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.

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 the audited Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2019, filed with the Securities and Exchange Commission, or SEC, on March 2, 2020. In the opinion of management, the accompanying interim financial information reflects all adjustments, consisting of 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.

In August 2018, the Financial Accounting Standards Board, or FASB, issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The amendments in this ASU apply to an entity that is a customer in a hosting arrangement that is a service contract. These amendments relate to accounting for implementation costs (e.g., implementation, setup and other upfront costs). These amendments require an entity in a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which costs to capitalize and which costs to expense. These amendments require the entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. This ASU is effective for annual and interim periods beginning after December 15, 2019. We adopted this ASU on January 1, 2020. The amendments in this ASU did not materially impact our Consolidated Balance Sheets or Consolidated Statements of Comprehensive Income.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement - Changes to the Disclosure Requirements for Fair Value Measurement. The amendments in this ASU remove certain disclosures from Topic 820, modify disclosures and/or require additional disclosures. The amendments in this Update required us to change our Fair Value disclosures beginning with the disclosures included in this Form 10-Q for the period ended March 31, 2020. We adopted this ASU on January 1, 2020. The amendments in this ASU did not materially impact our Consolidated Balance Sheets or Consolidated Statements of Comprehensive Income. Refer to Note 4. Fair Value Measurements.

In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment (Topic 350). The main objective of this ASU is to simplify the current requirements for testing goodwill for impairment by eliminating step two from the goodwill impairment test. The amendments are expected to reduce the complexity and costs associated with performing the goodwill impairment test, which could result in recording impairment charges sooner. This Update is effective for any interim and annual impairment tests in reporting periods in fiscal years beginning after December 15, 2019. We adopted the amendments of this ASU on January 1, 2020. The amendments in this ASU did not have any impact on our Consolidated Balance Sheets or Consolidated Statements of Comprehensive Income.

On January 1, 2020, we adopted ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which replaces the incurred loss methodology for determining our provision for credit losses, and allowance for credit losses, or ACL, with an expected loss methodology that is referred to as the Current Expected Credit Loss, or CECL, model. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including our loans and off-balance sheet credit exposures. In addition, ASU 2016-13 made changes to the accounting for available-for-sale debt securities. Credit losses related to available-for-sale debt securities (regardless of whether the impairment is considered to be other-than-temporary) will be measured in a manner similar to the present, except that such losses will be recorded as allowances rather than as reductions in the amortized cost of the related securities.

We adopted ASU 2016-13 using the modified retrospective method for all financial assets measured at amortized cost and off-balance sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASU 2016-13 while prior period amounts continue to be reported in accordance with previously applicable GAAP.

In connection with our adoption of ASU 2016-13, we made changes to our loan portfolio segments to align with the methodology applied in determining the allowance under CECL. Refer to Note 7 Allowance for Credit Losses for further discussion of these portfolio segments. Our new segmentation breaks out business banking loans from our other loan segments: Commercial Real Estate, or CRE, Commercial and Industrial, or C&I , Commercial Construction, Consumer Real Estate and Other Consumer. Business banking loans are commercial loans made to small businesses that are standard, non-complex products and evaluated through a streamlined credit approval process that has been designed to maximize efficiency while maintaining high credit quality standards.



	January 1, 2020
(dollars in thousands)	As Reported Under ASU 2016-13				Pre-ASU 2016-13				Impact of ASU 2016-13 Adoption
Assets:
Loans held for investment (outstanding balance)
Commercial real estate		$	2,946,319			$	3,416,518			$	(470,199	)
Commercial and industrial		1,458,541				1,720,833				(262,292		)
Commercial construction		345,263				375,445				(30,182		)
Business banking		1,092,908				—				1,092,908
Consumer real estate		1,235,352				1,545,323				(309,971		)
Other consumer		58,769				79,033				(20,264		)
Allowance for credit losses on loans		(89,577		)		(62,224		)		(27,353		)
Total loans held for investment, net		$	7,047,575			$	7,074,928			$	(27,353	)
Net deferred tax asset		$	19,317			$	13,206			$	6,111
Liabilities:
Allowance for credit losses on unfunded loan commitments		$	4,462			$	3,113			$	1,349
Equity:
Retained earnings		$	738,493			$	761,083			$	(22,590	)

The adoption of ASU 2016-13 resulted in an increase to our ACL of $27.4 million on January 1, 2020. The increase included $8.2 million for S&T legacy loans and $9.3 million for acquired loans from the DNB merger. Under the previously applicable accounting guidance, a credit reserve was not recorded for acquired loans upon acquisition, however, ASU 2016-13 requires an ACL to be recognized for acquired loan similar to originated loans. We also recorded a day one adjustment of $9.9 million primarily related to a Commercial and Industrial, or C&I, relationship that was charged off in the first quarter of 2020. We obtained information on the relationship subsequent to filing our December 31, 2019 Form 10-K, but before the end of the first quarter of 2020. The updated information supported a loss existed at January 1, 2020. As of January 1, 2020, we recorded a cumulative-effect adjustment of $22.6 million to decrease retained earnings related to the adoption of ASU 2016-13.

The ACL is a valuation reserve established and maintained by charges against operating income and is deducted from the amortized cost basis of loans to present the net amount expected to be collected on the loans. Loans, or portions thereof, are charged off against the ACL when they are deemed uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. The ACL is an estimate of expected credit losses, measured over the contractual life of a loan, that considers our historical loss experience, current conditions and forecasts of future economic conditions. Determination of an appropriate ACL is inherently subjective and may have significant changes from period to period.

The ACL for homogeneous loans is calculated using a life-time loss rate methodology with both a quantitative and a qualitative analysis that is applied on a quarterly basis. The ACL model is comprised of six distinct portfolio segments: 1) Construction, 2) Commercial Real Estate, or CRE, 3) C&I, 4) Business Banking, 5) Consumer Real Estate and 6) Other Consumer. Each segment has a distinct set of risk characteristics monitored by management. We further evaluate the ACL at a disaggregated level which includes type of collateral, loan participations, non-owner occupied and our internal risk rating system for the commercial segments and type of collateral, lien position, and FICO score, for the consumer segments. Historical credit loss experience is the basis for the estimation of expected credit losses. We apply historical loss rates to pools of loans with similar risk characteristics. After consideration of the historic loss calculation, management applies qualitative adjustments to reflect the current conditions and reasonable and supportable forecasts not already reflected in the historical loss information at the balance sheet date. Our reasonable and supportable forecast adjustment is based on the unemployment forecast and management judgment. For periods beyond our two year reasonable and supportable forecast, we revert to the historical loss rate. We revert to historical loss rates utilizing a straight-line method over a one year reversion period. The qualitative adjustments for current conditions are based upon changes in lending policies and practices, experience and ability of lending staff, quality of the bank’s loan review system, value of underlying

collateral for collateral dependent loans, the existence of and changes in concentrations and other external factors. These modified historical loss rates are multiplied by the outstanding principal balance of each loan to calculate a required reserve. A similar process is employed to calculate a reserve assigned to off-balance sheet commitments, specifically unfunded loan commitments and letters of credit, and any needed reserve is recorded in other liabilities.

The ACL for individual loans begins with the use of normal credit review procedures to identify whether a loan no longer shares similar risk characteristics with other pooled loans and therefore, should be individually assessed. We evaluate all commercial loans greater than $0.5 million that meet the following criteria: 1) when it is determined that foreclosure is probable, 2) substandard, doubtful and nonperforming loans when repayment is expected to be provided substantially through the operation or sale of the collateral, 3) any commercial troubled debt restructuring, or TDR, or any loan reasonably expected to become a TDR whether on accrual or nonaccrual status and 4) when it is determined by management that a loan does not share similar risk characteristics with other loans. Specific reserves are established based on the following three acceptable methods for measuring the ACL: 1) the present value of expected future cash flows discounted at the loan’s original effective interest rate; 2) the loan’s observable market price; or 3) the fair value of the collateral when the loan is collateral dependent. Our individual loan evaluations consist primarily of the fair value of collateral method because most of our loans are collateral dependent. Collateral values are discounted to consider disposition costs when appropriate. A specific reserve is established or a charge-off is taken if the fair value of the loan is less than the loan balance.

Although we believe our process for determining the ACL appropriately considers all the factors that would likely result in credit losses, the process includes subjective elements and may be susceptible to significant change. To the extent actual losses are higher than management estimates, additional provision for credit losses could be required and could adversely affect our earnings or financial position in future periods.

In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Changes to the Disclosure Requirements for Defined Benefit Plans. The amendments in this ASU apply to all employers that sponsor defined benefit pension or other postretirement plans. These amendments remove certain disclosures from Topic 715-20 and require additional disclosures. The amendments in this ASU will require S&T to update our employee benefits disclosures beginning with our Form 10-Q for the period ended March 31, 2021. The amendments in this ASU will have no impact on our consolidated financial statements.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in this ASU simplifies the accounting for income taxes by removing certain exceptions and improves the consistent application of GAAP by clarifying and amending other existing guidance. The amendments in this ASU will be effective on January 1, 2021 and are not expected to have any impact on our consolidated financial statements.

In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments in this ASU provide optional guidance for a limited period of time to ease the potential burden in accounting for or recognizing the effects of reference rate reform on financial reporting. The amendments provide optional expedients and exceptions for applying GAAP to loan and lease agreements, derivative contracts, and other transactions affected by the anticipated transition away from LIBOR toward new interest rate benchmarks. Modified contracts that meet certain scope guidance are eligible for relief from the modification accounting requirements in US GAAP. The optional guidance generally allows for the modified contract to be accounted for as a continuation of the existing contract and does not require contract remeasurement at the modification date or reassessment of a previous accounting determination. The amendments in this ASU are effective as of March 12, 2020 through December 31, 2022. We are evaluating the impacts of this ASU and have not yet determined whether LIBOR transition and this ASU will have material effects on our business operations and consolidated financial statements.