in other comprehensive income (loss) for the years ended December 31, 2017 , 2016 , and 2015 : For the years ended December 31, 2017 2016 2015 Unrecognized postretirement benefits at beginning of year $ (102,000 ) $ (156,000 ) $ (125,000 ) Change in unamortized net actuarial loss (30,000 ) 84,000 (48,000 ) Related deferred taxes 11,000 (30,000 ) 17,000 Reclassification adjustment for effect of enacted tax law changes (26,000 ) $ — $ — Net change (45,000 ) $ 54,000 $ (31,000 ) Unrecognized postretirement benefits at end of year $ (147,000 ) $ (102,000 ) $ (156,000 )

Financial Derivative Instrume47

Financial Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The details of the interest rate swap agreements are as follows: As of December 31, 2017 2016 Notional Amount Effective Date Maturity Date Variable Index Received Fixed Rate Paid Fair Value (1) Fair Value (1) $ 30,000,000 June 28, 2016 June 28, 2021 1-Month USD LIBOR 0.94 % $ 1,154,000 $ 1,049,000 $ 20,000,000 June 27, 2016 June 27, 2021 1-Month USD LIBOR 0.89 % $ 801,000 741,000 $ 50,000,000 $ 1,955,000 $ 1,790,000 (1) Presented within other assets in the consolidated balance sheet.

Stock Options and Stock-Based48

Stock Options and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Nonvested Restricted Stock Units Activity	At the 2010 Annual Meeting, shareholders approved the 2010 Equity Incentive Plan (the "2010 Plan"). This reserves 400,000 shares of common stock for issuance in connection with stock option

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Basic and diluted earnings per share (EPS)	The following table provides detail for basic earnings per share (EPS) and diluted (EPS) for the years ended December 31, 2017 , 2016 and 2015 : Income (Numerator) Shares (Denominator) Per-Share Amount For the year ended December 31, 2017 Net income as reported $ 19,588,000 Basic EPS: Income available to common shareholders 19,588,000 10,747,306 $ 1.82 Effect of dilutive securities: restricted stock 71,712 Diluted EPS: Income available to common shareholders plus assumed conversions $ 19,588,000 10,819,018 $ 1.81 For the year ended December 31, 2016 Net income as reported $ 18,009,000 Basic EPS: Income available to common shareholders 18,009,000 10,713,290 $ 1.68 Effect of dilutive securities: restricted stock and warrants 116,512 Diluted EPS: Income available to common shareholders plus assumed conversions $ 18,009,000 10,829,802 $ 1.66 For the year ended December 31, 2015 Net income as reported $ 16,206,000 Basic EPS: Income available to common shareholders 16,206,000 10,674,755 $ 1.52 Effect of dilutive securities: restricted stock and warrants 90,114 Diluted EPS: Income available to common shareholders plus assumed conversions $ 16,206,000 10,764,869 $ 1.51
Number of options and warrants outstanding and amount above or below the strike price	The following table presents the number of options and warrants outstanding as of December 31, 2015 and the amount for which the average price at year end is above or below the strike price: Outstanding In-the-Money Out-of-the-Money As of December 31, 2015 Warrants issued to private parties 226,819 226,819 — Total dilutive securities 226,819 226,819 —

Regulatory Capital Requiremen50

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2017
Regulatory Capital Requirements [Abstract]
The actual and minimum capital amounts and ratios	The actual and minimum capital amounts and ratios for the Bank are presented in the following table: Actual For capital adequacy purposes To be well-capitalized under prompt corrective action provisions As of December 31, 2017 Tier 2 capital to $ 162,355,000 $ 86,063,000 $ 107,579,000 risk-weighted assets 15.09 % 8.00 % 10.00 % Tier 1 capital to $ 151,526,000 $ 64,548,000 $ 86,063,000 risk-weighted assets 14.09 % 6.00 % 8.00 % Common equity Tier 1 capital to $ 151,526,000 $ 48,411,000 $ 69,926,000 risk-weighted assets 14.09 % 4.50 % 6.50 % Tier 1 capital to $ 151,526,000 $ 71,386,000 $ 89,233,000 average assets 8.49 % 4.00 % 5.00 % As of December 31, 2016 Tier 2 capital to $ 151,487,000 $ 77,928,000 $ 97,410,000 risk-weighted assets 15.55 % 8.00 % 10.00 % Tier 1 capital to $ 141,249,000 $ 58,446,000 $ 77,928,000 risk-weighted assets 14.50 % 6.00 % 8.00 % Common equity Tier 1 capital to $ 141,249,000 $ 43,835,000 $ 63,317,000 risk-weighted assets 14.50 % 4.50 % 6.50 % Tier 1 capital to $ 141,249,000 $ 65,437,000 $ 81,797,000 average assets 8.63 % 4.00 % 5.00 % The actual and minimum capital amounts and ratios for the Company, on a consolidated basis, are presented in the following table: Actual For capital adequacy purposes To be well-capitalized under prompt corrective action provisions As of December 31, 2017 Tier 2 capital to $ 163,943,000 $ 86,070,000 n/a risk-weighted assets 15.24 % 8.00 % n/a Tier 1 capital to $ 153,114,000 $ 64,553,000 n/a risk-weighted assets 14.23 % 6.00 % n/a Common equity Tier 1 capital to $ 153,114,000 $ 48,415,000 n/a risk-weighted assets 14.23 % 4.50 % n/a Tier 1 capital to $ 153,114,000 $ 71,435,000 n/a average assets 8.57 % 4.00 % n/a As of December 31, 2016 Tier 2 capital to $ 152,802,000 $ 77,928,000 n/a risk-weighted assets 15.69 % 8.00 % n/a Tier 1 capital to $ 142,564,000 $ 58,446,000 n/a risk-weighted assets 14.64 % 6.00 % n/a Common equity Tier 1 capital to $ 142,564,000 $ 43,835,000 n/a risk-weighted assets 14.64 % 4.50 % n/a Tier 1 capital to $ 142,564,000 $ 65,470,000 n/a average assets 8.71 % 4.00 % n/a

Off-Balance-Sheet Financial I51

Off-Balance-Sheet Financial Instruments and Concentrations of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Off-Balance-Sheet Financial instruments	At December 31, 2017 and 2016 , the Bank had the following off-balance-sheet financial instruments, whose contract amounts represent credit risk: As of December 31, 2017 2016 Unused lines, collateralized by residential real estate $ 76,887,000 $ 76,646,000 Other unused commitments 62,771,000 57,738,000 Standby letters of credit 3,497,000 4,198,000 Commitments to extend credit 8,724,000 10,684,000 Total $ 151,879,000 $ 149,266,000

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measured on recurring basis measured at fair value	The following tables present the balances of assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2017 and 2016 . At December 31, 2017 Level 1 Level 2 Level 3 Total Securities available for sale Mortgage-backed securities $ — $ 289,989,000 $ — $ 289,989,000 State and political subdivisions — 6,769,000 — 6,769,000 Other equity securities — 3,414,000 — 3,414,000 Total securities available for sale $ — $ 300,172,000 $ — $ 300,172,000 Interest rate swap agreements $ — $ 1,955,000 $ — $ 1,955,000 Total assets $ — $ 302,127,000 $ — $ 302,127,000 At December 31, 2016 Level 1 Level 2 Level 3 Total Securities available for sale Mortgage-backed securities $ — $ 280,604,000 $ — $ 280,604,000 State and political subdivisions — 16,482,000 — 16,482,000 Other equity securities — 3,330,000 — 3,330,000 Total securities available for sale $ — $ 300,416,000 $ — $ 300,416,000 Interest rate swap agreements $ — $ 1,790,000 $ — $ 1,790,000 Total assets $ — $ 302,206,000 $ — $ 302,206,000
Assets and liabilities measured on non-recurring basis measured at fair value	The following tables present assets measured at fair value on a nonrecurring basis that have had a fair value adjustment since their initial recognition. Other real estate owned is presented net of an allowance for losses of $53,000 and $205,000 at December 31, 2017 and 2016 , respectively. Only collateral-dependent impaired loans with a related specific allowance for loan losses or a partial charge off are included in impaired loans for purposes of fair value disclosures. Impaired loans below are presented net of specific allowances of $1,531,000 and $478,000 at December 31, 2017 and 2016 , respectively. At December 31, 2017 Level 1 Level 2 Level 3 Total Other real estate owned $ — $ 1,012,000 $ — $ 1,012,000 Impaired loans — 6,521,000 — 6,521,000 Total assets $ — $ 7,533,000 $ — $ 7,533,000 At December 31, 2016 Level 1 Level 2 Level 3 Total Other real estate owned $ — $ 375,000 $ — $ 375,000 Impaired loans — 827,000 — 827,000 Total assets $ — $ 1,202,000 $ — $ 1,202,000
Estimated fair value of financial instruments	The carrying amounts and estimated fair values for financial instruments as of December 31, 2017 were as follows: Carrying Estimated As of December 31, 2017 value fair value Level 1 Level 2 Level 3 Financial assets Cash and cash equivalents $ 19,207,000 $ 19,207,000 $ 19,207,000 $ — $ — Interest-bearing deposits in other banks 860,000 860,000 860,000 — — Securities available for sale 300,172,000 300,172,000 — 300,172,000 — Securities to be held to maturity 256,567,000 259,655,000 — 259,655,000 — Restricted equity securities 10,358,000 10,358,000 — 10,358,000 — Loans held for sale 386,000 386,000 — 386,000 — Loans (net of allowance for loan losses) Commercial Real estate 319,691,000 311,321,000 — 72,000 311,249,000 Construction 37,594,000 36,610,000 — — 36,610,000 Other 177,956,000 175,455,000 — 6,018,000 169,437,000 Municipal 33,370,000 33,280,000 — — 33,280,000 Residential Term 431,459,000 431,028,000 — 391,000 430,637,000 Construction 17,830,000 17,613,000 — — 17,613,000 Home equity line of credit 110,566,000 109,012,000 — 40,000 108,972,000 Consumer 24,944,000 24,408,000 — — 24,408,000 Total loans 1,153,410,000 1,138,727,000 — 6,521,000 1,132,206,000 Mortgage servicing rights 1,268,000 2,321,000 — 2,321,000 — Interest rate swap agreements 1,955,000 1,955,000 — 1,955,000 — Accrued interest receivable 5,867,000 5,867,000 — 5,867,000 — Financial liabilities Demand deposits $ 181,970,000 $ 174,481,000 $ — $ 174,481,000 $ — NOW deposits 281,405,000 261,702,000 — 261,702,000 — Money market deposits 163,898,000 153,497,000 — 153,497,000 — Savings deposits 232,605,000 203,799,000 — 203,799,000 — Local certificates of deposit 223,074,000 220,734,000 — 220,734,000 — National certificates of deposit 335,927,000 335,775,000 — 335,775,000 — Total deposits 1,418,879,000 1,349,988,000 — 1,349,988,000 — Repurchase agreements 70,564,000 67,976,000 — 67,976,000 — Federal Home Loan Bank advances 158,194,000 156,396,000 — 156,396,000 — Total borrowed funds 228,758,000 224,372,000 — 224,372,000 — Accrued interest payable 642,000 642,000 — 642,000 — The carrying amounts and estimated fair values for financial instruments as of December 31, 2016 were as follows: Carrying Estimated As of December 31, 2016 value fair value Level 1 Level 2 Level 3 Financial assets Cash and cash equivalents $ 17,366,000 $ 17,366,000 $ 17,366,000 $ — $ — Interest-bearing deposits in other banks 293,000 293,000 293,000 — — Securities available for sale 300,416,000 300,416,000 — 300,416,000 — Securities to be held to maturity 226,828,000 225,537,000 — 225,537,000 — Restricted equity securities 11,930,000 11,930,000 — 11,930,000 — Loans held for sale 782,000 782,000 — 782,000 — Loans (net of allowance for loan losses) Commercial Real estate 297,952,000 293,103,000 — 558,000 292,545,000 Construction 24,954,000 24,548,000 — — 24,548,000 Other 148,737,000 147,394,000 — 33,000 147,361,000 Municipal 27,035,000 27,446,000 — — 27,446,000 Residential Term 409,999,000 410,327,000 — 236,000 410,091,000 Construction 18,253,000 18,125,000 — — 18,125,000 Home equity line of credit 109,986,000 108,740,000 — — 108,740,000 Consumer 24,472,000 24,131,000 — — 24,131,000 Total loans 1,061,388,000 1,053,814,000 — 827,000 1,052,987,000 Mortgage servicing rights 1,113,000 1,696,000 — 1,696,000 — Interest rate swap agreements 1,790,000 1,790,000 — 1,790,000 — Accrued interest receivable 5,532,000 5,532,000 — 5,532,000 — Financial liabilities Demand deposits $ 140,482,000 $ 133,342,000 $ — $ 133,342,000 $ — NOW deposits 282,971,000 259,418,000 — 259,418,000 — Money market deposits 125,544,000 115,087,000 — 115,087,000 — Savings deposits 217,340,000 188,260,000 — 188,260,000 — Local certificates of deposit 210,316,000 209,370,000 — 209,370,000 — National certificates of deposit 266,304,000 266,372,000 — 266,372,000 — Total deposits 1,242,957,000 1,171,849,000 — 1,171,849,000 — Repurchase agreements 84,174,000 79,827,000 — 79,827,000 — Federal Home Loan Bank advances 194,727,000 193,733,000 — 193,733,000 — Total borrowed funds 278,901,000 273,560,000 — 273,560,000 — Accrued interest payable 479,000 479,000 — 479,000 —

Other Operating Income and Ex53

Other Operating Income and Expense (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other operating income and expense	Other operating income and other operating expense include the following items greater than 1% of revenues. For the years ended December 31, 2017 2016 2015 Other operating income ATM and debit card income $ 3,378,000 $ 3,024,000 $ 2,714,000 Other operating expense Advertising and marketing expense $ 1,208,000 $ 1,099,000 $ 1,178,000 Accounting and auditing expenses 818,000 690,000 797,000 ATM and interchange expense 886,000 853,000 814,000

Condensed Financial Informati54

Condensed Financial Information of Parent (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed financial information for Parent	Condensed financial information for The First Bancorp, Inc. exclusive of its subsidiary is as follows: Balance Sheets As of December 31, 2017 2016 Assets Cash and cash equivalents $ 958,000 $ 613,000 Dividends receivable 2,500,000 3,800,000 Investments 441,000 432,000 Investment in subsidiary 152,174,000 143,611,000 Premises and equipment 3,000 4,000 Goodwill 27,559,000 27,559,000 Other assets 312,000 300,000 Total assets $ 183,947,000 $ 176,319,000 Liabilities and shareholders' equity Dividends payable $ 2,599,000 $ 3,778,000 Other liabilities 27,000 20,000 Total liabilities 2,626,000 3,798,000 Shareholders' equity Common stock 108,000 108,000 Additional paid-in capital 61,747,000 60,723,000 Retained earnings 119,373,000 111,653,000 Accumulated other comprehensive income Net unrealized gain on available for sale securities, net of tax 93,000 37,000 Total accumulated other comprehensive income 93,000 37,000 Total shareholders' equity 181,321,000 172,521,000 Total liabilities and shareholders' equity $ 183,947,000 $ 176,319,000 Statements of Income For the years ended December 31, 2017 2016 2015 Interest and dividends on investments $ 15,000 $ 22,000 $ 18,000 Net securities losses (3,000 ) (6,000 ) — Total income 12,000 16,000 18,000 Occupancy expense 5,000 9,000 12,000 Other operating expense 588,000 528,000 488,000 Total expense 593,000 537,000 500,000 Loss before income taxes and Bank earnings (581,000 ) (521,000 ) (482,000 ) Applicable income taxes (187,000 ) (186,000 ) (172,000 ) Loss before Bank earnings (394,000 ) (335,000 ) (310,000 ) Equity in earnings of Bank Remitted 11,180,000 11,300,000 10,000,000 Unremitted 8,802,000 7,044,000 6,516,000 Net income $ 19,588,000 $ 18,009,000 $ 16,206,000 Statements of Cash Flows For the years ended December 31, 2017 2016 2015 Cash flows from operating activities: Net income $ 19,588,000 $ 18,009,000 $ 16,206,000 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation 5,000 8,000 12,000 Equity compensation expense 392,000 298,000 296,000 Loss on sale of investments 3,000 6,000 — Tax benefit from vesting of restricted stock — 32,000 — (Increase) decrease in other assets 27,000 136,000 (135,000 ) (Increase) decrease in dividends receivable 1,300,000 (1,300,000 ) (50,000 ) Increase (decrease) in dividends payable (1,179,000 ) 112,000 — Increase (decrease) in other liabilities (3,000 ) (4,000 ) 160,000 Unremitted earnings of Bank (8,802,000 ) (7,044,000 ) (6,516,000 ) Net cash provided by operating activities 11,331,000 10,253,000 9,973,000 Cash flows from investing activities: Proceeds from sales/maturities of investments — 87,000 — Capital expenditures (4,000 ) — — Net cash provided by (used in) investing activities (4,000 ) 87,000 — Cash flows from financing activities: Purchase of common stock (154,000 ) (129,000 ) (180,000 ) Proceeds from sale of common stock 632,000 531,000 465,000 Repurchase of warrants — (1,750,000 ) — Dividends paid (11,460,000 ) (9,810,000 ) (9,349,000 ) Net cash used in financing activities (10,982,000 ) (11,158,000 ) (9,064,000 ) Net increase (decrease) in cash and cash equivalents 345,000 (818,000 ) 909,000 Cash and cash equivalents at beginning of year 613,000 1,431,000 522,000 Cash and cash equivalents at end of year $ 958,000 $ 613,000 $ 1,431,000

Quarterly Information (Tables)

Quarterly Information (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly information	The following tables provide unaudited financial information by quarter for each of the past two years: Dollars in thousands except per share data 2016Q1 2016Q2 2016Q3 2016Q4 2017Q1 2017Q2 2017Q3 2017Q4 Balance Sheets Cash and cash equivalents $ 14,533 $ 20,838 $ 23,456 $ 17,366 $ 17,600 $ 23,718 $ 22,375 $ 19,207 Interest-bearing deposits in other banks 6,372 7,568 15,098 293 3,272 291 584 860 Investments 453,336 457,599 471,063 527,244 553,453 552,269 541,678 556,739 Restricted equity securities 13,875 14,441 14,048 11,930 13,363 12,311 10,798 10,358 Net loans and loans held for sale 994,947 1,029,568 1,019,922 1,062,170 1,080,347 1,110,919 1,110,508 1,153,796 Other assets 91,618 91,440 91,501 93,872 95,793 96,143 95,758 101,970 Total assets $ 1,574,681 $ 1,621,454 $ 1,635,088 $ 1,712,875 $ 1,763,828 $ 1,795,651 $ 1,781,701 $ 1,842,930 Deposits $ 1,109,441 $ 1,145,709 $ 1,173,749 $ 1,242,957 $ 1,346,483 $ 1,319,259 $ 1,350,049 $ 1,418,879 Borrowed funds 276,531 283,095 268,098 278,901 226,467 282,277 234,328 228,758 Other liabilities 17,165 17,862 17,247 18,496 15,968 16,578 17,442 13,972 Shareholders' equity 171,544 174,788 175,994 172,521 174,910 177,537 179,882 181,321 Total liabilities & equity $ 1,574,681 $ 1,621,454 $ 1,635,088 $ 1,712,875 $ 1,763,828 $ 1,795,651 $ 1,781,701 $ 1,842,930 Income and Comprehensive Income Statements Interest income $ 13,276 $ 13,600 $ 13,283 $ 13,600 $ 14,491 $ 15,002 $ 15,517 $ 15,822 Interest expense 2,547 2,649 2,754 2,862 3,015 3,337 3,563 3,614 Net interest income 10,729 10,951 10,529 10,738 11,476 11,665 11,954 12,208 Provision for loan losses 375 375 375 475 500 500 750 250 Net interest income after provision for loan losses 10,354 10,576 10,154 10,263 10,976 11,165 11,204 11,958 Non-interest income 2,964 3,006 3,469 3,060 2,843 3,002 3,493 3,210 Non-interest expense 7,200 7,245 7,405 7,533 7,698 7,640 8,013 8,300 Income before taxes 6,118 6,337 6,218 5,790 6,121 6,527 6,684 6,868 Income taxes 1,615 1,713 1,656 1,470 1,484 1,644 1,702 1,782 Net income $ 4,503 $ 4,624 $ 4,562 $ 4,320 $ 4,637 $ 4,883 $ 4,982 $ 5,086 Basic earnings per share $ 0.42 $ 0.43 $ 0.43 $ 0.40 $ 0.43 $ 0.45 $ 0.46 $ 0.48 Diluted earnings per share $ 0.42 $ 0.43 $ 0.42 $ 0.39 $ 0.43 $ 0.45 $ 0.46 $ 0.47 Other comprehensive income (loss), net of tax Net unrealized gain (loss) on securities available for sale $ 1,852 $ 1,025 $ (1,292 ) $ (3,643 ) $ 1 $ 349 $ (240 ) $ (1,562 ) Net unrealized gain (loss) on securities transfered from available for sale to held to maturity (11 ) (10 ) 9 (5 ) (4 ) (4 ) (3 ) (3 ) Net unrealized gain (loss) on cash flow hedging derivative instruments — (135 ) 193 1,105 63 (171 ) (20 ) 235 Unrecognized gain (loss) on postretirement benefit costs — — — 54 — — — (19 ) Other comprehensive income (loss) $ 1,841 $ 880 $ (1,090 ) $ (2,489 ) $ 60 $ 174 $ (263 ) $ (1,349 ) Comprehensive income $ 6,344 $ 5,504 $ 3,472 $ 1,831 $ 4,697 $ 5,057 $ 4,719 $ 3,737

Summary of Significant Accoun56

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Finite lived intangible asset, amortization (in years)	10 years
Amortization of identified intangibles	$ 43	$ 43	$ 58
Net tax deferred assets	$ 134
Number of reportable operating segments | segment	1
Bank Acquisitions From Camden National Bank | Core Deposits
Business Acquisition [Line Items]
Finite lived intangible asset, amortization (in years)	10 years
Amortization of identified intangibles	$ 43	43	43
Yearly amortization expense until fully amortized	43
FNB Bankshares | Core Deposits
Business Acquisition [Line Items]
Amortization of identified intangibles	$ 0	$ 0	$ 15

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) $ in Thousands	Dec. 31, 2017USD ($)
Cash and Cash Equivalents [Abstract]
Contractual clearing balance	$ 500
Cash held in Reserve at Federal Reserve Bank	$ 2,654

Investment Securities - Summary

Investment Securities - Summary of Amortized Cost and Estimated Fair Value (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Securities available for sale
Amortized Cost	$ 303,845,000	$ 301,854,000
Unrealized Gains	859,000	1,872,000
Unrealized Losses	(4,532,000)	(3,310,000)
Fair Value (Estimated)	300,172,000	300,416,000
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	256,567,000	226,828,000
Unrealized Gains	4,499,000	2,973,000
Unrealized Losses	(1,411,000)	(4,264,000)
Fair Value (Estimated)	259,655,000	225,537,000
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	10,358,000	11,930,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	10,358,000	11,930,000
Federal Home Loan Bank Stock
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	9,321,000	10,893,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	9,321,000	10,893,000
Federal Reserve Bank Stock
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	1,037,000	1,037,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	1,037,000	1,037,000
Mortgage-backed securities
Securities available for sale
Amortized Cost-Debt	293,689,000	282,397,000
Unrealized Gains	722,000	1,334,000
Unrealized Losses	(4,422,000)	(3,127,000)
Fair Value (Estimated)	289,989,000	280,604,000
State and political subdivisions
Securities available for sale
Amortized Cost-Debt	6,860,000	16,183,000
Unrealized Gains	16,000	475,000
Unrealized Losses	(107,000)	(176,000)
Fair Value (Estimated)	6,769,000	16,482,000
Other equity securities
Securities available for sale
Amortized Cost-Debt	3,296,000	3,274,000
Unrealized Gains	121,000	63,000
Unrealized Losses	(3,000)	(7,000)
Fair Value (Estimated)	3,414,000	3,330,000
U.S. Government-sponsored agencies
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	11,155,000	11,943,000
Unrealized Gains	0	35,000
Unrealized Losses	(180,000)	(233,000)
Fair Value (Estimated)	10,975,000	11,745,000
Mortgage-backed securities
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	23,284,000	31,201,000
Unrealized Gains	568,000	967,000
Unrealized Losses	(128,000)	(147,000)
Fair Value (Estimated)	23,724,000	32,021,000
State and political subdivisions
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	217,828,000	179,384,000
Unrealized Gains	3,931,000	1,971,000
Unrealized Losses	(1,103,000)	(3,884,000)
Fair Value (Estimated)	220,656,000	177,471,000
Corporate securities
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	4,300,000	4,300,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value (Estimated)	$ 4,300,000	$ 4,300,000

Investment Securities - Summa59

Investment Securities - Summary of Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities [Abstract]
Amortized Cost, Due in 1 year or less	$ 111	$ 253
Fair Value (Estimated), Due in 1 year or less	112	253
Amortized Cost, Due in 1 to 5 years	841	2,251
Fair Value (Estimated), Due in 1 to 5 years	842	2,298
Amortized Cost, Due in 5 to 10 years	29,003	21,043
Fair Value (Estimated), Due in 1 to 5 years	29,177	21,505
Amortized Cost, Due after 10 years	270,594	275,033
Fair Value (Estimated), Due after 10 years	266,627	273,030
Amortized Cost-Equity	3,296	3,274
Fair Value (Estimated)-Equity	3,414	3,330
Amortized Cost	303,845	301,854
Fair Value (Estimated)	300,172	300,416
Held-to-maturity Securities, Debt Maturities [Abstract]
Amortized Cost, Due in 1 year or less	635	906
Fair Value (Estimated), Due in 1 year or less	637	913
Amortized Cost, Due in 1 to 5 years	18,059	13,451
Fair Value (Estimated), Due in 1 to 5 years	18,164	13,714
Amortized Cost, Due in 5 to 10 years	37,182	41,588
Fair Value (Estimated), Due in 1 to 5 years	37,719	42,448
Amortized Cost, Due after 10 years	200,691	170,883
Fair Value (Estimated), Due after 10 years	203,135	168,462
Amortized Cost	256,567	226,828
Fair Value (Estimated)	$ 259,655	$ 225,537

Investment Securities - Narrati

Investment Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)securitystate	Dec. 31, 2016USD ($)security	Sep. 30, 2014USD ($)
Investments, Debt and Equity Securities [Abstract]
Securities pledged as collateral	$ 231,516,000	$ 222,328,000
Number of securities temporarily impaired (security) | security	241	299
Number of securities temporarily impaired for 12 months or more (security) | security	157	15
Period of temporary impairment	12 months	12 months
Amortized cost of securities transferred			$ 89,780,000
Fair value of securities transferred			89,757,000
Net unrealized losses on securities transferred			$ 15,000
Net unrealized loss on securities transferred from available for sale to held to maturity	$ 174,000	$ 129,000
Number of states | state	6
FHLB stock	$ 9,321,000	10,893,000
Impairment losses	$ 0	$ 0

Investment Securities - Securit

Investment Securities - Securities Gains and Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of securities	$ 15,587	$ 10,309	$ 35,468
Gross realized gains	471	673	1,399
Gross realized losses	0	0	0
Net gain	471	673	1,399
Related income taxes	$ 165	$ 236	$ 490

Investment Securities - Secur62

Investment Securities - Securities Temporarily Impaired (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 148,611	$ 276,518
Less than 12 months, Unrealized Losses	(2,100)	(7,383)
12 months or more, Fair Value	144,394	3,033
12 months or more, Unrealized Losses	(3,843)	(191)
Fair Value	293,005	279,551
Unrealized Losses	(5,943)	(7,574)
U.S. Government-sponsored agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	7,161	6,642
Less than 12 months, Unrealized Losses	(94)	(233)
12 months or more, Fair Value	3,814	0
12 months or more, Unrealized Losses	(86)	0
Fair Value	10,975	6,642
Unrealized Losses	(180)	(233)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	132,025	197,528
Less than 12 months, Unrealized Losses	(1,857)	(3,090)
12 months or more, Fair Value	101,707	2,905
12 months or more, Unrealized Losses	(2,693)	(184)
Fair Value	233,732	200,433
Unrealized Losses	(4,550)	(3,274)
State and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	9,425	72,348
Less than 12 months, Unrealized Losses	(149)	(4,060)
12 months or more, Fair Value	38,864	0
12 months or more, Unrealized Losses	(1,061)	0
Fair Value	48,289	72,348
Unrealized Losses	(1,210)	(4,060)
Other equity securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Unrealized Losses	0	0
12 months or more, Fair Value	9	128
12 months or more, Unrealized Losses	(3)	(7)
Fair Value	9	128
Unrealized Losses	$ (3)	$ (7)

Mortgage Servicing Rights (Deta

Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Transfers and Servicing [Abstract]
Outstanding principal balance of loans serviced for others	$ 260,258	$ 250,083
Net gain from sale of loans	(737)	(1,211)	$ (714)
Mortgage servicing rights capitalized	567	554
Amortization of mortgage servicing rights	362	459
Fair value of mortgage servicing rights	$ 2,321	1,696
Moving average of weekly prepayment data (in months)	3 months
Anticipated loan prepayment rate of servicing assets (in hundredths)	10.00%
Servicing assets and servicing liabilities at fair value, assumptions used to estimate fair value, discount rate adjustment factor (in hundredths)	9.50%
Summary of mortgage servicing rights [Abstract]
Mortgage servicing rights	$ 5,428	5,901
Accumulated amortization	(4,160)	(4,680)
Impairment reserve	0	(108)
Mortgage servicing rights, net	$ 1,268	$ 1,113

Loans - Loan Portfolio (Details

Loans - Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 1,164,139	$ 1,071,526	$ 988,638
Percentage of loans receivable	100.00%	100.00%
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 323,809	$ 302,506	269,462
Percentage of loans receivable	27.80%	28.20%
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 38,056	$ 25,406	24,881
Percentage of loans receivable	3.30%	2.40%
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 181,528	$ 150,769	128,341
Percentage of loans receivable	15.60%	14.10%
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 33,391	$ 27,056	19,751
Percentage of loans receivable	2.90%	2.50%
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 17,868	$ 18,303	8,451
Percentage of loans receivable	1.50%	1.70%
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 432,661	$ 411,469	403,030
Percentage of loans receivable	37.10%	38.40%
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 111,302	$ 110,907	110,202
Percentage of loans receivable	9.60%	10.40%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 25,524	$ 25,110	$ 24,520
Percentage of loans receivable	2.20%	2.30%

Loans - Narrative (Details)

Loans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan	Dec. 31, 2015USD ($)
Schedule of Financing Receivables [Line Items]
Net deferred loan costs included in loan balances	$ 5,748	$ 4,921
Loans used to collateralize borrowings from the Federal Home Loan Bank of Boston	239,805	257,122
Commercial, construction and home equity loans used to collateralize unused line of credit at the Federal Reserve Bank of Boston	290,247	261,463
Nonaccrual loans	14,736	7,774
Interest income which would have been recognized on these loans, if interest had been accrued	496	288	$ 369
90 Plus Days And Accruing	445	777
Loans to directors, officers and employees	$ 34,715	$ 34,889
Number of loans | loan	62	71
TDR recorded investment	$ 17,801	$ 21,526
Number of loans | loan	12	12
TDR recorded investment more than 30 days past due	$ 1,407	$ 2,303
Number of loans placed on TDR status in previous 12 months | loan	0	0
Number of loans | loan	0
Loans classified as TDRs that are involved in bankruptcy	$ 688
Number of loans classified as TDRs that were on non-accrual status | loan	9
Loans classified as TDRs that were on non-accrual status	$ 1,145
Number of loans classified as TDRs that are involved in foreclosure | loan	3
Loans classified as TDRs that are involved in foreclosure	$ 458
Number of mortgage loans in the process of foreclosure | loan	12	15
Mortgage loans in the process of foreclosure	$ 1,777	$ 2,058
Loans Receivable in Bankruptcy
Schedule of Financing Receivables [Line Items]
Number of loans | loan	4

Loans - Summary of Loans to Dir

Loans - Summary of Loans to Directors and Executive Officers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance	$ 23,293	$ 20,401
New loans	867	6,278
Repayments	(1,863)	(3,386)
Ending balance	$ 22,297	$ 23,293

Loans - Past-due Status of Loan

Loans - Past-due Status of Loans by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 18,676	$ 12,658
Current	1,145,463	1,058,868
Loans	1,164,139	1,071,526	$ 988,638
90 Plus Days And Accruing	445	777
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	874	3,476
Current	322,935	299,030
Loans	323,809	302,506	269,462
90 Plus Days And Accruing	0	753
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
Current	38,056	25,406
Loans	38,056	25,406	24,881
90 Plus Days And Accruing	0	0
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	7,779	1,031
Current	173,749	149,738
Loans	181,528	150,769	128,341
90 Plus Days And Accruing	0	20
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
Current	33,391	27,056
Loans	33,391	27,056	19,751
90 Plus Days And Accruing	0	0
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	471	0
Current	17,397	18,303
Loans	17,868	18,303	8,451
90 Plus Days And Accruing	0	0
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	7,659	6,403
Current	425,002	405,066
Loans	432,661	411,469	403,030
90 Plus Days And Accruing	436	0
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,707	1,564
Current	109,595	109,343
Loans	111,302	110,907	110,202
90 Plus Days And Accruing	0	0
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	186	184
Current	25,338	24,926
Loans	25,524	25,110	$ 24,520
90 Plus Days And Accruing	9	4
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,944	2,711
30-59 Days Past Due | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	574	1,039
30-59 Days Past Due | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
30-59 Days Past Due | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	542	202
30-59 Days Past Due | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
30-59 Days Past Due | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	101	0
30-59 Days Past Due | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,031	631
30-59 Days Past Due | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	537	704
30-59 Days Past Due | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	159	135
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	11,948	4,227
60-89 Days Past Due | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	80	22
60-89 Days Past Due | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
60-89 Days Past Due | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	6,663	33
60-89 Days Past Due | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
60-89 Days Past Due | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	370	0
60-89 Days Past Due | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	4,372	3,970
60-89 Days Past Due | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	445	157
60-89 Days Past Due | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	18	45
90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	3,784	5,720
90 Days Past Due | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	220	2,415
90 Days Past Due | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
90 Days Past Due | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	574	796
90 Days Past Due | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
90 Days Past Due | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
90 Days Past Due | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,256	1,802
90 Days Past Due | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	725	703
90 Days Past Due | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 9	$ 4

Loans - Nonaccrual Loans (Detai

Loans - Nonaccrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 14,736	$ 7,774
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	752	1,907
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	0	0
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	9,357	964
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	0	0
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	0	0
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,778	4,060
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	833	843
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 16	$ 0

Loans - Information Regarding I

Loans - Information Regarding Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Average investment in impaired loans	$ 29,108	$ 28,217	$ 32,698
Interest income recognized on impaired loans, all on cash basis	784	1,104	1,220
Balance of impaired loans	31,392	27,583	29,531
Less portion for which no allowance for loan losses is allocated	(18,023)	(19,716)
Portion of impaired loan balance for which an allowance for loan losses is allocated	13,369	7,867
Portion of allowance for loan losses allocated to the impaired loan balance	$ 1,812	$ 974	$ 754

Loans - Impaired Loans by Class

Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	$ 18,023	$ 19,716	$ 20,889
Recorded Investment, With Related Allowance	13,369	7,867	8,642
Balance of impaired loans	31,392	27,583	29,531
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	19,775	21,853	22,947
Unpaid Principal Balance, With Related Allowance	13,698	8,116	8,959
Unpaid Principal Balance	33,473	29,969	31,906
Related Allowance	1,812	974	754
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	19,227	19,605	22,808
Average Recorded Investment, With Related Allowance	9,881	8,612	9,890
Average Recorded Investment	29,108	28,217	32,698
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	553	781	839
Recognized Interest Income, With Related Allowance	231	323	381
Recognized Interest Income	784	1,104	1,220
Commercial | Real Estate
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	3,791	5,201	7,173
Recorded Investment, With Related Allowance	3,999	4,820	3,544
Balance of impaired loans	7,790	10,021	10,717
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	3,996	5,614	7,496
Unpaid Principal Balance, With Related Allowance	4,116	4,925	3,627
Unpaid Principal Balance	8,112	10,539	11,123
Related Allowance	224	505	89
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	5,124	6,252	8,990
Average Recorded Investment, With Related Allowance	4,460	4,153	3,066
Average Recorded Investment	9,584	10,405	12,056
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	164	220	301
Recognized Interest Income, With Related Allowance	152	186	149
Recognized Interest Income	316	406	450
Commercial | Construction
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	741	0	30
Recorded Investment, With Related Allowance	0	763	996
Balance of impaired loans	741	763	1,026
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	741	0	30
Unpaid Principal Balance, With Related Allowance	0	763	996
Unpaid Principal Balance	741	763	1,026
Related Allowance	0	100	302
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	62	32	3
Average Recorded Investment, With Related Allowance	699	816	1,153
Average Recorded Investment	761	848	1,156
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	38	0	1
Recognized Interest Income, With Related Allowance	0	36	44
Recognized Interest Income	38	36	45
Commercial | Other
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	2,591	1,671	1,163
Recorded Investment, With Related Allowance	7,327	72	71
Balance of impaired loans	9,918	1,743	1,234
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	2,671	1,852	1,210
Unpaid Principal Balance, With Related Allowance	7,371	72	77
Unpaid Principal Balance	10,042	1,924	1,287
Related Allowance	1,309	39	8
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	1,908	1,074	1,893
Average Recorded Investment, With Related Allowance	2,584	317	256
Average Recorded Investment	4,492	1,391	2,149
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	36	86	76
Recognized Interest Income, With Related Allowance	0	0	5
Recognized Interest Income	36	86	81
Municipal
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	0	0	0
Recorded Investment, With Related Allowance	0	0	0
Balance of impaired loans	0	0	0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	0	0	0
Unpaid Principal Balance, With Related Allowance	0	0	0
Unpaid Principal Balance	0	0	0
Related Allowance	0	0	0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	0	0	0
Average Recorded Investment, With Related Allowance	0	0	0
Average Recorded Investment	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	0	0	0
Recognized Interest Income, With Related Allowance	0	0	0
Recognized Interest Income	0	0	0
Residential | Construction
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	0	0	0
Recorded Investment, With Related Allowance	0	0	0
Balance of impaired loans	0	0	0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	0	0	0
Unpaid Principal Balance, With Related Allowance	0	0	0
Unpaid Principal Balance	0	0	0
Related Allowance	0	0	0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	0	0	0
Average Recorded Investment, With Related Allowance	0	0	0
Average Recorded Investment	0	0	0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	0	0	0
Recognized Interest Income, With Related Allowance	0	0	0
Recognized Interest Income	0	0	0
Residential | Term
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	9,769	11,483	11,122
Recorded Investment, With Related Allowance	1,979	2,186	3,966
Balance of impaired loans	11,748	13,669	15,088
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	10,909	12,654	12,157
Unpaid Principal Balance, With Related Allowance	2,144	2,328	4,193
Unpaid Principal Balance	13,053	14,982	16,350
Related Allowance	255	304	326
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	10,770	11,025	10,480
Average Recorded Investment, With Related Allowance	2,106	3,209	5,228
Average Recorded Investment	12,876	14,234	15,708
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	297	442	415
Recognized Interest Income, With Related Allowance	79	101	180
Recognized Interest Income	376	543	595
Home Equity LIne of Credit
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	1,115	1,361	1,401
Recorded Investment, With Related Allowance	64	26	65
Balance of impaired loans	1,179	1,387	1,466
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	1,429	1,733	2,054
Unpaid Principal Balance, With Related Allowance	67	28	66
Unpaid Principal Balance	1,496	1,761	2,120
Related Allowance	24	26	29
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	1,351	1,213	1,400
Average Recorded Investment, With Related Allowance	32	69	187
Average Recorded Investment	1,383	1,282	1,587
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	18	33	43
Recognized Interest Income, With Related Allowance	0	0	3
Recognized Interest Income	18	33	46
Consumer
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, No Related Allowance	16	0	0
Recorded Investment, With Related Allowance	0	0	0
Balance of impaired loans	16	0	0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, No Related Allowance	29	0	0
Unpaid Principal Balance, With Related Allowance	0	0	0
Unpaid Principal Balance	29	0	0
Related Allowance	0	0	0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, No Related Allowance	12	9	42
Average Recorded Investment, With Related Allowance	0	48	0
Average Recorded Investment	12	57	42
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Recognized Interest Income, No Related Allowance	0	0	3
Recognized Interest Income, With Related Allowance	0	0	0
Recognized Interest Income	$ 0	$ 0	$ 3

Loans - TDRs by Class and Speci

Loans - TDRs by Class and Specific Reserve (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	62	71
Balance	$ 17,801	$ 21,526
Specific Reserves	$ 323	$ 736
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	8	10
Balance	$ 7,038	$ 8,937
Specific Reserves	$ 90	$ 375
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1	1
Balance	$ 741	$ 763
Specific Reserves	$ 0	$ 100
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	4	5
Balance	$ 561	$ 779
Specific Reserves	$ 0	$ 0
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	46	52
Balance	$ 8,948	$ 10,503
Specific Reserves	$ 233	$ 261
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3	3
Balance	$ 513	$ 544
Specific Reserves	$ 0	$ 0
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0

Loans - TDRs by Class and Assoc

Loans - TDRs by Class and Associated Specific Reserves (Details) $ in Thousands	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	12	12
Balance	$ 1,407	$ 2,303
Specific Reserves	$ 44	$ 290
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	1
Balance	$ 0	$ 822
Specific Reserves	$ 0	$ 264
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	11	10
Balance	$ 1,240	$ 1,314
Specific Reserves	$ 44	$ 26
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1	1
Balance	$ 167	$ 167
Specific Reserves	$ 0	$ 0
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	0	0
Balance	$ 0	$ 0
Specific Reserves	$ 0	$ 0

Allowance for Loan Losses - Nar

Allowance for Loan Losses - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan_class	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan classes | loan_class	8
Percent of related loans	0.45%	0.39%
Increase (decrease) in qualitative portion	$ 1,027
Allowance for loan losses	$ 10,729	$ 10,138	$ 9,916	$ 10,344
Allowance for loan losses as a percent of total loans	0.92%	0.95%
Number of commercial loan classes | loan_class	3
Loan-to-value percent, commercial real estate	80.00%
Number of residential loan classes | loan_class	2
Construction loans, percent of capital	34.40%
Construction loans, maximum percent of capital	100.00%
Construction loans and non-owner-occupied commercial real estate loans, percent of capital	129.20%
Construction loans and non-owner-occupied commercial real estate loans, maximum percent of capital	300.00%
Outstanding loans and commitments subject by independent consulting firm	50.00%
Residential loans, loan to value percent minimum	75.00%
Residential loans, loan to value percent, maximum	80.00%
Consumer loans, loan to value percent, minimum	80.00%
Consumer loans, loan to value percent, maximum	90.00%
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 434	$ 396	580	823
Loan maturities	2 years
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 692	807	893	1,060
Loan maturities	300 months
Loan to value ratio	0.8
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan to value ratio	0.80
Amortization term (in years)	30 years
Delinquent period before residential loans are placed on non-accrual status	90 days
Delinquent period for loans charged off	180 days
Delinquent period for loans charged off after receipt of notification	60 days
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 36	44	24	20
Loan maturities	1 year
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 545	559	$ 566	$ 542
Delinquent period before consumer loans are charged off	120 days
Unallocated Reserves
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 642	$ 1,258
Percent of total allowance reserve	6.00%	12.40%
Unallocated Reserves | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0	$ 0
Unallocated Reserves | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0	$ 0

Allowance for Loan Losses - Com

Allowance for Loan Losses - Composition of Allowance for Loans Losses, by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	$ 1,812	$ 974	$ 754
Allowance for Loans Evaluated Collectively for Impairment	8,917	9,164	9,162
Total Allowance for Loan Losses	10,729	10,138	9,916	$ 10,344
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	224	505	89
Allowance for Loans Evaluated Collectively for Impairment	3,648	3,483	3,031
Total Allowance for Loan Losses	3,872	3,988	3,120	3,532
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	0	100	302
Allowance for Loans Evaluated Collectively for Impairment	434	296	278
Total Allowance for Loan Losses	434	396	580	823
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	1,309	39	8
Allowance for Loans Evaluated Collectively for Impairment	2,049	1,741	1,444
Total Allowance for Loan Losses	3,358	1,780	1,452	1,505
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	0	0	0
Allowance for Loans Evaluated Collectively for Impairment	20	18	17
Total Allowance for Loan Losses	20	18	17	15
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	0	0	0
Allowance for Loans Evaluated Collectively for Impairment	36	44	24
Total Allowance for Loan Losses	36	44	24	20
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	255	304	326
Allowance for Loans Evaluated Collectively for Impairment	875	984	1,065
Total Allowance for Loan Losses	1,130	1,288	1,391	1,185
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	24	26	29
Allowance for Loans Evaluated Collectively for Impairment	668	781	864
Total Allowance for Loan Losses	692	807	893	1,060
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	0	0	0
Allowance for Loans Evaluated Collectively for Impairment	545	559	566
Total Allowance for Loan Losses	545	559	566	542
Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loans Evaluated Individually for Impairment	0	0	0
Allowance for Loans Evaluated Collectively for Impairment	642	1,258	1,873
Total Allowance for Loan Losses	$ 642	$ 1,258	$ 1,873	$ 1,662

Allowance for Loan Losses - Fin

Allowance for Loan Losses - Financing Receivable and Allowance Element by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 10,729	$ 10,138	$ 9,916	$ 10,344
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	3,872	3,988	3,120	3,532
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	434	396	580	823
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	3,358	1,780	1,452	1,505
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	20	18	17	15
Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	36	44	24	20
Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,130	1,288	1,391	1,185
Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	692	807	893	1,060
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	545	559	566	542
Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	642	1,258	$ 1,873	$ 1,662
Specific Reserves on Loans Evaluated Individually for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,812	974
Specific Reserves on Loans Evaluated Individually for Impairment | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	224	505
Specific Reserves on Loans Evaluated Individually for Impairment | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	100
Specific Reserves on Loans Evaluated Individually for Impairment | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,309	39
Specific Reserves on Loans Evaluated Individually for Impairment | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Specific Reserves on Loans Evaluated Individually for Impairment | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Specific Reserves on Loans Evaluated Individually for Impairment | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	255	304
Specific Reserves on Loans Evaluated Individually for Impairment | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	24	26
Specific Reserves on Loans Evaluated Individually for Impairment | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Specific Reserves on Loans Evaluated Individually for Impairment | Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
General Reserves on Loans Based on Historical Loss Experience
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	3,033	3,691
General Reserves on Loans Based on Historical Loss Experience | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,285	1,471
General Reserves on Loans Based on Historical Loss Experience | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	153	125
General Reserves on Loans Based on Historical Loss Experience | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	723	735
General Reserves on Loans Based on Historical Loss Experience | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
General Reserves on Loans Based on Historical Loss Experience | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	13	25
General Reserves on Loans Based on Historical Loss Experience | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	311	563
General Reserves on Loans Based on Historical Loss Experience | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	297	444
General Reserves on Loans Based on Historical Loss Experience | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	251	328
General Reserves on Loans Based on Historical Loss Experience | Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Reserves for Qualitative Factors
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	5,242	4,215
Reserves for Qualitative Factors | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	2,363	2,012
Reserves for Qualitative Factors | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	281	171
Reserves for Qualitative Factors | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,326	1,006
Reserves for Qualitative Factors | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	20	18
Reserves for Qualitative Factors | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	23	19
Reserves for Qualitative Factors | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	564	421
Reserves for Qualitative Factors | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	371	337
Reserves for Qualitative Factors | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	294	231
Reserves for Qualitative Factors | Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	642	1,258
Unallocated Reserves | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Residential | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Residential | Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Home Equity LIne of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	0
Unallocated Reserves | Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 642	$ 1,258

Allowance for Loan Losses - Ris

Allowance for Loan Losses - Risk Ratings by Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	$ 576,784	$ 505,737
Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	323,809	302,506
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	38,056	25,406
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	181,528	150,769
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	33,391	27,056
1 Strong
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	1,586	852
1 Strong | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	2
1 Strong | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
1 Strong | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	1,586	850
1 Strong | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
2 Above average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	51,023	48,491
2 Above average | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	12,534	13,981
2 Above average | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	40	49
2 Above average | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	5,776	8,934
2 Above average | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	32,673	25,527
3 Satisfactory
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	115,624	132,372
3 Satisfactory | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	73,899	81,286
3 Satisfactory | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	2,856	1,345
3 Satisfactory | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	38,151	48,212
3 Satisfactory | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	718	1,529
4 Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	280,762	221,073
4 Average | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	173,956	139,421
4 Average | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	22,446	16,506
4 Average | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	84,360	65,146
4 Average | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
5 Watch
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	88,300	67,394
5 Watch | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	41,652	43,181
5 Watch | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	12,714	7,349
5 Watch | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	33,934	16,864
5 Watch | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
6 OAEM
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	6,207	6,156
6 OAEM | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	3,442	4,569
6 OAEM | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
6 OAEM | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	2,765	1,587
6 OAEM | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
8 Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	33,159	29,399
8 Doubtful | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	18,203	20,066
8 Doubtful | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	157
8 Doubtful | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	14,956	9,176
8 Doubtful | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
8 Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	123	0
8 Doubtful | Commercial | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	123	0
8 Doubtful | Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
8 Doubtful | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	0	0
8 Doubtful | Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rated loans receivable	$ 0	$ 0

Allowance for Loan Losses - Act

Allowance for Loan Losses - Activity by Class (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
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 10,138				$ 9,916	$ 10,138	$ 9,916	$ 10,344
Chargeoffs									1,618	1,721	2,373
Recoveries									209	343	395
Provision for loan losses	$ 250	$ 750	$ 500	500	$ 475	$ 375	$ 375	375	2,000	1,600	1,550
Ending balance	10,729				10,138				10,729	10,138	9,916
Ending balance specifically evaluated for impairment	1,812				974				1,812	974	754
Ending balance collectively evaluated for impairment	8,917				9,164				8,917	9,164	9,162
Loans	1,164,139				1,071,526				1,164,139	1,071,526	988,638
Ending balance specifically evaluated for impairment	31,392				27,583				31,392	27,583	29,531
Ending balance collectively evaluated for impairment	1,132,747				1,043,943				1,132,747	1,043,943	959,107
Commercial | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				3,988				3,120	3,988	3,120	3,532
Chargeoffs									587	294	280
Recoveries									0	0	2
Provision for loan losses									471	1,162	(134)
Ending balance	3,872				3,988				3,872	3,988	3,120
Ending balance specifically evaluated for impairment	224				505				224	505	89
Ending balance collectively evaluated for impairment	3,648				3,483				3,648	3,483	3,031
Loans	323,809				302,506				323,809	302,506	269,462
Ending balance specifically evaluated for impairment	7,790				10,021				7,790	10,021	10,717
Ending balance collectively evaluated for impairment	316,019				292,485				316,019	292,485	258,745
Commercial | Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				396				580	396	580	823
Chargeoffs									0	75	9
Recoveries									0	8	1
Provision for loan losses									38	(117)	(235)
Ending balance	434				396				434	396	580
Ending balance specifically evaluated for impairment	0				100				0	100	302
Ending balance collectively evaluated for impairment	434				296				434	296	278
Loans	38,056				25,406				38,056	25,406	24,881
Ending balance specifically evaluated for impairment	741				763				741	763	1,026
Ending balance collectively evaluated for impairment	37,315				24,643				37,315	24,643	23,855
Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				1,780				1,452	1,780	1,452	1,505
Chargeoffs									212	376	732
Recoveries									49	129	88
Provision for loan losses									1,741	575	591
Ending balance	3,358				1,780				3,358	1,780	1,452
Ending balance specifically evaluated for impairment	1,309				39				1,309	39	8
Ending balance collectively evaluated for impairment	2,049				1,741				2,049	1,741	1,444
Loans	181,528				150,769				181,528	150,769	128,341
Ending balance specifically evaluated for impairment	9,918				1,743				9,918	1,743	1,234
Ending balance collectively evaluated for impairment	171,610				149,026				171,610	149,026	127,107
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				18				17	18	17	15
Chargeoffs									0	0	0
Recoveries									0	0	0
Provision for loan losses									2	1	2
Ending balance	20				18				20	18	17
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	20				18				20	18	17
Loans	33,391				27,056				33,391	27,056	19,751
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	33,391				27,056				33,391	27,056	19,751
Residential | Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				44				24	44	24	20
Chargeoffs									0	0	0
Recoveries									0	0	0
Provision for loan losses									(8)	20	4
Ending balance	36				44				36	44	24
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	36				44				36	44	24
Loans	17,868				18,303				17,868	18,303	8,451
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	17,868				18,303				17,868	18,303	8,451
Residential | Term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				1,288				1,391	1,288	1,391	1,185
Chargeoffs									456	379	420
Recoveries									40	93	152
Provision for loan losses									258	183	474
Ending balance	1,130				1,288				1,130	1,288	1,391
Ending balance specifically evaluated for impairment	255				304				255	304	326
Ending balance collectively evaluated for impairment	875				984				875	984	1,065
Loans	432,661				411,469				432,661	411,469	403,030
Ending balance specifically evaluated for impairment	11,748				13,669				11,748	13,669	15,088
Ending balance collectively evaluated for impairment	420,913				397,800				420,913	397,800	387,942
Home Equity LIne of Credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				807				893	807	893	1,060
Chargeoffs									28	147	582
Recoveries									11	5	31
Provision for loan losses									(98)	56	384
Ending balance	692				807				692	807	893
Ending balance specifically evaluated for impairment	24				26				24	26	29
Ending balance collectively evaluated for impairment	668				781				668	781	864
Loans	111,302				110,907				111,302	110,907	110,202
Ending balance specifically evaluated for impairment	1,179				1,387				1,179	1,387	1,466
Ending balance collectively evaluated for impairment	110,123				109,520				110,123	109,520	108,736
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				559				566	559	566	542
Chargeoffs									335	450	350
Recoveries									109	108	121
Provision for loan losses									212	335	253
Ending balance	545				559				545	559	566
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	545				559				545	559	566
Loans	25,524				25,110				25,524	25,110	24,520
Ending balance specifically evaluated for impairment	16				0				16	0	0
Ending balance collectively evaluated for impairment	25,508				25,110				25,508	25,110	24,520
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 1,258				$ 1,873	1,258	1,873	1,662
Chargeoffs									0	0	0
Recoveries									0	0	0
Provision for loan losses									(616)	(615)	211
Ending balance	642				1,258				642	1,258	1,873
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	642				1,258				642	1,258	1,873
Loans	0				0				0	0	0
Ending balance specifically evaluated for impairment	0				0				0	0	0
Ending balance collectively evaluated for impairment	$ 0				$ 0				$ 0	$ 0	$ 0

Premises and Equipment - Schedu

Premises and Equipment - Schedule of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 41,092	$ 39,416
Less accumulated depreciation	18,590	17,214
Premises and equipment, net	22,502	22,202
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,639	4,742
Land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	1,052	1,041
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	22,254	21,601
Equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 13,147	$ 12,032

Premises and Equipment - Antici

Premises and Equipment - Anticipated Rental Revenue (Details) $ in Thousands	Dec. 31, 2017USD ($)
Property, Plant and Equipment [Abstract]
2,018	$ 192
2,019	141
2,020	101
2,021	97
2,022	94
Thereafter	9
Total	$ 634

Other Real Estate Owned (Detail

Other Real Estate Owned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Other Real Estate Owned [Abstract]
Real estate acquired in settlement of loans	$ 1,012	$ 375
Real Estate Owned Valuation Allowance [Roll Forward]
Balance at beginning of year	205	162	$ 654
Losses charged to allowance	(169)	(89)	(803)
Provision charged to operating expenses	17	132	311
Balance at end of year	$ 53	$ 205	$ 162

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)limited_partnership	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)limited_partnership	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)limited_partnership	Dec. 31, 2016USD ($)limited_partnership	Dec. 31, 2015USD ($)
Federal income tax
Current									$ 4,184,000	$ 6,276,000	$ 4,895,000
Deferred									2,083,000	(139,000)	332,000
Federal income tax expense									6,267,000	6,137,000	5,227,000
State franchise tax									345,000	317,000	287,000
Income tax expense	$ 1,782,000	$ 1,702,000	$ 1,644,000	$ 1,484,000	$ 1,470,000	$ 1,656,000	$ 1,713,000	$ 1,615,000	6,612,000	6,454,000	5,514,000
Reconciliation between US expected tax rate and actual tax expense
Expected tax expense									9,170,000	8,562,000	7,602,000
Non-taxable income									(2,625,000)	(2,176,000)	(2,086,000)
State franchise tax, net of federal tax benefit									224,000	206,000	187,000
Equity compensation									(83,000)	0	0
Tax credits, net of amortization									(88,000)	(105,000)	(185,000)
Change in federal tax rate									134,000	0	0
Other									(120,000)	(33,000)	(4,000)
Income tax expense	1,782,000	$ 1,702,000	$ 1,644,000	$ 1,484,000	1,470,000	$ 1,656,000	$ 1,713,000	$ 1,615,000	6,612,000	6,454,000	$ 5,514,000
Components of deferred tax assets and liabilities
Allowance for loan losses	2,253,000				3,548,000				2,253,000	3,548,000
OREO	11,000				72,000				11,000	72,000
Accrued pension and post-retirement	1,036,000				1,730,000				1,036,000	1,730,000
Goodwill	0				2,000				0	2,000
Unrealized loss on securities transferred from available for sale to held to maturity	46,000				70,000				46,000	70,000
Unrealized loss on securities available for sale	772,000				503,000				772,000	503,000
Restricted stock grants	173,000				237,000				173,000	237,000
Core deposit intangible	15,000				20,000				15,000	20,000
Investment in flow through entities	22,000				29,000				22,000	29,000
Other assets	28,000				48,000				28,000	48,000
Total deferred tax asset	4,356,000				6,259,000				4,356,000	6,259,000
Net deferred loan costs	(1,313,000)				(1,895,000)				(1,313,000)	(1,895,000)
Depreciation	(1,306,000)				(1,808,000)				(1,306,000)	(1,808,000)
Goodwill	(39,000)				0				(39,000)	0
Mortgage servicing rights	(266,000)				(390,000)				(266,000)	(390,000)
Unrealized gain on derivative instruments	(410,000)				(626,000)				(410,000)	(626,000)
Prepaid expense	(821,000)				0				(821,000)	0
Total deferred tax liability	(4,155,000)				(4,719,000)				(4,155,000)	(4,719,000)
Net deferred tax asset	$ 201,000				$ 1,540,000				$ 201,000	$ 1,540,000
Limited partnerships
Limited partnerships held as investments | limited_partnership	2				2				2	2
Tax credits from investments in limited partnerships									$ 204,000	$ 231,000
Amortization of investments in limited partnerships									178,000	194,000
Carrying value of investments in limited partnerships	$ 1,408,000				$ 1,503,000				1,408,000	1,503,000
Total exposure to limited partnerships	$ 1,408,000				$ 1,503,000				$ 1,408,000	$ 1,503,000

Certificates of Deposit (Detail

Certificates of Deposit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Maturities Of Certificates Of Deposit [Line Items]
Certificates of deposit less than $100,000	$ 284,066	$ 195,115
Certificates $100,000 to $250,000	232,759	240,904
Certificates $250,000 and over	42,176	40,601
Total	559,001	476,620
Maturity of certificates of deposit [Abstract]
2,018	393,316
2,019	53,565
2,020	51,226
2,021	30,197
2,022	30,667
2023 and thereafter	30
Total	559,001	476,620
Interest expense on certificates of deposit of $100,000 or greater	2,105	$ 1,970	$ 2,431
Less than $100,000
Maturities Of Certificates Of Deposit [Line Items]
Total	284,066
Maturity of certificates of deposit [Abstract]
2,018	215,571
2,019	26,401
2,020	17,516
2,021	13,137
2,022	11,411
2023 and thereafter	30
Total	284,066
$100,000 and Greater
Maturities Of Certificates Of Deposit [Line Items]
Total	274,935
Maturity of certificates of deposit [Abstract]
2,018	177,745
2,019	27,164
2,020	33,710
2,021	17,060
2,022	19,256
2023 and thereafter	0
Total	$ 274,935

Borrowed Funds (Details)

Borrowed Funds (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Disclosure of Repurchase Agreements [Abstract]
Range of repurchase agreements' maturity dates	one to 365
Amount of line of credit with correspondent banks	$ 44,000
Credit facility with Federal Reserve Bank	$ 168,000
Federal Home Loan Bank, Advances, Maturities Summary [Abstract]
Interest rate, due in year four	1.55%
Interest rate, due in year five	0.00%	1.55%
Due in twelve months maturity	$ 43,074	$ 74,600
Due in year two maturity		30,000
Due in year three maturity	55,000
Due in year four maturity	10,000	55,000
Due in year five maturity		10,000
Due thereafter	50,120	25,127
Total	158,194	194,727
Repurchase agreements for municipal and commercial customers	70,564	84,174
Total	$ 228,758	$ 278,901	$ 234,328	$ 282,277	$ 226,467	$ 268,098	$ 283,095	$ 276,531
Minimum
Disclosure of Repurchase Agreements [Abstract]
Range of repurchase agreements' maturity dates (days)	1 day
Federal Home Loan Bank, Advances, Maturities Summary [Abstract]
Interest rate, due in next twelve months	1.59%	0.99%
Interest rate, due in year two		2.25%
Interest rate, due in year three	1.60%	0.00%
Interest rate, due in year four		1.60%
Interest rate, due thereafter	0.00%	0.00%
Interest rate, Repurchase agreements for municipal and commercial customers	0.15%	0.15%
Maximum
Disclosure of Repurchase Agreements [Abstract]
Range of repurchase agreements' maturity dates (days)	365 days
Federal Home Loan Bank, Advances, Maturities Summary [Abstract]
Interest rate, due in next twelve months	3.25%	3.69%
Interest rate, due in year two		3.25%
Interest rate, due in year three	1.97%	0.00%
Interest rate, due in year four		1.97%
Interest rate, due thereafter	0.99%	0.59%
Interest rate, Repurchase agreements for municipal and commercial customers	1.93%	1.93%

Employee Benefit Plans (Details

Employee Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2017USD ($)planemployee	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined contribution plan [Abstract]
Defined contribution plan service period (in months)	3 months
Defined contribution plan employer maximum percentage match of annual salary based on employee contribution (in hundredths)	3.00%
Defined contribution plan employer maximum percentage of annual profit-sharing contribution to plan for benefit of employee (in hundredths)	2.00%	2.00%	2.00%
Expense related to 401(k) plan	$ 554,000	$ 435,000	$ 462,000
Defined benefit plans, general information	The Bank also provides unfunded supplemental retirement benefits for certain officers, payable in installments over 20 years upon retirement or death. The agreements consist of individual contracts with differing characteristics that, when taken together, do not constitute a post-retirement plan.
Non-qualified deferred compensation payable period (in years)	2 years
Supplemental retirement benefits, period of benefits to be received	20 years
Pension expense	$ 219,000	215,000	$ 312,000
Accrued pension liability	$ 3,060,000	$ 3,073,000
Number of post-retirement benefit plans | plan	2
Number of active employees aged 50 and over | employee	7
Employee benefit plan age (in years)	50 years
Post-retirement benefit plan health insurance subsidy range minimum per month per person	$ 40
Post-retirement benefit plan health insurance subsidy range maximum per month per person	1,200
Expected future benefit payments in 2018	128,000
Expected future benefit payments in 2019	128,000
Expected future benefit payments in 2020	127,000
Expected future benefit payments in 2021	126,000
Expected future benefit payments in 2022	124,000
Expected future benefit payments in 2022 through 2026	636,000
Estimated plan expense	$ 77,000
Federal statutory income tax rate (percent)	35.00%	35.00%	35.00%

Employee Benefit Plans - Accumu

Employee Benefit Plans - Accumulated Post-Retirement Benefit Obligation, Funded Status, and Net Periodic Benefit Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Change in Benefit Obligations [Roll Forward]
Benefit obligation at beginning of year	$ 1,870	$ 1,967	$ 1,928
Interest cost	77	81	80
Benefits paid	(113)	(109)	(102)
Actuarial (gain) loss				$ 40	$ (69)	$ 61
Benefit obligation at end of period	1,874	1,870	1,967
Funded Status of Plan [Abstract]
Benefit obligation at end of period	(1,870)	(1,967)	(1,928)	(1,874)	(1,870)	(1,967)
Unamortized loss				186	156	240
Accrued benefit cost				$ (1,688)	$ (1,714)	$ (1,727)
Weighted average discount rate as of December 31				0.0425	0.0425	0.0425
Components of Net Periodic Benefit Cost [Abstract]
Interest cost	77	81	80
Amortization of loss	0	4	0
Other settlement expense	11	11	12
Net periodic benefit cost	$ 88	$ 96	$ 92
Weighted average discount rate for net periodic cost	4.25%	4.25%	4.25%

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Net Periodic Benefit Cost Not Yet Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits, Description [Abstract]
Unamortized net actuarial loss	$ (186)	$ (156)
Deferred tax benefit at 35%	65	54
Reclassification adjustment for effect of enacted tax law changes	(26)	0
Net unrecognized post-retirement benefits included in accumulated other comprehensive income (loss)	(147)	$ (102)
Portion to Be Recognized in Income in 2018
Unamortized net actuarial loss	(185)
Deferred tax benefit at 35%	65
Reclassification adjustment for effect of enacted tax law changes	0
Net unrecognized post-retirement benefits included in accumulated other comprehensive income (loss)	$ (120)

Other Comprehensive Income (L87

Other Comprehensive Income (Loss), Summary of Unrealized Gains and Losses on Available-for-Sale Securities (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
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance	$ 179,882	$ 177,537	$ 174,910	$ 172,521	$ 175,994	$ 174,788	$ 171,544	$ 167,498	$ 172,521	$ 167,498	$ 161,554
Other comprehensive loss	(1,349)	(263)	174	60	(2,489)	(1,090)	880	1,841	(1,378)	(858)	(1,494)
Balance	181,321	$ 179,882	$ 177,537	174,910	172,521	$ 175,994	$ 174,788	171,544	181,321	172,521	167,498
Accumulated Net Unrealized Investment Gain (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance				$ (935)				$ 1,123	(935)	1,123	2,522
Unrealized gains (losses) during the period									(1,763)	(2,493)	(754)
Realized gains during the period									(471)	(673)	(1,399)
Related deferred taxes									782	1,108	754
Reclassification adjustment for effect of enacted tax law changes									(514)	0	0
Other comprehensive loss									(1,966)	(2,058)	(1,399)
Balance	$ (2,901)				$ (935)				$ (2,901)	$ (935)	$ 1,123

Other Comprehensive Income (L88

Other Comprehensive Income (Loss), Summary of Transfer of AFS Securities to HTM (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
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance	$ 179,882	$ 177,537	$ 174,910	$ 172,521	$ 175,994	$ 174,788	$ 171,544	$ 167,498	$ 172,521	$ 167,498	$ 161,554
Other comprehensive loss	(1,349)	(263)	174	60	(2,489)	(1,090)	880	1,841	(1,378)	(858)	(1,494)
Balance	181,321	$ 179,882	$ 177,537	174,910	172,521	$ 175,994	$ 174,788	171,544	181,321	172,521	167,498
Accumulated Net Gain (Loss) on Securities Transferred from Available-for-Sale to Held-to-Maturity
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance				$ (129)				$ (112)	(129)	(112)	(48)
Amortization of unrealized losses									(22)	(26)	(98)
Related deferred taxes									8	9	34
Reclassification adjustment for effect of enacted tax law changes									(31)	0	0
Other comprehensive loss									(45)	(17)	(64)
Balance	$ (174)				$ (129)				$ (174)	$ (129)	$ (112)

Other Comprehensive Income (L89

Other Comprehensive Income (Loss), Summary of Derivative Financial Instruments (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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 179,882	$ 177,537	$ 174,910	$ 172,521	$ 175,994	$ 174,788	$ 171,544	$ 167,498	$ 172,521	$ 167,498	$ 161,554
Other comprehensive loss	(1,349)	(263)	174	60	(2,489)	(1,090)	880	1,841	(1,378)	(858)	(1,494)
Balance	181,321	$ 179,882	$ 177,537	174,910	172,521	$ 175,994	$ 174,788	171,544	181,321	172,521	167,498
Accumulated Net Gain (Loss) from Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance				$ 1,163				$ 0	1,163	0	0
Unrealized gains (losses) during the period									165	1,790	0
Related deferred taxes									(58)	(627)	0
Reclassification adjustment for effect of enacted tax law changes									274	0	0
Other comprehensive loss									381	1,163	0
Balance	$ 1,544				$ 1,163				$ 1,544	$ 1,163	$ 0

Other Comprehensive Income (L90

Other Comprehensive Income (Loss), Summary of Unrealized Gains and Losses on Postretirement Benefits (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
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance	$ 179,882	$ 177,537	$ 174,910	$ 172,521	$ 175,994	$ 174,788	$ 171,544	$ 167,498	$ 172,521	$ 167,498	$ 161,554
Other comprehensive loss	(1,349)	(263)	174	60	(2,489)	(1,090)	880	1,841	(1,378)	(858)	(1,494)
Balance	181,321	$ 179,882	$ 177,537	174,910	172,521	$ 175,994	$ 174,788	171,544	181,321	172,521	167,498
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance				$ (102)				$ (156)	(102)	(156)	(125)
Unrealized gains (losses) during the period									(30)	84	(48)
Related deferred taxes									11	(30)	17
Reclassification adjustment for effect of enacted tax law changes									(26)	0	0
Other comprehensive loss									(45)	54	(31)
Balance	$ (147)				$ (102)				$ (147)	$ (102)	$ (156)

Financial Derivative Instrume91

Financial Derivative Instruments (Details) - Cash Flow Hedging - Designated as Hedging Instrument - USD ($)	Dec. 31, 2017	Dec. 31, 2016
June 28, 2016
Derivative [Line Items]
Notional Amount	$ 30,000,000
Fixed Rate Paid	0.94%
Fair Value	$ 1,154,000	$ 1,049,000
June 27, 2016
Derivative [Line Items]
Notional Amount	$ 20,000,000
Fixed Rate Paid	0.89%
Fair Value	$ 801,000	741,000
Interest Rate Swap
Derivative [Line Items]
Notional Amount	50,000,000
Fair Value	$ 1,955,000	$ 1,790,000

Preferred and Common Stock (Det

Preferred and Common Stock (Details) - USD ($)	Jan. 09, 2009	Nov. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	May 31, 2015	Dec. 31, 2001
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Proceeds from issuance of CPP Shares	$ 25,000,000
Number of shares of common stock issuable pursuant to the Warrants, maximum (in shares)	225,904				226,819		226,819
Exercise price of the Warrants (in dollars per share)	$ 16.60						$ 16.53
Term of warrants (in years)	10 years
Repurchase of warrants		$ 1,750,000	$ 0	$ 1,750,000	$ 0
Common stock
Number of shares available to directors and employees for stock purchase or savings and investment plans (in shares)			250,000	700,000		700,000
Number of shares issued under employee savings and investment plan (in shares)			27,273
Number of shares available for future use under employee savings and investment plan (in shares)			222,727
Number of shares issued during period, employee benefit plan (in shares)			12,762	14,511	13,787
Number of shares registered with SEC for dividend reinvestment plan (in shares)								600,000
Number of shares issued during period, dividend reinvestment plan (in shares)			9,922	10,889	11,668	257,759
Number of shares for future use (in shares)			342,241
Number of trading days immediately preceding dividend payment date used in determining per share price of shares purchased			5 days
Proceeds from sale of common stock			$ 632,000	$ 531,000	$ 465,000
Capital Purchase Program
Common stock
Proceeds from sale of common stock			$ 632,000	$ 531,000	$ 465,000

Stock Options and Stock-Based93

Stock Options and Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 1995	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock reserved for issuance (in shares)				400,000
Shares	127,560
Compensation cost related to restricted stock grants	$ 1,428
Compensation expense recognized for restricted shares	392	$ 298
Unrecognized compensation costs	$ 601	$ 457
Vesting Term (In Years)			10 years
Percentage of options vesting two years (in hundredths)			50.00%
Vesting term, option one (in years)			2 years
Percentage of options vesting five years (in hundredths)			50.00%
Vesting term, option two (in years)			5 years
1995 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in 1995 (in shares)			600,000
Plan 2010 | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares	71,086

Stock Options and Stock-Based94

Stock Options and Stock-Based Compensation - Summary of Restricted Stock Granted (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 1995
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)						10 years
Shares	127,560
Plan 2010 | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares	71,086
Remaining Term (In Years)	2 years
Plan 2010 | Restricted Stock | One Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	1 year
Shares	3,976
Remaining Term (In Years)	4 months 24 days
Plan 2010 | Restricted Stock | Five Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	5 years	5 years	5 years	5 years	5 years
Shares	9,972	15,015	12,023	10,422	14,776
Remaining Term (In Years)	4 years 3 months 18 days	3 years 3 months 18 days	2 years 3 months 18 days	1 year 3 months 18 days	3 months 18 days
Plan 2010 | Restricted Stock | Three Years [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Term (In Years)	3 years
Shares	4,902
Remaining Term (In Years)	2 years 3 months 18 days

Earnings Per Share (Details)

Earnings Per Share (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	May 31, 2015	Jan. 09, 2009
Income (Numerator) [Abstract]
Net income as reported	$ 5,086	$ 4,982	$ 4,883	$ 4,637	$ 4,320	$ 4,562	$ 4,624	$ 4,503	$ 19,588	$ 18,009	$ 16,206
Basic EPS: Income available to common shareholders									19,588	18,009	16,206
Diluted EPS: Income available to common shareholders plus assumed conversions									$ 19,588	$ 18,009	$ 16,206
Shares (Denominator) [Abstract]
Weighted average number of common shares outstanding (in shares)									10,747,306	10,713,290	10,674,755
Incremental shares (in shares)									71,712	116,512	90,114
Diluted EPS: Income available to common shareholders plus assumed conversions (in shares)									10,819,018	10,829,802	10,764,869
Per-Share Amount [Abstract]
Basic EPS: Income available to common shareholders (in dollars per share)	$ 0.48	$ 0.46	$ 0.45	$ 0.43	$ 0.40	$ 0.43	$ 0.43	$ 0.42	$ 1.82	$ 1.68	$ 1.52
Diluted EPS: Income available to common shareholders plus assumed conversions (in dollars per share)	$ 0.47	$ 0.46	$ 0.45	$ 0.43	$ 0.39	$ 0.42	$ 0.43	$ 0.42	$ 1.81	$ 1.66	$ 1.51
Warrants issued to private parties											226,819	226,819	225,904
Total Dilutive Securities											226,819
In-the-Money
Per-Share Amount [Abstract]
Warrants issued to private parties											226,819
Total Dilutive Securities											226,819
Out-of-the-Money
Per-Share Amount [Abstract]
Warrants issued to private parties											0
Total Dilutive Securities											0

Regulatory Capital Requiremen96

Regulatory Capital Requirements (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings from prior two years available for dividends	$ 15,850,000
Capital conservation buffer phase in, minimum (as a percentage)	2.25%		0.00%
Capital conservation buffer phase in, maximum (as a percentage)			2.50%
Capital conservation buffer (as a percentage)	7.24%
Tier 1 capital to risk-weighted assets [Abstract]
Actual	$ 153,114,000	$ 142,564,000
Actual	153,114,000	142,564,000
For capital adequacy purposes		$ 43,835,000
Risk-weighted assets [Abstract]
Actual (in hundredths)		14.64%
For capital adequacy purposes (in hundredths)		4.50%
Non Consolidated
Tier 2 capital to risk-weighted asets [Abstract]
Actual	162,355,000	$ 151,487,000
For capital adequacy purposes	86,063,000	77,928,000
To be well-capitalized under prompt corrective action provisions	107,579,000	97,410,000
Tier 1 capital to risk-weighted assets [Abstract]
Actual	151,526,000	141,249,000
For capital adequacy purposes	64,548,000	58,446,000
To be well-capitalized under prompt corrective action provisions	86,063,000	77,928,000
Actual	151,526,000	141,249,000
For capital adequacy purposes	48,411,000	43,835,000
To be well-capitalized under prompt corrective action provisions	$ 69,926,000	$ 63,317,000
Risk-weighted assets [Abstract]
Actual (in hundredths)	15.09%	15.55%
For capital adequacy purposes (in hundredths)	8.00%	8.00%
To be well-capitalized under prompt corrective action provisions (in hundredths)	10.00%	10.00%
Actual (in hundredths)	14.09%	14.50%
For capital adequacy purposes (in hundredths)	6.00%	6.00%
To be well-capitalized under prompt corrective action provisions (in hundredths)	8.00%	8.00%
Actual (in hundredths)	14.09%	14.50%
For capital adequacy purposes (in hundredths)	4.50%	4.50%
To be well-capitalized under prompt corrective action provisions (in hundredths)	6.50%	6.50%
Tier 1 capital to average assets [Abstract]
Actual	$ 151,526,000	$ 141,249,000
For capital adequacy purpose	71,386,000	65,437,000
To be well-capitalized under prompt corrective action provisions	$ 89,233,000	$ 81,797,000
Average assets [Abstract]
Actual (in hundredths)	8.49%	8.63%
For capital adequacy purpose (in hundredths)	4.00%	4.00%
To be well-capitalized under prompt corrective action provisions (in hundredths)	5.00%	5.00%
Consolidated
Tier 2 capital to risk-weighted asets [Abstract]
Actual	$ 163,943,000	$ 152,802,000
For capital adequacy purposes	86,070,000	77,928,000
Tier 1 capital to risk-weighted assets [Abstract]
For capital adequacy purposes	64,553,000	$ 58,446,000
For capital adequacy purposes	$ 48,415,000
Risk-weighted assets [Abstract]
Actual (in hundredths)	15.24%	15.69%
For capital adequacy purposes (in hundredths)	8.00%	8.00%
Actual (in hundredths)	14.23%	14.64%
For capital adequacy purposes (in hundredths)	6.00%	6.00%
Actual (in hundredths)	14.23%
For capital adequacy purposes (in hundredths)	4.50%
Tier 1 capital to average assets [Abstract]
Actual	$ 153,114,000	$ 142,564,000
For capital adequacy purpose	$ 71,435,000	$ 65,470,000
Average assets [Abstract]
Actual (in hundredths)	8.57%	8.71%
For capital adequacy purpose (in hundredths)	4.00%	4.00%

Off-Balance-Sheet Financial I97

Off-Balance-Sheet Financial Instruments and Concentrations of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2017USD ($)derivative	Dec. 31, 2016USD ($)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet financial instruments	$ 151,879,000	$ 149,266,000
Designated as Hedging Instrument | Interest Rate Swap | Cash Flow Hedging
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Number of derivative instruments (derivative) | derivative	2
Notional Amount	$ 50,000,000
Unrealized gain on derivative	1,544,000
Unused lines, collateralized by residential real estate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet financial instruments	76,887,000	76,646,000
Other unused commitments
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet financial instruments	62,771,000	57,738,000
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet financial instruments	3,497,000	4,198,000
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet financial instruments	$ 8,724,000	$ 10,684,000

Fair Value Disclosures - Assets

Fair Value Disclosures - Assets and Liabilities Recorded on a Recurring and Nonrecurring Basis(Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 300,172	$ 300,416
Allowance for loan losses, other real estate owned	53	205	$ 162	$ 654
Allowance for impaired loans	1,531	478
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Interest rate swap agreements	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	300,172	300,416
Interest rate swap agreements	1,955	1,790
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Interest rate swap agreements	0	0
Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	300,172	300,416
Interest rate swap agreements	1,955	1,790
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	289,989	280,604
State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	6,769	16,482
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	300,172	300,416
Assets measured at fair value	302,127	302,206
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	300,172	300,416
Assets measured at fair value	302,127	302,206
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	0	0
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	1,955	1,790
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	0	0
Fair Value, Measurements, Recurring | Interest Rate Swap | Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	1,955	1,790
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	289,989	280,604
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Mortgage-backed securities | Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	289,989	280,604
Fair Value, Measurements, Recurring | State and political subdivisions | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | State and political subdivisions | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	6,769	16,482
Fair Value, Measurements, Recurring | State and political subdivisions | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | State and political subdivisions | Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	6,769	16,482
Fair Value, Measurements, Recurring | Other equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Other equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,414	3,330
Fair Value, Measurements, Recurring | Other equity securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Other equity securities | Estimate of Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,414	3,330
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	1,012	375
Impaired loans	6,521	827
Assets measured at fair value	7,533	1,202
Fair Value, Measurements, Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans	0	0
Assets measured at fair value	0	0
Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	1,012	375
Impaired loans	6,521	827
Assets measured at fair value	7,533	1,202
Fair Value, Measurements, Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans	0	0
Assets measured at fair value	$ 0	$ 0

Fair Value Disclosures - Carryi

Fair Value Disclosures - Carrying Amounts and Estimated Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Financial assets
Securities available for sale	$ 300,172				$ 300,416
Securities to be held to maturity, fair value	259,655				225,537
Restricted equity securities, at cost	10,358				11,930
Loans (net of allowance for loan losses)
Mortgage servicing rights	2,321				1,696
Financial liabilities
Demand deposits	181,970				140,482
NOW deposits	281,405				282,971
Money market deposits	163,898				125,544
Savings deposits	232,605				217,340
Certificates of deposit	559,001				476,620
Total deposits	1,418,879	$ 1,350,049	$ 1,319,259	$ 1,346,483	1,242,957	$ 1,173,749	$ 1,145,709	$ 1,109,441
Level 1
Financial assets
Cash and cash equivalents	19,207				17,366
Interest-bearing deposits in other banks	860				293
Securities available for sale	0				0
Securities to be held to maturity, fair value	0				0
Restricted equity securities, at cost	0				0
Loans held for sale	0				0
Loans (net of allowance for loan losses)
Loans	0				0
Mortgage servicing rights	0				0
Interest rate swap agreements	0				0
Accrued interest receivable	0				0
Financial liabilities
Demand deposits	0				0
NOW deposits	0				0
Money market deposits	0				0
Savings deposits	0				0
Certificates of deposit	0				0
National certificates of deposit	0				0
Total deposits	0				0
Repurchase agreements	0				0
Federal Home Loan Bank advances	0				0
Total borrowed funds	0				0
Accrued interest payable	0				0
Level 1 | Commercial | Real Estate
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Commercial | Construction
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Commercial | Other
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Municipal
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Residential | Construction
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Residential | Term
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Home Equity LIne of Credit
Loans (net of allowance for loan losses)
Loans	0				0
Level 1 | Consumer
Loans (net of allowance for loan losses)
Loans	0				0
Level 2
Financial assets
Cash and cash equivalents	0				0
Interest-bearing deposits in other banks	0				0
Securities available for sale	300,172				300,416
Securities to be held to maturity, fair value	259,655				225,537
Restricted equity securities, at cost	10,358				11,930
Loans held for sale	386				782
Loans (net of allowance for loan losses)
Loans	6,521				827
Mortgage servicing rights	2,321				1,696
Interest rate swap agreements	1,955				1,790
Accrued interest receivable	5,867				5,532
Financial liabilities
Demand deposits	174,481				133,342
NOW deposits	261,702				259,418
Money market deposits	153,497				115,087
Savings deposits	203,799				188,260
Certificates of deposit	220,734				209,370
National certificates of deposit	335,775				266,372
Total deposits	1,349,988				1,171,849
Repurchase agreements	67,976				79,827
Federal Home Loan Bank advances	156,396				193,733
Total borrowed funds	224,372				273,560
Accrued interest payable	642				479
Level 2 | Commercial | Real Estate
Loans (net of allowance for loan losses)
Loans	72				558
Level 2 | Commercial | Construction
Loans (net of allowance for loan losses)
Loans	0				0
Level 2 | Commercial | Other
Loans (net of allowance for loan losses)
Loans	6,018				33
Level 2 | Municipal
Loans (net of allowance for loan losses)
Loans	0				0
Level 2 | Residential | Construction
Loans (net of allowance for loan losses)
Loans	0				0
Level 2 | Residential | Term
Loans (net of allowance for loan losses)
Loans	391				236
Level 2 | Home Equity LIne of Credit
Loans (net of allowance for loan losses)
Loans	40				0
Level 2 | Consumer
Loans (net of allowance for loan losses)
Loans	0				0
Level 3
Financial assets
Cash and cash equivalents	0				0
Interest-bearing deposits in other banks	0				0
Securities available for sale	0				0
Securities to be held to maturity, fair value	0				0
Restricted equity securities, at cost	0				0
Loans held for sale	0				0
Loans (net of allowance for loan losses)
Loans	1,132,206				1,052,987
Mortgage servicing rights	0				0
Interest rate swap agreements	0				0
Accrued interest receivable	0				0
Financial liabilities
Demand deposits	0				0
NOW deposits	0				0
Money market deposits	0				0
Savings deposits	0				0
Certificates of deposit	0				0
National certificates of deposit	0				0
Total deposits	0				0
Repurchase agreements	0				0
Federal Home Loan Bank advances	0				0
Total borrowed funds	0				0
Accrued interest payable	0				0
Level 3 | Commercial | Real Estate
Loans (net of allowance for loan losses)
Loans	311,249				292,545
Level 3 | Commercial | Construction
Loans (net of allowance for loan losses)
Loans	36,610				24,548
Level 3 | Commercial | Other
Loans (net of allowance for loan losses)
Loans	169,437				147,361
Level 3 | Municipal
Loans (net of allowance for loan losses)
Loans	33,280				27,446
Level 3 | Residential | Construction
Loans (net of allowance for loan losses)
Loans	17,613				18,125
Level 3 | Residential | Term
Loans (net of allowance for loan losses)
Loans	430,637				410,091
Level 3 | Home Equity LIne of Credit
Loans (net of allowance for loan losses)
Loans	108,972				108,740
Level 3 | Consumer
Loans (net of allowance for loan losses)
Loans	24,408				24,131
Carrying Amount
Financial assets
Cash and cash equivalents	19,207				17,366
Interest-bearing deposits in other banks	860				293
Securities available for sale	300,172				300,416
Securities to be held to maturity, fair value	256,567				226,828
Restricted equity securities, at cost	10,358				11,930
Loans held for sale	386				782
Loans (net of allowance for loan losses)
Loans	1,153,410				1,061,388
Mortgage servicing rights	1,268				1,113
Interest rate swap agreements	1,955				1,790
Accrued interest receivable	5,867				5,532
Financial liabilities
Demand deposits	181,970				140,482
NOW deposits	281,405				282,971
Money market deposits	163,898				125,544
Savings deposits	232,605				217,340
Certificates of deposit	223,074				210,316
National certificates of deposit	335,927				266,304
Total deposits	1,418,879				1,242,957
Repurchase agreements	70,564				84,174
Federal Home Loan Bank advances	158,194				194,727
Total borrowed funds	228,758				278,901
Accrued interest payable	642				479
Carrying Amount | Commercial | Real Estate
Loans (net of allowance for loan losses)
Loans	319,691				297,952
Carrying Amount | Commercial | Construction
Loans (net of allowance for loan losses)
Loans	37,594				24,954
Carrying Amount | Commercial | Other
Loans (net of allowance for loan losses)
Loans	177,956				148,737
Carrying Amount | Municipal
Loans (net of allowance for loan losses)
Loans	33,370				27,035
Carrying Amount | Residential | Construction
Loans (net of allowance for loan losses)
Loans	17,830				18,253
Carrying Amount | Residential | Term
Loans (net of allowance for loan losses)
Loans	431,459				409,999
Carrying Amount | Home Equity LIne of Credit
Loans (net of allowance for loan losses)
Loans	110,566				109,986
Carrying Amount | Consumer
Loans (net of allowance for loan losses)
Loans	24,944				24,472
Estimate of Fair Value
Financial assets
Cash and cash equivalents	19,207				17,366
Interest-bearing deposits in other banks	860				293
Securities available for sale	300,172				300,416
Securities to be held to maturity, fair value	259,655				225,537
Restricted equity securities, at cost	10,358				11,930
Loans held for sale	386				782
Loans (net of allowance for loan losses)
Loans	1,138,727				1,053,814
Mortgage servicing rights	2,321				1,696
Interest rate swap agreements	1,955				1,790
Accrued interest receivable	5,867				5,532
Financial liabilities
Demand deposits	174,481				133,342
NOW deposits	261,702				259,418
Money market deposits	153,497				115,087
Savings deposits	203,799				188,260
Certificates of deposit	220,734				209,370
National certificates of deposit	335,775				266,372
Total deposits	1,349,988				1,171,849
Repurchase agreements	67,976				79,827
Federal Home Loan Bank advances	156,396				193,733
Total borrowed funds	224,372				273,560
Accrued interest payable	642				479
Estimate of Fair Value | Commercial | Real Estate
Loans (net of allowance for loan losses)
Loans	311,321				293,103
Estimate of Fair Value | Commercial | Construction
Loans (net of allowance for loan losses)
Loans	36,610				24,548
Estimate of Fair Value | Commercial | Other
Loans (net of allowance for loan losses)
Loans	175,455				147,394
Estimate of Fair Value | Municipal
Loans (net of allowance for loan losses)
Loans	33,280				27,446
Estimate of Fair Value | Residential | Construction
Loans (net of allowance for loan losses)
Loans	17,613				18,125
Estimate of Fair Value | Residential | Term
Loans (net of allowance for loan losses)
Loans	431,028				410,327
Estimate of Fair Value | Home Equity LIne of Credit
Loans (net of allowance for loan losses)
Loans	109,012				108,740
Estimate of Fair Value | Consumer
Loans (net of allowance for loan losses)
Loans	$ 24,408				$ 24,131

Other Operating Income and E100

Other Operating Income and Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other operating expense
Advertising and marketing expense	$ 1,208	$ 1,099	$ 1,178
Accounting and auditing expenses	818	690	797
ATM and interchange expense	886	853	814
ATM and debit card income
Other operating income
ATM and debit card income	$ 3,378	$ 3,024	$ 2,714

Condensed Financial Informat101

Condensed Financial Information of Parent (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Nov. 30, 2016	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	Dec. 31, 2014
Assets
Cash and cash equivalents		$ 19,207	$ 22,375	$ 23,718	$ 17,600	$ 17,366	$ 23,456	$ 20,838	$ 14,533	$ 19,207	$ 17,366
Investments		556,739	541,678	552,269	553,453	527,244	471,063	457,599	453,336	556,739	527,244
Premises and equipment		22,502				22,202				22,502	22,202
Goodwill		29,805				29,805				29,805	29,805
Other assets		42,784				35,958				42,784	35,958
Total assets		1,842,930	1,781,701	1,795,651	1,763,828	1,712,875	1,635,088	1,621,454	1,574,681	1,842,930	1,712,875
Liabilities and shareholders' equity
Other liabilities		13,972	17,442	16,578	15,968	18,496	17,247	17,862	17,165	13,972	18,496
Total liabilities		1,661,609				1,540,354				1,661,609	1,540,354
Shareholders' equity
Common stock		108				108				108	108
Additional paid-in capital		61,747				60,723				61,747	60,723
Retained earnings		121,144				111,693				121,144	111,693
Accumulated other comprehensive income (loss)
Net unrealized gain on available for sale securities, net of tax		(2,901)				(935)				(2,901)	(935)
Total shareholders' equity		181,321	179,882	177,537	174,910	172,521	175,994	174,788	171,544	181,321	172,521	$ 167,498	$ 161,554
Total liabilities and shareholders' equity		1,842,930	1,781,701	1,795,651	1,763,828	1,712,875	1,635,088	1,621,454	1,574,681	1,842,930	1,712,875
Statements of Income
Net securities gains										471	673	1,399
Income before income taxes		6,868	6,684	6,527	6,121	5,790	6,218	6,337	6,118	26,200	24,463	21,720
Applicable tax expense		1,782	1,702	1,644	1,484	1,470	1,656	1,713	1,615	6,612	6,454	5,514
Equity in earnings of Bank
Net income		5,086	4,982	4,883	4,637	4,320	4,562	4,624	4,503	19,588	18,009	16,206
Cash flows from operating activities
Net income		5,086	$ 4,982	$ 4,883	4,637	4,320	$ 4,562	$ 4,624	4,503	19,588	18,009	16,206
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation										1,864	1,745	1,720
Equity compensation expense										392	298	296
Loss on sale of investments										(471)	(673)	(1,399)
Tax benefit from vesting of restricted stock										0	32	0
(Increase) decrease in other assets										(4,742)	(2,460)	(455)
Increase (decrease) in other liabilities										(2,020)	665	1,418
Net cash provided by operating activities										22,526	21,646	20,742
Cash flows from investing activities
Proceeds from maturities, payments, calls of securities available for sale										157,013	79,223	36,588
Capital expenditures										(2,529)	(2,131)	(927)
Net cash used in investing activities										(130,313)	(148,633)	(86,347)
Cash flows from financing activities
Purchase of common stock										(154)	(129)	(180)
Proceeds from sale of common stock										632	531	465
Repurchase of warrants	$ (1,750)									0	(1,750)	0
Dividends paid										(11,460)	(9,810)	(9,349)
Net cash provided by financing activities										109,628	130,054	66,847
Net increase (decrease) in cash and cash equivalents										1,841	3,067	1,242
Cash and cash equivalents at beginning of year					17,366				14,299	17,366	14,299	13,057
Cash and cash equivalents at end of year		19,207				17,366				19,207	17,366	14,299
Parent Company
Assets
Cash and cash equivalents		958				613				958	613
Dividends receivable		2,500				3,800				2,500	3,800
Investments		441				432				441	432
Investment in subsidiary		152,174				143,611				152,174	143,611
Premises and equipment		3				4				3	4
Goodwill		27,559				27,559				27,559	27,559
Other assets		312				300				312	300
Total assets		183,947				176,319				183,947	176,319
Liabilities and shareholders' equity
Dividends payable		2,599				3,778				2,599	3,778
Other liabilities		27				20				27	20
Total liabilities		2,626				3,798				2,626	3,798
Shareholders' equity
Common stock		108				108				108	108
Additional paid-in capital		61,747				60,723				61,747	60,723
Retained earnings		119,373				111,653				119,373	111,653
Accumulated other comprehensive income (loss)
Net unrealized gain on available for sale securities, net of tax		93				37				93	37
Total accumulated other comprehensive income		93				37				93	37
Total shareholders' equity		181,321				172,521				181,321	172,521
Total liabilities and shareholders' equity		183,947				176,319				183,947	176,319
Statements of Income
Interest and dividends on investments										15	22	18
Net securities gains										(3)	(6)	0
Total income										12	16	18
Occupancy expense										5	9	12
Other operating expense										588	528	488
Total expense										593	537	500
Income before income taxes										(581)	(521)	(482)
Applicable tax expense										(187)	(186)	(172)
Loss before Bank earnings										(394)	(335)	(310)
Equity in earnings of Bank
Remitted										11,180	11,300	10,000
Unremitted										8,802	7,044	6,516
Net income										19,588	18,009	16,206
Cash flows from operating activities
Net income										19,588	18,009	16,206
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation										5	8	12
Equity compensation expense										392	298	296
Loss on sale of investments										3	6	0
Tax benefit from vesting of restricted stock										0	32	0
(Increase) decrease in other assets										27	136	(135)
(Increase) decrease in dividends receivable										1,300	(1,300)	(50)
Increase (decrease) in dividends payable										(1,179)	112	0
Increase (decrease) in other liabilities										(3)	(4)	160
Unremitted earnings of Bank										(8,802)	(7,044)	(6,516)
Net cash provided by operating activities										11,331	10,253	9,973
Cash flows from investing activities
Proceeds from maturities, payments, calls of securities available for sale										0	87	0
Capital expenditures										(4)	0	0
Net cash used in investing activities										(4)	87	0
Cash flows from financing activities
Purchase of common stock										(154)	(129)	(180)
Proceeds from sale of common stock										632	531	465
Repurchase of warrants										0	(1,750)	0
Dividends paid										(11,460)	(9,810)	(9,349)
Net cash provided by financing activities										(10,982)	(11,158)	(9,064)
Net increase (decrease) in cash and cash equivalents										345	(818)	909
Cash and cash equivalents at beginning of year					$ 613				$ 1,431	613	1,431	522
Cash and cash equivalents at end of year		$ 958				$ 613				$ 958	$ 613	$ 1,431

New Accounting Pronouncements (

New Accounting Pronouncements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification adjustment for effect of enacted tax law changes	$ 297

Quarterly Information (Details)

Quarterly Information (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	Dec. 31, 2014
Balance Sheets
Cash and cash equivalents	$ 19,207	$ 22,375	$ 23,718	$ 17,600	$ 17,366	$ 23,456	$ 20,838	$ 14,533	$ 19,207	$ 17,366
Interest-bearing deposits in other banks	860	584	291	3,272	293	15,098	7,568	6,372	860	293
Investments	556,739	541,678	552,269	553,453	527,244	471,063	457,599	453,336	556,739	527,244
Restricted equity securities	10,358	10,798	12,311	13,363	11,930	14,048	14,441	13,875	10,358	11,930
Net loans and loans held for sale	1,153,796	1,110,508	1,110,919	1,080,347	1,062,170	1,019,922	1,029,568	994,947	1,153,796	1,062,170
Other assets	101,970	95,758	96,143	95,793	93,872	91,501	91,440	91,618	101,970	93,872
Total assets	1,842,930	1,781,701	1,795,651	1,763,828	1,712,875	1,635,088	1,621,454	1,574,681	1,842,930	1,712,875
Deposits	1,418,879	1,350,049	1,319,259	1,346,483	1,242,957	1,173,749	1,145,709	1,109,441	1,418,879	1,242,957
Borrowed funds	228,758	234,328	282,277	226,467	278,901	268,098	283,095	276,531	228,758	278,901
Other liabilities	13,972	17,442	16,578	15,968	18,496	17,247	17,862	17,165	13,972	18,496
Shareholders' equity	181,321	179,882	177,537	174,910	172,521	175,994	174,788	171,544	181,321	172,521	$ 167,498	$ 161,554
Total liabilities and shareholders' equity	1,842,930	1,781,701	1,795,651	1,763,828	1,712,875	1,635,088	1,621,454	1,574,681	1,842,930	1,712,875
Statements of Income
Interest income	15,822	15,517	15,002	14,491	13,600	13,283	13,600	13,276	60,832	53,759	50,810
Interest expense	3,614	3,563	3,337	3,015	2,862	2,754	2,649	2,547	13,529	10,812	9,874
Net interest income	12,208	11,954	11,665	11,476	10,738	10,529	10,951	10,729	47,303	42,947	40,936
Provision for loan losses	250	750	500	500	475	375	375	375	2,000	1,600	1,550
Net interest income after provision for loan losses	11,958	11,204	11,165	10,976	10,263	10,154	10,576	10,354	45,303	41,347	39,386
Non-interest income	3,210	3,493	3,002	2,843	3,060	3,469	3,006	2,964	12,548	12,499	12,230
Non-interest expense	8,300	8,013	7,640	7,698	7,533	7,405	7,245	7,200	31,651	29,383	29,896
Income before income taxes	6,868	6,684	6,527	6,121	5,790	6,218	6,337	6,118	26,200	24,463	21,720
Applicable tax expense	1,782	1,702	1,644	1,484	1,470	1,656	1,713	1,615	6,612	6,454	5,514
Net income	$ 5,086	$ 4,982	$ 4,883	$ 4,637	$ 4,320	$ 4,562	$ 4,624	$ 4,503	$ 19,588	$ 18,009	$ 16,206
Basic earnings per common share (in usd per share)	$ 0.48	$ 0.46	$ 0.45	$ 0.43	$ 0.40	$ 0.43	$ 0.43	$ 0.42	$ 1.82	$ 1.68	$ 1.52
Diluted earnings per common share (in usd per share)	$ 0.47	$ 0.46	$ 0.45	$ 0.43	$ 0.39	$ 0.42	$ 0.43	$ 0.42	$ 1.81	$ 1.66	$ 1.51
Other comprehensive income (loss), net of tax
Net unrealized gain (loss) on securities available for sale	$ (1,562)	$ (240)	$ 349	$ 1	$ (3,643)	$ (1,292)	$ 1,025	$ 1,852	$ (1,452)	$ (2,058)	$ (1,399)
Net unrealized loss on securities transferred from available for sale to held to maturity, net of tax	(3)	(3)	(4)	(4)	(5)	9	(10)	(11)	(14)	(17)	(64)
Net unrealized gain on cash flow hedging derivative instruments	235	(20)	(171)	63	1,105	193	(135)	0	107	1,163	0
Unrecognized gain (loss) on postretirement benefit costs	(19)	0	0	0	54	0	0	0	(19)	54	(31)
Other comprehensive loss	(1,349)	(263)	174	60	(2,489)	(1,090)	880	1,841	(1,378)	(858)	(1,494)
Comprehensive income	$ 3,737	$ 4,719	$ 5,057	$ 4,697	$ 1,831	$ 3,472	$ 5,504	$ 6,344	$ 18,210	$ 17,151	$ 14,712