Basis of Presentation	6 Months Ended
Jun. 30, 2014
Accounting Policies [Abstract]
Basis of Presentation	BASIS OF PRESENTATION Principles of Consolidation The interim Consolidated Financial Statements include the accounts of S&T Bancorp, Inc., or S&T, and its wholly owned subsidiaries. All significant intercompany transactions have been eliminated in consolidation. Investments of 20 percent to 50 percent of the outstanding common stock of investees are accounted for using the equity method of accounting. Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements of S&T have been prepared in accordance with generally accepted accounting principles, or GAAP, in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with our annual report on Form 10-K for the year ended December 31, 2013, filed with the Securities and Exchange Commission, or SEC, on February 21, 2014. In the opinion of management, the accompanying interim financial information reflects all adjustments, including normal recurring adjustments, necessary to present fairly our financial position and the results of operations for each of the interim periods presented. Results of operations for interim periods are not necessarily indicative of the results of operations that may be expected for a full year or any future period. Reclassification Certain amounts in the prior periods’ financial statements and footnotes have been reclassified to conform to the current period’s presentation. The reclassifications had no significant effect on our results of operations or financial condition. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates. Recently Adopted Accounting Standards Updates, or ASU Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Tax Credit Carry forward Exists In July 2013, the Financial Accounting Standards Board (FASB) issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Tax Credit Carry forward Exists. The ASU requires that entities should present an unrecognized tax benefit as a reduction of the deferred tax asset for a net operating loss, or NOL, or similar tax loss or tax credit carry forward rather than as a liability when the uncertain tax position would reduce the NOL or other carry forward under the tax law. The new standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013, and should be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The adoption of this ASU had no impact on our results of operations or financial position. Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date In February 2013, the FASB issued ASU No. 2013-04, Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date. The ASU requires the measurement of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of the amount the reporting entity agreed to pay on the basis of its arrangement with its co-obligors as well as any additional amount that the entity expects to pay on behalf of its co-obligors. The new standard is effective retrospectively for fiscal years and interim periods within those years, beginning after December 15, 2013, and early adoption is permitted. The adoption of this ASU had no impact on our results of operations or financial position. Recently Issued Accounting Standards Updates not yet Adopted Share-Based Payment Awards with Performance Targets In June 2014, the FASB issued ASU No. 2014-12, Share-Based Payment Awards with Performance Targets. The main provisions of ASU 2014-12 require that a performance target included in a share-based payment award that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. Therefore, under the existing stock compensation guidance in Topic 718, the performance target should not be reflected in estimating the grant-date fair value of the award. The standard is effective for annual periods and interim periods beginning after December 15, 2015. We do not expect that this ASU will have a material impact on our results of operations or financial position. Repurchase-To-Maturity Transactions, Repurchase Financings and New Disclosures In June 2014, the FASB issued ASU No. 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and New Disclosures to change the accounting for repurchase-to-maturity transactions and certain linked repurchase financings. This will result in accounting for both types of arrangements as secured borrowings on the balance sheet and require new disclosures to (i) increase transparency about the types of collateral pledged in secured borrowing transactions and (ii) enable users to better understand transactions in which the transferor retains substantially all of the exposure to the economic return on the transferred financial asset throughout the term of the transaction. The disclosure for repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions accounted for as secured borrowings is required to be presented for annual periods beginning after December 15, 2014, and for interim periods beginning after March 15, 2015. All other accounting and disclosure amendments in the ASU are effective for the first interim or annual period beginning after December 15, 2014. Earlier application for a public business entity is prohibited. We do not expect that this ASU will have a material impact on our results of operations or financial position. Revenues from Contracts with Customers In May 2014, the FASB issued ASU No. 2014-09, Revenues from Contracts with Customers. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2016. The provisions do not apply to lease contracts, insurance contracts, financial instruments and other contractual rights or obligations (e.g. receivables, debt and equity securities, liabilities, debt, derivatives transfers, and servicing, etc.), guarantees, or non-monetary exchanges between entities. We are currently evaluating the impact of the adoption of this pronouncement on our consolidated financial statements. Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity In April 2014, the FASB issued ASU No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, which changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. The guidance applies to all entities that dispose of components. It will significantly change current practices for assessing discontinued operations and affect an entity’s income and earnings per share from continuing operations. An entity is required to reclassify assets and liabilities of a discontinued operation that are classified as held for sale or disposed of in the current period for all comparative periods presented. The ASU requires that an entity present in the statement of cash flows or disclose in a note either total operating and investing cash flows for discontinued operations, or depreciation, amortization, capital expenditures and significant operating and investing noncash items related to discontinued operations. Additional disclosures are required when an entity retains significant continuing involvement with a discontinued operation after its disposal, including the amount of cash flows to and from a discontinued operation. The new standard applies prospectively after the effective date of December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position. Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure In January 2014, the FASB issued ASU No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure. The ASU clarifies that an in substance repossession or foreclosure has occurred and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure. Interim and annual disclosure is required of both the amount of foreclosed residential real estate property held by the creditor and the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The new standard is effective using either the modified retrospective transition method or a prospective transition method for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position. Accounting for Investments in Qualified Affordable Housing Projects In January 2014, the FASB issued ASU No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects. The ASU permits reporting entities to make an accounting policy election to account for investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. The proportional amortization method permits the amortization of the initial cost of the investment in proportion to the tax credits and other tax benefits received, and recognizes the net investment performance in the income statement as a component of income tax expense (benefit). The new standard is effective retrospectively for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position.

BASIS OF PRESENTATION

Principles of Consolidation

The interim Consolidated Financial Statements include the accounts of S&T Bancorp, Inc., or S&T, and its wholly owned subsidiaries. All significant intercompany transactions have been eliminated in consolidation. Investments of 20 percent to 50 percent of the outstanding common stock of investees are accounted for using the equity method of accounting.

Basis of Presentation

The accompanying unaudited interim Consolidated Financial Statements of S&T have been prepared in accordance with generally accepted accounting principles, or GAAP, in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with our annual report on Form 10-K for the year ended December 31, 2013, filed with the Securities and Exchange Commission, or SEC, on February 21, 2014. In the opinion of management, the accompanying interim financial information reflects all adjustments, including normal recurring adjustments, necessary to present fairly our financial position and the results of operations for each of the interim periods presented. Results of operations for interim periods are not necessarily indicative of the results of operations that may be expected for a full year or any future period.

Reclassification

Certain amounts in the prior periods’ financial statements and footnotes have been reclassified to conform to the current period’s presentation. The reclassifications had no significant effect on our results of operations or financial condition.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.

Recently Adopted Accounting Standards Updates, or ASU

Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Tax Credit Carry forward Exists

In July 2013, the Financial Accounting Standards Board (FASB) issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Tax Credit Carry forward Exists. The ASU requires that entities should present an unrecognized tax benefit as a reduction of the deferred tax asset for a net operating loss, or NOL, or similar tax loss or tax credit carry forward rather than as a liability when the uncertain tax position would reduce the NOL or other carry forward under the tax law. The new standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013, and should be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The adoption of this ASU had no impact on our results of operations or financial position.

Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date

In February 2013, the FASB issued ASU No. 2013-04, Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date. The ASU requires the measurement of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of the amount the reporting entity agreed to pay on the basis of its arrangement with its co-obligors as well as any additional amount that the entity expects to pay on behalf of its co-obligors. The new standard is effective retrospectively for fiscal years and interim periods within those years, beginning after December 15, 2013, and early adoption is permitted. The adoption of this ASU had no impact on our results of operations or financial position.

Recently Issued Accounting Standards Updates not yet Adopted

Share-Based Payment Awards with Performance Targets

In June 2014, the FASB issued ASU No. 2014-12, Share-Based Payment Awards with Performance Targets. The main provisions of ASU 2014-12 require that a performance target included in a share-based payment award that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. Therefore, under the existing stock compensation guidance in Topic 718, the performance target should not be reflected in estimating the grant-date fair value of the award. The standard is effective for annual periods and interim periods beginning after December 15, 2015. We do not expect that this ASU will have a material impact on our results of operations or financial position.

Repurchase-To-Maturity Transactions, Repurchase Financings and New Disclosures

In June 2014, the FASB issued ASU No. 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and New Disclosures to change the accounting for repurchase-to-maturity transactions and certain linked repurchase financings. This will result in accounting for both types of arrangements as secured borrowings on the balance sheet and require new disclosures to (i) increase transparency about the types of collateral pledged in secured borrowing transactions and (ii) enable users to better understand transactions in which the transferor retains substantially all of the exposure to the economic return on the transferred financial asset throughout the term of the transaction. The disclosure for repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions accounted for as secured borrowings is required to be presented for annual periods beginning after December 15, 2014, and for interim periods beginning after March 15, 2015. All other accounting and disclosure amendments in the ASU are effective for the first interim or annual period beginning after December 15, 2014. Earlier application for a public business entity is prohibited. We do not expect that this ASU will have a material impact on our results of operations or financial position.

Revenues from Contracts with Customers

In May 2014, the FASB issued ASU No. 2014-09, Revenues from Contracts with Customers. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2016. The provisions do not apply to lease contracts, insurance contracts, financial instruments and other contractual rights or obligations (e.g. receivables, debt and equity securities, liabilities, debt, derivatives transfers, and servicing, etc.), guarantees, or non-monetary exchanges between entities. We are currently evaluating the impact of the adoption of this pronouncement on our consolidated financial statements.

Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity

In April 2014, the FASB issued ASU No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, which changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. The guidance applies to all entities that dispose of components. It will significantly change current practices for assessing discontinued operations and affect an entity’s income and earnings per share from continuing operations. An entity is required to reclassify assets and liabilities of a discontinued operation that are classified as held for sale or disposed of in the current period for all comparative periods presented. The ASU requires that an entity present in the statement of cash flows or disclose in a note either total operating and investing cash flows for discontinued operations, or depreciation, amortization, capital expenditures and significant operating and investing noncash items related to discontinued operations. Additional disclosures are required when an entity retains significant continuing involvement with a discontinued operation after its disposal, including the amount of cash flows to and from a discontinued operation. The new standard applies prospectively after the effective date of December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position.

Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure

In January 2014, the FASB issued ASU No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure. The ASU clarifies that an in substance repossession or foreclosure has occurred and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure. Interim and annual disclosure is required of both the amount of foreclosed residential real estate property held by the creditor and the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The new standard is effective using either the modified retrospective transition method or a prospective transition method for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position.

Accounting for Investments in Qualified Affordable Housing Projects

In January 2014, the FASB issued ASU No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects. The ASU permits reporting entities to make an accounting policy election to account for investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. The proportional amortization method permits the amortization of the initial cost of the investment in proportion to the tax credits and other tax benefits received, and recognizes the net investment performance in the income statement as a component of income tax expense (benefit). The new standard is effective retrospectively for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption is permitted. We do not expect that this ASU will have a material impact on our results of operations or financial position.