Summary of Significant Accounting And Reporting Policies	12 Months Ended
Dec. 31, 2016
Significant Accounting And Reporting Policies [Abstract]
Significant Accounting And Reporting Policies	SOUTHWEST BANCORP, INC. Notes to the Consolidated Financial Statements For the Years Ended December 31, 2016, 2015 and 2014 Note 1: Summary of Significant Accounting and Reporting Policies Organization and Nature of Operations – Southwest Bancorp Inc. (“we”, “our”, “us”, or “Southwest”), incorporated in 1981, is a financial holding company headquartered in Stillwater, Oklahoma engaged primarily in commercial and retail financial services in the states of Oklahoma, Texas, Kansas, and Colorado. The accompanying consolidated financial statements include the accounts of Bank SNB, an Oklahoma banking corporation established in 1894, and the consolidated subsidiaries of Bank SNB. Bank SNB is a wholly owned, direct subsidiary of ours. All significant intercompany balances and transactions have been eliminated in consolidation. On October 9, 2015, we completed the acquisition of Bancshares through the merger of Bancshares with and into us. The Bancshares Merger was consummated pursuant to the Bancshares Merger Agreement dated as of May 27, 2015. The Bancshares Merger expanded our presence in the Oklahoma City metro area with five additional banking centers, increasing our total to ten. It also expanded our geographic footprint to Colorado with three full-service banking centers and one loan production office in Denver. Basis of Presentation – The accounting and reporting policies conform to accounting principles generally accepted in the United States and to generally accepted practices within the banking industry. The Consolidated Financial Statements include the accounts of Southwest and all other entities in which we have a controlling financial interest. All significant intercompany accounts and transactions have been eliminated in consolidation. Certain reclassifications have been made to prior year amounts on the Consolidated Statements of Operations to conform to current year presentation. We have evaluated subsequent events for potential recognition and disclosure through the issue date of the Consolidated Financial Statements included in this Annual Report on Form 10-K. Management Estimates – In preparing our financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the dates shown on the Consolidated Statements of Financial Condition and revenues and expenses during the periods reported. Actual results could differ significantly from those estimates. Changes in economic conditions could affect the determination of material estimates such as the allowance for loan losses, the valuation of real estate acquired in connection with foreclosures or in satisfaction of loans, income taxes, and the fair value of financial instruments. Cash and Cash Equivalents – For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from depository institutions, and federal funds sold. Interest-bearing balances held at depository institutions were $38.8 million at December 31, 2016 and $53.2 million at December 31, 2015. Federal funds sold are sold for one-to-four day periods. Cash paid for interest totaled $9.7 million in 2016, $7.0 million in 2015, and $6.9 million in 2014. Cash paid for income taxes totaled $9.4 million in 2016, $7.1 million in 2015, and $4.0 million in 2014. Noncash transactions included stock issued for the acquisition of Bancshares of $21.4 million in 2015 and transfer of loans to other real estate totaling $0.5 million in 2016 and $0.3 million in 2015 and $2.2 million in 2014. Bank SNB is required by the FRB to maintain average reserve balances. Cash and cash equivalents in the Consolidated Statements of Financial Condition include restricted amounts of $1.0 million and $7.0 million at December 31, 2016 and December 31, 2015, respectively. Investment Securities – Investments in debt and equity securities are identified as held to maturity or available for sale based on management considerations of asset/liability strategy, changes in interest rates and prepayment risk, the need to increase liquidity, and other factors, including management’s intent and ability to hold securities to maturity. We have the ability and intent to hold to maturity our investment securities classified as held to maturity. We had no investments held for trading purposes for any period presented. Under certain circumstances (including the deterioration of the issuer’s creditworthiness, a change in tax law, or statutory or regulatory requirements), we may change the investment security classification. The classifications we utilize determine the related accounting treatment for each category of investments. Available for sale securities are accounted for at fair value with unrealized gains or losses, net of taxes, excluded from operations and reported as accumulated other comprehensive income or loss. Held to maturity securities are accounted for at amortized cost. Securities with limited marketability, such as FRB stock, FHLB stock, and certain other investments, are carried at cost and included in other assets. All investment securities are adjusted for amortization of premiums and accretion of discounts. Amortization of premiums and accretion of discounts are recorded to operations over the contractual maturity or estimated life of the individual investment using the level yield method. Gain or loss on sale of investments is based upon the specific identification method. Income earned on our investments in state and political subdivisions generally is not subject to ordinary Federal income tax. In accordance with authoritative accounting guidance under ASC 320, Debt and Equity Securities, declines in fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other-than-temporary are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized in other comprehensive income. Under this guidance, we evaluate investment securities for other-than-temporary impairment on at least a quarterly basis, or more frequently when economic or market conditions warrant such an evaluation. Federal Reserve Bank and Federal Home Loan Bank Stock – Bank SNB is a member of its regional FRB and FHLB system. FHLB members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional accounts. Both FRB and FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income. Loans – Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Loan origination fees and certain costs of originated loans are amortized as an adjustment to the yield over the term of the loan. Net unamortized deferred loan fees were $2.5 million at December 31, 2016 and $1.5 million at 2015. Loans are reported at the principal balance outstanding net of the unamortized deferred loan fees. In general, our policy for nonaccrual loans requires that accrued interest income on nonaccrual loans is written off after the loan is 90 days past due, and that subsequent interest income is recorded when cash receipts are received from the borrower. We identify past due loans based on contractual terms on a loan by loan basis. A loan is considered to be impaired when, based on current information and events, it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan agreement. The allowance for loan losses related to loans that are evaluated for impairment is based either on the discounted cash flows using the loan’s initial effective interest rate or on the fair value of the collateral for certain collateral dependent loans. Smaller balance, homogeneous loans, including mortgage, and consumer, are collectively evaluated for impairment. This evaluation is inherently subjective as it requires material estimates including the amounts and timing of future cash flows expected to be received on impaired loans that may be susceptible to significant change. Loans Held for Sale -- We originate real estate mortgage loans for either portfolio investment or sale in the secondary market. During the period of origination, real estate mortgage loans are designated as held either for investment purposes or sale. Mortgage loans held for sale are generally sold within a one-month period from loan closing at amounts determined by the investor commitment based upon the pricing of the loan. Loans Acquired through Business Combination with Deteriorated Credit Quality – The accounting guidance of ASC 310.30, Loan and Debt Securities Acquired with Deteriorated Credit Quality, applies to loans acquired in a business combination that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that we will be unable to collect all contractually required payment receivables. In accordance with this guidance, these loans are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the investment in the loan, or the “accretable yield”, is recognized as interest income over the life of the loan using a method that approximates the level-yield method. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference”, are not recognized as a yield adjustment, a loss accrual, or a valuation allowance. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairments. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition. Allowance for Loan Losses – The allowance for loan losses is a reserve established through a provision for loan losses charged to operations. Loan amounts which are determined to be uncollectible are charged against this allowance, and recoveries, if any, are added to the allowance. The appropriate amount of the allowance is based on continuous review and evaluation of the loan portfolio and ongoing, quarterly assessments of the probable losses inherent in the loan portfolio. The allowance for loan losses is determined in accordance with regulatory guidelines and generally accepted accounting principles and is comprised of two primary components, specific and general. Allocations of the allowance for loan losses may be made for specific loans, but the entire allowance is available for any loan that, in management’s judgment, should be charged off. The specific component relates to loans that are individually classified as impaired. Loans deemed to be impaired are evaluated on an individual basis consistent with ASC 310.10.35, Receivables: Subsequent Measurement. The amount and level of the impairment allowance is ultimately determined by management’s estimate of the amount of expected future cash flows or, if the loan is collateral dependent, on the value of the collateral, which may vary from period to period depending on changes in the financial condition of the borrower or changes in the estimated value of the collateral. Loans for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties, are considered troubled debt restructurings and deemed as impaired, and classified as nonperforming, potential problem, or performing restructured as applicable. Charge-offs against the allowance for impaired loans are made when and to the extent the loan is deemed uncollectible. The general component of the allowance is calculated based on ASC 450, Contingencies. Loans not evaluated for specific allowance are segmented into loan pools by type of loan. The commercial real estate and real estate construction pools are further segmented by the market in which the loan collateral is located. Our primary markets are Oklahoma, Texas, Kansas, and Colorado, and loans secured by real estate in those states are included in the “in-market” pool, with the remaining defaulting to the “out-of-market” pool. Estimated allowances are based on historical loss trends with adjustments factored in based on qualitative risk factors both internal and external to us. The historical loss trend is determined by loan pool and segmentation and is based on the actual loss history experienced by us over the most recent three years. The qualitative risk factors include, but are not limited to, economic and business conditions, changes in lending staff, lending policies and procedures, quality of loan review, changes in the nature and volume of the portfolios, loss and recovery trends, asset quality trends, and legal and regulatory considerations. Independent appraisals on real estate collateral securing loans are obtained at origination. New appraisals are obtained periodically and upon discovery of factors that may significantly affect the value of the collateral. Appraisals usually are received within 30 days of request. Results of appraisals on nonperforming and potential problem loans are reviewed promptly upon receipt and also are reviewed monthly and considered in the determination of the allowance for loan losses. We are not aware of any significant time lapses in the process that have resulted, or would result in, a significant delay in determination of a credit weakness, the identification of a loan as nonperforming, or the measurement of an impairment. Management strives to carefully monitor credit quality and to identify loans that may become nonperforming. At any time, however, there are loans included in the portfolio that will result in losses but that have not been identified as nonperforming or potential problem loans. Because the loan portfolio contains a significant number of commercial and commercial real estate loans with relatively large balances, the unexpected deterioration of one or a few of such loans may cause a significant increase in nonperforming assets and may lead to a material increase in charge-offs and the provision for loan losses in future periods. Liability for Credit Losses on Unfunded Loan Commitments – Financial instruments include off-balance sheet credit instruments, such as commitments to make loans and commercial letters of credit, issued to meet customer financing needs. The face amount for these items represents the exposure to loss, before considering customer collateral or ability to repay. Such financial instruments are recorded when they are funded. The reserve for unfunded loan commitments is a liability on our Consolidated Statements of Financial Condition in other liabilities. The reserve is computed using a methodology similar to that used to determine the allowance for loan losses, modified to take into account the probability of a drawdown on the commitment. At December 31, 2016 and 2015, the balances were $2.5 million and $2.4 million, respectively. Premises and Equipment – Land is carried at cost. Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recorded on a straight-line basis over the estimated useful life of each asset. Useful lives range from 10 years to 40 years for buildings and improvements, and 3 years to 10 years for furniture, fixtures, and equipment. We review the carrying value of long-lived assets used in operations when changes in events or circumstances indicate that the assets might have become impaired. If circumstances required, the review would initially include a comparison of carrying value to the undiscounted cash flows estimated to be generated by those assets. If this review indicates that an asset is impaired, we would record a charge to operations to reduce the asset’s carrying value to fair value, which is based on estimated discounted cash flows. Long-lived assets that are held for disposal are valued at the lower of the carrying amount or fair value less costs to sell. Other Real Estate – Assets acquired through or instead of loan foreclosure are considered other real estate. Other real estate is initially recorded at the lesser of the carrying value or fair value less the estimated costs to sell the asset. Write-downs of carrying value required at the time of foreclosure are recorded as a charge to the allowance for loan losses. Costs related to the development of such real estate are capitalized, and costs related to holding the property are expensed. Foreclosed property is subject to periodic revaluation based upon estimates of fair value. In determining the valuation of other real estate, management obtains independent appraisals for significant properties. Valuation adjustments are provided, as necessary, by charges to operations. Profits and losses from operations or sales of foreclosed property are recognized as incurred. At December 31, 2016 and 2015, the balances of other real estate were $0.4 million and $2.3 million, respectively. Goodwill and Other Intangible Assets – Intangible assets consist of goodwill, core deposit intangibles, and loan servicing rights. Goodwill and core deposit intangibles, which generally result from a business combination, are accounted for under the provisions of ASC 350, Intangibles - Goodwill and Other, and ASC 805, Business Combinations. Loan servicing rights are accounted for under the provisions of ASC 860, Transfers and Servicing. Goodwill represents the excess of the cost of businesses acquired over the fair value of the net assets acquired and is assigned to reporting units. Goodwill is not amortized, but is tested for impairment at least annually or more frequently if conditions indicate impairment may exist. The evaluation of possible impairment involves significant judgment based upon short-term and long-term projections of future performance of each reporting unit. Core deposit intangibles are amortized using an economic life method based on deposit attrition. As a result, amortization will decline over time with most of the amortization occurring during the initial years. The net book value of core deposit intangibles is adjusted for applicable branch sales, if any, and is evaluated for impairment when economic conditions indicate impairment may exist. When real estate mortgage loans and other loans are sold with servicing retained, an intangible servicing right is initially capitalized based on estimated fair value at the point of origination with the income statement effect recorded in gains on sales of loans. The servicing rights are amortized over the period of estimated net servicing income. Impairment of loan servicing rights is assessed based on the fair value of those rights. We review the carrying value of loan servicing rights quarterly for impairment. At least annually, we obtain estimates of fair value from outside sources to corroborate the results of the valuation model. At December 31, 2016 and 2015, the fair values of loan servicing rights were $4.2 million and $3.7 million, respectively. Fair Value Measurements – ASC 820, Fair Value Measurements, defines fair value, establishes a framework for measuring fair value in accordance with generally accepted accounting principles, and expands disclosures about fair value measurements. In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. Derivative Financial Instruments – Our derivative credit risk policy and our hedging policy permits the use of various derivative financial instruments to manage interest rate risk or to hedge specified assets and liabilities. All derivatives are recorded at fair value on our balance sheet. To qualify for hedge accounting, derivatives must be highly effective at reducing the risk associated with the exposure being hedged and must be designated as a hedge at the inception of the derivative contract. We consider a hedge to be highly effective if the change in fair value of the derivative hedging instrument is within 80% to 125% of the opposite change in the fair value of the hedged item attributable to the hedged risk. If derivative instruments are designated as hedges of fair values, and such hedges are highly effective, both the change in the fair value of the hedge and the hedged item are included in current earnings. Fair value adjustments related to cash flow hedges are recorded in other comprehensive income and are reclassified to earnings when the hedged transaction is reflected in earnings. Ineffective portions of hedges are reflected in earnings as they occur. Actual cash receipts and/or payments and related accruals on derivatives related to hedges are recorded as adjustments to the interest income or interest expense associated with the hedged item. During the life of the hedge, we will formally assess whether derivatives designated as hedging instruments continue to be highly effective in offsetting changes in the fair value or cash flows of hedged items. If it is determined that a hedge has ceased to be highly effective, we will discontinue hedge accounting prospectively. At such time, previous adjustments to the carrying value of the hedged item are reversed into current earnings and the derivative instrument is reclassified to a trading position recorded at fair value. Our qualified customers have the opportunity to participate in our interest rate swap program for the purpose of managing interest rate risk on their variable rate loans with us. If we enter into such agreements with customers, then offsetting agreements are executed between us and approved dealer counterparties to minimize our market risk from changes in interest rates. The counterparty contracts are identical to customer contracts in terms of notional amounts, interest rates, and maturity dates, except for a fixed pricing spread or fee paid to us by the dealer counterparty. These interest rate swaps carry varying degrees of credit, interest rate and market or liquidity risks. The fair value of such derivative instruments are recognized as either non-hedge derivative assets or liabilities in the Consolidated Statements of Financial Condition. Loan Servicing Income – We earn fees for servicing real estate mortgages and other loans owned by others. These fees are generally calculated on the outstanding principal balance of the loans serviced and are recorded as income when earned. Taxes on Income – We file consolidated income tax returns with our subsidiaries. Income tax expense is the total of the current year income tax due or refundable, adjusted for permanent differences between items reported in the financial statements and those reported for tax purposes and the change in deferred tax assets and liabilities. Under the asset and liability method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The net deferred tax asset is reflected as a component of other assets on the Consolidated Statements of Financial Condition. A valuation allowance, if needed, reduces deferred tax assets to the expected amount most likely to be realized. Realization of deferred tax assets is dependent upon the generation of a sufficient level of future taxable income and recoverable taxes paid in prior years. We recognize net deferred tax assets to the extent that we believe these assets are more likely than not to be realized. In making such determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. Management reviewed all evidence and concluded that a valuation allowance was not needed. Earnings per Common Share – ASC 260, Earnings Per Share, provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. We have determined that our unvested restricted stock awards are participating securities. Accordingly, earnings per common share is computed using the two-class method prescribed by ASC 260. Using this method, basic earnings per common share is computed based upon net income available to common shareholders divided by the weighted average number of common shares outstanding during each period, which exclude the outstanding unvested restricted stock. Diluted earnings per share is computed using the weighted average number of common shares determined for the basic earnings per common share computation plus the dilutive effect of restricted stock awards using the treasury stock method. Restricted stock awards, where the exercise price was greater than the average market price of common shares, were not included in the computation of earnings per diluted share as they would have been anti-dilutive. At December 31, 2016 and 2015, there were 6,573 and 38,145 anti-dilutive restricted stock awards outstanding, respectively. A reconciliation of the weighted-average common shares used in the calculations of basic and diluted earnings per common share for the reported periods is provided at “Note 15: Earnings per Common Share” on page 86. Share-Based Compensation – The Southwest Bancorp, Inc. 2008 Stock Based Award Plan (the “2008 Stock Plan”), provides selected key employees with the opportunity to acquire common stock through stock options or restricted stock awards. Compensation cost is recognized based on the fair value of these awards at the date of grant. The exercise price of all options granted under the 2008 Stock Plan is the fair market value on the grant date, while the market price of our common stock at the date of grant is used for restricted stock awards. Compensation cost is recognized over the required service period, generally defined as the vesting period. Depending upon terms of the stock option agreements, stock options generally become exercisable on an annual basis and expire from five to ten years after the date of grant. The 2008 Stock Plan authorized awards for up to 800,000 shares of our common stock over its ten-year term. Comprehensive Income – Our comprehensive income (net income plus all other changes in shareholders’ equity from non-equity sources) consists of our net income, the after tax effect of changes in the net unrealized gains (losses) in our available for sale securities, reclassification adjustments for net (gains) losses, and changes in the accumulated gain (loss) on the effective cash flow hedging instrument. Simmons First National Corporation (Pending Merger) – On December 14, 2016, we entered into a Merger Agreement with Simmons, an Arkansas corporation, pursuant to which, and subject to its terms and conditions, Simmons will acquire all of our outstanding capital stock for $95.0 million in cash and 7,250,000 shares of Simmons’s common stock, representing an aggregate Merger consideration of approximately $564.4 million (based on Simmons’ common stock closing price as of December 13, 2016), subject to potential adjustments. Simmons conducts banking operations through 150 financial centers located in communities throughout Arkansas, Kansas, Missouri and Tennessee. As of December 31, 2016, Simmons had $8.4 billion in total assets, $5.6 billion in loans and $6.7 billion in deposits. The completion of the Merger is subject to, among other things, regulatory and shareholder approval and other customary closing conditions.

SOUTHWEST BANCORP, INC.

Notes to the Consolidated Financial Statements

For the Years Ended December 31, 2016, 2015 and 2014

Note 1: Summary of Significant Accounting and Reporting Policies

Organization and Nature of Operations – Southwest Bancorp Inc. (“we”, “our”, “us”, or “Southwest”), incorporated in 1981, is a financial holding company headquartered in Stillwater, Oklahoma engaged primarily in commercial and retail financial services in the states of Oklahoma, Texas, Kansas, and Colorado. The accompanying consolidated financial statements include the accounts of Bank SNB, an Oklahoma banking corporation established in 1894, and the consolidated subsidiaries of Bank SNB. Bank SNB is a wholly owned, direct subsidiary of ours. All significant intercompany balances and transactions have been eliminated in consolidation.

On October 9, 2015, we completed the acquisition of Bancshares through the merger of Bancshares with and into us. The Bancshares Merger was consummated pursuant to the Bancshares Merger Agreement dated as of May 27, 2015. The Bancshares Merger expanded our presence in the Oklahoma City metro area with five additional banking centers, increasing our total to ten. It also expanded our geographic footprint to Colorado with three full-service banking centers and one loan production office in Denver.

Basis of Presentation – The accounting and reporting policies conform to accounting principles generally accepted in the United States and to generally accepted practices within the banking industry. The Consolidated Financial Statements include the accounts of Southwest and all other entities in which we have a controlling financial interest. All significant intercompany accounts and transactions have been eliminated in consolidation.

Certain reclassifications have been made to prior year amounts on the Consolidated Statements of Operations to conform to current year presentation.

We have evaluated subsequent events for potential recognition and disclosure through the issue date of the Consolidated Financial Statements included in this Annual Report on Form 10-K.

Management Estimates – In preparing our financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the dates shown on the Consolidated Statements of Financial Condition and revenues and expenses during the periods reported. Actual results could differ significantly from those estimates. Changes in economic conditions could affect the determination of material estimates such as the allowance for loan losses, the valuation of real estate acquired in connection with foreclosures or in satisfaction of loans, income taxes, and the fair value of financial instruments.

Cash and Cash Equivalents – For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from depository institutions, and federal funds sold. Interest-bearing balances held at depository institutions were $38.8 million at December 31, 2016 and $53.2 million at December 31, 2015. Federal funds sold are sold for one-to-four day periods.

Cash paid for interest totaled $9.7 million in 2016, $7.0 million in 2015, and $6.9 million in 2014. Cash paid for income taxes totaled $9.4 million in 2016, $7.1 million in 2015, and $4.0 million in 2014. Noncash transactions included stock issued for the acquisition of Bancshares of $21.4 million in 2015 and transfer of loans to other real estate totaling $0.5 million in 2016 and $0.3 million in 2015 and $2.2 million in 2014.

Bank SNB is required by the FRB to maintain average reserve balances. Cash and cash equivalents in the Consolidated Statements of Financial Condition include restricted amounts of $1.0 million and $7.0 million at December 31, 2016 and December 31, 2015, respectively.

Investment Securities – Investments in debt and equity securities are identified as held to maturity or available for sale based on management considerations of asset/liability strategy, changes in interest rates and prepayment risk, the need to increase liquidity, and other factors, including management’s intent and ability to hold securities to maturity. We have the ability and intent to hold to maturity our investment securities classified as held to maturity. We had no investments held for trading purposes for any period presented. Under certain circumstances (including the deterioration of the issuer’s creditworthiness, a change in tax law, or statutory or regulatory requirements), we may change the investment security classification. The classifications we utilize determine the related accounting treatment for each category of investments. Available for sale securities are accounted for at fair value with unrealized gains or losses, net of taxes, excluded from operations and reported as accumulated other comprehensive income or loss. Held to maturity securities are accounted for at amortized cost. Securities with limited marketability, such as FRB stock, FHLB stock, and certain other investments, are carried at cost and included in other assets.

All investment securities are adjusted for amortization of premiums and accretion of discounts. Amortization of premiums and accretion of discounts are recorded to operations over the contractual maturity or estimated life of the individual investment using the level yield method. Gain or loss on sale of investments is based upon the specific identification method. Income earned on our investments in state and political subdivisions generally is not subject to ordinary Federal income tax.

In accordance with authoritative accounting guidance under ASC 320, Debt and Equity Securities, declines in fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other-than-temporary are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized in other comprehensive income. Under this guidance, we evaluate investment securities for other-than-temporary impairment on at least a quarterly basis, or more frequently when economic or market conditions warrant such an evaluation.

Federal Reserve Bank and Federal Home Loan Bank Stock – Bank SNB is a member of its regional FRB and FHLB system. FHLB members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional accounts. Both FRB and FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income.

Loans – Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Loan origination fees and certain costs of originated loans are amortized as an adjustment to the yield over the term of the loan. Net unamortized deferred loan fees were $2.5 million at December 31, 2016 and $1.5 million at 2015. Loans are reported at the principal balance outstanding net of the unamortized deferred loan fees.

In general, our policy for nonaccrual loans requires that accrued interest income on nonaccrual loans is written off after the loan is 90 days past due, and that subsequent interest income is recorded when cash receipts are received from the borrower. We identify past due loans based on contractual terms on a loan by loan basis.

A loan is considered to be impaired when, based on current information and events, it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan agreement. The allowance for loan losses related to loans that are evaluated for impairment is based either on the discounted cash flows using the loan’s initial effective interest rate or on the fair value of the collateral for certain collateral dependent loans. Smaller balance, homogeneous loans, including mortgage, and consumer, are collectively evaluated for impairment. This evaluation is inherently subjective as it requires material estimates including the amounts and timing of future cash flows expected to be received on impaired loans that may be susceptible to significant change.

Loans Held for Sale -- We originate real estate mortgage loans for either portfolio investment or sale in the secondary market. During the period of origination, real estate mortgage loans are designated as held either for investment purposes or sale. Mortgage loans held for sale are generally sold within a one-month period from loan closing at amounts determined by the investor commitment based upon the pricing of the loan.

Loans Acquired through Business Combination with Deteriorated Credit Quality – The accounting guidance of ASC 310.30, Loan and Debt Securities Acquired with Deteriorated Credit Quality, applies to loans acquired in a business combination that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that we will be unable to collect all contractually required payment receivables. In accordance with this guidance, these loans are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the investment in the loan, or the “accretable yield”, is recognized as interest income over the life of the loan using a method that approximates the level-yield method. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference”, are not recognized as a yield adjustment, a loss accrual, or a valuation allowance. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairments. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition.

Allowance for Loan Losses – The allowance for loan losses is a reserve established through a provision for loan losses charged to operations. Loan amounts which are determined to be uncollectible are charged against this allowance, and recoveries, if any, are added to the allowance. The appropriate amount of the allowance is based on continuous review and evaluation of the loan portfolio and ongoing, quarterly assessments of the probable losses inherent in the loan portfolio. The allowance for loan losses is determined in accordance with regulatory guidelines and generally accepted accounting principles and is comprised of two primary components, specific and general. Allocations of the allowance for loan losses may be made for specific loans, but the entire allowance is available for any loan that, in management’s judgment, should be charged off.

The specific component relates to loans that are individually classified as impaired. Loans deemed to be impaired are evaluated on an individual basis consistent with ASC 310.10.35, Receivables: Subsequent Measurement. The amount and level of the impairment allowance is ultimately determined by management’s estimate of the amount of expected future cash flows or, if the loan is collateral dependent, on the value of the collateral, which may vary from period to period depending on changes in the financial condition of the borrower or changes in the estimated value of the collateral. Loans for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties, are considered troubled debt restructurings and deemed as impaired, and classified as nonperforming, potential problem, or performing restructured as applicable. Charge-offs against the allowance for impaired loans are made when and to the extent the loan is deemed uncollectible.

The general component of the allowance is calculated based on ASC 450, Contingencies. Loans not evaluated for specific allowance are segmented into loan pools by type of loan. The commercial real estate and real estate construction pools are further segmented by the market in which the loan collateral is located. Our primary markets are Oklahoma, Texas, Kansas, and Colorado, and loans secured by real estate in those states are included in the “in-market” pool, with the remaining defaulting to the “out-of-market” pool. Estimated allowances are based on historical loss trends with adjustments factored in based on qualitative risk factors both internal and external to us. The historical loss trend is determined by loan pool and segmentation and is based on the actual loss history experienced by us over the most recent three years. The qualitative risk factors include, but are not limited to, economic and business conditions, changes in lending staff, lending policies and procedures, quality of loan review, changes in the nature and volume of the portfolios, loss and recovery trends, asset quality trends, and legal and regulatory considerations.

Independent appraisals on real estate collateral securing loans are obtained at origination. New appraisals are obtained periodically and upon discovery of factors that may significantly affect the value of the collateral. Appraisals usually are received within 30 days of request. Results of appraisals on nonperforming and potential problem loans are reviewed promptly upon receipt and also are reviewed monthly and considered in the determination of the allowance for loan losses. We are not aware of any significant time lapses in the process that have resulted, or would result in, a significant delay in determination of a credit weakness, the identification of a loan as nonperforming, or the measurement of an impairment.

Management strives to carefully monitor credit quality and to identify loans that may become nonperforming. At any time, however, there are loans included in the portfolio that will result in losses but that have not been identified as nonperforming or potential problem loans. Because the loan portfolio contains a significant number of commercial and commercial real estate loans with relatively large balances, the unexpected deterioration of one or a few of such loans may cause a significant increase in nonperforming assets and may lead to a material increase in charge-offs and the provision for loan losses in future periods.

Liability for Credit Losses on Unfunded Loan Commitments – Financial instruments include off-balance sheet credit instruments, such as commitments to make loans and commercial letters of credit, issued to meet customer financing needs. The face amount for these items represents the exposure to loss, before considering customer collateral or ability to repay. Such financial instruments are recorded when they are funded.

The reserve for unfunded loan commitments is a liability on our Consolidated Statements of Financial Condition in other liabilities. The reserve is computed using a methodology similar to that used to determine the allowance for loan losses, modified to take into account the probability of a drawdown on the commitment. At December 31, 2016 and 2015, the balances were $2.5 million and $2.4 million, respectively.

Premises and Equipment – Land is carried at cost. Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recorded on a straight-line basis over the estimated useful life of each asset. Useful lives range from 10 years to 40 years for buildings and improvements, and 3 years to 10 years for furniture, fixtures, and equipment. We review the carrying value of long-lived assets used in operations when changes in events or circumstances indicate that the assets might have become impaired. If circumstances required, the review would initially include a comparison of carrying value to the undiscounted cash flows estimated to be generated by those assets. If this review indicates that an asset is impaired, we would record a charge to operations to reduce the asset’s carrying value to fair value, which is based on estimated discounted cash flows. Long-lived assets that are held for disposal are valued at the lower of the carrying amount or fair value less costs to sell.

Other Real Estate – Assets acquired through or instead of loan foreclosure are considered other real estate. Other real estate is initially recorded at the lesser of the carrying value or fair value less the estimated costs to sell the asset. Write-downs of carrying value required at the time of foreclosure are recorded as a charge to the allowance for loan losses. Costs related to the development of such real estate are capitalized, and costs related to holding the property are expensed. Foreclosed property is subject to periodic revaluation based upon estimates of fair value. In determining the valuation of other real estate, management obtains independent appraisals for significant properties. Valuation adjustments are provided, as necessary, by charges to operations. Profits and losses from operations or sales of foreclosed property are recognized as incurred. At December 31, 2016 and 2015, the balances of other real estate were $0.4 million and $2.3 million, respectively.

Goodwill and Other Intangible Assets – Intangible assets consist of goodwill, core deposit intangibles, and loan servicing rights. Goodwill and core deposit intangibles, which generally result from a business combination, are accounted for under the provisions of ASC 350, Intangibles - Goodwill and Other, and ASC 805, Business Combinations. Loan servicing rights are accounted for under the provisions of ASC 860, Transfers and Servicing.

Goodwill represents the excess of the cost of businesses acquired over the fair value of the net assets acquired and is assigned to reporting units. Goodwill is not amortized, but is tested for impairment at least annually or more frequently if conditions indicate impairment may exist. The evaluation of possible impairment involves significant judgment based upon short-term and long-term projections of future performance of each reporting unit.

Core deposit intangibles are amortized using an economic life method based on deposit attrition. As a result, amortization will decline over time with most of the amortization occurring during the initial years. The net book value of core deposit intangibles is adjusted for applicable branch sales, if any, and is evaluated for impairment when economic conditions indicate impairment may exist.

When real estate mortgage loans and other loans are sold with servicing retained, an intangible servicing right is initially capitalized based on estimated fair value at the point of origination with the income statement effect recorded in gains on sales of loans. The servicing rights are amortized over the period of estimated net servicing income. Impairment of loan servicing rights is assessed based on the fair value of those rights. We review the carrying value of loan servicing rights quarterly for impairment. At least annually, we obtain estimates of fair value from outside sources to corroborate the results of the valuation model. At December 31, 2016 and 2015, the fair values of loan servicing rights were $4.2 million and $3.7 million, respectively.

Fair Value Measurements – ASC 820, Fair Value Measurements, defines fair value, establishes a framework for measuring fair value in accordance with generally accepted accounting principles, and expands disclosures about fair value measurements. In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. These adjustments may include amounts to reflect counterparty credit quality and our creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time.

Derivative Financial Instruments – Our derivative credit risk policy and our hedging policy permits the use of various derivative financial instruments to manage interest rate risk or to hedge specified assets and liabilities. All derivatives are recorded at fair value on our balance sheet.

To qualify for hedge accounting, derivatives must be highly effective at reducing the risk associated with the exposure being hedged and must be designated as a hedge at the inception of the derivative contract. We consider a hedge to be highly effective if the change in fair value of the derivative hedging instrument is within 80% to 125% of the opposite change in the fair value of the hedged item attributable to the hedged risk. If derivative instruments are designated as hedges of fair values, and such hedges are highly effective, both the change in the fair value of the hedge and the hedged item are included in current earnings. Fair value adjustments related to cash flow hedges are recorded in other comprehensive income and are reclassified to earnings when the hedged transaction is reflected in earnings. Ineffective portions of hedges are reflected in earnings as they occur. Actual cash receipts and/or payments and related accruals on derivatives related to hedges are recorded as adjustments to the interest income or interest expense associated with the hedged item. During the life of the hedge, we will formally assess whether derivatives designated as hedging instruments continue to be highly effective in offsetting changes in the fair value or cash flows of hedged items. If it is determined that a hedge has ceased to be highly effective, we will discontinue hedge accounting prospectively. At such time, previous adjustments to the carrying value of the hedged item are reversed into current earnings and the derivative instrument is reclassified to a trading position recorded at fair value.

Our qualified customers have the opportunity to participate in our interest rate swap program for the purpose of managing interest rate risk on their variable rate loans with us. If we enter into such agreements with customers, then offsetting agreements are executed between us and approved dealer counterparties to minimize our market risk from changes in interest rates. The counterparty contracts are identical to customer contracts in terms of notional amounts, interest rates, and maturity dates, except for a fixed pricing spread or fee paid to us by the dealer counterparty. These interest rate swaps carry varying degrees of credit, interest rate and market or liquidity risks. The fair value of such derivative instruments are recognized as either non-hedge derivative assets or liabilities in the Consolidated Statements of Financial Condition.

Loan Servicing Income – We earn fees for servicing real estate mortgages and other loans owned by others. These fees are generally calculated on the outstanding principal balance of the loans serviced and are recorded as income when earned.

Taxes on Income – We file consolidated income tax returns with our subsidiaries. Income tax expense is the total of the current year income tax due or refundable, adjusted for permanent differences between items reported in the financial statements and those reported for tax purposes and the change in deferred tax assets and liabilities. Under the asset and liability method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The net deferred tax asset is reflected as a component of other assets on the Consolidated Statements of Financial Condition.

A valuation allowance, if needed, reduces deferred tax assets to the expected amount most likely to be realized. Realization of deferred tax assets is dependent upon the generation of a sufficient level of future taxable income and recoverable taxes paid in prior years. We recognize net deferred tax assets to the extent that we believe these assets are more likely than not to be realized. In making such determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. Management reviewed all evidence and concluded that a valuation allowance was not needed.

Earnings per Common Share – ASC 260, Earnings Per Share, provides that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share pursuant to the two-class method. We have determined that our unvested restricted stock awards are participating securities. Accordingly, earnings per common share is computed using the two-class method prescribed by ASC 260. Using this method, basic earnings per common share is computed based upon net income available to common shareholders divided by the weighted average number of common shares outstanding during each period, which exclude the outstanding unvested restricted stock. Diluted earnings per share is computed using the weighted average number of common shares determined for the basic earnings per common share computation plus the dilutive effect of restricted stock awards using the treasury stock method. Restricted stock awards, where the exercise price was greater than the average market price of common shares, were not included in the computation of earnings per diluted share as they would have been anti-dilutive. At December 31, 2016 and 2015, there were 6,573 and 38,145 anti-dilutive restricted stock awards outstanding, respectively.

A reconciliation of the weighted-average common shares used in the calculations of basic and diluted earnings per common share for the reported periods is provided at “Note 15: Earnings per Common Share” on page 86.

Share-Based Compensation – The Southwest Bancorp, Inc. 2008 Stock Based Award Plan (the “2008 Stock Plan”), provides selected key employees with the opportunity to acquire common stock through stock options or restricted stock awards. Compensation cost is recognized based on the fair value of these awards at the date of grant. The exercise price of all options granted under the 2008 Stock Plan is the fair market value on the grant date, while the market price of our common stock at the date of grant is used for restricted stock awards. Compensation cost is recognized over the required service period, generally defined as the vesting period. Depending upon terms of the stock option agreements, stock options generally become exercisable on an annual basis and expire from five to ten years after the date of grant.

The 2008 Stock Plan authorized awards for up to 800,000 shares of our common stock over its ten-year term.

Comprehensive Income – Our comprehensive income (net income plus all other changes in shareholders’ equity from non-equity sources) consists of our net income, the after tax effect of changes in the net unrealized gains (losses) in our available for sale securities, reclassification adjustments for net (gains) losses, and changes in the accumulated gain (loss) on the effective cash flow hedging instrument.

Simmons First National Corporation (Pending Merger) – On December 14, 2016, we entered into a Merger Agreement with Simmons, an Arkansas corporation, pursuant to which, and subject to its terms and conditions, Simmons will acquire all of our outstanding capital stock for $95.0 million in cash and 7,250,000 shares of Simmons’s common stock, representing an aggregate Merger consideration of approximately $564.4 million (based on Simmons’ common stock closing price as of December 13, 2016), subject to potential adjustments.

Simmons conducts banking operations through 150 financial centers located in communities throughout Arkansas, Kansas, Missouri and Tennessee. As of December 31, 2016, Simmons had $8.4 billion in total assets, $5.6 billion in loans and $6.7 billion in deposits. The completion of the Merger is subject to, among other things, regulatory and shareholder approval and other customary closing conditions.