Wilson Bank Holding (WBHC) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 09, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	WBHC
Entity Registrant Name	WILSON BANK HOLDING CO
Entity Central Index Key	885,275
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		10,523,445

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Loans	$ 1,827,729	$ 1,751,162
Less: Allowance for loan losses	(24,846)	(23,909)
Net loans	1,802,883	1,727,253
Securities:
Held to maturity, at cost (market value $30,602 and $32,111, respectively)	31,490	32,480
Available-for-sale, at market (amortized cost $336,766 and $338,449, respectively)	324,580	332,716
Total securities	356,070	365,196
Loans held for sale	5,750	5,106
Interest bearing deposits	52,092	44,465
Restricted equity securities	3,012	3,012
Federal funds sold	15,000	0
Total earning assets	2,234,807	2,145,032
Cash and due from banks	40,342	51,053
Bank premises and equipment, net	57,229	54,215
Accrued interest receivable	6,303	6,266
Deferred income tax asset	9,185	7,424
Other real estate	1,620	1,635
Bank owned life insurance	29,689	29,475
Other assets	16,921	17,128
Goodwill	4,805	4,805
Total assets	2,400,901	2,317,033
Liabilities and Stockholders’ Equity
Deposits	2,115,234	2,037,745
Securities sold under repurchase agreements	0	864
Accrued interest and other liabilities	15,644	10,694
Total liabilities	2,130,878	2,049,303
Stockholders’ equity:
Common stock, $2.00 par value; authorized 50,000,000 shares, issued and outstanding 10,522,277 and 10,450,711 shares, respectively	21,045	20,901
Additional paid-in capital	69,140	66,047
Retained earnings	188,839	185,017
Net unrealized losses on available-for-sale securities, net of income taxes of $3,185 and $1,498, respectively	(9,001)	(4,235)
Total stockholders’ equity	270,023	267,730
Total liabilities and stockholders’ equity	$ 2,400,901	$ 2,317,033

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Held-to-maturity, market value	$ 30,602	$ 32,111
Available-for-sale, amortized cost	$ 336,766	$ 338,449
Common stock, par value (in dollars per share)	$ 2	$ 2
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	10,522,277	10,450,711
Common stock, shares, outstanding	10,522,277	10,450,711
Net unrealized losses on available-for-sale securities, income taxes	$ 3,185	$ 1,498

Consolidated Statements of Earn

Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest income:
Interest and fees on loans	$ 21,833	$ 19,945
Interest and dividends on securities:
Taxable securities	1,666	1,283
Exempt from Federal income taxes	303	337
Interest on loans held for sale	39	66
Interest on Federal funds sold	154	71
Interest on balances held at depository institutions	67	25
Interest and dividends on restricted securities	32	31
Total interest income	24,094	21,758
Interest expense:
Interest on negotiable order of withdrawal accounts	344	319
Interest on money market and savings accounts	707	446
Interest on time deposits	1,592	1,250
Interest on federal funds purchased	0	8
Interest on securities sold under repurchase agreements	16	1
Total interest expense	2,659	2,024
Net interest income before provision for loan losses	21,435	19,734
Provision for loan losses	1,023	389
Net interest income after provision for loan losses	20,412	19,345
Non-interest income:
Service charges on deposit accounts	1,542	1,429
Other fees and commissions	3,003	2,641
Income on BOLI and annuity contracts	214	222
Gain on sale of loans	1,031	976
Gain (loss) on sale of other real estate	0	24
Gain (loss) on sale of securities	0	(38)
Total non-interest income	5,790	5,254
Non-interest expense:
Salaries and employee benefits	9,823	8,847
Occupancy expenses, net	963	851
Advertising & public relations expense	482	399
Furniture and equipment expense	585	520
Data processing expense	710	646
ATM & interchange expense	684	580
Directors’ fees	149	162
Other operating expenses	2,653	2,232
Total non-interest expense	16,049	14,237
Earnings before income taxes	10,153	10,362
Income taxes	2,673	3,867
Net earnings	$ 7,480	$ 6,495
Weighted average number of common shares outstanding-basic	10,507,273	10,360,776
Weighted average number of common shares outstanding-diluted	10,513,076	10,365,717
Basic earnings per common share (in dollars per share)	$ 0.71	$ 0.63
Diluted earnings per common share (in dollars per share)	0.71	0.63
Dividends per share (in dollars per share)	$ 0.35	$ 0.30

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 7,480	$ 6,495
Other comprehensive earnings (loss), net of tax:
Unrealized gains (losses) on available-for-sale securities arising during period, net of taxes of $1,687 and $57, respectively	(4,766)	(89)
Reclassification adjustment for net losses (gains) included in net earnings, net of taxes of $0 and $15, respectively	0	23
Other comprehensive earnings (loss)	(4,766)	(66)
Comprehensive earnings	$ 2,714	$ 6,429

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Earnings (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gains on available-for-sale securities arising during period, tax expense	$ 1,687	$ 57
Reclassification adjustment for net losses (gains) included in net earnings, income tax (expense) benefit	$ 0	$ 15

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Interest received	$ 24,710	$ 23,059
Fees and commissions received	4,545	4,070
Proceeds from sale of loans held for sale	28,865	31,920
Origination of loans held for sale	(28,478)	(24,449)
Interest paid	(2,562)	(2,157)
Cash paid to suppliers and employees	(11,926)	(10,955)
Income taxes paid	(974)	(792)
Net cash provided by operating activities	14,180	20,696
Cash flows from investing activities:
Proceeds from maturities, calls, and principal payments of held-to-maturity securities	928	1,046
Proceeds from maturities, calls, and principal payments of available-for-sale securities	10,210	9,556
Proceeds from the sale of available-for-sale securities	0	12,446
Purchase of available-for-sale securities	(9,118)	(12,563)
Loans made to customers, net of repayments	(76,653)	(48,327)
Purchase of premises and equipment	(3,750)	(2,727)
Proceeds from sale of other real estate	15	2,053
Net cash used in investing activities	(78,368)	(38,516)
Cash flows from financing activities:
Net increase in non-interest bearing, savings and NOW deposit accounts	52,874	68,610
Net increase in time deposits	24,615	14,126
Net increase (decrease) in securities sold under repurchase agreements	(864)	773
Dividends paid	(3,658)	(3,096)
Proceeds from sale of common stock pursuant to dividend reinvestment	2,902	2,398
Proceeds from exercise of stock options	235	93
Net cash provided by financing activities	76,104	82,904
Net increase (decrease) in cash and cash equivalents	11,916	65,084
Cash and cash equivalents at beginning of period	95,518	47,918
Cash and cash equivalents at end of period	107,434	113,002
Reconciliation of net earnings to net cash provided by operating activities:
Net earnings	7,480	6,495
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation, amortization, and accretion	1,389	1,421
Provision for loan losses	1,023	389
Gain on sale of other real estate	0	(24)
Loss on sale of securities	0	38
Stock-based compensation expense	100	79
Decrease (increase) in loans held for sale	(644)	6,495
Increase in deferred tax asset	(74)	(131)
Decrease (increase) in other assets, bank owned life insurance and annuity contract earnings, net	(7)	178
Decrease (increase) in interest receivable	(37)	592
Increase in other liabilities	3,080	2,091
Increase in taxes payable	1,773	3,206
Increase (decrease) in interest payable	97	(133)
Total adjustments	6,700	14,201
Net cash provided by operating activities	14,180	20,696
Supplemental schedule of non-cash activities:
Unrealized gain (loss) in value of securities available-for-sale, net of taxes of $1,687 and $42 for the three months ended March 31, 2018 and 2017, respectively	(4,766)	(66)
Non-cash transfers from loans to other real estate	0	80
Non-cash transfers from other real estate to loans	0	16
Non-cash transfers from loans to other assets	$ 0	$ 2

Consolidated Statements of Cas8

Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Cash Flows [Abstract]
Unrealized gain (loss) in values of securities available-for-sale, taxes	$ 1,687	$ 42

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Business — Wilson Bank Holding Company (the “Company”) is a bank holding company whose primary business is conducted by its wholly-owned subsidiary, Wilson Bank & Trust (the “Bank”). The Bank is a commercial bank headquartered in Lebanon, Tennessee. The Bank provides a full range of banking services in its primary market areas of Wilson, Davidson, Rutherford, Trousdale, Sumner, Dekalb, Putnam and Smith Counties, Tennessee. Basis of Presentation — The accompanying unaudited, consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and therefore do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows in conformity with U.S. generally accepted accounting principles. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods covered by the report have been included. The accompanying unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated audited financial statements and related notes appearing in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . These consolidated financial statements include the accounts of the Company and the Bank. Significant intercompany transactions and accounts are eliminated in consolidation. Use of Estimates — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the balance sheet date and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term include the determination of the allowance for loan losses, the valuation of deferred tax assets, determination of any impairment of intangibles, other-than-temporary impairment of securities, the valuation of other real estate, and the fair value of financial instruments. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . There have been no significant changes to the Company’s significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . Loans — Loans are reported at their outstanding principal balances less unearned income, the allowance for loan losses and any deferred fees or costs on originated loans. Interest income on loans is accrued based on the principal balance outstanding. Loan origination fees, net of certain loan origination costs, are deferred and recognized as an adjustment to the related loan yield using a method which approximates the interest method. Loans are charged off when management believes that the full collectability of the loan is unlikely. As such, a loan may be partially charged-off after a “confirming event” has occurred which serves to validate that full repayment pursuant to the terms of the loan is unlikely. Loans are placed on nonaccrual status when there is a significant deterioration in the financial condition of the borrower, which often is determined when the principal or interest on the loan is more than 90 days past due, unless the loan is both well-secured and in the process of collection. Generally, all interest accrued but not collected for loans that are placed on nonaccrual status, is reversed against current income. Interest income is subsequently recognized only to the extent cash payments are received while the loan is classified as nonaccrual, but interest income recognition is reviewed on a case-by-case basis. A nonaccrual loan is returned to accruing status once the loan has been brought current and collection is reasonably assured or the loan has been “well-secured” through other techniques. Past due status is determined based on the contractual due date per the underlying loan agreement. All loans that are placed on nonaccrual are further analyzed to determine if they should be classified as impaired loans. At December 31, 2017 and March 31, 2018 , there were no loans classified as nonaccrual that were not also deemed to be impaired except for those loans not individually evaluated for impairment as described below. A loan is considered to be impaired when it is probable the Company will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan. This determination is made using a variety of techniques, which include a review of the borrower’s financial condition, debt-service coverage ratios, global cash flow analysis, guarantor support, other loan file information, meetings with borrowers, inspection or reappraisal of collateral and/or consultation with legal counsel as well as results of reviews of other similar industry credits (e.g. builder loans, development loans, church loans, etc). Loans with an identified weakness and principal balance of $500,000 or more are subject to individual identification for impairment. Individually identified impaired loans are measured based on the present value of expected payments using the loan’s original effective rate as the discount rate, the loan’s observable market price, or the fair value of the collateral if the loan is collateral dependent. If the recorded investment in the impaired loan exceeds the measure of fair value, a specific valuation allowance is established as a component of the allowance for loan losses or, in the case of collateral dependent loans, the excess may be charged off. Changes to the valuation allowance are recorded as a component of the provision for loan losses. Any subsequent adjustments to present value calculations for impaired loan valuations as a result of the passage of time, such as changes in the anticipated payback period for repayment, are recorded as a component of the provision for loan losses. For loans less than $500,000 , the Company assigns a valuation allowance to these loans utilizing an allocation rate equal to the allocation rate calculated for non-impaired loans of a similar type. Allowance for Loan Losses — The allowance for loan losses is maintained at a level that management believes to be adequate to absorb probable losses in the loan portfolio. Loan losses are charged against the allowance when they are known. Subsequent recoveries are credited to the allowance. Management’s determination of the adequacy of the allowance is based on an evaluation of the portfolio, current economic conditions, volume, growth, composition of the loan portfolio, homogeneous pools of loans, risk ratings of specific loans, historical loan loss factors, loss experience of various loan segments, identified impaired loans and other factors related to the portfolio. This evaluation is performed quarterly and is inherently subjective, as it requires material estimates that are susceptible to significant change including the amounts and timing of future cash flows expected to be received on any impaired loans. In assessing the adequacy of the allowance, we also consider the results of our ongoing independent loan review process. We undertake this process both to ascertain whether there are loans in the portfolio whose credit quality has weakened over time and to assist in our overall evaluation of the risk characteristics of the entire loan portfolio. Our loan review process includes the judgment of management, independent loan reviewers, and reviews that may have been conducted by third-party reviewers. We incorporate relevant loan review results in the loan impairment determination. In addition, regulatory agencies, as an integral part of their examination process, will periodically review the Company’s allowance for loan losses, and may require the Company to record adjustments to the allowance based on their judgment about information available to them at the time of their examinations. Recently Issued Accounting Pronouncements In February 2016, FASB issued ASU 2016-02, "Leases (Topic 842) ." The amendments in this ASU are effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted. As a result of the amendment, lessees will need to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, subject to adjustments, such as adjustments for initial direct costs. For income statement purposes, FASB retained a dual model, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) while finance leases will result in a front-loaded expense pattern (similar to current capital leases). Classification will be based on criteria that are largely similar to those applied in current lease accounting, but without explicit bright lines. We currently do not expect this ASU to have a material impact on our consolidated financial statements. In June 2016, FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments." ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on held-to-maturity debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. We are currently evaluating the potential impact of ASU 2016-13 on our financial statements. We are also evaluating the sufficiency of current systems and data needed to comply with this ASU. While we are currently unable to reasonably estimate the impact of adopting ASU 2016-13, we expect that the impact of adoption will be significantly influenced by the composition, characteristics and quality of our loan and securities portfolios as well as the prevailing economic conditions and forecasts as of the adoption date. In January 2017, FASB issued ASU 2017-04, “Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment.” ASU 2017-04 eliminates Step 2 from the goodwill impairment test which required entities to compute the implied fair value of goodwill. Under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 will be effective for us on January 1, 2020, with early adoption permitted for interim or annual impairment tests beginning in 2017. ASU 2017-04 is not expected to have a significant impact on our financial statements. In March 2017, FASB issued ASU 2017-08, “Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 provides guidance on the amortization period for certain purchased callable debt securities held at a premium. This update shortens the amortization period for the premium to the earliest call date. Under current generally accepted accounting principles, entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument related to certain cash flow issues. ASU 2017-08 will be effective for us on January 1, 2019. We are currently evaluating the potential impact of ASU 2017-08 on our financial statements. In February 2018, FASB Issued ASU 2018-02 , “Income Statement - Reporting Comprehensive Income (Topic 220).” On December 22, 2017, the U.S. federal government enacted a tax bill, H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (Tax Cuts and Jobs Act). The amendments in this update allow a reclassification from accumulated other comprehensive income 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. The Company elected to adopt this update as of December 31, 2017 and as a result reclassified $697,000 from retained earnings to accumulated other comprehensive income. Other than those previously discussed, there were no other recently issued accounting pronouncements that may materially impact the Company. Subsequent Events - Accounting Standards Codification (ASC) Topic 855, Subsequent Events, establishes general standards of accounting for and disclosure of events that occur after the balance sheet date but before financial statements are issued. Wilson Bank Holding Company evaluated all events or transactions that occurred after March 31, 2018 through the date of the issued financial statements.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans and Allowance for Loan Losses	Loans and Allowance for Loan Losses For financial reporting purposes, the Company classifies its loan portfolio based on the underlying collateral utilized to secure each loan. This classification is consistent with those utilized in the Quarterly Report of Condition and Income filed by the Bank with the Federal Deposit Insurance Corporation (“FDIC”). The following schedule details the loans of the Company at March 31, 2018 and December 31, 2017 : (In Thousands) March 31, December 31, Mortgage loans on real estate Residential 1-4 family $ 412,919 $ 406,667 Multifamily 92,322 91,992 Commercial 691,320 661,223 Construction and land development 429,689 392,039 Farmland 30,065 34,212 Second mortgages 9,077 8,952 Equity lines of credit 65,404 60,650 Total mortgage loans on real estate 1,730,796 1,655,735 Commercial loans 50,797 47,939 Agricultural loans 1,833 1,665 Consumer installment loans Personal 38,554 39,624 Credit cards 3,463 3,385 Total consumer installment loans 42,017 43,009 Other loans 9,732 10,193 Total loans before net deferred loan fees 1,835,175 1,758,541 Net deferred loan fees (7,446 ) (7,379 ) Total loans 1,827,729 1,751,162 Less: Allowance for loan losses (24,846 ) (23,909 ) Net loans $ 1,802,883 $ 1,727,253 Risk characteristics relevant to each portfolio segment are as follows: Construction and land development: Loans for non-owner-occupied real estate construction or land development are generally repaid through cash flow related to the operation, sale or refinance of the property. The Company also finances construction loans for owner-occupied properties. A portion of the Company’s construction and land portfolio segment is comprised of loans secured by residential product types (residential land and single-family construction). With respect to construction loans to developers and builders that are secured by non-owner occupied properties that the Company may originate from time to time, the Company generally requires the borrower to have had an existing relationship with the Company and have a proven record of success. Construction and land development loans are underwritten utilizing independent appraisal reviews, sensitivity analysis of absorption and lease rates, market sales activity, and financial analysis of the developers and property owners. Construction loans are generally based upon estimates of costs and value associated with the complete project. These estimates may be inaccurate. Construction loans often involve the disbursement of substantial funds with repayments substantially dependent on the success of the ultimate project. Sources of repayment for these types of loans may be pre-committed permanent loans from approved long-term lenders, sales of developed property or an interim loan commitment from the Company until permanent financing is obtained. These loans are closely monitored by on-site inspections and are considered to have higher risks than other real estate loans due to their ultimate repayment being sensitive to interest rate changes, governmental regulation of real property, general economic conditions and the availability of long-term financing. 1-4 family residential real estate: Residential real estate loans represent loans to consumers or investors to finance a residence. These loans are typically financed on 15 to 30 year amortization terms, but generally with shorter maturities of 5 to 15 years. Many of these loans are extended to borrowers to finance their primary or secondary residence. Loans to an investor secured by a 1-4 family residence will be repaid from either the rental income from the property or from the sale of the property. This loan segment also includes closed-end home equity loans that are secured by a first or second mortgage on the borrower’s residence. This allows customers to borrow against the equity in their home. Loans in this portfolio segment are underwritten and approved based on a number of credit quality criteria including limits on maximum Loan-to-Value ("LTV"), minimum credit scores, and maximum debt to income. Real estate market values as of the time the loan is made directly affect the amount of credit extended and, in addition, changes in these residential property values impact the depth of potential losses in this portfolio segment. 1-4 family HELOC: This loan segment includes open-end home equity loans that are secured by a first or second mortgage on the borrower’s residence. This allows customers to borrow against the equity in their home utilizing a revolving line of credit. These loans are underwritten and approved based on a number of credit quality criteria including limits on maximum LTV, minimum credit scores, and maximum debt to income. Real estate market values as of the time the loan is made directly affect the amount of credit extended and, in addition, changes in these residential property values impact the depth of potential losses in this portfolio segment. Because of the revolving nature of these loans, as well as the fact that many represent second mortgages, this portfolio segment can contain more risk than the amortizing 1-4 family residential real estate loans. Multi-family and commercial real estate: Multi-family and commercial real estate loans are subject to underwriting standards and processes similar to commercial and industrial loans, in addition to those of real estate loans. These loans are viewed primarily as cash flow loans and secondarily as loans secured by real estate. Commercial real estate lending typically involves higher loan principal amounts and the repayment of these loans is generally largely dependent on the successful operation of the property securing the loan or the business conducted on the property securing the loan. Commercial real estate loans may be more adversely affected by conditions in the real estate markets or in the general economy. The properties securing the Company’s commercial real estate portfolio are diverse in terms of type. This diversity helps reduce the Company’s exposure to adverse economic events that affect any single market or industry. Management monitors and evaluates commercial real estate loans based on collateral, geography and risk grade criteria. The Company also utilizes third-party experts to provide insight and guidance about economic conditions and trends affecting the market areas it serves. In addition, management tracks the level of owner-occupied commercial real estate loans versus non-owner occupied loans. Non-owner occupied commercial real estate loans are loans secured by multifamily and commercial properties where the primary source of repayment is derived from rental income associated with the property (that is, loans for which 50 percent or more of the source of repayment comes from third party, nonaffiliated, rental income) or the proceeds of the sale, refinancing, or permanent financing of the property. These loans are made to finance income-producing properties such as apartment buildings, office and industrial buildings, and retail properties. Owner-occupied commercial real estate loans are loans where the primary source of repayment is the cash flow from the ongoing operations and business activities conducted by the party, or affiliate of the party, who owns the property. Commercial and Industrial: The commercial and industrial loan portfolio segment includes commercial and industrial loans to commercial customers for use in normal business operations to finance working capital needs, equipment purchases or other expansion projects. Collection risk in this portfolio is driven by the creditworthiness of underlying borrowers, particularly cash flow from customers’ business operations. Commercial and industrial loans are primarily made based on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. The cash flows of borrowers, however, may not be as expected and the collateral securing these loans may fluctuate in value. Most commercial and industrial loans are secured by the assets being financed or other business assets such as accounts receivable or inventory and usually incorporate a personal guarantee; however, some short-term loans may be made on an unsecured basis. In the case of loans secured by accounts receivable, the availability of funds for the repayment of these loans may be substantially dependent on the ability of the borrower to collect amounts due from its customers. Consumer: The consumer loan portfolio segment includes non-real estate secured direct loans to consumers for household, family, and other personal expenditures. Consumer loans may be secured or unsecured and are usually structured with short or medium term maturities. These loans are underwritten and approved based on a number of consumer credit quality criteria including limits on maximum LTV on secured consumer loans, minimum credit scores, and maximum debt to income. Many traditional forms of consumer installment credit have standard monthly payments and fixed repayment schedules of one to five years. These loans are made with either fixed or variable interest rates that are based on specific indices. Installment loans fill a variety of needs, such as financing the purchase of an automobile, a boat, a recreational vehicle or other large personal items, or for consolidating debt. These loan may be unsecured or secured by an assignment of title, as in an automobile loan, or by money in a bank account. In addition to consumer installment loans, this portfolio segment also includes secured and unsecured personal lines of credit as well as overdraft protection lines. Loans in this portfolio segment are sensitive to unemployment and other key consumer economic measures. The adequacy of the allowance for loan losses is assessed at the end of each calendar quarter. The level of the allowance is based upon evaluation of the loan portfolio, past loan loss experience, current asset quality trends, known and inherent risks in the portfolio, adverse situations that may affect the borrowers’ ability to repay (including the timing of future payment), the estimated value of any underlying collateral, composition of the loan portfolio, current and anticipated economic conditions, historical loss experience, industry and peer bank loan quality indications and other pertinent factors, including regulatory recommendations. Transactions in the allowance for loan losses for the three months ended March 31, 2018 and year ended December 31, 2017 are summarized as follows: (In Thousands) Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, Installment and Other Total March 31, 2018 Allowance for loan losses: Beginning balance $ 5,156 1,011 9,267 6,094 487 94 723 401 676 23,909 Provision 555 5 111 200 (59 ) 2 45 25 139 1,023 Charge-offs — — — (2 ) — — — — (235 ) (237 ) Recoveries 6 — — 22 — — — 2 121 151 Ending balance $ 5,717 1,016 9,378 6,314 428 96 768 428 701 24,846 Ending balance individually evaluated for impairment $ 946 — 328 — — — — — — 1,274 Ending balance collectively evaluated for impairment $ 4,771 1,016 9,050 6,314 428 96 768 428 701 23,572 Loans: Ending balance $ 412,919 92,322 691,320 429,689 30,065 9,077 65,404 50,797 53,582 1,835,175 Ending balance individually evaluated for impairment $ 4,136 — 2,487 903 310 — — — — 7,836 Ending balance collectively evaluated for impairment $ 408,783 92,322 688,833 428,786 29,755 9,077 65,404 50,797 53,582 1,827,339 Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, Installment and Other Total December 31, 2017 Allowance for loan losses: Beginning balance $ 4,571 839 9,541 5,387 658 112 675 386 562 22,731 Provision 675 172 (414 ) 586 (168 ) (10 ) 45 9 786 1,681 Charge-offs (118 ) — — — (3 ) (11 ) — — (1,090 ) (1,222 ) Recoveries 28 — 140 121 — 3 3 6 418 719 Ending balance $ 5,156 1,011 9,267 6,094 487 94 723 401 676 23,909 Ending balance individually evaluated for impairment $ 136 — 291 — — — — — — 427 Ending balance collectively evaluated for impairment $ 5,020 1,011 8,976 6,094 487 94 723 401 676 23,482 Loans: Ending balance $ 406,667 91,992 661,223 392,039 34,212 8,952 60,650 47,939 54,867 1,758,541 Ending balance individually evaluated for impairment $ 2,678 — 3,046 1,182 — — — — — 6,906 Ending balance collectively evaluated for impairment $ 403,989 91,992 658,177 390,857 34,212 8,952 60,650 47,939 54,867 1,751,635 Impaired Loans At March 31, 2018 , the Company had certain impaired loans of $ 2.1 million which were on non-accruing interest status. At December 31, 2017 , the Company had certain impaired loans of $1.7 million which were on non-accruing interest status. In each case, at the date such loans were placed on nonaccrual status, the Company reversed all previously accrued interest income against current year earnings. The following table presents the Company’s impaired loans at March 31, 2018 and December 31, 2017 . In Thousands Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized March 31, 2018 With no related allowance recorded: Residential 1-4 family $ 2,284 2,321 — 2,299 35 Multifamily — — — — — Commercial real estate 324 323 — 609 4 Construction 906 903 — 1,046 13 Farmland 310 310 — 155 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 3,824 3,857 — 4,109 52 With allowance recorded: Residential 1-4 family $ 1,870 2,041 946 1,140 14 Multifamily — — — — — Commercial real estate 2,165 2,164 328 2,161 4 Construction — — — — — Farmland — — — — — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 4,035 4,205 1,274 3,301 18 Total Residential 1-4 family $ 4,154 4,362 946 3,439 49 Multifamily — — — — — Commercial real estate 2,489 2,487 328 2,770 8 Construction 906 903 — 1,046 13 Farmland 310 310 — 155 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 7,859 8,062 1,274 7,410 70 In Thousands Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized December 31, 2017 With no related allowance recorded: Residential 1-4 family $ 2,314 2,322 — 742 103 Multifamily — — — — — Commercial real estate 893 889 — 902 39 Construction 1,185 1,182 — 1,354 64 Farmland — — — 26 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 4,392 4,393 — 3,024 206 With allowance recorded: Residential 1-4 family $ 409 581 136 461 29 Multifamily — — — — — Commercial real estate 2,157 2,157 291 2,894 17 Construction — — — — — Farmland — — — — — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 2,566 2,738 427 3,355 46 Total: Residential 1-4 family $ 2,723 2,903 136 1,203 132 Multifamily — — — — — Commercial real estate 3,050 3,046 291 3,796 56 Construction 1,185 1,182 — 1,354 64 Farmland — — — 26 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 6,958 7,131 427 6,379 252 Impaired loans also include loans that the Bank may elect to formally restructure due to the weakening credit status of a borrower such that the restructuring may facilitate a repayment plan that minimizes the potential losses that the Bank may otherwise incur. These loans are classified as impaired loans and, if on non-accruing status as of the date of restructuring, the loans are included in the nonperforming loan balances. Not included in nonperforming loans are loans that have been restructured that were performing as of the restructure date. Troubled Debt Restructuring The Bank’s loan portfolio includes certain loans that have been modified in a troubled debt restructuring ("TDR"), where economic or other concessions have been granted to borrowers who have experienced or are expected to experience financial difficulties. These concessions typically result from the Bank’s loss mitigation activities and could include reductions in the interest rate, payment extensions, forgiveness of principal, forbearance or other actions. Certain TDRs are classified as nonperforming at the time of restructure and may only be returned to performing status after considering the borrower’s sustained repayment performance for a reasonable period, generally six months. The following table summarizes the carrying balances of TDRs at March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 (In thousands) Performing TDRs $ 1,710 $ 2,250 Nonperforming TDRs 1,261 1,834 Total TDRS $ 2,971 $ 4,084 The following table outlines the amount of each troubled debt restructuring categorized by loan classification for the three months ended March 31, 2018 and the year ended December 31, 2017 (in thousands, except for number of contracts): March 31, 2018 December 31, 2017 Number of Contracts Pre Modification Outstanding Recorded Investment Post Modification Outstanding Recorded Investment, Net of Related Allowance Number of Contracts Pre Modification Outstanding Recorded Investment Post Modification Outstanding Recorded Investment, Net of Related Allowance Residential 1-4 family — $ — $ — 6 $ 610 $ 535 Multifamily — — — — — — Commercial real estate — — — — — — Construction — — — — — — Farmland 1 310 310 1 86 86 Second mortgages — — — — — — Equity lines of credit — — — — — — Commercial — — — — — — Agricultural, installment and other — — — 1 3 3 Total 1 $ 310 $ 310 8 $ 699 $ 624 As of March 31, 2018 the Company had two loan relationships totaling $413,000 that had been previously classified as a TDR subsequently default within twelve months of restructuring. As of December 31, 2017 , the Company had one loan relationship totaling $103,000 that had been previously classified as a TDR subsequently default within twelve months of restructuring. A default is defined as an occurrence which violates the terms of the receivable’s contract. As of March 31, 2018 and December 31, 2017 , the Company’s recorded investment in consumer mortgage loans in the process of foreclosure amounted to $341,000 and $201,000 , respectively. Potential problem loans, which include nonperforming loans, amounted to approximately $16.7 million at March 31, 2018 and $16.2 million at December 31, 2017 . Potential problem loans represent those loans with a well-defined weakness and where information about possible credit problems of borrowers has caused management to have serious doubts about the borrower’s ability to comply with present repayment terms. This definition is believed to be substantially consistent with the standards established by the FDIC, the Bank’s primary federal regulator, for loans classified as special mention, substandard, or doubtful. The following summary presents the Bank's loan balances by primary loan classification and the amount classified within each risk rating category. Pass rated loans include all credits other than those included in special mention, substandard and doubtful which are defined as follows: • Special mention loans have potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the Bank’s credit position at some future date. • Substandard loans are inadequately protected by the current sound worth and paying capacity of the obligor or of the collateral pledged, if any. Assets so classified must have a well-defined weakness or weaknesses that jeopardize liquidation of the debt. Substandard loans are characterized by the distinct possibility that the Bank will sustain some loss if the deficiencies are not corrected. • Doubtful loans have all the characteristics of substandard loans with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. The Bank considers all doubtful loans to be impaired and places such loans on nonaccrual status. The following table is a summary of the Bank’s loan portfolio by risk rating at March 31, 2018 and December 31, 2017 : (In Thousands) Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, installment and other Total March 31, 2018 Credit Risk Profile by Internally Assigned Rating Pass $ 400,952 92,322 688,446 429,208 29,379 8,688 65,257 50,797 53,419 1,818,468 Special Mention 5,273 — 640 80 122 248 — — 78 6,441 Substandard 6,694 — 2,234 401 564 141 147 — 85 10,266 Doubtful — — — — — — — — — — Total $ 412,919 92,322 691,320 429,689 30,065 9,077 65,404 50,797 53,582 1,835,175 December 31, 2017 Credit Risk Profile by Internally Assigned Rating Pass $ 395,664 91,992 657,456 391,778 33,500 8,765 60,553 47,937 54,697 1,742,342 Special Mention 5,677 — 646 84 125 43 41 2 77 6,695 Substandard 5,326 — 3,121 177 587 144 56 — 93 9,504 Doubtful — — — — — — — — — — Total $ 406,667 91,992 661,223 392,039 34,212 8,952 60,650 47,939 54,867 1,758,541

Debt and Equity Securities

Debt and Equity Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Debt and Equity Securities	Debt and Equity Securities Debt and equity securities have been classified in the consolidated balance sheet according to management’s intent. Debt and equity securities at March 31, 2018 and December 31, 2017 are summarized as follows: March 31, 2018 Securities Available-For-Sale In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value U.S. Government-sponsored enterprises (GSEs)* $ 74,692 $ — $ 3,576 $ 71,116 Mortgage-backed: GSE residential 196,569 341 5,985 190,925 Asset-backed: SBAP 25,261 10 1,149 24,122 Obligations of states and political subdivisions 40,244 — 1,827 38,417 $ 336,766 $ 351 $ 12,537 $ 324,580 March 31, 2018 Securities Held-to-Maturity In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Mortgage-backed: Government-sponsored enterprises (GSEs)* residential $ 9,532 $ 12 $ 374 $ 9,170 Obligations of states and political subdivisions 21,958 42 568 21,432 $ 31,490 $ 54 $ 942 $ 30,602 December 31, 2017 Securities Available-For-Sale In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value U.S. Government-sponsored enterprises (GSEs)* $ 74,690 $ 4 $ 1,714 $ 72,980 Mortgage-backed: GSE residential 200,175 302 2,551 197,926 Asset-backed: SBAP 26,387 — 789 25,598 Obligations of states and political subdivisions 37,197 7 992 36,212 $ 338,449 $ 313 $ 6,046 $ 332,716 December 31, 2017 Securities Held-To-Maturity In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Mortgage-backed: Government-sponsored enterprises (GSEs)* residential $ 9,886 $ 31 $ 156 $ 9,761 Obligations of states and political subdivisions 22,594 66 310 22,350 $ 32,480 $ 97 $ 466 $ 32,111 * Such as Federal National Mortgage Association, Federal Home Loan Mortgage Corporation, Federal Home Loan Bank, Federal Farm Credit Bank, and Government National Mortgage Association. The amortized cost and estimated market value of debt securities at March 31, 2018 , by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Held-to-Maturity Available-For-Sale In Thousands Amortized Cost Estimated Market Value Amortized Cost Estimated Market Value Due in one year or less $ 3,698 $ 3,696 $ — $ — Due after one year through five years 6,496 6,501 23,881 23,219 Due after five years through ten years 10,255 9,855 130,640 124,982 Due after ten years 11,041 10,550 182,245 176,379 $ 31,490 $ 30,602 $ 336,766 $ 324,580 The following table shows the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at March 31, 2018 and December 31, 2017 . In Thousands, Except Number of Securities Less than 12 Months 12 Months or More Total March 31, 2018 Fair Value Unrealized Losses Number of Securities Included Fair Value Unrealized Losses Number of Securities Included Fair Value Unrealized Losses Held-to-Maturity Securities: Mortgage-backed: Government-sponsored enterprises (GSEs) residential $ 4,179 $ 126 6 $ 4,769 $ 248 5 $ 8,948 $ 374 Obligations of states and political subdivisions 9,277 61 26 7,028 507 18 16,305 568 $ 13,456 $ 187 32 $ 11,797 $ 755 23 $ 25,253 $ 942 Available-for-Sale Securities: GSEs $ 16,821 $ 619 9 $ 54,295 $ 2,957 21 $ 71,116 $ 3,576 Mortgage-backed: GSE residential 92,250 2,648 43 76,041 3,337 55 168,291 5,985 Asset-backed: SBAP 7,246 276 6 15,773 873 8 23,019 1,149 Obligations of states and political subdivisions 17,279 380 28 21,138 1,447 56 38,417 1,827 $ 133,596 $ 3,923 86 $ 167,247 $ 8,614 140 $ 300,843 $ 12,537 In Thousands, Except Number of Securities Less than 12 Months 12 Months or More Total Fair Unrealized Number of Securities Fair Unrealized Number of Securities Fair Unrealized December 31, 2017 Value Losses Included Value Losses Included Value Losses Held-to-Maturity Securities: Mortgage-backed: Government-sponsored enterprises (GSEs) residential $ 3,316 $ 21 4 $ 5,206 $ 135 5 $ 8,522 $ 156 Obligations of states and political subdivisions 10,137 46 27 7,278 264 18 17,415 310 $ 13,453 $ 67 31 $ 12,484 $ 399 23 $ 25,937 $ 466 Available-for-Sale Securities: GSEs $ 16,099 $ 190 8 $ 55,726 $ 1,524 21 $ 71,825 $ 1,714 Mortgage-backed: GSE residential 92,180 769 43 81,434 1,782 54 173,614 2,551 Asset-backed: SBAP 9,087 181 7 16,510 608 8 25,597 789 Obligations of states and political subdivisions 12,128 113 22 21,762 879 56 33,890 992 $ 129,494 $ 1,253 80 $ 175,432 $ 4,793 139 $ 304,926 $ 6,046 Unrealized losses on securities have not been recognized into income because the Company does not consider these securities to be other-than-temporarily impaired at March 31, 2018 , as the issuers’ securities are of high credit quality, management does not intend to sell the securities and it is not more likely than not that management will be required to sell the securities prior to their anticipated recovery, and the decline in fair value is largely due to changes in interest rates and other market conditions. The issuers continue to make timely principal and interest payment on the securities. The fair value is expected to recover as the securities approach maturity. The carrying values of the Company’s investment securities could decline in the future if the financial condition of issuers deteriorates and management determines it is probable that the Company will not recover the entire amortized cost bases of the securities. As a result, there is a risk that other-than-temporary impairment charges may occur in the future given the current economic environment.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The computation of basic earnings per share is based on the weighted average number of common shares outstanding during the period, adjusted for stock splits. The computation of diluted earnings per share for the Company begins with the basic earnings per share plus the effect of common shares contingently issuable from stock options. The following is a summary of components comprising basic and diluted earnings per share (“EPS”) for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (Dollars in Thousands Except Share and Per Share Amounts) Basic EPS Computation: Numerator – Earnings available to common stockholders $ 7,480 $ 6,495 Denominator – Weighted average number of common shares outstanding 10,507,273 10,360,776 Basic earnings per common share $ 0.71 $ 0.63 Diluted EPS Computation: Numerator – Earnings available to common stockholders $ 7,480 $ 6,495 Denominator – Weighted average number of common shares outstanding 10,507,273 10,360,776 Dilutive effect of stock options 5,803 4,941 Weighted average diluted common shares outstanding 10,513,076 10,365,717 Diluted earnings per common share $ 0.71 $ 0.63

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Accounting Standards Codification (“ASC”) 740, Income Taxes , defines the threshold for recognizing the benefits of tax return positions in the financial statements as “more-likely-than-not” to be sustained by the taxing authority. This section also provides guidance on the derecognition, measurement and classification of income tax uncertainties, along with any related interest and penalties, and includes guidance concerning accounting for income tax uncertainties in interim periods. As of March 31, 2018 , the Company had no unrecognized tax benefits related to Federal or state income tax matters and does not anticipate any material increase or decrease in unrecognized tax benefits relative to any tax positions taken prior to March 31, 2018 . As of March 31, 2018 , the Company has not accrued or recognized interest or penalties related to uncertain tax positions. The Company’s policy is to recognize interest and/or penalties related to income tax matters in income tax expense. The Company and the Bank file consolidated U.S. Federal and State of Tennessee income tax returns. The Company is currently open to audit under the statute of limitations by the State of Tennessee for the years ended December 31, 2014 through 2017 and the IRS for the years ended December 31, 2015 through 2017 . In December 2017, the Tax Cuts and Jobs Act was signed into law. As a result, the statutory corporate tax rate was lowered from 35% to 21%, effective January 1, 2018.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities In the normal course of business, the Bank has entered into off-balance sheet financial instruments which include commitments to extend credit (i.e., including unfunded lines of credit) and standby letters of credit. Commitments to extend credit are usually the result of lines of credit granted to existing borrowers under agreements that the total outstanding indebtedness will not exceed a specific amount during the term of the indebtedness. Typical borrowers are commercial concerns that use lines of credit to supplement their treasury management functions, thus their total outstanding indebtedness may fluctuate during any time period based on the seasonality of their business and the resultant timing of their cash flows. Other typical lines of credit are related to home equity loans granted to consumers. Commitments to extend credit generally have fixed expiration dates or other termination clauses and may require payment of a fee. Standby letters of credit are generally issued on behalf of an applicant (the Bank's customer) to a specifically named beneficiary and are the result of a particular business arrangement that exists between the applicant and the beneficiary. Standby letters of credit have fixed expiration dates and are usually for terms of two years or less unless terminated sooner due to criteria specified in the standby letter of credit. A typical arrangement involves the applicant routinely being indebted to the beneficiary for such items as inventory purchases, insurance, utilities, lease guarantees or other third party commercial transactions. The standby letter of credit would permit the beneficiary to obtain payment from the Bank under certain prescribed circumstances. Subsequently, the Bank would then seek reimbursement from the applicant pursuant to the terms of the standby letter of credit. The Bank follows the same credit policies and underwriting practices when making these commitments as it does for on-balance sheet instruments. Each customer’s creditworthiness is evaluated on a case-by-case basis, and the amount of collateral obtained, if any, is based on management’s credit evaluation of the customer. Collateral held varies but may include cash, real estate and improvements, marketable securities, accounts receivable, inventory, equipment, and personal property. The contractual amounts of these commitments are not reflected in the consolidated financial statements and would only be reflected if drawn upon. Since many of the commitments are expected to expire without being drawn upon, the contractual amounts do not necessarily represent future cash requirements. However, should the commitments be drawn upon and should our customers default on their resulting obligation to us, the Company’s maximum exposure to credit loss, without consideration of collateral, is represented by the contractual amount of those instruments. A summary of the Company’s total contractual amount for all off-balance sheet commitments at March 31, 2018 is as follows: Commitments to extend credit $ 602,140,000 Standby letters of credit $ 70,530,000 The Company originates residential mortgage loans, sells them to third-party purchasers, and does not retain the servicing rights. These loans are originated internally and are primarily to borrowers in the Company’s geographic market footprint. These sales are on a best efforts basis to investors that follow conventional government sponsored entities ("GSE") and the Department of Housing and Urban Development/U.S. Department of Veterans Affairs ("HUD/VA") guidelines. Generally, loans held for sale are underwritten by the Company, including HUD/VA loans. Each purchaser has specific guidelines and criteria for sellers of loans, and the risk of credit loss with regard to the principal amount of the loans sold is generally transferred to the purchasers upon sale. While the loans are sold without recourse, the purchase agreements require the Company to make certain representations and warranties regarding the existence and sufficiency of file documentation and the absence of fraud by borrowers or other third parties such as appraisers in connection with obtaining the loan. If it is determined that the loans sold were in breach of these representations or warranties or the loan had an early payoff or payment default, the Company has obligations to either repurchase the loan for the unpaid principal balance and related investor fees or make the purchaser whole for the economic benefits of the loan. To date, repurchase activity pursuant to the terms of these representations and warranties has been insignificant and has resulted in insignificant losses to the Company. Based on information currently available, management believes that it does not have significant exposure to contingent losses that may arise relating to the representations and warranties that it has made in connection with its mortgage loan sales. Various legal claims also arise from time to time in the normal course of business. In the opinion of management, the resolution of these claims outstanding at March 31, 2018 will not have a material impact on the Company’s financial statements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements FASB ASC 820, Fair Value Measurements and Disclosures , which defines fair value, establishes a framework for measuring fair value in U.S. GAAP and expands disclosures about fair value measurements. The definition of fair value focuses on the exit price, i.e., the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, not the entry price (i.e., the price that would be paid to acquire the asset or received to assume the liability at the measurement date). The statement emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, the fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. Valuation Hierarchy FASB ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. The three levels are defined as follows: • Level 1 — inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2 — inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets, and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument. • Level 3 — inputs to the valuation methodology are unobservable and significant to the fair value measurement. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Following is a description of the valuation methodologies used for assets and liabilities measured at fair value, as well as the general classification of such assets and liabilities pursuant to the valuation hierarchy. Assets Securities available-for-sale — Where quoted prices are available for identical securities in an active market, securities are classified within Level 1 of the valuation hierarchy. Level 1 securities include highly liquid government securities and certain other financial products. If quoted market prices are not available, then fair values are estimated by using pricing models that use observable inputs or quoted prices of securities with similar characteristics and are classified within Level 2 of the valuation hierarchy. In certain cases where there is limited activity or less transparency around inputs to the valuation and more complex pricing models or discounted cash flows are used, securities are classified within Level 3 of the valuation hierarchy. Impaired loans — A loan is considered to be impaired when it is probable the Company will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan agreement. Impaired loans are measured based on the present value of expected payments using the loan’s original effective rate as the discount rate, the loan’s observable market price, or the fair value of the collateral less selling costs if the loan is collateral dependent. If the recorded investment in the impaired loan exceeds the measure of fair value, a valuation allowance may be established as a component of the allowance for loan losses or the expense is recognized as a charge-off. Impaired loans are classified within Level 3 of the valuation hierarchy due to the unobservable inputs used in determining their fair value such as collateral values and the borrower’s underlying financial condition. Other real estate owned — Other real estate owned (“OREO”) represents real estate foreclosed upon by the Company through loan defaults by customers or acquired in lieu of foreclosure. Substantially all of these amounts relate to construction and land development, other loans secured by land, and commercial real estate loans for which the Company believes it has adequate collateral. Upon foreclosure, the property is recorded at the lower of cost or fair value, based on appraised value, less selling costs estimated as of the date acquired with any loss recognized as a charge-off through the allowance for loan losses. Additional OREO losses for subsequent valuation downward adjustments are determined on a specific property basis and are included as a component of noninterest expense along with holding costs. Any gains or losses realized at the time of disposal are also reflected in noninterest expense, as applicable. OREO is included in Level 3 of the valuation hierarchy due to the lack of observable market inputs into the determination of fair value. Appraisal values are property-specific and sensitive to the changes in the overall economic environment. Mortgage loans held-for-sale — Mortgage loans held-for-sale are carried at the fair value. The fair value of mortgage loans held-for-sale is determined using quoted prices for similar assets, adjusted for specific attributes of that loan (Level 2). Other assets — Included in other assets are certain assets carried at fair value, including the cash surrender value of bank owned life insurance policies. The Company uses financial information received from insurance carriers indicating the performance of the insurance policies and cash surrender values in determining the carrying value. The Company reflects these assets within Level 3 of the valuation hierarchy due to the unobservable inputs included in the valuation of these items. The Company does not consider the fair values of these policies and contracts to be materially sensitive to changes in these unobservable inputs. The following tables present the financial instruments carried at fair value as of March 31, 2018 and December 31, 2017 , by caption on the consolidated balance sheet and by FASB ASC 820 valuation hierarchy (as described above) (in thousands): Assets and Liabilities Measured at Fair Value on a Recurring Basis (In Thousands) Total Carrying Value in the Consolidated Balance Sheet Quoted Market Prices in an Active Market (Level 1) Models with Significant Observable Market Parameters (Level 2) Models with Significant Unobservable Market Parameters (Level 3) March 31, 2018 Investment securities available-for-sale: U.S. Government sponsored enterprises $ 71,116 — 71,116 — Mortgage-backed securities 190,925 — 190,925 — Asset-backed securities 24,122 — 24,122 — State and municipal securities 38,417 803 37,614 — Total investment securities available-for-sale 324,580 803 323,777 — Loans held for sale 5,750 — 5,750 — Other assets 29,689 — — 29,689 Total assets at fair value $ 360,019 803 329,527 29,689 December 31, 2017 Investment securities available-for-sale: U.S. Government sponsored enterprises $ 72,980 — 72,980 — Mortgage-backed securities 197,926 — 197,926 — Asset-backed securities 25,598 — 25,598 — State and municipal securities 36,212 — 36,212 — Total investment securities available-for-sale 332,716 — 332,716 — Loans held for sale 5,106 — 5,106 — Other assets 29,475 — — 29,475 Total assets at fair value $ 367,297 — 337,822 29,475 Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (In Thousands) Total Carrying Value in the Consolidated Balance Sheet Quoted Market Prices in an Active Market (Level 1) Models with Significant Observable Market Parameters (Level 2) Models with Significant Unobservable Market Parameters (Level 3) March 31, 2018 Other real estate owned $ 1,620 — — 1,620 Impaired loans, net (¹) 6,585 — — 6,585 Total $ 8,205 — — 8,205 December 31, 2017 Other real estate owned $ 1,635 — — 1,635 Impaired loans, net (¹) 6,531 — — 6,531 Total $ 8,166 — — 8,166 (1) Amount is net of a valuation allowance of $1,274,000 at March 31, 2018 and $427,000 at December 31, 2017 as required by ASC 310, “Receivables.” The following table presents additional quantitative information about assets measured at fair value on a nonrecurring basis and for which we have utilized Level 3 inputs to determine fair value at March 31, 2018 and December 31, 2017 : Valuation Techniques (¹) Significant Unobservable Inputs Range (Weighted Average) Impaired loans Appraisal Estimated costs to sell 10% Other real estate owned Appraisal Estimated costs to sell 10% (¹) The fair value is generally determined through independent appraisals of the underlying collateral, which may include Level 3 inputs that are not identifiable, or by using the discounted cash flow method if the loan is not collateral dependent. In the case of the bond portfolio, the Company monitors the valuation technique utilized by various pricing agencies to ascertain when transfers between levels have been affected. The nature of the remaining assets and liabilities is such that transfers in and out of any level are expected to be rare. For the three months ended March 31, 2018 , there were no transfers between Levels 1, 2 or 3. The table below includes a rollforward of the balance sheet amounts for the three months ended March 31, 2018 and 2017 (including the change in fair value) for financial instruments classified by the Company within Level 3 of the valuation hierarchy for assets and liabilities measured at fair value on a recurring basis. When a determination is made to classify a financial instrument within Level 3 of the valuation hierarchy, the determination is based upon the significance of the unobservable factors to the overall fair value measurement. However, since Level 3 financial instruments typically include, in addition to the unobservable or Level 3 components, observable components (that is, components that are actively quoted and can be validated to external sources), the gains and losses in the table below include changes in fair value due in part to observable factors that are part of the valuation methodology (in thousands): For the Three Months Ended March 31, 2018 2017 Other Assets Other Liabilities Other Assets Other Liabilities Fair value, January 1 $ 29,475 — $ 28,616 — Total realized gains included in income 214 — 222 — Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at March 31 — — — — Purchases, issuances and settlements, net — — — — Transfers out of Level 3 — — — — Fair value, March 31 $ 29,689 — $ 28,838 — Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at March 31 $ 214 — $ 222 — The following methods and assumptions were used by the Company in estimating its fair value disclosures for financial instruments that are not measured at fair value. In cases where quoted market prices or observable components are not available, fair values are based on estimates using discounted cash flow models. Those models are significantly affected by the assumptions used, including the discount rates, estimates of future cash flows and borrower creditworthiness. The fair value estimates presented herein are based on pertinent information available to management as of March 31, 2018 and December 31, 2017 . Such amounts have not been revalued for purposes of these consolidated financial statements since those dates and, therefore, current estimates of fair value may differ significantly from the amounts presented herein. Held-to-maturity securities — Estimated fair values for investment securities are based on quoted market prices where available. If quoted market prices are not available, then fair values are estimated by using pricing models that use observable inputs or quoted prices of securities with similar characteristics. Loans — The fair value of our loan portfolio includes a credit risk factor in the determination of the fair value of our loans. This credit risk assumption is intended to approximate the fair value that a market participant would realize in a hypothetical orderly transaction. Our loan portfolio is initially fair valued using a segmented approach. We divide our loan portfolio into the following categories: variable rate loans, impaired loans and all other loans. The results are then adjusted to account for credit risk. For variable-rate loans that reprice frequently and have no significant change in credit risk, fair values approximate carrying values. Fair values for impaired loans are estimated using discounted cash flow models or based on the fair value of the underlying collateral. For other loans, fair values are estimated using discounted cash flow models, using current market interest rates offered for loans with similar terms to borrowers of similar credit quality. The values derived from the discounted cash flow approach for each of the above portfolios are then further discounted to incorporate credit risk to determine the exit price. Deposits and Securities sold under agreements to repurchase — Fair values for deposits and securities sold under agreements to repurchase are estimated using discounted cash flow models, using current market interest rates offered on deposits with similar remaining maturities. Off-Balance Sheet Instruments — The fair values of the Company’s off-balance-sheet financial instruments are based on fees charged to enter into similar agreements. However, commitments to extend credit do not represent a significant value to the Company until such commitments are funded. The following table presents the carrying amounts, estimated fair value and placement in the fair valuation hierarchy of the Company’s financial instruments at March 31, 2018 and December 31, 2017 . This table excludes financial instruments for which the carrying amount approximates fair value. For short-term financial assets such as cash and cash equivalents, the carrying amount is a reasonable estimate of fair value due to the relatively short time between the origination of the instrument and its expected realization. Carrying/ Notional Estimated Quoted Market Prices in an Active Market Models with Significant Observable Market Parameters Models with Significant Unobservable Market Parameters (in Thousands) Amount Fair Value (¹) (Level 1) (Level 2) (Level 3) March 31, 2018 Financial assets: Securities held-to-maturity $ 31,490 30,602 — 30,602 — Loans, net 1,802,883 1,793,105 — — 1,793,105 Financial liabilities: Deposits and securities sold under agreements to repurchase 2,115,234 1,847,706 — — 1,847,706 Off-balance sheet instruments: Commitments to extend credit — — — — — Standby letters of credit — — — — — December 31, 2017 Financial assets: Securities held-to-maturity $ 32,480 32,111 — 32,111 — Loans, net 1,727,253 1,724,937 — — 1,724,937 Financial liabilities: Deposits and securities sold under agreements to repurchase 2,038,609 1,812,011 — — 1,812,011 Off-balance sheet instruments: Commitments to extend credit — — — — — Standby letters of credit — — — — — (1) Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.

Stock Option Plan, Equity Incen

Stock Option Plan, Equity Incentive Plan & Charter Amendment	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plan, Equity Incentive Plan & Charter Amendment	Equity Incentive Plans In April 1999, the stockholders of the Company approved the Wilson Bank Holding Company 1999 Stock Option Plan (the “1999 Stock Option Plan”). The Stock Option Plan provided for the granting of stock options, and authorized the issuance of common stock upon the exercise of such options, for up to 200,000 shares of common stock, to officers and other key employees of the Company and its subsidiary. Furthermore, the Company and its subsidiary could reserve additional shares for issuance under the 1999 Stock Option Plan as needed in order that the aggregate number of shares that may be issued during the term of the 1999 Stock Option Plan is equal to five percent ( 5% ) of the shares of common stock then issued and outstanding. The 1999 Stock Option Plan terminated on April 13, 2009 , and no additional rewards may be issued under the 1999 Stock Option Plan. The awards granted under the 1999 Stock Option Plan prior to the plan's termination will remain outstanding until exercised or otherwise terminated. In April 2009, the Company’s shareholders approved the Wilson Bank Holding Company 2009 Stock Option Plan (the “2009 Stock Option Plan”). The 2009 Stock Option Plan was effective as of April 14, 2009 and replaced the 1999 Stock Option Plan. Under the 2009 Stock Option Plan, awards may be in the form of options to acquire common stock of the Company. Subject to adjustment as provided by the terms of the 2009 Stock Option Plan, the maximum number of shares of common stock with respect to which awards may be granted under the 2009 Stock Option Plan is 100,000 shares. As of March 31, 2018 , the Company has available to grant 51,222 options to employees pursuant to the 2009 Stock Option Plan. Under the 2009 Stock Option Plan, stock option awards may be granted in the form of incentive stock options or nonstatutory stock options and are generally exercisable for up to ten years following the date such option awards are granted. Exercise prices of incentive stock options must be equal to or greater than 100% of the fair market value of the common stock on the grant date. During the second quarter of 2016, the Company’s shareholders approved the Wilson Bank Holding Company 2016 Equity Incentive Plan, which authorizes awards of up to 750,000 shares of common stock. The 2016 Equity Incentive Plan was approved by the Board of Directors and effective as of January 25, 2016 and approved by the Company’s shareholders on April 12, 2016. On September 26, 2016, the Board of Directors approved an amendment and restatement of the 2016 Equity Incentive Plan (as amended and restated the “2016 Equity Incentive Plan”) to make clear that directors who are not also employees of the Company may be awarded stock appreciation rights. The primary purpose of the 2016 Equity Incentive Plan is to promote the interest of the Company and its shareholders by, among other things, (i) attracting and retaining key officers, employees and directors of, and consultants to, the Company and its subsidiaries and affiliates, (ii) motivating those individuals by means of performance-related incentives to achieve long-range performance goals, (iii) enabling such individuals to participate in the long-term growth and financial success of the Company, (iv) encouraging ownership of stock in the Company by such individuals, and (v) linking their compensation to the long-term interests of the Company and its shareholders. Except for certain limitations, awards can be in the form of stock options (both incentive stock options and non-qualified stock options), stock appreciation rights, restricted shares and restricted share units, performance awards and other stock-based awards. As of March 31, 2018 , the Company has 500,170 shares remaining available for issuance under the 2016 Equity Incentive Plan. As of March 31, 2018 , the Company had outstanding 152,981 stock options with a weighted average price of $38.62 and 126,565 cash-settled stock appreciation rights each with a weighted average price of $40.53 . The following tables summarize information about stock options and cash-settled SARs for the three months ended March 31, 2018 and 2017: March 31, 2018 March 31, 2017 Shares Weighted Shares Weighted Options and SARs outstanding at beginning of period 285,780 $ 39.31 $ 183,847 $ 38.08 Granted 2,500 44.75 105,833 40.78 Exercised 7,234 35.30 3,286 28.03 Forfeited or expired 1,500 36.60 322 24.13 Outstanding at end of period 279,546 $ 39.48 $ 286,072 $ 39.21 Options and SARs exercisable at March 31 59,378 $ 37.77 $ 15,382 $ 29.59 As of March 31, 2018, there was $2,458,000 of total unrecognized cost related to non-vested share-based compensation arrangements granted under the Company's equity incentive plans. The cost is expected to be recognized over a weighted-average period of 3.73 years.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Nature of Business	Nature of Business — Wilson Bank Holding Company (the “Company”) is a bank holding company whose primary business is conducted by its wholly-owned subsidiary, Wilson Bank & Trust (the “Bank”). The Bank is a commercial bank headquartered in Lebanon, Tennessee. The Bank provides a full range of banking services in its primary market areas of Wilson, Davidson, Rutherford, Trousdale, Sumner, Dekalb, Putnam and Smith Counties, Tennessee.
Basis of Presentation	Basis of Presentation — The accompanying unaudited, consolidated financial statements have been prepared in accordance with instructions to Form 10-Q and therefore do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, and cash flows in conformity with U.S. generally accepted accounting principles. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods covered by the report have been included. The accompanying unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated audited financial statements and related notes appearing in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . These consolidated financial statements include the accounts of the Company and the Bank. Significant intercompany transactions and accounts are eliminated in consolidation.
Use of Estimates	Use of Estimates — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the balance sheet date and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term include the determination of the allowance for loan losses, the valuation of deferred tax assets, determination of any impairment of intangibles, other-than-temporary impairment of securities, the valuation of other real estate, and the fair value of financial instruments. These financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . There have been no significant changes to the Company’s significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 .
Loans	Loans — Loans are reported at their outstanding principal balances less unearned income, the allowance for loan losses and any deferred fees or costs on originated loans. Interest income on loans is accrued based on the principal balance outstanding. Loan origination fees, net of certain loan origination costs, are deferred and recognized as an adjustment to the related loan yield using a method which approximates the interest method. Loans are charged off when management believes that the full collectability of the loan is unlikely. As such, a loan may be partially charged-off after a “confirming event” has occurred which serves to validate that full repayment pursuant to the terms of the loan is unlikely. Loans are placed on nonaccrual status when there is a significant deterioration in the financial condition of the borrower, which often is determined when the principal or interest on the loan is more than 90 days past due, unless the loan is both well-secured and in the process of collection. Generally, all interest accrued but not collected for loans that are placed on nonaccrual status, is reversed against current income. Interest income is subsequently recognized only to the extent cash payments are received while the loan is classified as nonaccrual, but interest income recognition is reviewed on a case-by-case basis. A nonaccrual loan is returned to accruing status once the loan has been brought current and collection is reasonably assured or the loan has been “well-secured” through other techniques. Past due status is determined based on the contractual due date per the underlying loan agreement. All loans that are placed on nonaccrual are further analyzed to determine if they should be classified as impaired loans. At December 31, 2017 and March 31, 2018 , there were no loans classified as nonaccrual that were not also deemed to be impaired except for those loans not individually evaluated for impairment as described below. A loan is considered to be impaired when it is probable the Company will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan. This determination is made using a variety of techniques, which include a review of the borrower’s financial condition, debt-service coverage ratios, global cash flow analysis, guarantor support, other loan file information, meetings with borrowers, inspection or reappraisal of collateral and/or consultation with legal counsel as well as results of reviews of other similar industry credits (e.g. builder loans, development loans, church loans, etc). Loans with an identified weakness and principal balance of $500,000 or more are subject to individual identification for impairment. Individually identified impaired loans are measured based on the present value of expected payments using the loan’s original effective rate as the discount rate, the loan’s observable market price, or the fair value of the collateral if the loan is collateral dependent. If the recorded investment in the impaired loan exceeds the measure of fair value, a specific valuation allowance is established as a component of the allowance for loan losses or, in the case of collateral dependent loans, the excess may be charged off. Changes to the valuation allowance are recorded as a component of the provision for loan losses. Any subsequent adjustments to present value calculations for impaired loan valuations as a result of the passage of time, such as changes in the anticipated payback period for repayment, are recorded as a component of the provision for loan losses. For loans less than $500,000 , the Company assigns a valuation allowance to these loans utilizing an allocation rate equal to the allocation rate calculated for non-impaired loans of a similar type.
Allowance for Loan Losses	Allowance for Loan Losses — The allowance for loan losses is maintained at a level that management believes to be adequate to absorb probable losses in the loan portfolio. Loan losses are charged against the allowance when they are known. Subsequent recoveries are credited to the allowance. Management’s determination of the adequacy of the allowance is based on an evaluation of the portfolio, current economic conditions, volume, growth, composition of the loan portfolio, homogeneous pools of loans, risk ratings of specific loans, historical loan loss factors, loss experience of various loan segments, identified impaired loans and other factors related to the portfolio. This evaluation is performed quarterly and is inherently subjective, as it requires material estimates that are susceptible to significant change including the amounts and timing of future cash flows expected to be received on any impaired loans. In assessing the adequacy of the allowance, we also consider the results of our ongoing independent loan review process. We undertake this process both to ascertain whether there are loans in the portfolio whose credit quality has weakened over time and to assist in our overall evaluation of the risk characteristics of the entire loan portfolio. Our loan review process includes the judgment of management, independent loan reviewers, and reviews that may have been conducted by third-party reviewers. We incorporate relevant loan review results in the loan impairment determination. In addition, regulatory agencies, as an integral part of their examination process, will periodically review the Company’s allowance for loan losses, and may require the Company to record adjustments to the allowance based on their judgment about information available to them at the time of their examinations.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, FASB issued ASU 2016-02, "Leases (Topic 842) ." The amendments in this ASU are effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted. As a result of the amendment, lessees will need to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, subject to adjustments, such as adjustments for initial direct costs. For income statement purposes, FASB retained a dual model, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) while finance leases will result in a front-loaded expense pattern (similar to current capital leases). Classification will be based on criteria that are largely similar to those applied in current lease accounting, but without explicit bright lines. We currently do not expect this ASU to have a material impact on our consolidated financial statements. In June 2016, FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments." ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on held-to-maturity debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. We are currently evaluating the potential impact of ASU 2016-13 on our financial statements. We are also evaluating the sufficiency of current systems and data needed to comply with this ASU. While we are currently unable to reasonably estimate the impact of adopting ASU 2016-13, we expect that the impact of adoption will be significantly influenced by the composition, characteristics and quality of our loan and securities portfolios as well as the prevailing economic conditions and forecasts as of the adoption date. In January 2017, FASB issued ASU 2017-04, “Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment.” ASU 2017-04 eliminates Step 2 from the goodwill impairment test which required entities to compute the implied fair value of goodwill. Under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 will be effective for us on January 1, 2020, with early adoption permitted for interim or annual impairment tests beginning in 2017. ASU 2017-04 is not expected to have a significant impact on our financial statements. In March 2017, FASB issued ASU 2017-08, “Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 provides guidance on the amortization period for certain purchased callable debt securities held at a premium. This update shortens the amortization period for the premium to the earliest call date. Under current generally accepted accounting principles, entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument related to certain cash flow issues. ASU 2017-08 will be effective for us on January 1, 2019. We are currently evaluating the potential impact of ASU 2017-08 on our financial statements. In February 2018, FASB Issued ASU 2018-02 , “Income Statement - Reporting Comprehensive Income (Topic 220).” On December 22, 2017, the U.S. federal government enacted a tax bill, H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (Tax Cuts and Jobs Act). The amendments in this update allow a reclassification from accumulated other comprehensive income 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. The Company elected to adopt this update as of December 31, 2017 and as a result reclassified $697,000 from retained earnings to accumulated other comprehensive income. Other than those previously discussed, there were no other recently issued accounting pronouncements that may materially impact the Company.
Subsequent Events	Subsequent Events - Accounting Standards Codification (ASC) Topic 855, Subsequent Events, establishes general standards of accounting for and disclosure of events that occur after the balance sheet date but before financial statements are issued. Wilson Bank Holding Company evaluated all events or transactions that occurred after March 31, 2018 through the date of the issued financial statements.
Income Taxes	Accounting Standards Codification (“ASC”) 740, Income Taxes , defines the threshold for recognizing the benefits of tax return positions in the financial statements as “more-likely-than-not” to be sustained by the taxing authority. This section also provides guidance on the derecognition, measurement and classification of income tax uncertainties, along with any related interest and penalties, and includes guidance concerning accounting for income tax uncertainties in interim periods. As of March 31, 2018 , the Company had no unrecognized tax benefits related to Federal or state income tax matters and does not anticipate any material increase or decrease in unrecognized tax benefits relative to any tax positions taken prior to March 31, 2018 .
Fair Value Measurements and Disclosures	FASB ASC 820, Fair Value Measurements and Disclosures , which defines fair value, establishes a framework for measuring fair value in U.S. GAAP and expands disclosures about fair value measurements. The definition of fair value focuses on the exit price, i.e., the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, not the entry price (i.e., the price that would be paid to acquire the asset or received to assume the liability at the measurement date). The statement emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, the fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability.

Loans and Allowance for Loan 18

Loans and Allowance for Loan Losses (Tables)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Schedule of Details on Loans of Company	The following schedule details the loans of the Company at March 31, 2018 and December 31, 2017 : (In Thousands) March 31, December 31, Mortgage loans on real estate Residential 1-4 family $ 412,919 $ 406,667 Multifamily 92,322 91,992 Commercial 691,320 661,223 Construction and land development 429,689 392,039 Farmland 30,065 34,212 Second mortgages 9,077 8,952 Equity lines of credit 65,404 60,650 Total mortgage loans on real estate 1,730,796 1,655,735 Commercial loans 50,797 47,939 Agricultural loans 1,833 1,665 Consumer installment loans Personal 38,554 39,624 Credit cards 3,463 3,385 Total consumer installment loans 42,017 43,009 Other loans 9,732 10,193 Total loans before net deferred loan fees 1,835,175 1,758,541 Net deferred loan fees (7,446 ) (7,379 ) Total loans 1,827,729 1,751,162 Less: Allowance for loan losses (24,846 ) (23,909 ) Net loans $ 1,802,883 $ 1,727,253
Transactions in Allowance for Loan Losses	Transactions in the allowance for loan losses for the three months ended March 31, 2018 and year ended December 31, 2017 are summarized as follows: (In Thousands) Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, Installment and Other Total March 31, 2018 Allowance for loan losses: Beginning balance $ 5,156 1,011 9,267 6,094 487 94 723 401 676 23,909 Provision 555 5 111 200 (59 ) 2 45 25 139 1,023 Charge-offs — — — (2 ) — — — — (235 ) (237 ) Recoveries 6 — — 22 — — — 2 121 151 Ending balance $ 5,717 1,016 9,378 6,314 428 96 768 428 701 24,846 Ending balance individually evaluated for impairment $ 946 — 328 — — — — — — 1,274 Ending balance collectively evaluated for impairment $ 4,771 1,016 9,050 6,314 428 96 768 428 701 23,572 Loans: Ending balance $ 412,919 92,322 691,320 429,689 30,065 9,077 65,404 50,797 53,582 1,835,175 Ending balance individually evaluated for impairment $ 4,136 — 2,487 903 310 — — — — 7,836 Ending balance collectively evaluated for impairment $ 408,783 92,322 688,833 428,786 29,755 9,077 65,404 50,797 53,582 1,827,339 Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, Installment and Other Total December 31, 2017 Allowance for loan losses: Beginning balance $ 4,571 839 9,541 5,387 658 112 675 386 562 22,731 Provision 675 172 (414 ) 586 (168 ) (10 ) 45 9 786 1,681 Charge-offs (118 ) — — — (3 ) (11 ) — — (1,090 ) (1,222 ) Recoveries 28 — 140 121 — 3 3 6 418 719 Ending balance $ 5,156 1,011 9,267 6,094 487 94 723 401 676 23,909 Ending balance individually evaluated for impairment $ 136 — 291 — — — — — — 427 Ending balance collectively evaluated for impairment $ 5,020 1,011 8,976 6,094 487 94 723 401 676 23,482 Loans: Ending balance $ 406,667 91,992 661,223 392,039 34,212 8,952 60,650 47,939 54,867 1,758,541 Ending balance individually evaluated for impairment $ 2,678 — 3,046 1,182 — — — — — 6,906 Ending balance collectively evaluated for impairment $ 403,989 91,992 658,177 390,857 34,212 8,952 60,650 47,939 54,867 1,751,635
Company's Impaired Loans	The following table presents the Company’s impaired loans at March 31, 2018 and December 31, 2017 . In Thousands Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized March 31, 2018 With no related allowance recorded: Residential 1-4 family $ 2,284 2,321 — 2,299 35 Multifamily — — — — — Commercial real estate 324 323 — 609 4 Construction 906 903 — 1,046 13 Farmland 310 310 — 155 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 3,824 3,857 — 4,109 52 With allowance recorded: Residential 1-4 family $ 1,870 2,041 946 1,140 14 Multifamily — — — — — Commercial real estate 2,165 2,164 328 2,161 4 Construction — — — — — Farmland — — — — — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 4,035 4,205 1,274 3,301 18 Total Residential 1-4 family $ 4,154 4,362 946 3,439 49 Multifamily — — — — — Commercial real estate 2,489 2,487 328 2,770 8 Construction 906 903 — 1,046 13 Farmland 310 310 — 155 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 7,859 8,062 1,274 7,410 70 In Thousands Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized December 31, 2017 With no related allowance recorded: Residential 1-4 family $ 2,314 2,322 — 742 103 Multifamily — — — — — Commercial real estate 893 889 — 902 39 Construction 1,185 1,182 — 1,354 64 Farmland — — — 26 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 4,392 4,393 — 3,024 206 With allowance recorded: Residential 1-4 family $ 409 581 136 461 29 Multifamily — — — — — Commercial real estate 2,157 2,157 291 2,894 17 Construction — — — — — Farmland — — — — — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 2,566 2,738 427 3,355 46 Total: Residential 1-4 family $ 2,723 2,903 136 1,203 132 Multifamily — — — — — Commercial real estate 3,050 3,046 291 3,796 56 Construction 1,185 1,182 — 1,354 64 Farmland — — — 26 — Second mortgages — — — — — Equity lines of credit — — — — — Commercial — — — — — Agricultural, installment and other — — — — — $ 6,958 7,131 427 6,379 252
Summary of Carrying Balances of TDR's	The following table summarizes the carrying balances of TDRs at March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 (In thousands) Performing TDRs $ 1,710 $ 2,250 Nonperforming TDRs 1,261 1,834 Total TDRS $ 2,971 $ 4,084
Troubled Debt Restructuring Categorized by Loan	The following table outlines the amount of each troubled debt restructuring categorized by loan classification for the three months ended March 31, 2018 and the year ended December 31, 2017 (in thousands, except for number of contracts): March 31, 2018 December 31, 2017 Number of Contracts Pre Modification Outstanding Recorded Investment Post Modification Outstanding Recorded Investment, Net of Related Allowance Number of Contracts Pre Modification Outstanding Recorded Investment Post Modification Outstanding Recorded Investment, Net of Related Allowance Residential 1-4 family — $ — $ — 6 $ 610 $ 535 Multifamily — — — — — — Commercial real estate — — — — — — Construction — — — — — — Farmland 1 310 310 1 86 86 Second mortgages — — — — — — Equity lines of credit — — — — — — Commercial — — — — — — Agricultural, installment and other — — — 1 3 3 Total 1 $ 310 $ 310 8 $ 699 $ 624
Summary of Loan Portfolio by Risk Rating	The following table is a summary of the Bank’s loan portfolio by risk rating at March 31, 2018 and December 31, 2017 : (In Thousands) Residential 1-4 Family Multifamily Commercial Real Estate Construction Farmland Second Mortgages Equity Lines of Credit Commercial Agricultural, installment and other Total March 31, 2018 Credit Risk Profile by Internally Assigned Rating Pass $ 400,952 92,322 688,446 429,208 29,379 8,688 65,257 50,797 53,419 1,818,468 Special Mention 5,273 — 640 80 122 248 — — 78 6,441 Substandard 6,694 — 2,234 401 564 141 147 — 85 10,266 Doubtful — — — — — — — — — — Total $ 412,919 92,322 691,320 429,689 30,065 9,077 65,404 50,797 53,582 1,835,175 December 31, 2017 Credit Risk Profile by Internally Assigned Rating Pass $ 395,664 91,992 657,456 391,778 33,500 8,765 60,553 47,937 54,697 1,742,342 Special Mention 5,677 — 646 84 125 43 41 2 77 6,695 Substandard 5,326 — 3,121 177 587 144 56 — 93 9,504 Doubtful — — — — — — — — — — Total $ 406,667 91,992 661,223 392,039 34,212 8,952 60,650 47,939 54,867 1,758,541

Debt and Equity Securities (Tab

Debt and Equity Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Summary of Debt and Equity Securities	Debt and equity securities have been classified in the consolidated balance sheet according to management’s intent. Debt and equity securities at March 31, 2018 and December 31, 2017 are summarized as follows: March 31, 2018 Securities Available-For-Sale In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value U.S. Government-sponsored enterprises (GSEs)* $ 74,692 $ — $ 3,576 $ 71,116 Mortgage-backed: GSE residential 196,569 341 5,985 190,925 Asset-backed: SBAP 25,261 10 1,149 24,122 Obligations of states and political subdivisions 40,244 — 1,827 38,417 $ 336,766 $ 351 $ 12,537 $ 324,580 March 31, 2018 Securities Held-to-Maturity In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Mortgage-backed: Government-sponsored enterprises (GSEs)* residential $ 9,532 $ 12 $ 374 $ 9,170 Obligations of states and political subdivisions 21,958 42 568 21,432 $ 31,490 $ 54 $ 942 $ 30,602 December 31, 2017 Securities Available-For-Sale In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value U.S. Government-sponsored enterprises (GSEs)* $ 74,690 $ 4 $ 1,714 $ 72,980 Mortgage-backed: GSE residential 200,175 302 2,551 197,926 Asset-backed: SBAP 26,387 — 789 25,598 Obligations of states and political subdivisions 37,197 7 992 36,212 $ 338,449 $ 313 $ 6,046 $ 332,716 December 31, 2017 Securities Held-To-Maturity In Thousands Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Mortgage-backed: Government-sponsored enterprises (GSEs)* residential $ 9,886 $ 31 $ 156 $ 9,761 Obligations of states and political subdivisions 22,594 66 310 22,350 $ 32,480 $ 97 $ 466 $ 32,111 * Such as Federal National Mortgage Association, Federal Home Loan Mortgage Corporation, Federal Home Loan Bank, Federal Farm Credit Bank, and Government National Mortgage Association.
Maturity of Amortized Cost and Estimated Market Value of Debt Securities	The amortized cost and estimated market value of debt securities at March 31, 2018 , by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Held-to-Maturity Available-For-Sale In Thousands Amortized Cost Estimated Market Value Amortized Cost Estimated Market Value Due in one year or less $ 3,698 $ 3,696 $ — $ — Due after one year through five years 6,496 6,501 23,881 23,219 Due after five years through ten years 10,255 9,855 130,640 124,982 Due after ten years 11,041 10,550 182,245 176,379 $ 31,490 $ 30,602 $ 336,766 $ 324,580
Gross Unrealized Losses and Fair Value of Company's Investments	The following table shows the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at March 31, 2018 and December 31, 2017 . In Thousands, Except Number of Securities Less than 12 Months 12 Months or More Total March 31, 2018 Fair Value Unrealized Losses Number of Securities Included Fair Value Unrealized Losses Number of Securities Included Fair Value Unrealized Losses Held-to-Maturity Securities: Mortgage-backed: Government-sponsored enterprises (GSEs) residential $ 4,179 $ 126 6 $ 4,769 $ 248 5 $ 8,948 $ 374 Obligations of states and political subdivisions 9,277 61 26 7,028 507 18 16,305 568 $ 13,456 $ 187 32 $ 11,797 $ 755 23 $ 25,253 $ 942 Available-for-Sale Securities: GSEs $ 16,821 $ 619 9 $ 54,295 $ 2,957 21 $ 71,116 $ 3,576 Mortgage-backed: GSE residential 92,250 2,648 43 76,041 3,337 55 168,291 5,985 Asset-backed: SBAP 7,246 276 6 15,773 873 8 23,019 1,149 Obligations of states and political subdivisions 17,279 380 28 21,138 1,447 56 38,417 1,827 $ 133,596 $ 3,923 86 $ 167,247 $ 8,614 140 $ 300,843 $ 12,537 In Thousands, Except Number of Securities Less than 12 Months 12 Months or More Total Fair Unrealized Number of Securities Fair Unrealized Number of Securities Fair Unrealized December 31, 2017 Value Losses Included Value Losses Included Value Losses Held-to-Maturity Securities: Mortgage-backed: Government-sponsored enterprises (GSEs) residential $ 3,316 $ 21 4 $ 5,206 $ 135 5 $ 8,522 $ 156 Obligations of states and political subdivisions 10,137 46 27 7,278 264 18 17,415 310 $ 13,453 $ 67 31 $ 12,484 $ 399 23 $ 25,937 $ 466 Available-for-Sale Securities: GSEs $ 16,099 $ 190 8 $ 55,726 $ 1,524 21 $ 71,825 $ 1,714 Mortgage-backed: GSE residential 92,180 769 43 81,434 1,782 54 173,614 2,551 Asset-backed: SBAP 9,087 181 7 16,510 608 8 25,597 789 Obligations of states and political subdivisions 12,128 113 22 21,762 879 56 33,890 992 $ 129,494 $ 1,253 80 $ 175,432 $ 4,793 139 $ 304,926 $ 6,046

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Summary of Components Comprising Basic and Diluted Earnings Per Share	The following is a summary of components comprising basic and diluted earnings per share (“EPS”) for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (Dollars in Thousands Except Share and Per Share Amounts) Basic EPS Computation: Numerator – Earnings available to common stockholders $ 7,480 $ 6,495 Denominator – Weighted average number of common shares outstanding 10,507,273 10,360,776 Basic earnings per common share $ 0.71 $ 0.63 Diluted EPS Computation: Numerator – Earnings available to common stockholders $ 7,480 $ 6,495 Denominator – Weighted average number of common shares outstanding 10,507,273 10,360,776 Dilutive effect of stock options 5,803 4,941 Weighted average diluted common shares outstanding 10,513,076 10,365,717 Diluted earnings per common share $ 0.71 $ 0.63

Commitments and Contingent Li21

Commitments and Contingent Liabilities (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Total Contractual Amount for All Off-Balance Sheet Commitments	A summary of the Company’s total contractual amount for all off-balance sheet commitments at March 31, 2018 is as follows: Commitments to extend credit $ 602,140,000 Standby letters of credit $ 70,530,000

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present the financial instruments carried at fair value as of March 31, 2018 and December 31, 2017 , by caption on the consolidated balance sheet and by FASB ASC 820 valuation hierarchy (as described above) (in thousands): Assets and Liabilities Measured at Fair Value on a Recurring Basis (In Thousands) Total Carrying Value in the Consolidated Balance Sheet Quoted Market Prices in an Active Market (Level 1) Models with Significant Observable Market Parameters (Level 2) Models with Significant Unobservable Market Parameters (Level 3) March 31, 2018 Investment securities available-for-sale: U.S. Government sponsored enterprises $ 71,116 — 71,116 — Mortgage-backed securities 190,925 — 190,925 — Asset-backed securities 24,122 — 24,122 — State and municipal securities 38,417 803 37,614 — Total investment securities available-for-sale 324,580 803 323,777 — Loans held for sale 5,750 — 5,750 — Other assets 29,689 — — 29,689 Total assets at fair value $ 360,019 803 329,527 29,689 December 31, 2017 Investment securities available-for-sale: U.S. Government sponsored enterprises $ 72,980 — 72,980 — Mortgage-backed securities 197,926 — 197,926 — Asset-backed securities 25,598 — 25,598 — State and municipal securities 36,212 — 36,212 — Total investment securities available-for-sale 332,716 — 332,716 — Loans held for sale 5,106 — 5,106 — Other assets 29,475 — — 29,475 Total assets at fair value $ 367,297 — 337,822 29,475
Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis	Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (In Thousands) Total Carrying Value in the Consolidated Balance Sheet Quoted Market Prices in an Active Market (Level 1) Models with Significant Observable Market Parameters (Level 2) Models with Significant Unobservable Market Parameters (Level 3) March 31, 2018 Other real estate owned $ 1,620 — — 1,620 Impaired loans, net (¹) 6,585 — — 6,585 Total $ 8,205 — — 8,205 December 31, 2017 Other real estate owned $ 1,635 — — 1,635 Impaired loans, net (¹) 6,531 — — 6,531 Total $ 8,166 — — 8,166 (1) Amount is net of a valuation allowance of $1,274,000 at March 31, 2018 and $427,000 at December 31, 2017 as required by ASC 310, “Receivables.”
Additional Quantitative Information	The following table presents additional quantitative information about assets measured at fair value on a nonrecurring basis and for which we have utilized Level 3 inputs to determine fair value at March 31, 2018 and December 31, 2017 : Valuation Techniques (¹) Significant Unobservable Inputs Range (Weighted Average) Impaired loans Appraisal Estimated costs to sell 10% Other real estate owned Appraisal Estimated costs to sell 10%
Changes in Fair Value Due to Observable Factors	The table below includes a rollforward of the balance sheet amounts for the three months ended March 31, 2018 and 2017 (including the change in fair value) for financial instruments classified by the Company within Level 3 of the valuation hierarchy for assets and liabilities measured at fair value on a recurring basis. When a determination is made to classify a financial instrument within Level 3 of the valuation hierarchy, the determination is based upon the significance of the unobservable factors to the overall fair value measurement. However, since Level 3 financial instruments typically include, in addition to the unobservable or Level 3 components, observable components (that is, components that are actively quoted and can be validated to external sources), the gains and losses in the table below include changes in fair value due in part to observable factors that are part of the valuation methodology (in thousands): For the Three Months Ended March 31, 2018 2017 Other Assets Other Liabilities Other Assets Other Liabilities Fair value, January 1 $ 29,475 — $ 28,616 — Total realized gains included in income 214 — 222 — Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at March 31 — — — — Purchases, issuances and settlements, net — — — — Transfers out of Level 3 — — — — Fair value, March 31 $ 29,689 — $ 28,838 — Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet at March 31 $ 214 — $ 222 —
Carrying Value and Estimated Fair Value of Financial Instruments	The following table presents the carrying amounts, estimated fair value and placement in the fair valuation hierarchy of the Company’s financial instruments at March 31, 2018 and December 31, 2017 . This table excludes financial instruments for which the carrying amount approximates fair value. For short-term financial assets such as cash and cash equivalents, the carrying amount is a reasonable estimate of fair value due to the relatively short time between the origination of the instrument and its expected realization. Carrying/ Notional Estimated Quoted Market Prices in an Active Market Models with Significant Observable Market Parameters Models with Significant Unobservable Market Parameters (in Thousands) Amount Fair Value (¹) (Level 1) (Level 2) (Level 3) March 31, 2018 Financial assets: Securities held-to-maturity $ 31,490 30,602 — 30,602 — Loans, net 1,802,883 1,793,105 — — 1,793,105 Financial liabilities: Deposits and securities sold under agreements to repurchase 2,115,234 1,847,706 — — 1,847,706 Off-balance sheet instruments: Commitments to extend credit — — — — — Standby letters of credit — — — — — December 31, 2017 Financial assets: Securities held-to-maturity $ 32,480 32,111 — 32,111 — Loans, net 1,727,253 1,724,937 — — 1,724,937 Financial liabilities: Deposits and securities sold under agreements to repurchase 2,038,609 1,812,011 — — 1,812,011 Off-balance sheet instruments: Commitments to extend credit — — — — — Standby letters of credit — — — — — (1) Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.

Stock Option Plan, Equity Inc23

Stock Option Plan, Equity Incentive Plan & Charter Amendment (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity	The following tables summarize information about stock options and cash-settled SARs for the three months ended March 31, 2018 and 2017: March 31, 2018 March 31, 2017 Shares Weighted Shares Weighted Options and SARs outstanding at beginning of period 285,780 $ 39.31 $ 183,847 $ 38.08 Granted 2,500 44.75 105,833 40.78 Exercised 7,234 35.30 3,286 28.03 Forfeited or expired 1,500 36.60 322 24.13 Outstanding at end of period 279,546 $ 39.48 $ 286,072 $ 39.21 Options and SARs exercisable at March 31 59,378 $ 37.77 $ 15,382 $ 29.59

Summary of Significant Accoun24

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Minimum past due of loans for nonaccrual status	90 days
Loans with identified weakness and principal balance	$ 500,000
Assignment of valuation allowance for specified amount of loan (less than)	500,000
Retained earnings	$ (188,839,000)	$ (185,017,000)
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		697,000
Accumulated other comprehensive income		$ 697,000

Loans and Allowance for Loan 25

Loans and Allowance for Loan Losses - Schedule of Details on Loans of Company (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 1,835,175	$ 1,758,541
Net deferred loan fees	(7,446)	(7,379)
Total loans	1,827,729	1,751,162
Less: Allowance for loan losses	(24,846)	(23,909)	$ (22,731)
Net loans	1,802,883	1,727,253
Agricultural [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,833	1,665
Residential 1-4 Family [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	412,919	406,667
Multifamily [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	92,322	91,992
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	691,320	661,223
Farmland [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	30,065	34,212
Construction and land development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	429,689	392,039
Second mortgages [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	9,077	8,952
Less: Allowance for loan losses	(96)	(94)	$ (112)
Equity lines of credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	65,404	60,650
Mortgage loans on real estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,730,796	1,655,735
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	50,797	47,939
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	42,017	43,009
Consumer [Member] | Personal [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	38,554	39,624
Consumer [Member] | Credit Cards [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	3,463	3,385
Other [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 9,732	$ 10,193

Loans and Allowance for Loan 26

Loans and Allowance for Loan Losses - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)loan
Financing Receivable, Recorded Investment [Line Items]
Threshold percentage of repayment derived from non-affiliated third party (as a percent)	50.00%
Impaired loans, net	$ 2,100	$ 1,700
Troubled debt restructuring number of loans | loan	2	1
Troubled debt restructuring amount	$ 413	$ 103
Consumer mortgage loans	$ 341	201
Residential 1-4 Family [Member] | Mortgage loans on real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortization period, lower range	15 years
Amortization period, upper range	30 years
Maturity period, lower range	5 years
Maturity period, upper range	15 years
Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Potential problem loans	$ 16,700	$ 16,200

Loans and Allowance for Loan 27

Loans and Allowance for Loan Losses - Transactions in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Allowance for loan losses:
Beginning balance	$ 23,909	$ 22,731
Provision	1,023	1,681
Charge-offs	(237)	(1,222)
Recoveries	151	719
Ending balance	24,846	23,909
Ending balance individually evaluated for impairment	1,274	427
Ending balance collectively evaluated for impairment	23,572	23,482
Loans:
Ending balance	1,835,175	1,758,541
Ending balance individually evaluated for impairment	7,836	6,906
Ending balance collectively evaluated for impairment	1,827,339	1,751,635
Residential 1-4 Family [Member]
Allowance for loan losses:
Beginning balance	5,156	4,571
Provision	555	675
Charge-offs	0	(118)
Recoveries	6	28
Ending balance	5,717	5,156
Ending balance individually evaluated for impairment	946	136
Ending balance collectively evaluated for impairment	4,771	5,020
Loans:
Ending balance	412,919	406,667
Ending balance individually evaluated for impairment	4,136	2,678
Ending balance collectively evaluated for impairment	408,783	403,989
Multifamily [Member]
Allowance for loan losses:
Beginning balance	1,011	839
Provision	5	172
Charge-offs	0	0
Recoveries	0	0
Ending balance	1,016	1,011
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	1,016	1,011
Loans:
Ending balance	92,322	91,992
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	92,322	91,992
Commercial Real Estate [Member]
Allowance for loan losses:
Beginning balance	9,267	9,541
Provision	111	(414)
Charge-offs	0	0
Recoveries	0	140
Ending balance	9,378	9,267
Ending balance individually evaluated for impairment	328	291
Ending balance collectively evaluated for impairment	9,050	8,976
Loans:
Ending balance	691,320	661,223
Ending balance individually evaluated for impairment	2,487	3,046
Ending balance collectively evaluated for impairment	688,833	658,177
Construction [Member]
Allowance for loan losses:
Beginning balance	6,094	5,387
Provision	200	586
Charge-offs	(2)	0
Recoveries	22	121
Ending balance	6,314	6,094
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	6,314	6,094
Loans:
Ending balance	429,689	392,039
Ending balance individually evaluated for impairment	903	1,182
Ending balance collectively evaluated for impairment	428,786	390,857
Farmland [Member]
Allowance for loan losses:
Beginning balance	487	658
Provision	(59)	(168)
Charge-offs	0	(3)
Recoveries	0	0
Ending balance	428	487
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	428	487
Loans:
Ending balance	30,065	34,212
Ending balance individually evaluated for impairment	310	0
Ending balance collectively evaluated for impairment	29,755	34,212
Second mortgages [Member]
Allowance for loan losses:
Beginning balance	94	112
Provision	2	(10)
Charge-offs	0	(11)
Recoveries	0	3
Ending balance	96	94
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	96	94
Loans:
Ending balance	9,077	8,952
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	9,077	8,952
Equity Lines of Credit [Member]
Allowance for loan losses:
Beginning balance	723	675
Provision	45	45
Charge-offs	0	0
Recoveries	0	3
Ending balance	768	723
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	768	723
Loans:
Ending balance	65,404	60,650
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	65,404	60,650
Commercial [Member]
Allowance for loan losses:
Beginning balance	401	386
Provision	25	9
Charge-offs	0	0
Recoveries	2	6
Ending balance	428	401
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	428	401
Loans:
Ending balance	50,797	47,939
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	50,797	47,939
Agricultural, Installment and Other [Member]
Allowance for loan losses:
Beginning balance	676	562
Provision	139	786
Charge-offs	(235)	(1,090)
Recoveries	121	418
Ending balance	701	676
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	701	676
Loans:
Ending balance	53,582	54,867
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	$ 53,582	$ 54,867

Loans and Allowance for Loan 28

Loans and Allowance for Loan Losses - Company's Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 7,859	$ 6,958
Unpaid Principal Balance	8,062	7,131
Related Allowance	1,274	427
Average Recorded Investment	7,410	6,379
Interest Income Recognized	70	252
With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,824	4,392
Unpaid Principal Balance	3,857	4,393
Average Recorded Investment	4,109	3,024
Interest Income Recognized	52	206
With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,035	2,566
Unpaid Principal Balance	4,205	2,738
Related Allowance	1,274	427
Average Recorded Investment	3,301	3,355
Interest Income Recognized	18	46
Residential 1-4 Family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,154	2,723
Unpaid Principal Balance	4,362	2,903
Related Allowance	946	136
Average Recorded Investment	3,439	1,203
Interest Income Recognized	49	132
Residential 1-4 Family [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,284	2,314
Unpaid Principal Balance	2,321	2,322
Average Recorded Investment	2,299	742
Interest Income Recognized	35	103
Residential 1-4 Family [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,870	409
Unpaid Principal Balance	2,041	581
Related Allowance	946	136
Average Recorded Investment	1,140	461
Interest Income Recognized	14	29
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Multifamily [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Multifamily [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,489	3,050
Unpaid Principal Balance	2,487	3,046
Related Allowance	328	291
Average Recorded Investment	2,770	3,796
Interest Income Recognized	8	56
Commercial Real Estate [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	324	893
Unpaid Principal Balance	323	889
Average Recorded Investment	609	902
Interest Income Recognized	4	39
Commercial Real Estate [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,165	2,157
Unpaid Principal Balance	2,164	2,157
Related Allowance	328	291
Average Recorded Investment	2,161	2,894
Interest Income Recognized	4	17
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	906	1,185
Unpaid Principal Balance	903	1,182
Related Allowance	0	0
Average Recorded Investment	1,046	1,354
Interest Income Recognized	13	64
Construction [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	906	1,185
Unpaid Principal Balance	903	1,182
Average Recorded Investment	1,046	1,354
Interest Income Recognized	13	64
Construction [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Farmland [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	310	0
Unpaid Principal Balance	310	0
Related Allowance	0	0
Average Recorded Investment	155	26
Interest Income Recognized	0	0
Farmland [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	310	0
Unpaid Principal Balance	310	0
Average Recorded Investment	155	26
Interest Income Recognized	0	0
Farmland [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Second mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Second mortgages [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Second mortgages [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Equity Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Equity Lines of Credit [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Equity Lines of Credit [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Agricultural, Installment and Other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Agricultural, Installment and Other [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Agricultural, Installment and Other [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	$ 0	$ 0

Loans and Allowance for Loan 29

Loans and Allowance for Loan Losses - Summary of Carrying Balances of TDR's (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total TDRS	$ 2,971	$ 4,084
Performing [Member]
Financing Receivable, Modifications [Line Items]
Total TDRS	1,710	2,250
Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Total TDRS	$ 1,261	$ 1,834

Loans and Allowance for Loan 30

Loans and Allowance for Loan Losses - Troubled Debt Restructuring Categorized by Loan (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)contract	Dec. 31, 2017USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	1	8
Pre Modification Outstanding Recorded Investment	$ 310	$ 699
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 310	$ 624
Residential 1-4 Family [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	6
Pre Modification Outstanding Recorded Investment	$ 0	$ 610
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 535
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	1	1
Pre Modification Outstanding Recorded Investment	$ 310	$ 86
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 310	$ 86
Second mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Equity Lines of Credit [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre Modification Outstanding Recorded Investment	$ 0	$ 0
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 0
Agricultural, Installment and Other [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	1
Pre Modification Outstanding Recorded Investment	$ 0	$ 3
Post Modification Outstanding Recorded Investment, Net of Related Allowance	$ 0	$ 3

Loans and Allowance for Loan 31

Loans and Allowance for Loan Losses - Summary of Loan Portfolio by Risk Rating (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Credit Risk Profile by Internally Assigned Rating
Total Loans	$ 1,835,175	$ 1,758,541
Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	1,818,468	1,742,342
Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	6,441	6,695
Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	10,266	9,504
Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Residential 1-4 Family [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	412,919	406,667
Residential 1-4 Family [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	400,952	395,664
Residential 1-4 Family [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	5,273	5,677
Residential 1-4 Family [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	6,694	5,326
Residential 1-4 Family [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Multifamily [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	92,322	91,992
Multifamily [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	92,322	91,992
Multifamily [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Multifamily [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Multifamily [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Commercial Real Estate [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	691,320	661,223
Commercial Real Estate [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	688,446	657,456
Commercial Real Estate [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	640	646
Commercial Real Estate [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	2,234	3,121
Commercial Real Estate [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Construction [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	429,689	392,039
Construction [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	429,208	391,778
Construction [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	80	84
Construction [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	401	177
Construction [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Farmland [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	30,065	34,212
Farmland [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	29,379	33,500
Farmland [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	122	125
Farmland [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	564	587
Farmland [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Second mortgages [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	9,077	8,952
Second mortgages [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	8,688	8,765
Second mortgages [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	248	43
Second mortgages [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	141	144
Second mortgages [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Equity Lines of Credit [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	65,404	60,650
Equity Lines of Credit [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	65,257	60,553
Equity Lines of Credit [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	41
Equity Lines of Credit [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	147	56
Equity Lines of Credit [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Commercial [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	50,797	47,939
Commercial [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	50,797	47,937
Commercial [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	2
Commercial [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Commercial [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	0	0
Agricultural, Installment and Other [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	53,582	54,867
Agricultural, Installment and Other [Member] | Pass [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	53,419	54,697
Agricultural, Installment and Other [Member] | Special Mention [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	78	77
Agricultural, Installment and Other [Member] | Substandard [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	85	93
Agricultural, Installment and Other [Member] | Doubtful [Member]
Credit Risk Profile by Internally Assigned Rating
Total Loans	$ 0	$ 0

Debt and Equity Securities - Su

Debt and Equity Securities - Summary of Debt and Equity Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	$ 336,766	$ 338,449
Available-for-sale, Gross Unrealized Gains	351	313
Available-for-sale, Gross Unrealized Losses	12,537	6,046
Total investment securities available-for-sale	324,580	332,716
Held-to-maturity securities, Amortized Cost	31,490	32,480
Held-to-maturity securities, Gross Unrealized Gains	54	97
Held-to-maturity securities, Gross Unrealized Losses	942	466
Held-to-maturity securities, Estimated Market Value	30,602	32,111
US Government-Sponsored Enterprises (GSEs) [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	74,692	74,690
Available-for-sale, Gross Unrealized Gains	0	4
Available-for-sale, Gross Unrealized Losses	3,576	1,714
Total investment securities available-for-sale	71,116	72,980
Government- Sponsored Enterprises (GSEs) Residential Mortgage Backed [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	196,569	200,175
Available-for-sale, Gross Unrealized Gains	341	302
Available-for-sale, Gross Unrealized Losses	5,985	2,551
Total investment securities available-for-sale	190,925	197,926
Held-to-maturity securities, Amortized Cost	9,532	9,886
Held-to-maturity securities, Gross Unrealized Gains	12	31
Held-to-maturity securities, Gross Unrealized Losses	374	156
Held-to-maturity securities, Estimated Market Value	9,170	9,761
SBAP [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	25,261	26,387
Available-for-sale, Gross Unrealized Gains	10	0
Available-for-sale, Gross Unrealized Losses	1,149	789
Total investment securities available-for-sale	24,122	25,598
Obligations of States and Political Subdivisions [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	40,244	37,197
Available-for-sale, Gross Unrealized Gains	0	7
Available-for-sale, Gross Unrealized Losses	1,827	992
Total investment securities available-for-sale	38,417	36,212
Held-to-maturity securities, Amortized Cost	21,958	22,594
Held-to-maturity securities, Gross Unrealized Gains	42	66
Held-to-maturity securities, Gross Unrealized Losses	568	310
Held-to-maturity securities, Estimated Market Value	$ 21,432	$ 22,350

Debt and Equity Securities - Ma

Debt and Equity Securities - Maturity of Amortized Cost and Estimated Market Value of Debt Securities (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, Due in one year or less, Amortized Cost	$ 3,698
Held-to-maturity, Due after one year through five years, Amortized Cost	6,496
Held-to-maturity, Due after five years through ten years, Amortized Cost	10,255
Held-to-maturity, Due after ten years, Amortized Cost	11,041
Held-to-maturity, Gross Amortized Cost	31,490
Held-to-maturity, Due in one year or less, Estimated Market Value	3,696
Held-to-maturity, Due after one year through five years, Estimated Market Value	6,501
Held-to-maturity, Due after five years through ten years, Estimated Market Value	9,855
Held-to-maturity, Due after ten years, Estimated Market Value	10,550
Held-to-maturity, Gross Estimated Market Value	30,602
Available-for-sale securities, Due in one year or less, Amortized Cost	0
Available-for-sale securities, Due after one year through five years, Amortized Cost	23,881
Available-for-sale securities, Due after five years through ten years, Amortized Cost	130,640
Available-for-sale securities, Due after ten years, Amortized Cost	182,245
Available-for-sale securities, Gross Amortized Cost	336,766
Available-for-sale securities, Due in one year or less, Estimated Market Value	0
Available-for-sale securities, Due after one year through five years, Estimated Market Value	23,219
Available-for-sale securities, Due after five years through ten years, Estimated Market Value	124,982
Available-for-sale securities, Due after ten years, Estimated Market Value	176,379
Available-for-sale securities, Gross Estimated Market Value	$ 324,580

Debt and Equity Securities - Gr

Debt and Equity Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Detail) $ in Thousands	Mar. 31, 2018USD ($)security	Dec. 31, 2017USD ($)security
Held To Maturity Debt Securities [Line Items]
Held to Maturity Securities, Fair Value, Less than 12 Month	$ 13,456	$ 13,453
Held to Maturity Securities, Unrealized losses, Less than 12 Month	$ 187	$ 67
Held to Maturity Securities, Number of securities included, Less than 12 Month | security	32	31
Held to Maturity Securities, Fair Value, 12 Month or More	$ 11,797	$ 12,484
Held to Maturity Securities, Unrealized losses, 12 Month or More	$ 755	$ 399
Held to Maturity Securities, Number of securities included, 12 Month or More | security	23	23
Held to Maturity Securities, Total Fair Value	$ 25,253	$ 25,937
Held to Maturity Securities, Total Unrealized Losses	942	466
Available-for-Sale Securities, Fair Value, Less than 12 Month	133,596	129,494
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month	$ 3,923	$ 1,253
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | security	86	80
Available-for-Sale Securities, Fair Value, 12 Month or More	$ 167,247	$ 175,432
Available-for-Sale Securities, Unrealized Loss, 12 Month or More	$ 8,614	$ 4,793
Available-for-Sale Securities, Number of securities included, 12 Month or More | security	140	139
Available-for-Sale Securities, Total Fair Value	$ 300,843	$ 304,926
Available-for-Sale Securities, Total Unrealized Losses	12,537	6,046
US Government-Sponsored Enterprises (GSEs) [Member]
Held To Maturity Debt Securities [Line Items]
Available-for-Sale Securities, Fair Value, Less than 12 Month	16,821	16,099
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month	$ 619	$ 190
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | security	9	8
Available-for-Sale Securities, Fair Value, 12 Month or More	$ 54,295	$ 55,726
Available-for-Sale Securities, Unrealized Loss, 12 Month or More	$ 2,957	$ 1,524
Available-for-Sale Securities, Number of securities included, 12 Month or More | security	21	21
Available-for-Sale Securities, Total Fair Value	$ 71,116	$ 71,825
Available-for-Sale Securities, Total Unrealized Losses	3,576	1,714
Government- Sponsored Enterprises (GSEs) Residential Mortgage Backed [Member]
Held To Maturity Debt Securities [Line Items]
Held to Maturity Securities, Fair Value, Less than 12 Month	4,179	3,316
Held to Maturity Securities, Unrealized losses, Less than 12 Month	$ 126	$ 21
Held to Maturity Securities, Number of securities included, Less than 12 Month | security	6	4
Held to Maturity Securities, Fair Value, 12 Month or More	$ 4,769	$ 5,206
Held to Maturity Securities, Unrealized losses, 12 Month or More	$ 248	$ 135
Held to Maturity Securities, Number of securities included, 12 Month or More | security	5	5
Held to Maturity Securities, Total Fair Value	$ 8,948	$ 8,522
Held to Maturity Securities, Total Unrealized Losses	374	156
Available-for-Sale Securities, Fair Value, Less than 12 Month	92,250	92,180
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month	$ 2,648	$ 769
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | security	43	43
Available-for-Sale Securities, Fair Value, 12 Month or More	$ 76,041	$ 81,434
Available-for-Sale Securities, Unrealized Loss, 12 Month or More	$ 3,337	$ 1,782
Available-for-Sale Securities, Number of securities included, 12 Month or More | security	55	54
Available-for-Sale Securities, Total Fair Value	$ 168,291	$ 173,614
Available-for-Sale Securities, Total Unrealized Losses	5,985	2,551
SBAP [Member]
Held To Maturity Debt Securities [Line Items]
Available-for-Sale Securities, Fair Value, Less than 12 Month	7,246	9,087
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month	$ 276	$ 181
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | security	6	7
Available-for-Sale Securities, Fair Value, 12 Month or More	$ 15,773	$ 16,510
Available-for-Sale Securities, Unrealized Loss, 12 Month or More	$ 873	$ 608
Available-for-Sale Securities, Number of securities included, 12 Month or More | security	8	8
Available-for-Sale Securities, Total Fair Value	$ 23,019	$ 25,597
Available-for-Sale Securities, Total Unrealized Losses	1,149	789
Obligations of States and Political Subdivisions [Member]
Held To Maturity Debt Securities [Line Items]
Held to Maturity Securities, Fair Value, Less than 12 Month	9,277	10,137
Held to Maturity Securities, Unrealized losses, Less than 12 Month	$ 61	$ 46
Held to Maturity Securities, Number of securities included, Less than 12 Month | security	26	27
Held to Maturity Securities, Fair Value, 12 Month or More	$ 7,028	$ 7,278
Held to Maturity Securities, Unrealized losses, 12 Month or More	$ 507	$ 264
Held to Maturity Securities, Number of securities included, 12 Month or More | security	18	18
Held to Maturity Securities, Total Fair Value	$ 16,305	$ 17,415
Held to Maturity Securities, Total Unrealized Losses	568	310
Available-for-Sale Securities, Fair Value, Less than 12 Month	17,279	12,128
Available-for-Sale Securities, Unrealized Losses, Less than 12 Month	$ 380	$ 113
Available-for-Sale Securities, Number of Securities Included, Less than 12 Month | security	28	22
Available-for-Sale Securities, Fair Value, 12 Month or More	$ 21,138	$ 21,762
Available-for-Sale Securities, Unrealized Loss, 12 Month or More	$ 1,447	$ 879
Available-for-Sale Securities, Number of securities included, 12 Month or More | security	56	56
Available-for-Sale Securities, Total Fair Value	$ 38,417	$ 33,890
Available-for-Sale Securities, Total Unrealized Losses	$ 1,827	$ 992

Earnings Per Share - Summary of

Earnings Per Share - Summary of Components Comprising Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic EPS Computation:
Numerator – Earnings available to common stockholders	$ 7,480	$ 6,495
Denominator – Weighted average number of common shares outstanding	10,507,273	10,360,776
Basic earnings per common share (in dollars per share)	$ 0.71	$ 0.63
Diluted EPS Computation:
Numerator – Earnings available to common stockholders	$ 7,480	$ 6,495
Denominator – Weighted average number of common shares outstanding	10,507,273	10,360,776
Dilutive effect of stock options (in shares)	5,803	4,941
Weighted average number of shares outstanding-diluted	10,513,076	10,365,717
Diluted earnings per common share (in dollars per share)	$ 0.71	$ 0.63

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	Mar. 31, 2018USD ($)
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 0

Commitments and Contingent Li37

Commitments and Contingent Liabilities - Additional information (Detail)	3 Months Ended
	Mar. 31, 2018
Standby Letters of Credit [Member]
Commitment And Contingencies [Line Items]
Standby letters of credit term, or less	2 years

Commitments and Contingent Li38

Commitments and Contingent Liabilities - Total Contractual Amount for All Off-Balance Sheet Commitments (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Contractual amount for off-balance sheet commitments	$ 70,530
Commitments to Extend Credit [Member]
Loss Contingencies [Line Items]
Contractual amount for off-balance sheet commitments	$ 602,140

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	$ 324,580	$ 332,716
US Government-Sponsored Enterprises (GSEs) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	71,116	72,980
State and Municipal Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	38,417	36,212
Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	324,580	332,716
Loans held for sale	5,750	5,106
Other assets	29,689	29,475
Total assets at fair value	360,019	367,297
Fair Value Measurements Recurring [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	803	0
Loans held for sale	0	0
Other assets	0	0
Total assets at fair value	803	0
Fair Value Measurements Recurring [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	323,777	332,716
Loans held for sale	5,750	5,106
Other assets	0	0
Total assets at fair value	329,527	337,822
Fair Value Measurements Recurring [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Loans held for sale	0	0
Other assets	29,689	29,475
Total assets at fair value	29,689	29,475
Fair Value Measurements Recurring [Member] | US Government-Sponsored Enterprises (GSEs) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	71,116	72,980
Fair Value Measurements Recurring [Member] | US Government-Sponsored Enterprises (GSEs) [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | US Government-Sponsored Enterprises (GSEs) [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	71,116	72,980
Fair Value Measurements Recurring [Member] | US Government-Sponsored Enterprises (GSEs) [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | Mortgage Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	190,925	197,926
Fair Value Measurements Recurring [Member] | Mortgage Backed Securities [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | Mortgage Backed Securities [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	190,925	197,926
Fair Value Measurements Recurring [Member] | Mortgage Backed Securities [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | Asset-backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	24,122	25,598
Fair Value Measurements Recurring [Member] | Asset-backed Securities [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | Asset-backed Securities [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	24,122	25,598
Fair Value Measurements Recurring [Member] | Asset-backed Securities [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	0	0
Fair Value Measurements Recurring [Member] | State and Municipal Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	38,417	36,212
Fair Value Measurements Recurring [Member] | State and Municipal Securities [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	803	0
Fair Value Measurements Recurring [Member] | State and Municipal Securities [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	37,614	36,212
Fair Value Measurements Recurring [Member] | State and Municipal Securities [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Total investment securities available-for-sale	$ 0	$ 0

Fair Value Measurements - Ass40

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	$ 1,620	$ 1,635
Fair Value, Measurements, Nonrecurring [Member] | Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans, net	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring [Member] | Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans, net	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring [Member] | Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	1,620	1,635
Impaired loans, net	6,585	6,531
Total	8,205	8,166
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	1,620	1,635
Impaired loans, net	6,585	6,531
Total	$ 8,205	$ 8,166

Fair Value Measurements - Ass41

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis Narrative (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Valuation allowance	$ 1,274	$ 427
Reported Value Measurement [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Valuation allowance	$ 1,274	$ 427

Fair Value Measurements - Addit

Fair Value Measurements - Additional Quantitative Information (Details) - Appraisal - Fair Value, Measurements, Nonrecurring [Member] - Models with Significant Unobservable Market Parameters (Level 3) [Member]	3 Months Ended
	Mar. 31, 2018
Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assumptions, weighted average rate	10.00%
Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assumptions, weighted average rate	10.00%

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Fair Value Due to Observable Factors (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, Other Assets	$ 29,475	$ 28,616
Total realized gains included in income, Other Assets	214	222
Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held, Other Assets	0	0
Purchases, issuances and settlements, net, Other Assets	0	0
Transfers out of Level 3, Other Assets	0	0
Fair value, Other Assets	29,689	28,838
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet	214	222
Other Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, Other Liabilities	0	0
Total realized gains included in income, Other Liabilities	0	0
Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held, Other Liabilities	0	0
Purchases, issuances and settlements, net, Other Liabilities	0	0
Transfers out of Level 3, Other Liabilities	0	0
Fair value, Other Liabilities	0	0
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet	$ 0	$ 0

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held-to-maturity, Carrying/Notional Amount	$ 31,490	$ 32,480
Loans, net, Carrying/Notional Amount	1,802,883	1,727,253
Deposits and securities sold under agreements to repurchase, Carrying/Notional Amount	2,115,234	2,038,609
Commitments to extend credit, Carrying/Notional Amount	0	0
Standby letters of credit, Carrying/Notional Amount	0	0
Securities held-to-maturity, Estimated Fair Value	30,602	32,111
Loans, net, Estimated Fair Value	1,793,105	1,724,937
Deposits and securities sold under agreements to repurchase, Estimated Fair Value	1,847,706	1,812,011
Commitments to extend credit, Estimated Fair Value	0	0
Standby letters of credit, Estimated Fair Value	0	0
Quoted Market Prices in an Active Market (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held-to-maturity, Estimated Fair Value	0	0
Loans, net, Estimated Fair Value	0	0
Deposits and securities sold under agreements to repurchase, Estimated Fair Value	0	0
Commitments to extend credit, Estimated Fair Value	0	0
Standby letters of credit, Estimated Fair Value	0	0
Models with Significant Observable Market Parameters (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held-to-maturity, Estimated Fair Value	30,602	32,111
Loans, net, Estimated Fair Value	0	0
Deposits and securities sold under agreements to repurchase, Estimated Fair Value	0	0
Commitments to extend credit, Estimated Fair Value	0	0
Standby letters of credit, Estimated Fair Value	0	0
Models with Significant Unobservable Market Parameters (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held-to-maturity, Estimated Fair Value	0	0
Loans, net, Estimated Fair Value	1,793,105	1,724,937
Deposits and securities sold under agreements to repurchase, Estimated Fair Value	1,847,706	1,812,011
Commitments to extend credit, Estimated Fair Value	0	0
Standby letters of credit, Estimated Fair Value	$ 0	$ 0

Stock Option Plan, Equity Inc45

Stock Option Plan, Equity Incentive Plan & Charter Amendment - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Apr. 30, 1999	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2016	Apr. 30, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized, as a percentage of shares issued and outstanding	5.00%
Stock option expiration period			10 years
Purchase price, as a percentage of the fair market value of common stock on grant date (equal to or greater than)			100.00%
Nonvested awards, unrecognized compensation cost		$ 2,458,000
Nonvested awards, unrecognized compensation cost recognition period		3 years 8 months 22 days
1999 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for issuance (in shares)	200,000
2009 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for issuance (in shares)					100,000
Options available for grant (in shares)			51,222
2016 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for issuance (in shares)				750,000
Options [Member] | 2016 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for grant (in shares)		500,170
Grants in period (in shares)		152,981
Weighted average price of grants in period (in dollars per share)		$ 38.62
Stock Appreciation Rights (SARs) [Member] | 2016 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average price of grants in period (in dollars per share)		$ 40.53
Stock appreciation rights granted in period (in shares)		126,565

Stock Option Plan, Equity Inc46

Stock Option Plan, Equity Incentive Plan & Charter Amendment - Summary of Stock Option Activity (Details) - Employee Stock Options and Stock Appreciation Rights (SARs) [Member] - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Shares
Options and SARs outstanding at beginning of year (in shares)	285,780	183,847
Granted (in shares)	2,500	105,833
Exercised (in shares)	7,234	3,286
Forfeited or expired (in shares)	1,500	322
Options and SARs outstanding at end of year (in shares)	279,546	286,072
Options and SARs exercisable at year end (in shares)	59,378	15,382
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options and SARs outstanding at beginning of year (in dollars per share)	$ 39.31	$ 38.08
Granted (in dollars per share)	44.75	40.78
Exercised (in dollars per share)	35.30	28.03
Forfeited or expired (in dollars per share)	36.60	24.13
Options and SARs outstanding at end of year (in dollars per share)	39.48	39.21
Options and SARs exercisable at year end (in dollars per share)	$ 37.77	$ 29.59