Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2012
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	(1) Summary of Significant Accounting Policies The unaudited interim condensed consolidated financial statements include the accounts of Suffolk Bancorp (“Suffolk”) and its wholly owned subsidiary, Suffolk County National Bank and its subsidiaries (the “Bank”). Suffolk and the Bank are collectively referred to hereafter as the “Company.” All material intercompany accounts and transactions have been eliminated in consolidation. The unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) and predominant practices within the banking industry. They do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, please refer to the audited consolidated financial statements and footnotes thereto included in the Company’s 2011 Annual Report on Form 10-K. The following footnotes describe the Company’s most significant accounting policies. The results of operations for the three and nine months ended September 30, 2012 are not necessarily indicative of the results of operations to be expected for the remainder of the year. Loans and Loan Interest Income Recognition - Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of unearned discounts, deferred loan fees and costs and an allowance for loan losses. Unearned discounts on installment loans are credited to income using methods that result in a level yield. Loan origination fees, net of certain direct origination costs, are deferred and recognized in interest income over the respective term of the loan without anticipating prepayments. Interest income is accrued on the unpaid principal balance. Recognition of interest income is discontinued when reasonable doubt exists as to whether principal or interest due can be collected. For all classes of loans, loans generally no longer accrue interest when over 90 days past due unless the loan is well-secured and in process of collection. When a loan is placed on non-accrual status, all interest previously accrued, but not collected, is reversed against current-year interest income. Interest received on such loans is applied against principal or interest, according to management’s judgment as to the collectability of the principal, until qualifying for return to accrual status. Loans start accruing interest again when they become current as to principal and interest, and when, in the opinion of management, the loans can be collected in full. For all classes of loans, an impaired loan is defined as a loan for which it is probable that the lender will not collect all amounts due under the contractual terms of the loan. Loans for which the terms have been modified and for which the borrower is experiencing financial difficulties and the Company has granted a concession are considered troubled debt restructurings and are classified as impaired. For impaired, accruing loans, interest income is recognized on an accrual basis with cash offsetting the recorded accruals upon receipt. Interest received on non-accrual, impaired loans is applied against principal or interest according to management’s judgment as to the collectibility of the principal. Allowance for Loan Losses - The allowance for loan losses is a valuation allowance for probable incurred credit losses, increased by the provision for loan losses and recoveries, and decreased by charge-offs of loans. For all classes of loans, when a loan, in full or in part, is deemed uncollectible, it is charged against the allowance. This happens when it is past due and the borrower has not shown the ability or intent to make the loan current, or the borrower does not have sufficient assets to pay the debt, or the value of the collateral is less than the balance of the loan and is not considered likely to improve soon. The allowance for loan losses is determined by continuous analysis of the loan portfolio. That analysis includes changes in the size and composition of the portfolio, the Company’s own historical loan losses, industry-wide losses, current and anticipated economic trends, and details about individual loans. It also includes estimates of the actual value of collateral, other possible sources of repayment and estimates that are susceptible to significant changes due to changes in appraisal values of collateral, national and regional economic conditions and other factors. All loans over $250,000 in the commercial and industrial, commercial real estate and construction loan classes rated substandard or worse and all troubled debt restructurings are evaluated individually for impairment. All other loans are generally evaluated as homogeneous pools. In assessing the adequacy of the allowance, the Company reviews its loan portfolio by separate classes which have similar risk and collateral characteristics; e.g., commercial, commercial real estate, construction, residential mortgages, home equity, and consumer loans. The allowance for loan losses consists of specific and general components. The specific component relates to loans that are individually classified as impaired. Specific reserves are established based on an analysis of the most probable sources of repayment and liquidation of collateral. Impaired loans that are collateral dependent are reviewed based on their collateral and the estimated time required to recover the Company’s investment in the loan, as well as the cost of doing so, and the estimate of the recovery. Non-collateral dependent impaired loans are reviewed based on the present value of estimated future cash flows, including balloon payments, if any, using the loan’s effective interest rate. While every non-performing loan is evaluated individually, not every loan requires a specific reserve. Specific reserves fluctuate based on changes in the underlying loans, anticipated sources of repayment, and charge-offs. The general component covers non-classified loans and is based on historical loss experience for each loan class from a trailing seven-quarter period, (which period will continue to be expanded for future calculations) and modifying those percentages, if necessary, after adjusting for current qualitative and environmental factors that reflect changes in the collectibility of the loan class not captured by historical loss data. These factors augment actual loss experience and help estimate the probability of loss within the loan portfolio based on emerging or inherent risk trends. These qualitative factors are applied as an adjustment to historical loss rates and require judgments that cannot be subjected to exact mathematical calculation. There are no formulas for translating them into a specific basis point adjustment of the Company’s historical loss rate for a pool of loans having similar risk characteristics. These adjustments reflect management’s overall estimate of the extent to which current losses on a pool of loans will differ from historical loss experience. These adjustments are subjective estimates and management reviews them on a quarterly basis. Troubled debt restructurings are also considered impaired with impairment generally measured at the present value of estimated future cash flows using the loan’s effective rate at inception or using the fair value of collateral, less estimated costs to sell, if repayment is expected solely from the collateral. Loans Held-For-Sale – Loans held-for-sale are carried at the lower of aggregate cost or fair value. Changes in fair value of loans held-for-sale are recognized in earnings. Dividend Restriction - Banking regulations and the Bank’s agreement with the Office of the Comptroller of the Currency (“OCC”) require maintaining certain capital levels and impose limitations on dividends paid by the Bank to the Company and by the Company to stockholders. This is discussed further in “Regulatory Matters” in the Notes to the Condensed Consolidated Financial Statements. Reclassifications - Items in the prior period financial statements were reclassified to conform to the current presentation.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2012

Summary of Significant Accounting Policies [Abstract]

Summary of Significant Accounting Policies

(1) Summary of Significant Accounting Policies

The unaudited interim condensed consolidated financial statements include the accounts of Suffolk Bancorp (“Suffolk”) and its wholly owned subsidiary, Suffolk County National Bank and its subsidiaries (the “Bank”). Suffolk and the Bank are collectively referred to hereafter as the “Company.” All material intercompany accounts and transactions have been eliminated in consolidation. The unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) and predominant practices within the banking industry. They do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, please refer to the audited consolidated financial statements and footnotes thereto included in the Company’s 2011 Annual Report on Form 10-K. The following footnotes describe the Company’s most significant accounting policies. The results of operations for the three and nine months ended September 30, 2012 are not necessarily indicative of the results of operations to be expected for the remainder of the year.

Loans and Loan Interest Income Recognition - Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of unearned discounts, deferred loan fees and costs and an allowance for loan losses. Unearned discounts on installment loans are credited to income using methods that result in a level yield. Loan origination fees, net of certain direct origination costs, are deferred and recognized in interest income over the respective term of the loan without anticipating prepayments.

Interest income is accrued on the unpaid principal balance. Recognition of interest income is discontinued when reasonable doubt exists as to whether principal or interest due can be collected. For all classes of loans, loans generally no longer accrue interest when over 90 days past due unless the loan is well-secured and in process of collection. When a loan is placed on non-accrual status, all interest previously accrued, but not collected, is reversed against current-year interest income. Interest received on such loans is applied against principal or interest, according to management’s judgment as to the collectability of the principal, until qualifying for return to accrual status. Loans start accruing interest again when they become current as to principal and interest, and when, in the opinion of management, the loans can be collected in full. For all classes of loans, an impaired loan is defined as a loan for which it is probable that the lender will not collect all amounts due under the contractual terms of the loan. Loans for which the terms have been modified and for which the borrower is experiencing financial difficulties and the Company has granted a concession are considered troubled debt restructurings and are classified as impaired. For impaired, accruing loans, interest income is recognized on an accrual basis with cash offsetting the recorded accruals upon receipt. Interest received on non-accrual, impaired loans is applied against principal or interest according to management’s judgment as to the collectibility of the principal.

Allowance for Loan Losses - The allowance for loan losses is a valuation allowance for probable incurred credit losses, increased by the provision for loan losses and recoveries, and decreased by charge-offs of loans. For all classes of loans, when a loan, in full or in part, is deemed uncollectible, it is charged against the allowance. This happens when it is past due and the borrower has not shown the ability or intent to make the loan current, or the borrower does not have sufficient assets to pay the debt, or the value of the collateral is less than the balance of the loan and is not considered likely to improve soon. The allowance for loan losses is determined by continuous analysis of the loan portfolio. That analysis includes changes in the size and composition of the portfolio, the Company’s own historical loan losses, industry-wide losses, current and anticipated economic trends, and details about individual loans. It also includes estimates of the actual value of collateral, other possible sources of repayment and estimates that are susceptible to significant changes due to changes in appraisal values of collateral, national and regional economic conditions and other factors. All loans over $250,000 in the commercial and industrial, commercial real estate and construction loan classes rated substandard or worse and all troubled debt restructurings are evaluated individually for impairment. All other loans are generally evaluated as homogeneous pools. In assessing the adequacy of the allowance, the Company reviews its loan portfolio by separate classes which have similar risk and collateral characteristics; e.g., commercial, commercial real estate, construction, residential mortgages, home equity, and consumer loans.

The allowance for loan losses consists of specific and general components. The specific component relates to loans that are individually classified as impaired. Specific reserves are established based on an analysis of the most probable sources of repayment and liquidation of collateral. Impaired loans that are collateral dependent are reviewed based on their collateral and the estimated time required to recover the Company’s investment in the loan, as well as the cost of doing so, and the estimate of the recovery. Non-collateral dependent impaired loans are reviewed based on the present value of estimated future cash flows, including balloon payments, if any, using the loan’s effective interest rate. While every non-performing loan is evaluated individually, not every loan requires a specific reserve. Specific reserves fluctuate based on changes in the underlying loans, anticipated sources of repayment, and charge-offs. The general component covers non-classified loans and is based on historical loss experience for each loan class from a trailing seven-quarter period, (which period will continue to be expanded for future calculations) and modifying those percentages, if necessary, after adjusting for current qualitative and environmental factors that reflect changes in the collectibility of the loan class not captured by historical loss data. These factors augment actual loss experience and help estimate the probability of loss within the loan portfolio based on emerging or inherent risk trends. These qualitative factors are applied as an adjustment to historical loss rates and require judgments that cannot be subjected to exact mathematical calculation. There are no formulas for translating them into a specific basis point adjustment of the Company’s historical loss rate for a pool of loans having similar risk characteristics. These adjustments reflect management’s overall estimate of the extent to which current losses on a pool of loans will differ from historical loss experience. These adjustments are subjective estimates and management reviews them on a quarterly basis. Troubled debt restructurings are also considered impaired with impairment generally measured at the present value of estimated future cash flows using the loan’s effective rate at inception or using the fair value of collateral, less estimated costs to sell, if repayment is expected solely from the collateral.

Loans Held-For-Sale – Loans held-for-sale are carried at the lower of aggregate cost or fair value. Changes in fair value of loans held-for-sale are recognized in earnings.

Dividend Restriction - Banking regulations and the Bank’s agreement with the Office of the Comptroller of the Currency (“OCC”) require maintaining certain capital levels and impose limitations on dividends paid by the Bank to the Company and by the Company to stockholders. This is discussed further in “Regulatory Matters” in the Notes to the Condensed Consolidated Financial Statements.

Reclassifications - Items in the prior period financial statements were reclassified to conform to the current presentation.

- Definition

The entire disclosure for all significant accounting policies of the reporting entity.

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