Basis of Presentation	3 Months Ended
Mar. 31, 2011
Basis of Presentation [Abstract]
Basis of Presentation	1. Basis of Presentation In this report, the words "the Company," "we," "us," and "our" refer to the combined entities of Southside Bancshares, Inc. and its subsidiaries. The words "Southside" and "Southside Bancshares" refer to Southside Bancshares, Inc. The words "Southside Bank" and "the Bank" refer to Southside Bank (which, subsequent to the internal merger of Fort Worth National Bank ("FWNB") with and into Southside Bank, includes FWNB). "FWBS" refers to Fort Worth Bancshares, Inc., a bank holding company acquired by Southside of which FWNB was a wholly-owned subsidiary. "SFG" refers to Southside Financial Group, LLC, of which Southside owns a 50% interest and consolidates for financial reporting. The consolidated balance sheet as of March 31, 2011, and the related consolidated statements of income, equity and cash flows and notes to the financial statements for the three month period ended March 31, 2011 and 2010 are unaudited; in the opinion of management, all adjustments necessary for a fair statement of such financial statements have been included. Such adjustments consisted only of normal recurring items. All significant intercompany accounts and transactions are eliminated in consolidation. The preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles ("GAAP") requires the use of management's estimates. These estimates are subjective in nature and involve matters of judgment. Actual amounts could differ from these estimates. Interim results are not necessarily indicative of results for a full year. These financial statements should be read in conjunction with the financial statements and notes thereto in our Annual Report on Form 10-K for the year ended December 31, 2010. All share data has been adjusted to give retroactive recognition to stock splits and stock dividends. Summary of Significant Accounting and Reporting Policies Securities Carried at Fair Value through Income. Debt securities purchased at significant premiums that contain an embedded derivative where the embedded derivative is not readily identifiable and measurable and as such cannot be bifurcated, are classified as securities carried at fair value through income. Fair value is determined using quoted market prices. If quoted market prices are not available, fair values are based on quoted market prices for similar securities or estimates from independent pricing services. Changes in fair value are reported through the income statement as fair value gain (loss) - securities. FHLB Advance Option Fees. Option fees paid to the FHLB giving us the option to enter into long-term advance commitments at specified interest rates in the future are capitalized and reviewed for impairment. Once the option is exercised, the FHLB advance option fee is amortized over the term of the advance as interest expense. For a description of our other significant accounting and reporting policies, refer to Note 1 of the Notes to Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2010. Accounting Standards ASU No. 2010-06, "Fair Value Measurements and Disclosures (Topic 820) - Improving Disclosures About Fair Value Measurements." ASU 2010-06 requires expanded disclosures related to fair value measurements including (i) the amounts of significant transfers of assets or liabilities between Levels 1 and 2 of the fair value hierarchy and the reasons for the transfers, (ii) the reasons for transfers of assets or liabilities in or out of Level 3 of the fair value hierarchy, with significant transfers disclosed separately, (iii) the policy for determining when transfers between levels of the fair value hierarchy are recognized and (iv) for recurring fair value measurements of assets and liabilities in Level 3 of the fair value hierarchy, a gross presentation of information about purchases, sales, issuances and settlements. ASU 2010-06 further clarifies that (i) fair value measurement disclosures should be provided for each class of assets and liabilities (rather than major category), which would generally be a subset of assets or liabilities within a line item in the statement of financial position and (ii) company should provide disclosures about the valuation techniques and inputs used to measure fair value for both recurring and nonrecurring fair value measurements for each class of assets and liabilities included in Levels 2 and 3 of the fair value hierarchy. The disclosures related to the gross presentation of purchases, sales, issuances and settlements of assets and liabilities included in Level 3 of the fair value hierarchy became effective for us on January 1, 2011. The remaining disclosure requirements and clarifications made by ASU 2010-06 became effective for us on January 1, 2010. See Note 9 - Fair Value Measurements. ASU No. 2010-18 "Effect of a Loan Modification When the Loan Is Part of a Pool That Is Accounted for as a Single Asset". ASU 2010-18 provides that modifications of loans that are accounted for within a pool do not result in the removal of those loans from the pool even if the modification of those loans would otherwise be considered a troubled debt restructuring. An entity will continue to be required to consider whether the pool of assets in which the loan is included is impaired if expected cash flows for the pool change. ASU 2010-18 does not affect the accounting for loans that are not accounted for within pools. Loans accounted for individually continue to be subject to the troubled debt restructuring accounting provisions. ASU 2010-18 is effective prospectively for modifications of loans accounted for within pools occurring in the first interim or annual period ending on or after July 15, 2010. Early application is permitted. Upon initial adoption of ASU 2010-18, an entity may make a one-time election to terminate accounting for loans as a pool. This election may be applied on a pool-by-pool basis and does not preclude an entity from applying pool accounting to subsequent acquisitions of loans with credit deterioration. The provisions of ASU 2010-18 did not have a significant impact on our consolidated financial statements. ASU No. 2010-20, "Receivables (Topic 310) - Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses." ASU 2010-20 requires entities to provide disclosures designed to facilitate financial statement users' evaluation of (i) the nature of credit risk inherent in the entity's portfolio of financing receivables, (ii) how that risk is analyzed and assessed in arriving at the allowance for credit losses and (iii) the changes and reasons for those changes in the allowance for credit losses. Disclosures must be disaggregated by portfolio segment, the level at which an entity develops and documents a systematic method for determining its allowance for credit losses, and class of financing receivable, which is generally a disaggregation of portfolio segment. The required disclosures include, among other things, a roll forward of the allowance for credit losses as well as information about modified, impaired, non-accrual and past due loans and credit quality indicators. ASU 2010-20 became effective for our financial statements as of December 31, 2010, as it relates to disclosures required as of the end of a reporting period. Disclosures that relate to activity during a reporting period became effective for our financial statements that include periods on or after January 1, 2011. ASU No. 2010-28, "Intangibles - Goodwill and Other (Topic 350) - When to Perform Step 2 of the Goodwill Impairment Test for Reporting Units with Zero or Negative Carrying Amounts." ASU 2010-28 modifies Step 1 of the goodwill impairment test for reporting units with zero or negative carrying amounts. For those reporting units, an entity is required to perform Step 2 of the goodwill impairment test if it is more likely than not that a goodwill impairment exists. In determining whether it is more likely than not that a goodwill impairment exists, an entity should consider whether there are any adverse qualitative factors indicating that an impairment may exist such as if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The provisions of ASU 2010-28 became effective on January 1, 2011 and did not have a significant impact on our financial statements. ASU No. 2011-01, "Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings in Update No. 2010-20 (Topic 310)", was issued January 2011 deferring the new disclosure requirements (paragraphs 310-10-50-31 through 50-34 of the FASB Accounting Standards Codification) about troubled debt restructurings to be concurrent with the effective date of the guidance for determining what constitutes a troubled debt restructuring, as presented in proposed Accounting Standards Update, Receivables (Topic 310): Clarifications to Accounting for Troubled Debt Restructurings by Creditors. As a result of the issuance of Update 2011-02, the provisions of Update 2011-01 are effective for the first interim or annual period beginning on or after June 15, 2011 or September 30, 2011, and should be applied retrospectively to the beginning of the annual period of adoption. We do not expect the adoption of the Update to have a material effect on our financial statements at the date of adoption. ASU No. 2011-02, "Receivables (Topic 310) - A Creditor's Determination of Whether a Restructuring Is a Troubled Debt Restructuring." ASU 2011-02 clarifies which loan modifications constitute troubled debt restructurings and is intended to assist creditors in determining whether a modification of the terms of a receivable meets the criteria to be considered a troubled debt restructuring, both for purposes of recording an impairment loss and for disclosure of troubled debt restructurings. In evaluating whether a restructuring constitutes a troubled debt restructuring, a creditor must separately conclude, under the guidance clarified by ASU 2011-02, that both of the following exist: (a) the restructuring constitutes a concession; and (b) the debtor is experiencing financial difficulties. ASU 2011-02 will be effective on July 1, 2011, and applies retrospectively to restructurings occurring on or after January 1, 2011. Adoption of ASU 2011-02 is not expected have a significant impact on our financial statements.

1. Basis of Presentation

In this report, the words "the Company," "we," "us," and "our" refer to the combined entities of Southside Bancshares, Inc. and its subsidiaries. The words "Southside" and "Southside Bancshares" refer to Southside Bancshares, Inc. The words "Southside Bank" and "the Bank" refer to Southside Bank (which, subsequent to the internal merger of Fort Worth National Bank ("FWNB") with and into Southside Bank, includes FWNB). "FWBS" refers to Fort Worth Bancshares, Inc., a bank holding company acquired by Southside of which FWNB was a wholly-owned subsidiary. "SFG" refers to Southside Financial Group, LLC, of which Southside owns a 50% interest and consolidates for financial reporting.

The consolidated balance sheet as of March 31, 2011, and the related consolidated statements of income, equity and cash flows and notes to the financial statements for the three month period ended March 31, 2011 and 2010 are unaudited; in the opinion of management, all adjustments necessary for a fair statement of such financial statements have been included. Such adjustments consisted only of normal recurring items. All significant intercompany accounts and transactions are eliminated in consolidation. The preparation of these consolidated financial statements in conformity with U.S. generally accepted accounting principles ("GAAP") requires the use of management's estimates. These estimates are subjective in nature and involve matters of judgment. Actual amounts could differ from these estimates.

Interim results are not necessarily indicative of results for a full year. These financial statements should be read in conjunction with the financial statements and notes thereto in our Annual Report on Form 10-K for the year ended December 31, 2010. All share data has been adjusted to give retroactive recognition to stock splits and stock dividends.

Summary of Significant Accounting and Reporting Policies

Securities Carried at Fair Value through Income. Debt securities purchased at significant premiums that contain an embedded derivative where the embedded derivative is not readily identifiable and measurable and as such cannot be bifurcated, are classified as securities carried at fair value through income. Fair value is determined using quoted market prices. If quoted market prices are not available, fair values are based on quoted market prices for similar securities or estimates from independent pricing services. Changes in fair value are reported through the income statement as fair value gain (loss) - securities.

FHLB Advance Option Fees. Option fees paid to the FHLB giving us the option to enter into long-term advance commitments at specified interest rates in the future are capitalized and reviewed for impairment. Once the option is exercised, the FHLB advance option fee is amortized over the term of the advance as interest expense.

For a description of our other significant accounting and reporting policies, refer to Note 1 of the Notes to Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2010.

Accounting Standards

ASU No. 2010-06, "Fair Value Measurements and Disclosures (Topic 820) - Improving Disclosures About Fair Value Measurements." ASU 2010-06 requires expanded disclosures related to fair value measurements including (i) the amounts of significant transfers of assets or liabilities between Levels 1 and 2 of the fair value hierarchy and the reasons for the transfers, (ii) the reasons for transfers of assets or liabilities in or out of Level 3 of the fair value hierarchy, with significant transfers disclosed separately, (iii) the policy for determining when transfers between levels of the fair value hierarchy are recognized and (iv) for recurring fair value measurements of assets and liabilities in Level 3 of the fair value hierarchy, a gross presentation of information about purchases, sales, issuances and settlements. ASU 2010-06 further clarifies that (i) fair value measurement disclosures should be provided for each class of assets and liabilities (rather than major category), which would generally be a subset of assets or liabilities within a line item in the statement of financial position and (ii) company should provide disclosures about the valuation techniques and inputs used to measure fair value for both recurring and nonrecurring fair value measurements for each class of assets and liabilities included in Levels 2 and 3 of the fair value hierarchy. The disclosures related to the gross presentation of purchases, sales, issuances and settlements of assets and liabilities included in Level 3 of the fair value hierarchy became effective for us on January 1, 2011. The remaining disclosure requirements and clarifications made by ASU 2010-06 became effective for us on January 1, 2010. See Note 9 - Fair Value Measurements.

ASU No. 2010-18 "Effect of a Loan Modification When the Loan Is Part of a Pool That Is Accounted for as a Single Asset". ASU 2010-18 provides that modifications of loans that are accounted for within a pool do not result in the removal of those loans from the pool even if the modification of those loans would otherwise be considered a troubled debt restructuring. An entity will continue to be required to consider whether the pool of assets in which the loan is included is impaired if expected cash flows for the pool change. ASU 2010-18 does not affect the accounting for loans that are not accounted for within pools. Loans accounted for individually continue to be subject to the troubled debt restructuring accounting provisions. ASU 2010-18 is effective prospectively for modifications of loans accounted for within pools occurring in the first interim or annual period ending on or after July 15, 2010. Early application is permitted. Upon initial adoption of ASU 2010-18, an entity may make a one-time election to terminate accounting for loans as a pool. This election may be applied on a pool-by-pool basis and does not preclude an entity from applying pool accounting to subsequent acquisitions of loans with credit deterioration. The provisions of ASU 2010-18 did not have a significant impact on our consolidated financial statements.

ASU No. 2010-20, "Receivables (Topic 310) - Disclosures about the Credit Quality of Financing Receivables and the Allowance for Credit Losses." ASU 2010-20 requires entities to provide disclosures designed to facilitate financial statement users' evaluation of (i) the nature of credit risk inherent in the entity's portfolio of financing receivables, (ii) how that risk is analyzed and assessed in arriving at the allowance for credit losses and (iii) the changes and reasons for those changes in the allowance for credit losses. Disclosures must be disaggregated by portfolio segment, the level at which an entity develops and documents a systematic method for determining its allowance for credit losses, and class of financing receivable, which is generally a disaggregation of portfolio segment. The required disclosures include, among other things, a roll forward of the allowance for credit losses as well as information about modified, impaired, non-accrual and past due loans and credit quality indicators. ASU 2010-20 became effective for our financial statements as of December 31, 2010, as it relates to disclosures required as of the end of a reporting period. Disclosures that relate to activity during a reporting period became effective for our financial statements that include periods on or after January 1, 2011.

ASU No. 2010-28, "Intangibles - Goodwill and Other (Topic 350) - When to Perform Step 2 of the Goodwill Impairment Test for Reporting Units with Zero or Negative Carrying Amounts." ASU 2010-28 modifies Step 1 of the goodwill impairment test for reporting units with zero or negative carrying amounts. For those reporting units, an entity is required to perform Step 2 of the goodwill impairment test if it is more likely than not that a goodwill impairment exists. In determining whether it is more likely than not that a goodwill impairment exists, an entity should consider whether there are any adverse qualitative factors indicating that an impairment may exist such as if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The provisions of ASU 2010-28 became effective on January 1, 2011 and did not have a significant impact on our financial statements.

ASU No. 2011-01, "Deferral of the Effective Date of Disclosures about Troubled Debt Restructurings in Update No. 2010-20 (Topic 310)", was issued January 2011 deferring the new disclosure requirements (paragraphs 310-10-50-31 through 50-34 of the FASB Accounting Standards Codification) about troubled debt restructurings to be concurrent with the effective date of the guidance for determining what constitutes a troubled debt restructuring, as presented in proposed Accounting Standards Update, Receivables (Topic 310): Clarifications to Accounting for Troubled Debt Restructurings by Creditors. As a result of the issuance of Update 2011-02, the provisions of Update 2011-01 are effective for the first interim or annual period beginning on or after June 15, 2011 or September 30, 2011, and should be applied retrospectively to the beginning of the annual period of adoption. We do not expect the adoption of the Update to have a material effect on our financial statements at the date of adoption.

ASU No. 2011-02, "Receivables (Topic 310) - A Creditor's Determination of Whether a Restructuring Is a Troubled Debt Restructuring." ASU 2011-02 clarifies which loan modifications constitute troubled debt restructurings and is intended to assist creditors in determining whether a modification of the terms of a receivable meets the criteria to be considered a troubled debt restructuring, both for purposes of recording an impairment loss and for disclosure of troubled debt restructurings. In evaluating whether a restructuring constitutes a troubled debt restructuring, a creditor must separately conclude, under the guidance clarified by ASU 2011-02, that both of the following exist: (a) the restructuring constitutes a concession; and (b) the debtor is experiencing financial difficulties. ASU 2011-02 will be effective on July 1, 2011, and applies retrospectively to restructurings occurring on or after January 1, 2011. Adoption of ASU 2011-02 is not expected have a significant impact on our financial statements.