STBA 10-Q Quarter ended Sept. 30, 2012

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q

(Mark One)

For the quarterly period ended September 30, 2012

OR

For the transition period from            To

Commission file number 000-12508

S&T BANCORP, INC.

(Exact name of registrant as specified in its charter)

800-325-2265

(Registrant’s telephone number, including area code)

Not Applicable

(Former name, former address, and former fiscal year, if changed since last report)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes x No ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (Section 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes x No ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definition of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ¨ No x

APPLICABLE ONLY TO CORPORATE ISSUERS:

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practical date.

Common Stock, $2.50 Par Value - 29,733,592 shares as of October 24, 2012

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INDEX

S&T BANCORP, INC. AND SUBSIDIARIES

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S&T BANCORP, INC. AND SUBSIDIARIES

See Notes to Consolidated Financial Statements

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S&T BANCORP, INC. AND SUBSIDIARIES

(Unaudited)

See Notes to Consolidated Financial Statements

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S&T BANCORP, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY

(Unaudited)

See Notes to Consolidated Financial Statements

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S&T BANCORP, INC. AND SUBSIDIARIES

(Unaudited)

See Notes to Consolidated Financial Statements

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S&T BANCORP, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

Principals 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 accounting principles generally accepted in the United States of America, or GAAP, 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, 2011, filed with the Securities and Exchange Commission, or SEC, on February 29, 2012. In the opinion of management, the accompanying interim financial information reflects all adjustments, including normal recurring adjustments, necessary to present fairly S&T’s financial position and 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 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

Technical Amendments and Corrections to SEC Sections

In August 2012, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2012-03, Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 114, Technical Amendments Pursuant to SEC Release No. 33-9250, and Corrections Related to FASB Accounting Standards Update 2010-22 (SEC Update), which were meant to codify various amendments and corrections included in these previously issued bulletins and releases. Since this is codification only of previously issued accounting guidance, it was adopted at September 30, 2012, and has not had an impact on our results of operations or financial position.

Presentation of Comprehensive Income

In December 2011, the FASB issued ASU No. 2011-12, which superseded certain pending paragraphs in ASU No. 2011-05. In June 2011, the FASB issued ASU No. 2011-05, the provisions of which allow an entity the option to present the total of comprehensive income, the components of net income and the components of other comprehensive income either in a single continuous statement of comprehensive income or in two separate but consecutive statements. Under both options, an entity is required to present each component of net income along with total net income, each component of other comprehensive income along with a total for other comprehensive income and a total amount for comprehensive income. ASU 2011-05 eliminates the option to present the components of other comprehensive income as part of the statement of changes in stockholders’ equity. ASU 2011-05 does not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income. ASU 2011-05 permits companies to present in the annual period the comprehensive income components in a single continuous statement or two consecutive statements and to present in the interim periods only the total for comprehensive income in a single continuous statement or two consecutive statements. ASU No. 2011-12 effectively defers changes that relate to the presentation of reclassification adjustments out of accumulated other comprehensive income. The amendments will be temporary to allow the FASB time to redeliberate the presentation requirements for reclassifications out of accumulated other comprehensive income for annual and interim financial statements. This amendment is effective at the same time as the amendments in ASU No. 2011-05. It should be applied retrospectively and is effective for public companies for fiscal years, and interim periods within those years, beginning after December 15, 2011. We have elected the option of a single continuous statement format for interim periods. ASU 2011-05 and ASU 2011-12 should be applied retrospectively and are effective for public companies for fiscal years, and interim periods within those years, beginning after December 15, 2011. The adoption of both ASU 2011-05 and 2011-12 has only impacted our presentation of comprehensive income and has not had an impact on our results of operations or financial position.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – continued

NOTE 1. BASIS OF PRESENTATION – continued

Testing Goodwill for Impairment

In September 2011, the FASB issued ASU No. 2011-08, which permits an entity to make a qualitative assessment of whether it is more likely than not that a reporting unit’s fair value is less than its carrying amount before applying the two-step goodwill impairment test. If an entity concludes it is not more likely than not that its fair value is less than its carrying amount, it need not perform the two-step impairment test. This ASU is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011. Early adoption is permitted. The adoption of this ASU has not had a material impact on our results of operations or financial position.

Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS

In May 2011, the FASB issued ASU No. 2011-04, which represents the convergence of the FASB’s and the International Accounting Standard Board’s, or IASB, guidance on fair value measurement. ASU 2011-04 reflects the common requirements under U.S. GAAP and international financial reporting standards, or IFRS, for measuring fair value and for disclosing information about fair value measurements, including a consistent meaning for the term “fair value.” The new guidance does not extend the use of fair value but, rather, provides guidance about how fair value should be applied where it is already required or permitted under U.S. GAAP or IFRS. For U.S. GAAP, most of the changes are clarifications of existing guidance or wording changes to align with IFRS 13 Fair Value Measurement. A public company is required to apply the ASU prospectively for interim and annual periods beginning after December 15, 2011. Early adoption is not permitted for a public company. The adoption of this ASU has impacted only disclosure requirements and did not have a material impact on our results of operations or financial position.

Reconsideration of Effective Control for Repurchase Agreements

In April 2011, the FASB issued ASU No. 2011-03, which is intended to improve financial reporting of repurchase agreements, or repos, and other agreements that both entitle and obligate a transferor to repurchase or redeem financial assets before their maturity. When an entity enters into a typical repo arrangement, it transfers financial assets to a counterparty in exchange for cash with an agreement for the counterparty to return the same or equivalent financial assets for a fixed price in the future. Current guidance prescribes when an entity may or may not recognize a sale upon the transfer of financial assets subject to a repo agreement. That determination is based, in part, on whether the entity has maintained effective control over the transferred financial assets. This ASU improves the accounting for these transactions by removing from the assessment of effective control the criterion requiring the transferor to have the ability to repurchase or redeem the financial assets and focuses the assessment on the transferor’s contractual rights. This guidance is effective for the first interim or annual period beginning on or after December 15, 2011. The guidance should be applied prospectively to transactions or modifications of existing transactions that occur on or after the effective date. Early adoption is not permitted. The adoption of this ASU did not have a material impact on our results of operations or financial position.

Recently Issued Accounting Standards Updates not yet Adopted

Testing Indefinite-Lived Intangible Assets for Impairment

In July 2012, the FASB issued ASU No. 2012-02, which permits an entity to first assess qualitative factors to determine whether it is more likely than not that an indefinite-lived intangible asset is impaired as a basis for determining whether it is necessary to perform the quantitative impairment test in accordance with Subtopic 350-30, Intangibles – Goodwill and Other – General Intangibles Other than Goodwill. The more-likely-than-not threshold is defined as having a likelihood of more than 50 percent. The guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012. Early adoption is permitted, including for annual and interim impairment tests performed as of a date before July 27, 2012, if a public entity’s financial statements for the most recent annual or interim period have not yet been issued. The adoption of this ASU is not expected to have a material impact on our results of operations or financial position.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – continued

Disclosures About Offsetting Assets and Liabilities

In December 2011, the FASB issued ASU, No. 2011-11, in conjunction with the issuance by the IASB, of amendments to Disclosures—Offsetting Financial Assets and Financial Liabilities (Amendments to IFRS 7). The disclosure requirements apply to recognized financial instruments and derivative instruments that are offset or subject to an enforceable master netting arrangement. An entity shall disclose information to enable users of its financial statements to evaluate the effect or potential effect of netting arrangements on its financial position, including the effect or potential effect of rights of setoff associated with recognized assets and recognized liabilities. While both the FASB and the IASB retained the existing offsetting models under U.S. GAAP and IFRS, the new standards require disclosures to allow investors to better compare financial statements prepared under U.S. GAAP with financial statements prepared under IFRS. The new standards are effective for annual periods beginning January 1, 2013, and interim periods within those annual periods. Retrospective application is required. The adoption of this ASU is expected to impact only our disclosure requirements and is not expected to have a material impact on our results of operations or financial position.

On August 13, 2012, we completed the acquisition of 100 percent of the voting shares of Gateway Bank of Pennsylvania, or Gateway, located in McMurray, Pennsylvania. The acquisition expanded our market share and footprint into Washington County, Pennsylvania. Gateway shareholders were entitled to receive $3.08 in cash and 0.4657 shares of S&T common stock in exchange for one share of Gateway common stock.

Gateway will operate as a separate wholly-owned subsidiary of S&T and all transactions since the acquisition date are consolidated in our financial statements. Cash paid to former Gateway shareholders was $5.2 million and the fair value of common shares issued was $13.3 million. We also settled outstanding equity awards for $1.0 million. As of September 30, 2012, S&T recognized Goodwill of $3.8 million from the Gateway acquisition.

On March 9, 2012, we completed the acquisition of 100 percent of the voting shares of Mainline Bancorp, Inc., or Mainline, located in Ebensburg, Pennsylvania, which was the sole shareholder of Mainline National Bank. The acquisition expanded our market share and footprint throughout Cambria and Blair Counties of Western Pennsylvania. Mainline shareholders were entitled to elect to receive for each share of Mainline common stock either $69.00 in cash or 3.6316 shares of S&T common stock. We also purchased Mainline’s preferred stock issued under the U.S. Treasury Capital Purchase Program, or CPP, for $4.7 million on March 9, 2012. The preferred stock was purchased and retired as part of the merger transaction. The measurement period for the Mainline acquisition ends March 9, 2013. Based on new information received about facts and circumstances that existed as of the acquisition date one measurement period adjustment for $0.5 million was recorded relating to a contingent liability for an IRS proposed penalty for tax year 2010. Cash paid to former Mainline shareholders was $8.2 million and the fair value of common shares issued was to $14.8 million. As of September 30, 2012, S&T recognized Goodwill of $6.7 million from the Mainline acquisition.

Both acquisitions were accounted for under the acquisition method of accounting, and all transactions since the acquisition dates are included in our consolidated financial statements. The assets acquired and liabilities assumed were recorded at their respective fair values and represent management’s estimates based on available information.

Goodwill was calculated as the excess of the consideration exchanged over the net identifiable assets acquired from each acquisition and will not be deductible for tax purposes. Goodwill from both acquisitions was assigned to our Community Banking segment.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – continued

The following table summarizes total consideration, assets acquired and liabilities assumed as of September 30, 2012 for both the Mainline and Gateway acquisitions: