S&T Bancorp (STBA) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 08, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	0-12508
Entity Registrant Name	S&T BANCORP INC
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	25-1434426
Entity Address, Address Line One	800 Philadelphia Street
Entity Address, City or Town	Indiana
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15701
City Area Code	800
Local Phone Number	325-2265
Title of 12(b) Security	Common Stock, $2.50 par value
Trading Symbol	STBA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		39,242,510
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000719220
Current Fiscal Year End Date	--12-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
ASSETS
Cash and due from banks, including interest-bearing deposits of $113,505 and $124,491 at March 31, 2020 and December 31, 2019	$ 187,684	$ 197,823
Securities, at fair value	799,532	784,283
Loans held for sale	7,309	5,256
Portfolio loans, net of unearned income	7,246,745	7,137,152
Allowance for credit losses on loans	(96,850)	(62,224)
Portfolio loans, net	7,149,895	7,074,928
Bank owned life insurance	80,978	80,473
Premises and equipment, net	56,659	56,940
Federal Home Loan Bank and other restricted stock, at cost	28,253	22,977
Goodwill	374,270	371,621
Other intangible assets, net	10,287	10,919
Other assets	310,629	159,429
Total Assets	9,005,496	8,764,649
Deposits:
Noninterest-bearing demand	1,702,960	1,698,082
Interest-bearing demand	962,937	962,331
Money market	1,967,692	1,949,811
Savings	836,237	830,919
Certificates of deposit	1,588,053	1,595,433
Total Deposits	7,057,879	7,036,576
Securities sold under repurchase agreements	69,644	19,888
Short-term borrowings	410,240	281,319
Long-term borrowings	50,180	50,868
Junior subordinated debt securities	64,038	64,277
Other liabilities	177,264	119,723
Total Liabilities	7,829,245	7,572,651
SHAREHOLDERS’ EQUITY
Common stock ($2.50 par value) Authorized—50,000,000 shares Issued—41,449,444 shares at March 31, 2020 and December 31, 2019 Outstanding— 39,125,425 shares at March 31, 2020 and 39,560,304 shares at December 31, 2019	103,623	103,623
Additional paid-in capital	400,387	399,944
Retained earnings	740,726	761,083
Accumulated other comprehensive loss	5,672	(11,670)
Treasury stock (2,324,019 shares at March 31, 2020 and 1,889,140 shares at December 31, 2019, at cost)	(74,157)	(60,982)
Total Shareholders’ Equity	1,176,251	1,191,998
Total Liabilities and Shareholders’ Equity	$ 9,005,496	$ 8,764,649

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Cash and due from banks, interest-bearing amounts	$ 113,505	$ 124,491
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	41,449,444	41,449,444
Common stock, shares outstanding (in shares)	39,125,425	39,560,304
Treasury stock, shares (in shares)	2,324,019	1,889,140

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
INTEREST AND DIVIDEND INCOME
Loans, including fees	$ 82,051	$ 73,392
Investment Securities:
Taxable	4,215	3,790
Tax-exempt	870	844
Dividends	453	564
Total Interest and Dividend Income	87,589	78,590
INTEREST EXPENSE
Deposits	15,338	14,981
Borrowings and junior subordinated debt securities	2,215	3,253
Total Interest Expense	17,553	18,234
NET INTEREST INCOME	70,036	60,356
Provision for credit losses	20,050	5,684
Net Interest Income After Provision for Credit Losses	49,986	54,672
NONINTEREST INCOME
Net gain on sale of securities	0	0
Commercial loan swap income	2,484	581
Mortgage banking	1,236	494
Other	(719)	2,112
Total Noninterest Income	12,403	11,362
NONINTEREST EXPENSE
Salaries and employee benefits	21,335	20,910
Data processing and information technology	3,868	3,233
Net occupancy	3,765	3,036
Furniture, equipment and software	2,519	2,230
Merger related expenses	2,342	0
Other taxes	1,600	1,185
Marketing	1,111	1,141
Professional services and legal	1,048	1,184
FDIC insurance	770	516
Other	8,033	5,449
Total Noninterest Expense	46,391	38,884
Income Before Taxes	15,998	27,150
Provision for income taxes	2,767	4,222
Net Income	$ 13,231	$ 22,928
Earnings per share—basic (in dollars per share)	$ 0.34	$ 0.67
Earnings per share—diluted (in dollars per share)	0.34	0.66
Dividends declared per share (in dollars per share)	$ 0.28	$ 0.27
Comprehensive Income	$ 30,573	$ 29,104
Service charges on deposit accounts
NONINTEREST INCOME
Revenues from contract with customers	3,558	3,153
Debit and credit card
NONINTEREST INCOME
Revenues from contract with customers	3,482	2,974
Wealth management
NONINTEREST INCOME
Revenues from contract with customers	$ 2,362	$ 2,048

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)/Income	Treasury Stock
Beginning Balance at Dec. 31, 2018	$ 935,761	$ 90,326	$ 210,345	$ 701,819	$ (23,107)	$ (43,622)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,928			22,928
Other comprehensive income (loss), net of tax	6,176				6,176
Cash dividends declared	(9,317)			(9,317)
Treasury stock issued for restricted stock awards	(876)			481		(1,357)
Repurchase of S&T Stock	(12,287)					(12,287)
Recognition of restricted stock compensation expense	604		604
Ending Balance at Mar. 31, 2019	943,156	90,326	210,949	716,078	(16,931)	(57,266)
Beginning Balance at Dec. 31, 2019	1,191,998	103,623	399,944	761,083	(11,670)	(60,982)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,231			13,231
Other comprehensive income (loss), net of tax	17,342				17,342
Cash dividends declared	(11,051)			(11,051)
Treasury stock issued for restricted stock awards	(563)			53		(616)
Repurchase of S&T Stock	(12,559)					(12,559)
Recognition of restricted stock compensation expense	443		443
Ending Balance at Mar. 31, 2020	$ 1,176,251	$ 103,623	$ 400,387	$ 740,726	$ 5,672	$ (74,157)

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Dividends declared per share (in dollars per share)	$ 0.28	$ 0.27
Retained Earnings
Dividends declared per share (in dollars per share)	$ 0.28	$ 0.27
Treasury stock issued for restricted awards, net of forfeitures (in shares)	3,290	0
Forfeitures of restricted stock (in shares)	26,739	39,834
Treasury Stock
Repurchase of common stock (in shares)	411,430	313,904

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 13,231	$ 22,928
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	20,050	5,684
Provision for credit losses		5,649
Provision for unfunded loan commitments	0	35
Net depreciation, amortization and accretion	1,171	1,420
Net amortization of discounts and premiums on securities	1,154	776
Stock-based compensation expense	443	604
Gain on the sale of mortgage loans, net	(536)	(293)
Mortgage loans originated for sale	(37,332)	(14,506)
Proceeds from the sale of mortgage loans	35,358	14,464
Net change in:
Interest receivable	26	(1,963)
Interest payable	(242)	(789)
Other assets	(149,186)	(3,466)
Other liabilities	55,902	5,600
Net Cash (Used in) Provided by Operating Activities	(59,961)	30,459
INVESTING ACTIVITIES
Purchases of securities	(30,292)	(9,437)
Proceeds from maturities, prepayments and calls of securities	33,869	20,193
Net (purchases of) proceeds from sales of Federal Home Loan Bank stock	(5,277)
Net (purchases of) proceeds from sales of Federal Home Loan Bank stock		9,477
Net (increase) decrease in loans	(122,507)
Net (increase) decrease in loans		4,760
Proceeds from sale of loans not originated for resale	0	465
Purchases of premises and equipment	(1,429)	(1,757)
Net Cash (Used in) Provided by Investing Activities	(125,636)	23,701
FINANCING ACTIVITIES
Net increase in core deposits	28,684	170,744
Net decrease in certificates of deposit	(7,042)	(11,241)
Net increase in securities sold under repurchase agreements	49,756	5,044
Net increase (decrease) in short-term borrowings	128,921
Net increase (decrease) in short-term borrowings		(235,000)
Proceeds from long-term borrowings	0	104
Repayments on long-term borrowings	(688)	0
Other assets	(563)	(876)
Cash dividends paid to common shareholders	(11,051)	(9,317)
Repurchase of common stock	(12,559)	(12,287)
Net Cash Provided by (Used in) Financing Activities	175,458	(92,829)
Net decrease in cash and cash equivalents	(10,139)	(38,669)
Cash and cash equivalents at beginning of period	197,823	155,489
Cash and Cash Equivalents at End of Period	187,684	116,820
Supplemental Disclosures
Leased right-of-use operating assets and lease liabilities added to the balance sheet	91	35,686
Interest paid	17,795	19,023
Income taxes paid, net of refunds	210	1,432
Transfers of loans to other real estate owned	$ 110	$ 80

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2020
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 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. On June 5, 2019 we entered into an agreement to acquire DNB Financial Corporation, or DNB, and the transaction was completed on November 30, 2019. Refer to Note 2, Business Combinations for further details on the merger. Reclassification A mounts in prior period financial statements and footnotes are reclassified whenever necessary to conform to the current period presentation. Reclassifications had no 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 or Update 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 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. Fair Value Measurement - Changes to the Disclosure Requirements for Fair Value Measurement 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. Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment 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. Financial Instruments - Credit Losses 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. We made the accounting policy election to not measure an ACL for accrued interest receivables for loans and securities. Accrued interest deemed uncollectible will be written off through interest income. The majority of our available-for-sale debt securities are government agency-backed securities for which the risk of loss is minimal, and accordingly the ACL is immaterial. 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. The following table details the impact of ASU 2016-13 and the reclassification of loans for the identification of new portfolio loan segments under CECL: 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. Allowance for Credit Losses Policy 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 methodology for determining the ACL has two main components: evaluation of expected credit losses for certain groups of homogeneous loans that share similar risk characteristics and evaluation of loans that do not share risk characteristics with other loans. 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. Accounting Standards Issued But Not Yet Adopted Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Changes to the Disclosure Requirements for Defined Benefit Plans 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. Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 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. Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting 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.

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS On November 30, 2019, we completed our acquisition of DNB Financial Corporation, or DNB, and DNB First National Association, its wholly-owned bank subsidiary, located in Downingtown, Pennsylvania. The acquisition of DNB expanded our Eastern Pennsylvania market by adding 14 banking locations, in an all-stock transaction structured as a merger of DNB with and into S&T, with S&T being the surviving entity. The related systems conversion of DNB into S&T Bank occurred on February 7, 2020. DNB shareholders received, without interest, 1.22 shares of S&T common stock for each share of DNB common stock. The total purchase price was approximately $201.0 million , which included $0.4 million of cash and 5,318,964 S&T common shares at a fair value of $37.72 per share. The fair value of $37.72 per share of S&T common stock was based on the November 30, 2019 closing price. The Merger was accounted for under the acquisition method of accounting and our Consolidated Financial Statements include all DNB Bank transactions beginning on December 1, 2019. Goodwill of $86.0 million at March 31, 2020 was calculated as the excess of the consideration exchanged over the fair value of the identifiable net assets acquired. All of the goodwill was assigned to our Community Banking segment. The goodwill recognized is not deductible for tax purposes. The following table provides a summary of the assets acquired and liabilities assumed by DNB, the preliminary estimates of the fair value adjustments necessary to adjust those acquired assets and assumed liabilities to estimated fair value and the preliminary estimates of the resultant fair values of those assets and liabilities by S&T at November 30, 2019, the acquisition date. Preliminary estimates were adjusted by $1.8 million during the three months ended March 31, 2020. These measurement period adjustments primarily related to $2.5 million reduction in the fair value of loans, $0.3 million reduction in the fair value of borrowings and $0.3 million in deferred taxes related to these valuation adjustments. Preliminary fair value adjustments continue to be evaluated by management and may be subject to further adjustment during the measurement period, which may not extend beyond one year following the acquisition. The following table presents the preliminary fair value adjustments and the measurement period adjustments as of the dates presented: November 30, 2019 March 31, 2020 As Recorded by DNB Preliminary Fair Value Adjustments (1) As Recorded by S&T Measurement Period Adjustments As Recorded by S&T Fair Value of Assets Acquired Cash and cash equivalents $ 64,119 $ — $ 64,119 $ — $ 64,119 Securities and other investments 108,715 183 108,898 — 108,898 Loans 917,127 (8,143 ) 908,984 (2,496 ) 906,488 Allowance for credit losses (6,487 ) 6,487 — — — Goodwill 15,525 (15,525 ) — — — Premises and equipment 6,782 8,090 14,872 — 14,872 Accrued interest receivable 4,138 — 4,138 — 4,138 Deferred income taxes 2,017 (3,298 ) (1,281 ) 311 (970 ) Core deposits and other intangible assets 269 (269 ) — — — Other assets 24,883 (4,278 ) 20,605 40 20,645 Total Assets Acquired 1,137,088 (16,753 ) 1,120,335 (2,145 ) 1,118,190 Fair Value of Liabilities Assumed Deposits 966,263 1,002 967,265 (12 ) 967,253 Borrowings 37,617 (276 ) 37,341 (257 ) 37,084 Accrued interest payable and other liabilities 11,157 (3,184 ) 7,973 (68 ) 7,905 Total Liabilities Assumed 1,015,037 (2,458 ) 1,012,579 (337 ) 1,012,242 Total Net Assets Acquired $ 122,051 $ (14,295 ) $ 107,756 $ (1,808 ) $ 105,948 Core Deposit Intangible Asset $ 7,288 $ — $ 7,288 Wealth Management Intangible Asset 1,772 — 1,772 Total Fair Value of Net Assets Acquired and Identified $ 116,816 $ (1,808 ) $ 115,008 Consideration Paid Cash $ 360 $ — $ 360 Common stock 200,631 — 200,631 Fair Value of Total Consideration $ 200,991 $ — $ 200,991 Goodwill $ 84,175 $ 1,808 $ 85,983 (1) Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, deferred and current income taxes until the final valuations are complete and final tax returns are filed. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition. Loans acquired in the Merger were recorded at fair value with no carryover of the related ACL from DNB. Determining the fair value of the loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. The preliminary fair value of the loans acquired was estimated at $909.0 million , net of a $10.5 million discount. The discount is accreted to interest income over the remaining contractual life of the loans. During the three month period ended March 31, 2020, the fair value of acquired loans was reduced by an additional $2.5 million as we continue to finalize our evaluation of the loan portfolio. As of March 31, 2020, direct costs related to the DNB merger of $13.7 million were recognized and expensed as incurred. During the three months ended March 31, 2020, we recognized $2.3 million of merger related expenses including $0.2 million in legal and professional fees, $1.4 million in severance payments and stay-bonuses, $0.4 million for data processing, and $0.3 million in other expenses. As of December 31, 2019, we recognized $11.4 million of merger related expenses, including $4.7 million for data processing contract termination and system conversion costs, $2.8 million in legal and professional expenses, $3.4 million in severance payments and $0.5 million in other expenses.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Diluted earnings per share is calculated using both the two-class and the treasury stock methods with the more dilutive method used to determine diluted earnings per share. The following table reconciles the numerators and denominators of basic and diluted earnings per share calculations for the periods presented. Three Months Ended March 31, (in thousands, except share and per share data) 2020 2019 Numerator for Earnings per Share—Basic: Net income $ 13,231 $ 22,928 Less: Income allocated to participating shares 29 62 Net Income Allocated to Shareholders $ 13,202 $ 22,866 Numerator for Earnings per Share—Diluted: Net income $ 13,231 $ 22,928 Net Income Available to Shareholders $ 13,231 $ 22,928 Denominators for Earnings per Share: Weighted Average Shares Outstanding—Basic 39,271,540 34,414,555 Add: Potentially dilutive shares 108,116 128,256 Denominator for Treasury Stock Method—Diluted 39,379,656 34,542,811 Weighted Average Shares Outstanding—Basic 39,271,540 34,414,555 Add: Average participating shares outstanding 54,398 92,659 Denominator for Two-Class Method—Diluted 39,325,938 34,507,214 Earnings per share—basic $ 0.34 $ 0.67 Earnings per share—diluted $ 0.34 $ 0.66 Restricted stock considered anti-dilutive excluded from potentially dilutive shares 41 68,314

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS We use fair value measurements when recording and disclosing certain financial assets and liabilities. Debt securities, equity securities and derivative financial instruments are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record other assets at fair value on a nonrecurring basis, such as loans held for sale, loans held for investment, other real estate owned, or OREO, and other repossessed assets, mortgage servicing rights, or MSRs, and certain other assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets or liabilities; it is not a forced transaction. In determining fair value, we use various valuation approaches, including market, income and cost approaches. The fair value standard establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability, which are developed based on market data that we have obtained from independent sources. Unobservable inputs reflect our estimates of assumptions that market participants would use in pricing an asset or liability, which are developed based on the best information available in the circumstances. The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: Level 1: valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2: valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3: valuation is derived from other valuation methodologies, including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our policy is to recognize transfers between any of the fair value hierarchy levels at the end of the reporting period in which the transfer occurred. The following are descriptions of the valuation methodologies that we use for financial instruments recorded at fair value on either a recurring or nonrecurring basis. Recurring Basis Available-for-Sale Debt Securities We obtain fair values for debt securities from a third-party pricing service which utilizes several sources for valuing fixed-income securities. We validate prices received from our pricing service through comparison to a secondary pricing service and broker quotes. We review the methodologies of the pricing services which provide us with a sufficient understanding of the valuation models, assumptions, inputs and pricing to reasonably measure the fair value of our debt securities. The market valuation sources for debt securities include observable inputs rather than significant unobservable inputs and are classified as Level 2. The service provider utilizes pricing models that vary by asset class and include available trade, bid and other market information. Generally, the methodologies include broker quotes, proprietary models, vast descriptive terms and conditions databases, and extensive quality control programs. Equity Securities Marketable equity securities that have an active, quotable market are classified as Level 1. Marketable equity securities that are quotable, but are thinly traded or inactive, are classified as Level 2. Marketable equity securities that are not readily traded and do not have a quotable market are classified as Level 3. Deferred Compensation Plan Assets We use quoted market prices to determine the fair value of our equity security assets. These securities are reported at fair value with the gains and losses included in noninterest income in our Consolidated Statements of Comprehensive Income. These assets are held in a deferred compensation plan and are invested in readily quoted mutual funds. Accordingly, these assets are classified as Level 1. Deferred compensation plan assets are reported in other assets in the Consolidated Balance Sheets. Derivative Financial Instruments We use derivative instruments, including interest rate swaps for commercial loans with our customers, interest rate lock commitments and the sale of mortgage loans in the secondary market. We calculate the fair value for derivatives using accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Each valuation considers the contractual terms of the derivative, including the period to maturity, and uses observable market-based inputs, such as interest rate curves and implied volatilities. Accordingly, derivatives are classified as Level 2. We incorporate credit valuation adjustments into the valuation models to appropriately reflect both our own nonperformance risk and the respective counterparties’ nonperformance risk in calculating fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements and collateral postings. Nonrecurring Basis Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and, from time to time, certain loans are transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. The fair value of 1-4 family residential loans is based on the principal or most advantageous market currently offered for similar loans using observable market data. The fair value of the loans transferred from the loan portfolio is based on the amounts offered for these loans in currently pending sales transactions. Loans held for sale carried at fair value are classified as Level 3. Loans Held for Investment Loans that are individually evaluated to determine whether a specific allocation of ACL is needed are reported at fair value. Fair value is determined using the following methods: 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 less estimated selling costs when the loan is collateral dependent and we expect to liquidate the collateral. However, if repayment is expected to come from the operation of the collateral, rather than liquidation, then we do not consider estimated selling costs in determining the fair value of the collateral. Collateral values are generally based upon appraisals by approved, independent state certified appraisers. Appraisals may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or our knowledge of the borrower and the borrower’s business. Loans carried at fair value are classified as Level 3. OREO and Other Repossessed Assets OREO and other repossessed assets obtained in partial or total satisfaction of a loan are recorded at the lower of recorded investment in the loan or fair value less cost to sell. Subsequent to foreclosure, these assets are carried at the lower of the amount recorded at acquisition date or fair value less cost to sell. Accordingly, it may be necessary to record nonrecurring fair value adjustments. Fair value, when recorded, is generally based upon appraisals by approved, independent state certified appraisers. Appraisals on OREO may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or other information available to us. OREO and other repossessed assets carried at fair value are classified as Level 3. Mortgage Servicing Rights The fair value of MSRs is determined by calculating the present value of estimated future net servicing cash flows, considering expected mortgage loan prepayment rates, discount rates, servicing costs and other economic factors, which are determined based on current market conditions. The expected rate of mortgage loan prepayments is the most significant factor driving the value of MSRs. MSRs are considered impaired if the carrying value exceeds fair value. Since the valuation model includes significant unobservable inputs as listed above, MSRs are classified as Level 3. MSRs are reported in other assets in the Consolidated Balance Sheets and are amortized into mortgage banking income in the Consolidated Statements of Comprehensive Income. Other Assets We measure certain other assets at fair value on a nonrecurring basis. Fair value is based on the application of lower of cost or fair value accounting, or write-downs of individual assets. Valuation methodologies used to measure fair value are consistent with overall principles of fair value accounting and consistent with those described above. Financial Instruments In addition to financial instruments recorded at fair value in our financial statements, fair value accounting guidance requires disclosure of the fair value of all of an entity’s assets and liabilities that are considered financial instruments. The majority of our assets and liabilities are considered financial instruments. Many of these instruments lack an available trading market as characterized by a willing buyer and a willing seller engaged in an exchange transaction. Also, it is our general practice and intent to hold our financial instruments to maturity and to not engage in trading or sales activities with respect to such financial instruments. For fair value disclosure purposes, we substantially utilize the fair value measurement criteria as required and explained above. In cases where quoted fair values are not available, we use present value methods to determine the fair value of our financial instruments. Cash and Cash Equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks, including interest-bearing deposits, approximate fair value. Loans The fair value of variable rate loans that may reprice frequently at short-term market rates is based on carrying values adjusted for liquidity and credit risk. The fair value of variable rate loans that reprice at intervals of one year or longer, such as adjustable rate mortgage products, is estimated using discounted cash flow analyses that utilize interest rates currently being offered for similar loans and adjusted for liquidity and credit risk. The fair value of fixed rate loans is estimated using a discounted cash flow analysis that utilizes interest rates currently being offered for similar loans adjusted for liquidity and credit risk. Bank Owned Life Insurance Fair value approximates net cash surrender value of bank owned life insurance, or BOLI. Federal Home Loan Bank, or FHLB, and Other Restricted Stock It is not practical to determine the fair value of our FHLB and other restricted stock due to the restrictions placed on the transferability of these stocks; it is presented at carrying value. Deposits The fair values disclosed for deposits without defined maturities ( e.g. , noninterest and interest-bearing demand, money market and savings accounts) are by definition equal to the amounts payable on demand. The carrying amounts for variable rate, fixed-term time deposits approximate their fair values. Estimated fair values for fixed rate and other time deposits are based on discounted cash flow analysis using interest rates currently offered for time deposits with similar terms. The carrying amount of accrued interest approximates fair value. Short-Term Borrowings The carrying amounts of securities sold under repurchase agreements, or REPOs, and other short-term borrowings approximate their fair values. Long-Term Borrowings The fair values disclosed for fixed rate long-term borrowings are determined by discounting their contractual cash flows using current interest rates for long-term borrowings of similar remaining maturities. The carrying amounts of variable rate long-term borrowings approximate their fair values. Junior Subordinated Debt Securities The interest rate on the variable rate junior subordinated debt securities is reset quarterly; therefore, the carrying values approximate their fair values. Loan Commitments and Standby Letters of Credit Off-balance sheet financial instruments consist of commitments to extend credit and letters of credit. Except for interest rate lock commitments, estimates of the fair value of these off-balance sheet items are not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Other Estimates of fair value are not made for items that are not defined as financial instruments, including such items as our core deposit intangibles and the value of our trust operations. Assets and Liabilities Recorded at Fair Value on a Recurring Basis The following tables present our assets and liabilities that are measured at fair value on a recurring basis by fair value hierarchy level at March 31, 2020 and December 31, 2019 . There were no transfers between Level 1 and Level 2 for items measured at fair value on a recurring basis during the periods presented. March 31, 2020 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Available-for-sale debt securities: U.S. Treasury securities $ — $ 10,372 $ — $ 10,372 Obligations of U.S. government corporations and agencies — 137,982 — 137,982 Collateralized mortgage obligations of U.S. government corporations and agencies — 189,472 — 189,472 Residential mortgage-backed securities of U.S. government corporations and agencies — 21,193 — 21,193 Commercial mortgage-backed securities of U.S. government corporations and agencies — 284,679 — 284,679 Corporate Bonds — 7,551 — 7,551 Obligations of states and political subdivisions — 144,717 — 144,717 Total Available-for-sale Debt Securities — 795,966 — 795,966 Marketable equity securities 3,504 62 — 3,566 Total Securities 3,504 796,028 — 799,532 Securities held in a deferred compensation plan 4,782 — — 4,782 Derivative financial assets: Interest rate swaps — 88,135 — 88,135 Interest rate lock commitments — 2,927 — 2,927 Total Assets $ 8,286 $ 887,090 $ — $ 895,376 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 87,989 $ — $ 87,989 Forward sale contracts — 1,292 — 1,292 Total Liabilities $ — $ 89,281 $ — $ 89,281 December 31, 2019 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Available-for-sale debt securities: U.S. Treasury securities $ — $ 10,040 $ — $ 10,040 Obligations of U.S. government corporations and agencies — 157,697 — 157,697 Collateralized mortgage obligations of U.S. government corporations and agencies — 189,348 — 189,348 Residential mortgage-backed securities of U.S. government corporations and agencies — 22,418 — 22,418 Commercial mortgage-backed securities of U.S. government corporations and agencies — 275,870 — 275,870 Corporate Bonds — 7,627 — 7,627 Obligations of states and political subdivisions — 116,133 — 116,133 Total Available-for-Sale Debt Securities — 779,133 — 779,133 Marketable equity securities 5,078 72 — 5,150 Total Securities 5,078 779,205 — 784,283 Securities held in a deferred compensation plan 5,987 — — 5,987 Derivative financial assets: Interest rate swaps — 25,647 — 25,647 Interest rate lock commitments — 321 — 321 Forward sale contracts — 1 — 1 Total Assets $ 11,065 $ 805,174 $ — $ 816,239 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 25,615 $ — $ 25,615 Total Liabilities $ — $ 25,615 $ — $ 25,615 Assets Recorded at Fair Value on a Nonrecurring Basis We may be required to measure certain assets and liabilities at fair value on a nonrecurring basis. Nonrecurring assets are recorded at the lower of cost or fair value in our financial statements. There were no liabilities measured at fair value on a nonrecurring basis at either March 31, 2020 or December 31, 2019 . For Level 3 assets measured at fair value on a nonrecurring basis as of March 31, 2020 and December 31, 2019, the significant unobservable inputs used in the fair value measurements were as follows: March 31, 2020 Valuation Technique(s) Significant Unobservable Inputs Range (dollars in thousands) Loans held for investment $ 20,926 Collateral Method Third party appraisal Costs to sell 0% - 17% Discounted cash flow method Discount rate Contractual loan rate 3.25% Other real estate owned 3,045 Collateral method Third party appraisal Costs to sell 7% Mortgage servicing rights 3,929 Discounted cash flow method Third party service provider Discount rate 9.39% - 12.54% Constant prepayment rates 7.46% - 12.74% Total Assets $ 27,900 December 31, 2019 Valuation Technique(s) Significant Unobservable Inputs Range (dollars in thousands) Impaired loans $ 38,697 Collateral Method Third party appraisal Costs to sell 0% - 20% Discounted cash flow method Discount rate Contractual loan rate 4.75% - 5.50% Other real estate owned 3,231 Collateral method Third party appraisal Costs to sell 7% Mortgage servicing rights 1,134 Discounted cash flow method Third party service provider Discount rate 9.39% - 12.54% Constant prepayment rates 7.46% - 12.74% Total Assets $ 43,062 The carrying values and fair values of our financial instruments at March 31, 2020 and December 31, 2019 are presented in the following tables: Carrying Value (1) Fair Value Measurements at March 31, 2020 (dollars in thousands) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 187,684 $ 187,684 $ 187,684 $ — $ — Securities 799,532 799,532 3,504 796,028 — Loans held for sale 7,309 7,309 — — 7,309 Portfolio loans, net 7,149,895 7,090,570 — — 7,090,570 Bank owned life insurance 80,978 80,798 — 80,798 — FHLB and other restricted stock 28,253 28,253 — — 28,253 Securities held in a deferred compensation plan 4,782 4,782 4,782 — — Mortgage servicing rights 3,979 3,982 — — 3,982 Interest rate swaps 88,135 88,135 — 88,135 — Interest rate lock commitments 2,927 2,927 — 2,927 — LIABILITIES Deposits $ 7,057,879 $ 7,065,896 $ 5,469,826 $ 1,596,070 $ — Securities sold under repurchase agreements 69,644 69,644 69,644 — — Short-term borrowings 410,240 410,240 410,240 — — Long-term borrowings 50,180 51,675 4,630 47,045 — Junior subordinated debt securities 64,038 64,038 64,038 — — Interest rate swaps 87,989 87,989 — 87,989 — Forward sales contracts 1,292 1,292 — 1,292 — (1) As reported in the Consolidated Balance Sheets Carrying Value (1) Fair Value Measurements at December 31, 2019 (dollars in thousands) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 197,823 $ 197,823 $ 197,823 $ — $ — Securities 784,283 784,283 5,078 779,205 — Loans held for sale 5,256 5,256 — — 5,256 Portfolio loans, net 7,074,928 6,940,875 — — 6,940,875 Bank owned life insurance 80,473 80,473 — 80,473 — FHLB and other restricted stock 22,977 22,977 — — 22,977 Securities held in a Deferred Compensation Plan 5,987 5,987 5,987 — — Mortgage servicing rights 4,662 4,650 — — 4,650 Interest rate swaps 25,647 25,647 — 25,647 — Interest rate lock commitments 321 321 — 321 — Forward sale contracts 1 1 — 1 — LIABILITIES Deposits $ 7,036,576 $ 7,034,595 $ 5,441,143 $ 1,593,452 $ — Securities sold under repurchase agreements 19,888 19,888 19,888 — — Short-term borrowings 281,319 281,319 281,319 — — Long-term borrowings 50,868 51,339 4,678 46,661 — Junior subordinated debt securities 64,277 64,277 64,277 — — Interest rate swaps 25,615 25,615 — 25,615 — (1) As reported in the Consolidated Balance Sheets

Securities

Securities	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
SECURITIES	SECURITIES The following table presents the fair values of our securities portfolio at the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Available-for-sale debt securities $ 795,966 $ 779,133 Marketable equity securities 3,566 5,150 Total Securities $ 799,532 $ 784,283 Available-for-Sale Debt Securities The following tables present the amortized cost and fair value of available-for-sale debt securities as of the dates presented: March 31, 2020 December 31, 2019 (dollars in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 9,972 $ 400 $ — $ 10,372 $ 9,969 $ 71 $ — $ 10,040 Obligations of U.S. government corporations and agencies 132,938 5,044 — 137,982 155,969 1,773 (45 ) 157,697 Collateralized mortgage obligations of U.S. government corporations and agencies 180,682 8,790 — 189,472 186,879 2,773 (304 ) 189,348 Residential mortgage-backed securities of U.S. government corporations and agencies 20,391 802 — 21,193 22,120 321 (23 ) 22,418 Commercial mortgage-backed securities of U.S. government corporations and agencies 272,651 12,028 — 284,679 273,771 2,680 (581 ) 275,870 Corporate obligations 7,532 30 (11 ) 7,551 7,603 24 — 7,627 Obligations of states and political subdivisions 139,530 5,187 — 144,717 112,116 4,017 — 116,133 Total Available-for-Sale Debt Securities (1) $ 763,696 $ 32,281 $ (11 ) $ 795,966 $ 768,427 $ 11,659 $ (953 ) $ 779,133 (1) Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets. The following tables present the fair value and the age of gross unrealized losses on available-for-sale debt securities by investment category as of the dates presented: March 31, 2020 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized U.S. Treasury securities — $ — $ — — $ — $ — — $ — $ — Obligations of U.S. government corporations and agencies — — — — — — — — — Collateralized mortgage obligations of U.S. government corporations and agencies — — — — — — — — — Residential mortgage-backed securities of U.S. government corporations and agencies — — — — — — — — — Commercial mortgage-backed securities of U.S. government corporations and agencies — — — — — — — — — Corporate bonds 2 2,989 (11 ) — — — 2 2,989 (11 ) Obligations of states and political subdivisions — — — — — — — — — Total 2 $ 2,989 $ (11 ) — $ — $ — 2 $ 2,989 $ (11 ) December 31, 2019 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized U.S. Treasury securities — $ — $ — — $ — $ — — $ — $ — Obligations of U.S. government corporations and agencies 3 22,638 (45 ) — — — 3 22,638 (45 ) Collateralized mortgage obligations of U.S. government corporations and agencies 6 23,393 (73 ) 6 25,254 (231 ) 12 48,647 (304 ) Residential mortgage-backed securities of U.S. government corporations and agencies 1 982 (2 ) 1 2,534 (21 ) 2 3,516 (23 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 9 90,005 (581 ) — — — 9 90,005 (581 ) Corporate bonds 1 79 — — — — 1 79 — Obligations of states and political subdivisions — — — — — — — — — Total Temporarily Impaired Debt Securities 20 $ 137,097 $ (701 ) 7 $ 27,788 $ (252 ) 27 $ 164,885 $ (953 ) We evaluate quarterly securities with unrealized losses to determine if the decline in fair value has resulted from credit losses or other factors. There were two debt securities in an unrealized loss position at March 31, 2020 and 27 debt securities in an unrealized loss position at December 31, 2019. We do not intend to sell and it is more likely than not that we will not be required to sell any of the securities in an unrealized loss position before recovery of their amortized cost. The unrealized losses on debt securities were attributable to changes in interest rates and not related to the credit quality of these issuers. All debt securities were determined to be investment grade and paying principal and interest according to the contractual terms of the security. We concluded that the allowance for credit losses for debt securities was immaterial at March 31, 2020. Prior to the adoption of ASU 2016-13 there was no other than temporary impairment, or OTTI, recorded during the three months ended March 31, 2019. The following table presents net unrealized gains and losses, net of tax, on available-for-sale debt securities included in accumulated other comprehensive income/(loss), for the periods presented: March 31, 2020 December 31, 2019 (dollars in thousands) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains/(Losses) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains/(Losses) Total unrealized gains/(losses) on available-for-sale debt securities $ 32,281 $ (11 ) $ 32,270 $ 11,659 $ (953 ) $ 10,706 Income tax (expense) benefit (6,873 ) 2 (6,871 ) (2,486 ) 203 (2,283 ) Net Unrealized Gains/(Losses), Net of Tax Included in Accumulated Other Comprehensive Income/(Loss) $ 25,408 $ (9 ) $ 25,399 $ 9,173 $ (750 ) $ 8,423 The amortized cost and fair value of available-for-sale debt securities at March 31, 2020 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2020 (dollars in thousands) Amortized Cost Fair Value Obligations of the U.S. Treasury, U.S. government corporations and agencies, and obligations of states and political subdivisions Due in one year or less $ 84,687 $ 85,259 Due after one year through five years 100,877 106,112 Due after five years through ten years 65,732 68,913 Due after ten years 31,144 32,786 Available-for-Sale Debt Securities With Maturities 282,440 293,070 Collateralized mortgage obligations of U.S. government corporations and agencies 180,682 189,473 Residential mortgage-backed securities of U.S. government corporations and agencies 20,391 21,193 Commercial mortgage-backed securities of U.S. government corporations and agencies 272,651 284,679 Corporate Securities 7,532 7,551 Total Available-for-Sale Debt Securities $ 763,696 $ 795,966 Debt securities with carrying values of $298.4 million at March 31, 2020 and $286.0 million at December 31, 2019 were pledged for various regulatory and legal requirements. Marketable Equity Securities The following table presents realized and unrealized net gains and losses for our marketable equity securities for the periods presented: Three Months Ended (dollars in thousands) 2020 2019 Marketable Equity Securities Net gains and losses recognized during the period on equity securities $ (1,585 ) $ (318 ) Less: Net gains and losses recognized during the period on equity securities sold during the period — — Unrealized Losses/Gains Recognized During the Reporting Period on Equity Securities Still Held at the Reporting Date $ (1,585 ) $ (318 ) Total unrealized gains and losses on marketable equity securities recognized during the current period are included in other noninterest income on the Consolidated Statements of Comprehensive Income.

Loans and Loans Held for Sale

Loans and Loans Held for Sale	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
LOANS AND LOANS HELD FOR SALE	LOANS AND LOANS HELD FOR SALE Loans are presented net of unearned income of $5.0 million at March 31, 2020 and $4.6 million at December 31, 2019 and net of a discount related to purchase accounting fair value adjustments of $10.9 million and $12.3 million at March 31, 2020 and December 31, 2019. The following table presents loans as of the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Commercial Commercial real estate $ 3,442,495 $ 3,416,518 Commercial and industrial 1,781,402 1,720,833 Commercial construction 396,518 375,445 Total Commercial Loans 5,620,415 5,512,796 Consumer Residential mortgage 988,816 998,585 Home Equity 544,405 538,348 Installment and other consumer 79,887 79,033 Consumer construction 13,222 8,390 Total Consumer Loans 1,626,330 1,624,356 Total Portfolio Loans 7,246,745 7,137,152 Loans held for sale 7,309 5,256 Total Loans (1) $ 7,254,054 $ 7,142,408 (1) Excludes interest receivable of $22.1 million at both March 31, 2020 and December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets. We attempt to limit our exposure to credit risk by diversifying our loan portfolio by segment, geography, collateral and industry and actively managing concentrations. When concentrations exist in certain segments, we mitigate this risk by reviewing the relevant economic indicators and internal risk rating trends and through stress testing of the loans in these segments. Total commercial loans represented 77.6 percent of total portfolio loans at March 31, 2020 and 77.2 percent at December 31, 2019 . Within our commercial portfolio, the CRE and Commercial Construction portfolios combined comprised $3.8 billion or 68.3 percent of total commercial loans at March 31, 2020 and $3.8 billion or 68.8 percent of total commercial loans at December 31, 2019 and 53.0 percent of total portfolio loans at March 31, 2020 and 53.1 percent at December 31, 2019 . Further segmentation of the CRE and commercial construction portfolios by collateral type reveals no concentration in excess of 13.6 percent of both total CRE and commercial construction loans at March 31, 2020 and 11 percent at December 31, 2019 . We lend primarily in Pennsylvania and the contiguous states of Ohio, New York, West Virginia and Maryland. The majority of our commercial and consumer loans are made to businesses and individuals in this geography, resulting in a concentration. We believe our knowledge and familiarity with customers and conditions locally outweighs this geographic concentration risk. The conditions of the local and regional economies are monitored closely through publicly available data and information supplied by our customers. We also use subscription services for additional geographic and industry specific information. Our CRE and commercial construction portfolios have exposure outside of this geography of 5.4 percent of the combined portfolios and 2.8 percent of total portfolio loans at March 31, 2020 . This compares to 5.4 percent of the combined portfolios and 2.9 percent of total portfolio loans at December 31, 2019 . We individually evaluate all substandard and nonaccrual commercial loans that have experienced a forbearance or change in terms agreement, and all substandard consumer and residential mortgage loans that entered into an agreement to modify their existing loan, to determine if they should be designated as troubled debt restructurings, or TDRs. All TDRs will be reported as such for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. TDRs can be returned to accruing status if the ultimate collectability of all contractual amounts due, according to the restructured agreement, is not in doubt and there is a period of a minimum of six months of satisfactory payment performance by the borrower either immediately before or after the restructuring. The following tables summarize restructured loans as of the dates presented: March 31, 2020 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 30 $ 28,973 $ 29,003 Commercial and industrial 4,566 4,665 9,231 Commercial construction 3,316 — 3,316 Business banking 1,524 352 1,876 Consumer real estate 5,749 2,064 7,813 Other consumer 4 — 4 Total (1) $ 15,189 $ 36,055 $ 51,243 (1) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. December 31, 2019 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 22,233 $ 6,713 $ 28,946 Commercial and industrial 6,909 695 7,604 Commercial construction 1,425 — 1,425 Residential mortgage 2,013 822 2,835 Home equity 4,371 678 5,049 Installment and other consumer 9 4 13 Total $ 36,960 $ 8,912 $ 45,872 The significant increase in nonperforming TDRs at March 31, 2020 compared to December 31, 2019 primarily related to a $20.9 million CRE relationship that became a performing TDR in the third quarter of 2019 and then moved to nonperforming in the first quarter of 2020 when the borrower experienced financial deterioration that led to cash flow issues. The relationship was individually assessed at March 31, 2020 resulting in no ACL due to the borrower being current on their payments under the modified terms and the relationship is fully collateralized. There were no TDRs that returned to accruing status during the three months ended March 31, 2020. There were three TDRs totaling $1.7 million that returned to accruing status during the three months ended March 31, 2019 . The following tables present the restructured loans by portfolio segment and by type of concession for the three months ended March 31, 2020 and 2019: Three Months Ended March 31, 2020 (dollars in thousands) Number of Pre-Modification (1) Post-Modification (1) Total Difference Totals by Loan Segment Commercial Real Estate Principal deferral and maturity date extension 1 $ 2,210 $ 2,210 $ — Total Commercial Real Estate 1 2,210 2,210 — Commercial and Industrial Principal deferral and maturity date extension 5 3,780 3,780 — Total Commercial and Industrial 5 3,780 3,780 — Commercial Construction — Maturity date extension 1 1,891 1,891 — Total Commercial Construction 1 1,891 1,891 — Consumer Real Estate Consumer bankruptcy (2) 6 388 388 — Maturity date extension and reduction in payment 1 27 27 — Total Consumer Real Estate 7 415 415 — Totals by Concession Type Principal deferral and maturity date extension 6 5,991 5,991 — Maturity date extension 1 1,891 1,891 — Consumer bankruptcy (2) 6 388 388 — Maturity date extension and payment reduction 1 27 27 — Total (3) 14 $ 8,297 $ 8,297 $ — (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. (3) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Three Months Ended March 31, 2019 (dollars in thousands) Number of Pre-Modification ( 1) Post-Modification (1) Total Difference Totals by Loan Segment Commercial and Industrial Maturity date extension and interest rate reduction 1 $ 5,201 $ 5,201 $ — Principal deferral and maturity date extension — — — — Total Commercial and Industrial 1 5,201 5,201 — Residential Mortgage Consumer bankruptcy (2) 1 49 49 — Total Residential Mortgage 1 49 49 — Home Equity Consumer bankruptcy (2) 7 191 168 (23 ) Interest rate reduction 1 81 81 — Maturity date extension and reduction in payment — — — — Total Home Equity 8 272 249 (23 ) Totals by Concession Type Maturity date extension and interest rate reduction 1 5,201 5,201 — Consumer bankruptcy (2) 8 240 217 (23 ) Interest rate reduction 1 81 81 — Total 10 $ 5,522 $ 5,499 $ (23 ) (1) Excludes loans that were fully paid-off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. In response to the COVID-19 pandemic and its economic impact to our customers, we implemented a short-term modification program that complies with the Coronavirus Aid, Relief, and Economic Security, or CARES Act to provide temporary payment relief to those borrowers directly impacted by COVID-19 who were not more than 30 days past due as of December 31, 2019. This program allows for a deferral of payments for 90 days, up to a maximum of 180 days for our commercial customers. The deferred payments along with interest accrued during the deferral period are due and payable on the maturity date. For our consumer customers interest does not accrue during the deferral period and the maturity date is extended by the length of the deferral period. Under the applicable guidance, none of these loans were considered restructured as of March 31, 2020. As of March 31, 2020 , we had 20 commitments to lend an additional $2.3 million on TDRs. Defaulted TDRs are defined as loans having a payment default of 90 days or more after the restructuring takes place. There were 11 TDRs that defaulted during the three months ended March 31, 2020 totaling $21.1 million and no TDRs that defaulted during the three months ended March 31, 2019 that were restructured within the last 12 months prior to defaulting. The large increase in defaulted TDRs is related to one CRE customer with five notes totaling $20.9 million discussed above. The following table is a summary of nonperforming assets as of the dates presented: Nonperforming Assets (dollars in thousands) March 31, 2020 December 31, 2019 Nonperforming Assets Nonaccrual loans $ 37,744 $ 45,145 Nonaccrual TDRs 36,055 8,912 Total Nonaccrual Loans 73,799 54,057 OREO 3,389 3,525 Total Nonperforming Assets $ 77,188 $ 57,582 The significant increase in nonperforming TDRs primarily related to a $20.9 million

Allowance for Credit Losses

Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
ALLOWANCE FOR CREDIT LOSSES	ALLOWANCE FOR CREDIT LOSSES We maintain an ACL at a level determined to be adequate to absorb estimated expected credit losses within the loan portfolio over the contractual life of an instrument that considers our historical loss experience, current conditions and forecasts of future economic conditions as of the balance sheet date. We develop and document a systematic ACL methodology based on the following portfolio segments: 1) Construction, 2) Commercial Real Estate, or CRE, 3) Commercial and Industrial, or C&I, 4) Business Banking, 5) Consumer Real Estate and 6) Other Consumer. The following are key risks within each portfolio segment: CRE —Loans secured by commercial purpose real estate, including both owner-occupied properties and investment properties for various purposes such as hotels, retail, multifamily, and health care. Operations of the individual projects and global cash flows of the debtors are the primary sources of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and the business prospects of the lessee, if the project is not owner-occupied. C&I —Loans made to operating companies or manufacturers for the purpose of production, operating capacity, accounts receivable, inventory or equipment financing. Cash flow from the operations of the company is the primary source of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the industry of the company. Collateral for these types of loans often does not have sufficient value in a distressed or liquidation scenario to satisfy the outstanding debt. Commercial Construction —Loans made to finance construction of buildings or other structures, as well as to finance the acquisition and development of raw land for various purposes. While the risk of these loans is generally confined to the construction period, if there are problems, the project may not be completed, and as such, may not provide sufficient cash flow on its own to service the debt or have sufficient value in a liquidation to cover the outstanding principal. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the type of project and the experience and resources of the developer. Business Banking —Commercial loans made to small businesses that are standard, non-complex products evaluated through a streamlined credit approval process that has been designed to maximize efficiency while maintaining high credit quality standards that meet small business market customers’ needs. The business banking portfolio is monitored by utilizing a standard and closely managed process focusing on behavioral and performance criteria. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and business. Consumer Real Estate —Loans secured by first and second liens such as home equity loans, home equity lines of credit and 1-4 family residential mortgages, including purchase money mortgages. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The state of the local housing market can also have a significant impact on this segment because low demand and/or declining home values can limit the ability of borrowers to sell a property and satisfy the debt. Other Consumer —Loans made to individuals that may be secured by assets other than 1-4 family residences, as well as unsecured loans. This segment includes auto loans, unsecured loans and lines and credit cards. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The value of the collateral, if there is any, is less likely to be a source of repayment due to less certain collateral values. Management monitors various credit quality indicators for the commercial, business banking and consumer loan portfolios, including changes in risk ratings, nonperforming status and delinquency on a monthly basis. We monitor the commercial loan portfolio through an internal risk rating system. Loan risk ratings are assigned based upon the creditworthiness of the borrower and are reviewed on an ongoing basis according to our internal policies. Loans within the pass rating generally have a lower risk of loss than loans risk rated as special mention or substandard. Our risk ratings are consistent with regulatory guidance and are as follows: Pass —The loan is currently performing and is of high quality. Special Mention —A special mention loan has potential weaknesses that warrant management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects or in the strength of our credit position at some future date. Substandard —A substandard loan is not adequately protected by the net worth and/or paying capacity of the borrower or by the collateral pledged, if any. Substandard loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. These loans are characterized by the distinct possibility that we will sustain some loss if the deficiencies are not corrected. Doubtful —Loans classified doubtful have all the weaknesses inherent in those classified substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently known facts, conditions, and values, highly questionable and improbable. The following table presents loan balances by year of origination and internally assigned risk rating for our portfolio segments as of March 31, 2020: Risk Rating (dollars in thousands) 2020 2019 2018 2017 2016 2015 and Prior Revolving Revolving-Term Total Commercial Real Estate Pass $ 169,367 $ 483,699 $ 452,024 $ 359,553 $ 416,420 $ 882,326 $ 59,032 — $ 2,822,421 Special Mention — 3,236 187 11,591 10,005 26,575 850 — 52,444 Substandard — — 1,462 — 25,285 50,348 3,008 21 80,124 Total Commercial Real Estate 169,367 486,935 453,673 371,144 451,710 959,249 62,890 21 2,954,989 Commercial and Industrial Pass 75,969 240,261 165,631 103,537 73,798 282,138 486,045 — 1,427,379 Special Mention — 6,239 3,525 947 1,883 9,437 31,890 — 53,921 Substandard — 5,666 2,301 3,785 1,621 12,232 17,316 — 42,921 Total Commercial and Industrial 75,969 252,166 171,457 108,269 77,302 303,807 535,251 — 1,524,221 Commercial Construction Pass 23,004 179,956 117,527 17,122 18,986 11,586 11,992 — 380,173 Special Mention — — — — — 5,117 91 — 5,208 Substandard — — — 1,041 — 3,780 — — 4,821 Total Commercial Construction 23,004 179,956 117,527 18,163 18,986 20,483 12,083 — 390,202 Business Banking Pass 40,952 181,242 148,419 103,027 89,925 327,333 125,800 — 1,016,698 Special Mention — 62 1,496 1,775 1,181 7,902 737 — 13,153 Substandard — 382 3,111 3,646 4,006 27,803 1,665 — 40,613 Total Business Banking 40,952 181,686 153,026 108,448 95,112 363,038 128,202 — 1,070,464 Consumer Real Estate Pass 33,737 149,942 86,463 83,402 92,013 316,169 432,274 20,966 1,214,966 Special Mention — — — — 798 304 — — 1,102 Substandard — 190 71 537 1,103 7,410 305 1,385 11,001 Total Consumer Real Estate 33,737 150,132 86,534 83,939 93,914 323,883 432,579 22,351 1,227,069 Other consumer Pass 8,706 9,522 10,670 6,474 5,088 3,365 28,156 773 72,754 Special Mention — — — — — — — — — Substandard — 488 132 132 594 4,252 322 1,126 7,046 Total Other Consumer 8,706 10,010 10,802 6,606 5,682 7,617 28,478 1,899 79,800 Total Loan Balance $ 351,735 $ 1,260,885 $ 993,019 $ 696,569 $ 742,706 $ 1,978,077 $ 1,199,483 $ 24,271 $ 7,246,745 We monitor the delinquent status of the commercial and consumer portfolios on a monthly basis. Loans are considered nonperforming when interest and principal are 90 days or more past due or management has determined that a material deterioration in the borrower’s financial condition exists. The risk of loss is generally highest for nonperforming loans. The following table presents loan balances by year of origination and performing and nonperforming status for our portfolio segments as of March 31, 2020: (dollars in thousands) 2020 2019 2018 2017 2016 2015 and Prior Revolving Revolving-Term Total Commercial Real Estate Performing $ 169,367 $ 486,935 $ 453,673 $ 371,144 $ 431,919 $ 935,536 $ 59,882 $ — $ 2,908,456 Nonperforming — — — — 19,791 23,713 3,008 21 46,533 Total Commercial Real Estate 169,367 486,935 453,673 371,144 451,710 959,249 62,890 21 2,954,989 Commercial and Industrial Performing 75,969 252,166 171,093 108,269 76,593 303,745 531,881 — 1,519,716 Nonperforming — — 364 — 709 62 3,370 — 4,505 Total Commercial and Industrial 75,969 252,166 171,457 108,269 77,302 303,807 535,251 — 1,524,221 Commercial Construction Performing 23,004 179,956 117,527 18,055 18,986 20,020 12,083 — 389,631 Nonperforming — — — 108 — 463 — — 571 Total Commercial Construction 23,004 179,956 117,527 18,163 18,986 20,483 12,083 — 390,202 Business Banking Performing 40,952 181,576 151,933 107,176 94,230 355,259 128,022 — 1,059,148 Nonperforming — 110 1,093 1,272 882 7,779 180 — 11,316 Total Business Banking 40,952 181,686 153,026 108,448 95,112 363,038 128,202 — 1,070,464 Consumer Real Estate Performing 33,737 149,942 86,401 83,526 90,151 318,926 432,403 21,367 1,216,453 Nonperforming — 190 133 413 3,763 4,957 176 984 10,616 Total Consumer Real Estate 33,737 150,132 86,534 83,939 93,914 323,883 432,579 22,351 1,227,069 Other Consumer Performing 8,706 10,010 10,802 6,606 5,682 7,359 28,478 1,899 79,542 Nonperforming — — — — — 258 — — 258 Total Other Consumer 8,706 10,010 10,802 6,606 5,682 7,617 28,478 1,899 79,800 Performing 351,735 1,260,585 991,429 694,776 717,561 1,940,845 1,192,749 23,266 7,172,946 Nonperforming — 300 1,590 1,793 25,145 37,232 6,734 1,005 73,799 Total Loan Balance $ 351,735 $ 1,260,885 $ 993,019 $ 696,569 $ 742,706 $ 1,978,077 $ 1,199,483 $ 24,271 $ 7,246,745 The following tables present the age analysis of past due loans segregated by class of loans as of the dates presented: March 31, 2020 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days Past Due (1) Non - performing Total Past Due Loans Total Loans Commercial real estate $ 2,901,375 $ 6,381 $ — $ 700 $ 46,533 $ 53,614 $ 2,954,989 Commercial and industrial 1,516,639 463 — 2,615 4,505 7,582 1,524,221 Commercial construction 388,122 576 — 933 571 2,080 390,202 Business banking 1,048,241 6,758 3,381 768 11,316 22,223 1,070,464 Consumer real estate 1,211,865 3,859 646 83 10,616 15,203 1,227,069 Other consumer 79,083 174 91 195 258 717 79,800 Total $ 7,145,326 $ 18,211 $ 4,117 $ 5,294 $ 73,799 $ 101,419 $ 7,246,745 (1) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument. December 31, 2019 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days Past Due (1) Non - performing Total Past Total Loans Commercial real estate $ 3,025,505 $ 7,749 $ 71 $ 911 $ 25,356 $ 34,087 $ 3,059,592 Commercial and industrial 1,466,460 126 1,589 1,443 10,911 14,069 1,480,529 Commercial construction 367,204 956 1,163 — 737 2,856 370,060 Business banking 830,735 5,093 1,099 — 9,863 16,055 846,790 Consumer real estate 1,283,591 2,620 1,758 1,175 6,063 11,616 1,295,207 Other consumer 81,866 1,448 305 228 1,127 3,108 84,974 Total $ 7,055,361 $ 17,992 $ 5,985 $ 3,757 $ 54,057 $ 81,791 $ 7,137,152 (1) Represents acquired loans that were recorded at fair value at the acquisition date and remain performing at March 31, 2020 and December 31, 2019. The following table presents loans on nonaccrual status and loans past due 90 days or more and still accruing by class of loan: As or for the Three Months Ended March 31, 2020 (dollars in thousands) Beginning of Period Nonaccrual End of Period Nonaccrual Nonaccrual With No Related Allowance Past Due 90+ Days Still Accruing Interest Income Recognized on Nonaccrual Commercial real estate $25,356 $ 46,533 $39,454 $ 700 $684 Commercial and industrial 10,911 4,505 4,054 2,615 64 Commercial construction 737 571 285 933 — Business banking 9,863 11,316 2,363 768 58 Consumer real estate 6,063 10,616 398 83 47 Other consumer 1,127 258 — 195 28 Total $54,057 $73,799 $46,554 $ 5,294 $881 The following table presents collateral-dependent loans by class of loan: March 31, 2020 Type of Collateral (dollars in thousands) Real Estate Blanket Lien Investment/Cash Other Commercial real estate $51,630 $— $— $— Commercial and industrial 4,686 4,545 40 — Commercial construction 3,602 — — — Business banking 2,322 876 — 689 Consumer real estate — — — — Other consumer 398 — — — Total $62,638 $5,421 $40 $689 The following table presents activity in the ACL for the three months ended March 31, 2020: Three Months Ended March 31, 2020 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Business Banking (1) Consumer Real Estate Other Consumer Total Loans Allowance for credit losses on loans: Balance at beginning of period $ 30,577 $ 15,681 $ 7,900 $ — $ 6,337 $ 1,729 $ 62,224 Impact of CECL adoption 4,810 7,853 (3,376 ) 12,898 4,525 642 27,352 Provision for credit losses on loans 7,639 6,196 2,309 1,194 472 620 18,430 Charge-offs (442 ) (9,879 ) (229 ) (460 ) (172 ) (248 ) (11,430 ) Recoveries 27 19 2 74 38 114 274 Net (Charge-offs)/Recoveries (415 ) (9,860 ) (227 ) (386 ) (134 ) (134 ) (11,156 ) Balance at End of Period $ 42,611 $ 19,870 $ 6,606 $ 13,706 $ 11,200 $ 2,857 $ 96,850 (1) 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. Our new segmentation breaks out business banking loans from our other loan segments: CRE, C&I , commercial construction, consumer real estate and other consumer. The business banking allowance balance at the beginning of period is included in the other segments and reclassified to business banking through the impact of CECL adoption line. 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. We also recorded a day one adjustment of $9.9 million primarily related to a 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 10-K, but before the end of the first quarter of 2020. The updated information supported a loss existed at January 1, 2020. The significant increase in the provision for credit losses during the three months ended March 31, 2020 was mainly due to the COVID-19 pandemic. We added approximately $14.9 million to the ACL in the first quarter of 2020 related to qualitative factors. This included $11.2 million for a revised economic forecast and the impact of that forecast on certain loan portfolios due to the COVID-19 pandemic. Changes in current conditions resulted in an additional $3.7 million increase in the ACL. Prior to the adoption of ASU 326 on January 1, 2020, we calculated our allowance for loan losses using an incurred loan loss methodology. The following tables are disclosures related to the allowance for loan losses in prior periods. The following table presents the recorded investment in commercial loan classes by internally assigned risk ratings as of December 31, 2019: December 31, 2019 (dollars in thousands) Commercial % of Commercial % of Commercial % of Total % of Pass $ 3,270,437 95.7 % $ 1,636,314 93.4 % $ 347,324 92.5 % $ 5,254,076 95.3 % Special mention 57,285 1.7 % 36,484 1.7 % 10,109 2.7 % 103,878 1.9 % Substandard 86,772 2.5 % 47,980 4.9 % 17,899 4.8 % 152,651 2.8 % Doubtful 2,023 — % 55 — % 133 — % 2,191 — % Total $ 3,416,518 100.0 % $ 1,720,833 100.0 % $ 375,445 100.0 % $ 5,512,796 100.0 % The following table presents the recorded investment in consumer loan classes by performing and nonperforming status as of December 31, 2019: December 31, 2019 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and Other Consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 991,066 99.2 % $ 535,709 99.5 % $ 78,993 99.9 % $ 8,390 100.0 % $ 1,614,158 99.4 % Nonperforming 7,519 0.8 % 2,639 0.5 % 40 0.1 % — — % 10,198 0.6 % Total $ 998,585 100.0 % $ 538,348 100.0 % $ 79,033 100.0 % $ 8,390 100.0 % $ 1,624,356 100.0 % The following table presents investments in loans considered to be impaired and related information on those impaired loans as of December 31, 2019: December 31, 2019 (dollars in thousands) Recorded Unpaid Related With a related allowance recorded: Commercial real estate $ 13,011 $ 14,322 $ 2,023 Commercial and industrial 10,001 10,001 55 Commercial construction 489 489 113 Consumer real estate — — — Other consumer 9 9 9 Total with a Related Allowance Recorded 23,510 24,821 2,200 Without a related allowance recorded: Commercial real estate 34,909 40,201 — Commercial and industrial 7,605 10,358 — Commercial construction 1,425 2,935 — Consumer real estate 7,884 8,445 — Other consumer 4 11 — Total without a Related Allowance Recorded 51,827 61,950 — Total: Commercial real estate 47,920 54,523 2,023 Commercial and industrial 17,606 20,359 55 Commercial construction 1,914 3,424 113 Consumer real estate 7,884 8,445 — Other consumer 13 20 9 Total $ 75,337 $ 86,771 $ 2,200 The following table presents average recorded investment and interest income recognized on impaired loans for the three months ended March 31, 2019: Three months ended March 31, 2019 (dollars in thousands) Average Recorded Investment Interest Income Recognized With a related allowance recorded: Commercial real estate $ 15,107 $ 144 Commercial and industrial 12,780 209 Commercial construction 2,319 140 Consumer real estate 8,846 417 Other consumer 4 — Total with a Related Allowance Recorded 39,056 910 Without a related allowance recorded: Commercial real estate 12,983 400 Commercial and industrial 980 35 Commercial construction 489 — Consumer real estate 14 1 Other consumer 10 1 Total without a Related Allowance Recorded 14,476 437 Total: Commercial real estate 28,090 544 Commercial and industrial 13,760 244 Commercial construction 2,808 140 Consumer real estate 8,860 418 Other consumer 14 1 Total $ 53,532 $ 1,347 The following table details activity in the allowance for loan losses for the three months ended March 31, 2019: Three Months Ended March 31, 2019 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of period $ 33,707 $ 11,596 $ 7,983 $ 6,187 $ 1,494 $ 6,996 Charge-offs (1 ) (5,477 ) — (162 ) (425 ) (6,023 ) Recoveries 122 417 — 148 169 787 Net (Charge-offs)/Recoveries 121 (5,060 ) — (14 ) (256 ) (5,236 ) Provision for credit losses 1,075 5,460 (1,226 ) 5 249 5,649 Balance at End of Period $ 34,903 $ 11,996 $ 6,757 $ 6,178 $ 1,487 $ 61,409 The following tables present the allowance for loan losses and recorded investments in loans by category as of December 31,2019: December 31, 2019 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ 2,023 $ 28,554 $ 30,577 $ 47,920 $ 3,368,598 $ 3,416,518 Commercial and industrial 55 15,626 15,681 17,606 1,703,227 1,720,833 Commercial construction 113 7,787 7,900 1,914 373,531 375,445 Consumer real estate — 6,337 6,337 7,884 1,537,439 1,545,323 Other consumer 9 1,720 1,729 13 79,020 79,033 Total $ 2,200 $ 60,024 $ 62,224 $ 75,337 $ 7,061,815 $ 7,137,152

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Interest Rate Swaps In accordance with applicable accounting guidance for derivatives and hedging, all derivatives are recognized as either assets or liabilities on the balance sheet at fair value. Interest rate swaps are contracts in which a series of interest rate flows (fixed and variable) are exchanged over a prescribed period. The notional amounts on which the interest payments are based are not exchanged. These derivative positions relate to transactions in which we enter into an interest rate swap with a commercial customer while at the same time entering into an offsetting interest rate swap with another financial institution. In connection with each transaction, we agree to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on the same notional amount at a fixed rate. At the same time, we agree to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. The transaction allows our customer to effectively convert a variable rate loan to a fixed rate loan with us receiving a variable rate. These agreements could have floors or caps on the contracted interest rates. Pursuant to our agreements with various financial institutions, we may receive collateral or may be required to post collateral based upon mark-to-market positions. Beyond unsecured threshold levels, collateral in the form of cash or securities may be made available to counterparties of interest rate swap transactions. Based upon our current positions and related future collateral requirements relating to them, we believe any effect on our cash flow or liquidity position to be immaterial. Derivatives contain an element of credit risk, the possibility that we will incur a loss because a counterparty, which may be a financial institution or a customer, fails to meet its contractual obligations. All derivative contracts with financial institutions may be executed only with counterparties approved by our Asset and Liability Committee, or ALCO, and derivatives with customers may only be executed with customers within credit exposure limits approved by our Senior Loan Committee. Interest rate swaps are considered derivatives but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives are recorded in current earnings and included in other noninterest income in the Consolidated Statements of Comprehensive Income. Interest Rate Lock Commitments and Forward Sale Contracts In the normal course of business, we sell originated mortgage loans into the secondary mortgage loan market. We also offer interest rate lock commitments to potential borrowers. The commitments are generally for a period of 60 days and guarantee a specified interest rate for a loan if underwriting standards are met, but the commitment does not obligate the potential borrower to close on the loan. Accordingly, some commitments expire prior to becoming loans. We may encounter pricing risks if interest rates increase significantly before the loan can be closed and sold. We may utilize forward sale contracts in order to mitigate this pricing risk. Whenever a customer desires these products, a mortgage originator quotes a secondary market rate guaranteed for that day by the investor. The rate lock is executed between the mortgagee and us and in turn a forward sale contract may be executed between us and the investor. Both the rate lock commitment and the corresponding forward sale contract for each customer are considered derivatives but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives during the commitment period are recorded in current earnings and included in mortgage banking in the Consolidated Statements of Comprehensive Income. The following table indicates the amounts representing the value of derivative assets and derivative liabilities as of the dates presented: Derivatives Derivatives (included in Other Liabilities) (dollars in thousands) March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Derivatives not Designated as Hedging Instruments: Interest Rate Swap Contracts - Commercial Loans Fair value $ 88,135 $ 25,647 $ 87,989 $ 25,615 Notional amount 918,481 740,762 918,481 740,762 Collateral posted — — 86,720 26,127 Interest Rate Lock Commitments - Mortgage Loans Fair value 2,927 321 — — Notional amount 86,674 9,829 — — Forward Sale Contracts - Mortgage Loans Fair value — 1 1,292 — Notional amount $ — $ 12,750 $ 91,750 $ — Presenting offsetting derivatives that are subject to legally enforceable netting arrangements with the same party is permitted. For example, we may have a derivative asset and a derivative liability with the same counterparty to a swap transaction and we are permitted to offset the asset position and the liability position resulting in a net presentation. The following table indicates the gross amounts of commercial loan swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets as of the dates presented: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Derivatives not Designated as Hedging Instruments: Gross amounts recognized $ 90,723 $ 26,146 $ 90,577 $ 26,114 Gross amounts offset (2,588 ) (499 ) (2,588 ) (499 ) Net Amounts Presented in the Consolidated Balance Sheets 88,135 25,647 87,989 25,615 Gross amounts not offset (1) — — (86,720 ) (26,127 ) Net Amount $ 88,135 $ 25,647 $ 1,269 $ (512 ) (1) Amounts represent collateral posted for the periods presented. The following table indicates the gain or loss recognized in income on derivatives for the periods presented: Three Months Ended March 31, (dollars in thousands) 2020 2019 Derivatives not Designated as Hedging Instruments Interest rate swap contracts—commercial loans $ 114 $ (122 ) Interest rate lock commitments—mortgage loans 2,606 88 Forward sale contracts—mortgage loans (1,293 ) 33 Total Derivatives Gain/(Loss) $ 1,427 $ (1 )

Borrowings

Borrowings	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
BORROWINGS	BORROWINGS Short-term borrowings are for terms under or equal to one year and are comprised of securities sold under repurchase agreements, or REPOs and FHLB advances. All REPOs are overnight short-term investments and are not insured by the Federal Deposit Insurance Corporation, or FDIC. Securities pledged as collateral under these REPO financing arrangements cannot be sold or repledged by the secured party and, therefore, the REPOs are accounted for as secured borrowings. Mortgage-backed securities with amortized cost of $66.4 million and carrying value of $70.0 million at March 31, 2020 and amortized cost of $22.7 million and carrying value of $23.0 million at December 31, 2019 , were pledged as collateral for these secured transactions. The pledged securities are held in safekeeping at the Federal Reserve. Due to the overnight short-term nature of REPOs, potential risk due to a decline in the value of the pledged collateral is low. Collateral pledging requirements with REPOs are monitored daily. FHLB advances are for various terms and are secured by a blanket lien on residential mortgages and other real estate secured loans. Long-term borrowings are for original terms greater than one year and are comprised of FHLB advances, finance leases and junior subordinated debt securities. Long-term FHLB advances are secured by the same loans as short-term FHLB advances. We had total long-term borrowings outstanding of $45.6 million at a fixed rate and $67.1 million at a variable rate at March 31, 2020 , excluding our finance leases. Information pertaining to borrowings is summarized in the table below as of the dates presented: March 31, 2020 December 31, 2019 (dollars in thousands) Balance Weighted Balance Weighted Short-term Borrowings Securities sold under repurchase agreements $ 69,644 0.25 % $ 19,888 0.74 % Short-term borrowings 410,240 0.44 % 281,319 1.84 % Total Short-term Borrowings 479,884 0.41 % 301,207 1.76 % Long-term Borrowings Long-term borrowings 50,180 2.59 % 50,868 2.60 % Junior subordinated debt securities 64,038 3.63 % 64,277 3.59 % Total Long-term Borrowings 114,218 3.17 % 115,145 3.15 % Total Borrowings $ 594,102 0.94 % $ 416,352 2.14 % We had total borrowings at the FHLB of Pittsburgh of $458.9 million at March 31, 2020 and $532.9 million at December 31, 2019 . The $458.9 million at March 31, 2020 consisted of $410.2 million in short-term borrowings and $50.2 million in long-term borrowings. Our maximum borrowing capacity with the FHLB of Pittsburgh was $3.1 billion at March 31, 2020 . We utilized $698.1 million of our borrowing capacity at March 31, 2020 consisting of $458.9 million for borrowings and $239.2 million for letters of credit to collateralize public funds. Our remaining borrowing availability at March 31, 2020 is $2.4 billion . We have completed three private placements of trust preferred securities to financial institutions. As a result, we own 100 percent of the common equity of STBA Capital Trust I, DNB Capital Trust I and DNB Capital Trust II, collectively the Trusts. The Trusts were formed to issue mandatorily redeemable capital securities to third-party investors. The proceeds from the sale of the securities and the issuance of the common equity by the Trusts were invested in junior subordinated debt securities issued by us. The Trusts are variable interest entities, and the third-party investors are the primary beneficiaries; therefore, the trusts are not consolidated into our financial statements. The Trusts pays dividends on the securities at the same rate as the interest paid by us on the junior subordinated debt held by the Trusts. DNB Capital Trust I and DNB Capital Trust II were acquired with the DNB merger.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments In the normal course of business, we offer off-balance sheet credit arrangements to enable our customers to meet their financing objectives. These instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the financial statements. Our exposure to credit loss, in the event the customer does not satisfy the terms of the agreement, equals the contractual amount of the obligation less the value of any collateral. We apply the same credit policies in making commitments and standby letters of credit that are used for the underwriting of loans to customers. Commitments generally have fixed expiration dates, annual renewals or other termination clauses and may require payment of a fee. Because many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. Estimates of the fair value of these off-balance sheet items were not made because of the short-term nature of these arrangements and the credit standing of the counterparties. The following table sets forth our commitments and letters of credit as of the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Commitments to extend credit $ 1,967,190 $ 1,910,805 Standby letters of credit 85,021 80,040 Total $ 2,052,211 $ 1,990,845 Allowance for Credit Losses on Unfunded Loan Commitments We maintain an allowance for credit losses on unfunded commercial lending commitments and letters of credit to provide for the risk of loss inherent in these arrangements. The allowance is computed using a methodology similar to that used to determine the allowance for credit losses for loans, modified to take into account the probability of a draw-down on the commitment. The provision for credit losses on unfunded loan commitments is included in the provision for credit losses on our Consolidated Statements of Comprehensive Income. The allowance for unfunded commitments is included in other liabilities in the Consolidated Balance Sheets. The activity in the allowance for credit losses on unfunded loan commitments for the three months ended March 31, 2020 was as follows: (dollars in thousands) Total Three months ended March 31, 2020 Allowance for credit losses on unfunded loan commitments: Balance at beginning of period $ 3,112 Impact of adopting ASU 2016-13 1,349 January 1, 2020 4,461 Provision for credit losses 1,616 March 31, 2020 $ 6,077 Litigation In the normal course of business, we are subject to various legal and administrative proceedings and claims. While any type of litigation contains a level of uncertainty, we believe that the outcome of such proceedings or claims pending will not have a material adverse effect on our consolidated financial position or results of operations.

Revenue From Contracts With Cus

Revenue From Contracts With Customers	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS	REVENUE FROM CONTRACTS WITH CUSTOMERS We earn revenue from contracts with our customers when we have completed our performance obligations and recognize that revenue when services are provided to our customers. Our contracts with customers are primarily in the form of account agreements. Generally, our services are transferred at a point in time in response to transactions initiated and controlled by our customers under service agreements with an expected duration of one year or less. Our customers have the right to terminate their service agreements at any time. We do not defer incremental direct costs to obtain contracts with customers that would be amortized in one year or less. These costs are primarily salaries and employee benefits recognized as expense in the period incurred. Service charges on deposit accounts - We recognize monthly service charges for both commercial and personal banking customers based on account fee schedules. Our performance obligation is generally satisfied and the related revenue recognized at a point in time or over time when the services are provided. Other fees are earned based on specific transactions or customer activity within the customers' deposit accounts. These are earned at the time the transaction or customer activity occurs. Debit and credit card services - Interchange fees are earned whenever debit and credit cards are processed through third-party card payment networks. ATM fees are based on transactions by our customers' and other customers' use of our ATMs or other ATMs. Debit and credit card revenue is recognized at a point in time when the transaction is settled. Our performance obligation to our customers is generally satisfied and the related revenue is recognized at a point in time when the service is provided. Third-party service contracts include annual volume and marketing incentives which are recognized over a period of twelve months when we meet thresholds as stated in the service contract. Wealth management services - Wealth management services are primarily comprised of fees earned from the management and administration of trusts, assets under administration and other financial advisory services. Generally, wealth management fees are earned over a period of time between monthly and annually, per the related fee schedules. Our performance obligations with our customers are generally satisfied when we provide the services as stated in the customers' agreements. The fees are based on a fixed amount or a scale based on the level of services provided or amount of assets under management. Other fee revenue - Other fee revenue includes a variety of other traditional banking services such as, electronic banking fees, letters of credit origination fees, wire transfer fees, money orders, treasury checks, checksale fees and transfer fees. Our performance obligations are generally satisfied at a point in time, while fee revenue is recognized when the services are provided or the transaction is settled. The information presented in the following table presents the point of revenue recognition for revenue from contracts with customers. Other revenue streams such as: interest income, net securities gains and losses, insurance, mortgage banking and other revenues that are accounted for under other generally accepted accounting principles are excluded. (dollars in thousands) Three Months Ended March 31, Revenue Streams Point of Revenue Recognition 2020 2019 Service charges on deposit accounts Over a period of time $ 484 $ 457 At a point in time 3,074 2,696 $ 3,558 $ 3,153 Debit and credit card Over a period of time $ 194 $ 185 At a point in time 3,287 2,789 $ 3,482 $ 2,974 Wealth management Over a period of time $ 345 $ 413 At a point in time 2,018 1,635 $ 2,362 $ 2,048 Other fee revenue At a point in time $ 919 $ 919

Other Comprehensive Income_(Los

Other Comprehensive Income/(Loss)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
OTHER COMPREHENSIVE INCOME/(LOSS)	OTHER COMPREHENSIVE INCOME/(LOSS) The following table presents the change in components of other comprehensive income/(loss) for the periods presented, net of tax effects. Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 (dollars in thousands) Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount Change in net unrealized gains/(losses) on available-for-sale debt securities (1) $ 21,568 $ (4,592 ) $ 16,976 $ 7,398 $ (1,578 ) $ 5,820 Adjustment to funded status of employee benefit plans 465 (99 ) 366 453 (97 ) 356 Other Comprehensive Income/(Loss) $ 22,033 $ (4,691 ) $ 17,342 $ 7,851 $ (1,675 ) $ 6,176 (1) Reclassification adjustments are comprised of realized security gains or losses. The realized gains or losses have been reclassified out of accumulated other comprehensive income/(loss) and have affected certain lines in the Consolidated Statements of Comprehensive Income as follows: the pre-tax amount is included in net gain on sale of securities, the tax expense amount is included in the provision for income taxes and the net of tax amount is included in net income. There were no reclassification adjustments for the three months ended March 31, 2020 or 2019.

Employee Benefits

Employee Benefits	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
EMPLOYEE BENEFITS	EMPLOYEE BENEFITS Our qualified and nonqualified defined benefit plans were amended to freeze benefit accruals for all persons entitled to benefits under the plans in 2016. We will continue recording pension expense related to these plans, primarily representing interest costs on the accumulated benefit obligation and amortization of actuarial losses accumulated in the plans, as well as income from expected investment returns on pension assets. Since the plans have been frozen, no service costs are included in net periodic pension expense. The defined benefit plan of DNB was merged into S&T's defined benefit plan at November 30, 2019 and the components of net periodic pension cost at March 31, 2020 include the impact of the addition of the DNB defined benefit plan. The investment policy for S&T's defined benefit plan is 85 percent to 95 percent fixed income and 5 percent to 15 percent equity and cash. The expected long-term rate of return on plan assets is 3.50 percent compared to 4.80 percent in prior periods. The following table summarizes the components of net periodic pension cost for the periods presented: Three Months Ended March 31, (dollars in thousands) 2020 2019 Components of Net Periodic Pension Cost Interest cost on projected benefit obligation $ 891 $ 989 Expected return on plan assets (972 ) (1,180 ) Net amortization 384 394 Net Periodic Pension Expense $ 303 $ 203 The components of net periodic pension expense are included in salaries and employee benefits on the Consolidated Statements of Comprehensive Income.

Qualified Affordable Housing

Qualified Affordable Housing	3 Months Ended
	Mar. 31, 2020
Investments in Affordable Housing Projects [Abstract]
QUALIFIED AFFORDABLE HOUSING	QUALIFIED AFFORDABLE HOUSING As part of our responsibilities under the Community Reinvestment Act and due to their favorable federal income tax benefits, we invest in Low Income Housing projects. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. We use the cost method to account for these partnerships. Our total investment in qualified affordable housing projects was $6.4 million at March 31, 2020 and $4.8 million at December 31, 2019 . Amortization expense, included in other noninterest expense in the Consolidated Statements of Comprehensive Income, was $0.6 million for the three months ended March 31, 2020 and $0.7 million for the three months ended March 31, 2019 . The amortization expense was offset by tax credits of $0.6 million for the three months ended March 31, 2020 and $0.7 million for the three months ended March 31, 2019 as a reduction to our federal tax provision. On September 11, 2019, we entered into a new qualified affordable housing project and committed to an investment of $10.2 million . As of March 31, 2020, we have invested $3.6 million in this new project. No amortization expense or tax credits will be recognized for this new project until complete, which we expect to be later in 2020.

Share Repurchase Plan

Share Repurchase Plan	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
SHARE REPURCHASE PLAN	SHARE REPURCHASE PLAN On September 16, 2019, our Board of Directors authorized a $50 million share repurchase plan. This repurchase authorization, which is effective through March 31, 2021, permits S&T to repurchase from time to time up to $50 million in aggregate value of shares of S&T's common stock through a combination of open market and privately negotiated repurchases. The specific timing, price and quantity of repurchases will be at the discretion of S&T and will depend on a variety of factors, including general market conditions, the trading price of common stock, legal and contractual requirements, applicable securities laws and S&T's financial performance. The repurchase plan does not obligate us to repurchase any particular number of shares. We expect to fund any repurchases from cash on hand and internally generated funds. During the three months ended March 31, 2020, we repurchased 411,430 common shares at a total cost of $12.6 million , or an average of $30.52 per share. Repurchase activity was suspended in March as the impact of the COVID-19 pandemic spread.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Paycheck Protection Program On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security, or CARES Act was signed into law. It contains substantial tax and spending provisions intended to address the impact of the COVID-19 pandemic. The CARES Act includes the Paycheck Protection Program, or PPP, a $349 billion program designed to aid small and medium sized businesses through federally guaranteed loans distributed through banks. The Paycheck Protection Program and Health Care Enhancement Act, or PPP/HCEA Act, was signed into law on April 24, 2020. Among other provisions, the PPP/HCEA Act authorized an additional $310 billion of funding under the CARES Act for PPP loans. These loans are intended to cover eight weeks of payroll and other costs to help those businesses remain viable. As of May 5, 2020, we had obtained approvals for 2,959 loans totaling $548.0 million .

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation	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	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 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.
Reclassification	Reclassification A mounts in prior period financial statements and footnotes are reclassified whenever necessary to conform to the current period presentation. Reclassifications had no effect on our results of operations or financial condition.
Use of Estimates	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 or Update	Accounting Standards Issued But Not Yet Adopted Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Changes to the Disclosure Requirements for Defined Benefit Plans 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. Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 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. Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting 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. Recently Adopted Accounting Standards Updates, or ASU or Update 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 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. Fair Value Measurement - Changes to the Disclosure Requirements for Fair Value Measurement 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. Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment 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. Financial Instruments - Credit Losses 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. We made the accounting policy election to not measure an ACL for accrued interest receivables for loans and securities. Accrued interest deemed uncollectible will be written off through interest income. The majority of our available-for-sale debt securities are government agency-backed securities for which the risk of loss is minimal, and accordingly the ACL is immaterial. 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. The following table details the impact of ASU 2016-13 and the reclassification of loans for the identification of new portfolio loan segments under CECL: 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
Allowance for Credit Losses Policy	Allowance for Credit Losses Policy 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 methodology for determining the ACL has two main components: evaluation of expected credit losses for certain groups of homogeneous loans that share similar risk characteristics and evaluation of loans that do not share risk characteristics with other loans. 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.
Accounting Standards Issued But Not Yet Adopted	Accounting Standards Issued But Not Yet Adopted Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Changes to the Disclosure Requirements for Defined Benefit Plans 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. Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 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. Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting 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. Recently Adopted Accounting Standards Updates, or ASU or Update 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 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. Fair Value Measurement - Changes to the Disclosure Requirements for Fair Value Measurement 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. Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment 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. Financial Instruments - Credit Losses 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. We made the accounting policy election to not measure an ACL for accrued interest receivables for loans and securities. Accrued interest deemed uncollectible will be written off through interest income. The majority of our available-for-sale debt securities are government agency-backed securities for which the risk of loss is minimal, and accordingly the ACL is immaterial. 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. The following table details the impact of ASU 2016-13 and the reclassification of loans for the identification of new portfolio loan segments under CECL: 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
Fair Value Measurements	We use fair value measurements when recording and disclosing certain financial assets and liabilities. Debt securities, equity securities and derivative financial instruments are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record other assets at fair value on a nonrecurring basis, such as loans held for sale, loans held for investment, other real estate owned, or OREO, and other repossessed assets, mortgage servicing rights, or MSRs, and certain other assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets or liabilities; it is not a forced transaction. In determining fair value, we use various valuation approaches, including market, income and cost approaches. The fair value standard establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability, which are developed based on market data that we have obtained from independent sources. Unobservable inputs reflect our estimates of assumptions that market participants would use in pricing an asset or liability, which are developed based on the best information available in the circumstances. The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: Level 1: valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2: valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3: valuation is derived from other valuation methodologies, including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our policy is to recognize transfers between any of the fair value hierarchy levels at the end of the reporting period in which the transfer occurred. The following are descriptions of the valuation methodologies that we use for financial instruments recorded at fair value on either a recurring or nonrecurring basis. Recurring Basis Available-for-Sale Debt Securities We obtain fair values for debt securities from a third-party pricing service which utilizes several sources for valuing fixed-income securities. We validate prices received from our pricing service through comparison to a secondary pricing service and broker quotes. We review the methodologies of the pricing services which provide us with a sufficient understanding of the valuation models, assumptions, inputs and pricing to reasonably measure the fair value of our debt securities. The market valuation sources for debt securities include observable inputs rather than significant unobservable inputs and are classified as Level 2. The service provider utilizes pricing models that vary by asset class and include available trade, bid and other market information. Generally, the methodologies include broker quotes, proprietary models, vast descriptive terms and conditions databases, and extensive quality control programs. Equity Securities Marketable equity securities that have an active, quotable market are classified as Level 1. Marketable equity securities that are quotable, but are thinly traded or inactive, are classified as Level 2. Marketable equity securities that are not readily traded and do not have a quotable market are classified as Level 3. Deferred Compensation Plan Assets We use quoted market prices to determine the fair value of our equity security assets. These securities are reported at fair value with the gains and losses included in noninterest income in our Consolidated Statements of Comprehensive Income. These assets are held in a deferred compensation plan and are invested in readily quoted mutual funds. Accordingly, these assets are classified as Level 1. Deferred compensation plan assets are reported in other assets in the Consolidated Balance Sheets. Derivative Financial Instruments We use derivative instruments, including interest rate swaps for commercial loans with our customers, interest rate lock commitments and the sale of mortgage loans in the secondary market. We calculate the fair value for derivatives using accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Each valuation considers the contractual terms of the derivative, including the period to maturity, and uses observable market-based inputs, such as interest rate curves and implied volatilities. Accordingly, derivatives are classified as Level 2. We incorporate credit valuation adjustments into the valuation models to appropriately reflect both our own nonperformance risk and the respective counterparties’ nonperformance risk in calculating fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements and collateral postings. Nonrecurring Basis Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and, from time to time, certain loans are transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. The fair value of 1-4 family residential loans is based on the principal or most advantageous market currently offered for similar loans using observable market data. The fair value of the loans transferred from the loan portfolio is based on the amounts offered for these loans in currently pending sales transactions. Loans held for sale carried at fair value are classified as Level 3. Loans Held for Investment Loans that are individually evaluated to determine whether a specific allocation of ACL is needed are reported at fair value. Fair value is determined using the following methods: 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 less estimated selling costs when the loan is collateral dependent and we expect to liquidate the collateral. However, if repayment is expected to come from the operation of the collateral, rather than liquidation, then we do not consider estimated selling costs in determining the fair value of the collateral. Collateral values are generally based upon appraisals by approved, independent state certified appraisers. Appraisals may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or our knowledge of the borrower and the borrower’s business. Loans carried at fair value are classified as Level 3. OREO and Other Repossessed Assets OREO and other repossessed assets obtained in partial or total satisfaction of a loan are recorded at the lower of recorded investment in the loan or fair value less cost to sell. Subsequent to foreclosure, these assets are carried at the lower of the amount recorded at acquisition date or fair value less cost to sell. Accordingly, it may be necessary to record nonrecurring fair value adjustments. Fair value, when recorded, is generally based upon appraisals by approved, independent state certified appraisers. Appraisals on OREO may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or other information available to us. OREO and other repossessed assets carried at fair value are classified as Level 3. Mortgage Servicing Rights The fair value of MSRs is determined by calculating the present value of estimated future net servicing cash flows, considering expected mortgage loan prepayment rates, discount rates, servicing costs and other economic factors, which are determined based on current market conditions. The expected rate of mortgage loan prepayments is the most significant factor driving the value of MSRs. MSRs are considered impaired if the carrying value exceeds fair value. Since the valuation model includes significant unobservable inputs as listed above, MSRs are classified as Level 3. MSRs are reported in other assets in the Consolidated Balance Sheets and are amortized into mortgage banking income in the Consolidated Statements of Comprehensive Income. Other Assets We measure certain other assets at fair value on a nonrecurring basis. Fair value is based on the application of lower of cost or fair value accounting, or write-downs of individual assets. Valuation methodologies used to measure fair value are consistent with overall principles of fair value accounting and consistent with those described above. Financial Instruments In addition to financial instruments recorded at fair value in our financial statements, fair value accounting guidance requires disclosure of the fair value of all of an entity’s assets and liabilities that are considered financial instruments. The majority of our assets and liabilities are considered financial instruments. Many of these instruments lack an available trading market as characterized by a willing buyer and a willing seller engaged in an exchange transaction. Also, it is our general practice and intent to hold our financial instruments to maturity and to not engage in trading or sales activities with respect to such financial instruments. For fair value disclosure purposes, we substantially utilize the fair value measurement criteria as required and explained above. In cases where quoted fair values are not available, we use present value methods to determine the fair value of our financial instruments. Cash and Cash Equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks, including interest-bearing deposits, approximate fair value. Loans The fair value of variable rate loans that may reprice frequently at short-term market rates is based on carrying values adjusted for liquidity and credit risk. The fair value of variable rate loans that reprice at intervals of one year or longer, such as adjustable rate mortgage products, is estimated using discounted cash flow analyses that utilize interest rates currently being offered for similar loans and adjusted for liquidity and credit risk. The fair value of fixed rate loans is estimated using a discounted cash flow analysis that utilizes interest rates currently being offered for similar loans adjusted for liquidity and credit risk. Bank Owned Life Insurance Fair value approximates net cash surrender value of bank owned life insurance, or BOLI. Federal Home Loan Bank, or FHLB, and Other Restricted Stock It is not practical to determine the fair value of our FHLB and other restricted stock due to the restrictions placed on the transferability of these stocks; it is presented at carrying value. Deposits The fair values disclosed for deposits without defined maturities ( e.g. , noninterest and interest-bearing demand, money market and savings accounts) are by definition equal to the amounts payable on demand. The carrying amounts for variable rate, fixed-term time deposits approximate their fair values. Estimated fair values for fixed rate and other time deposits are based on discounted cash flow analysis using interest rates currently offered for time deposits with similar terms. The carrying amount of accrued interest approximates fair value. Short-Term Borrowings The carrying amounts of securities sold under repurchase agreements, or REPOs, and other short-term borrowings approximate their fair values. Long-Term Borrowings The fair values disclosed for fixed rate long-term borrowings are determined by discounting their contractual cash flows using current interest rates for long-term borrowings of similar remaining maturities. The carrying amounts of variable rate long-term borrowings approximate their fair values. Junior Subordinated Debt Securities The interest rate on the variable rate junior subordinated debt securities is reset quarterly; therefore, the carrying values approximate their fair values. Loan Commitments and Standby Letters of Credit Off-balance sheet financial instruments consist of commitments to extend credit and letters of credit. Except for interest rate lock commitments, estimates of the fair value of these off-balance sheet items are not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Other Estimates of fair value are not made for items that are not defined as financial instruments, including such items as our core deposit intangibles and the value of our trust operations.
Allowance for Loans Losses	We maintain an ACL at a level determined to be adequate to absorb estimated expected credit losses within the loan portfolio over the contractual life of an instrument that considers our historical loss experience, current conditions and forecasts of future economic conditions as of the balance sheet date. We develop and document a systematic ACL methodology based on the following portfolio segments: 1) Construction, 2) Commercial Real Estate, or CRE, 3) Commercial and Industrial, or C&I, 4) Business Banking, 5) Consumer Real Estate and 6) Other Consumer. The following are key risks within each portfolio segment: CRE —Loans secured by commercial purpose real estate, including both owner-occupied properties and investment properties for various purposes such as hotels, retail, multifamily, and health care. Operations of the individual projects and global cash flows of the debtors are the primary sources of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and the business prospects of the lessee, if the project is not owner-occupied. C&I —Loans made to operating companies or manufacturers for the purpose of production, operating capacity, accounts receivable, inventory or equipment financing. Cash flow from the operations of the company is the primary source of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the industry of the company. Collateral for these types of loans often does not have sufficient value in a distressed or liquidation scenario to satisfy the outstanding debt. Commercial Construction —Loans made to finance construction of buildings or other structures, as well as to finance the acquisition and development of raw land for various purposes. While the risk of these loans is generally confined to the construction period, if there are problems, the project may not be completed, and as such, may not provide sufficient cash flow on its own to service the debt or have sufficient value in a liquidation to cover the outstanding principal. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the type of project and the experience and resources of the developer. Business Banking —Commercial loans made to small businesses that are standard, non-complex products evaluated through a streamlined credit approval process that has been designed to maximize efficiency while maintaining high credit quality standards that meet small business market customers’ needs. The business banking portfolio is monitored by utilizing a standard and closely managed process focusing on behavioral and performance criteria. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and business. Consumer Real Estate —Loans secured by first and second liens such as home equity loans, home equity lines of credit and 1-4 family residential mortgages, including purchase money mortgages. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The state of the local housing market can also have a significant impact on this segment because low demand and/or declining home values can limit the ability of borrowers to sell a property and satisfy the debt. Other Consumer —Loans made to individuals that may be secured by assets other than 1-4 family residences, as well as unsecured loans. This segment includes auto loans, unsecured loans and lines and credit cards. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The value of the collateral, if there is any, is less likely to be a source of repayment due to less certain collateral values. Management monitors various credit quality indicators for the commercial, business banking and consumer loan portfolios, including changes in risk ratings, nonperforming status and delinquency on a monthly basis. We monitor the commercial loan portfolio through an internal risk rating system. Loan risk ratings are assigned based upon the creditworthiness of the borrower and are reviewed on an ongoing basis according to our internal policies. Loans within the pass rating generally have a lower risk of loss than loans risk rated as special mention or substandard. Our risk ratings are consistent with regulatory guidance and are as follows: Pass —The loan is currently performing and is of high quality. Special Mention —A special mention loan has potential weaknesses that warrant management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects or in the strength of our credit position at some future date. Substandard —A substandard loan is not adequately protected by the net worth and/or paying capacity of the borrower or by the collateral pledged, if any. Substandard loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. These loans are characterized by the distinct possibility that we will sustain some loss if the deficiencies are not corrected. Doubtful —Loans classified doubtful have all the weaknesses inherent in those classified substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently known facts, conditions, and values, highly questionable and improbable.
Derivative Financial Instruments	Interest Rate Swaps In accordance with applicable accounting guidance for derivatives and hedging, all derivatives are recognized as either assets or liabilities on the balance sheet at fair value. Interest rate swaps are contracts in which a series of interest rate flows (fixed and variable) are exchanged over a prescribed period. The notional amounts on which the interest payments are based are not exchanged. These derivative positions relate to transactions in which we enter into an interest rate swap with a commercial customer while at the same time entering into an offsetting interest rate swap with another financial institution. In connection with each transaction, we agree to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on the same notional amount at a fixed rate. At the same time, we agree to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. The transaction allows our customer to effectively convert a variable rate loan to a fixed rate loan with us receiving a variable rate. These agreements could have floors or caps on the contracted interest rates. Pursuant to our agreements with various financial institutions, we may receive collateral or may be required to post collateral based upon mark-to-market positions. Beyond unsecured threshold levels, collateral in the form of cash or securities may be made available to counterparties of interest rate swap transactions. Based upon our current positions and related future collateral requirements relating to them, we believe any effect on our cash flow or liquidity position to be immaterial. Derivatives contain an element of credit risk, the possibility that we will incur a loss because a counterparty, which may be a financial institution or a customer, fails to meet its contractual obligations. All derivative contracts with financial institutions may be executed only with counterparties approved by our Asset and Liability Committee, or ALCO, and derivatives with customers may only be executed with customers within credit exposure limits approved by our Senior Loan Committee. Interest rate swaps are considered derivatives but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives are recorded in current earnings and included in other noninterest income in the Consolidated Statements of Comprehensive Income. Interest Rate Lock Commitments and Forward Sale Contracts In the normal course of business, we sell originated mortgage loans into the secondary mortgage loan market. We also offer interest rate lock commitments to potential borrowers. The commitments are generally for a period of 60 days and guarantee a specified interest rate for a loan if underwriting standards are met, but the commitment does not obligate the potential borrower to close on the loan. Accordingly, some commitments expire prior to becoming loans. We may encounter pricing risks if interest rates increase significantly before the loan can be closed and sold. We may utilize forward sale contracts in order to mitigate this pricing risk. Whenever a customer desires these products, a mortgage originator quotes a secondary market rate guaranteed for that day by the investor. The rate lock is executed between the mortgagee and us and in turn a forward sale contract may be executed between us and the investor. Both the rate lock commitment and the corresponding forward sale contract for each customer are considered derivatives but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives during the commitment period are recorded in current earnings and included in mortgage banking in the Consolidated Statements of Comprehensive Income.
Revenue From Contracts with Customer	We earn revenue from contracts with our customers when we have completed our performance obligations and recognize that revenue when services are provided to our customers. Our contracts with customers are primarily in the form of account agreements. Generally, our services are transferred at a point in time in response to transactions initiated and controlled by our customers under service agreements with an expected duration of one year or less. Our customers have the right to terminate their service agreements at any time. We do not defer incremental direct costs to obtain contracts with customers that would be amortized in one year or less. These costs are primarily salaries and employee benefits recognized as expense in the period incurred. Service charges on deposit accounts - We recognize monthly service charges for both commercial and personal banking customers based on account fee schedules. Our performance obligation is generally satisfied and the related revenue recognized at a point in time or over time when the services are provided. Other fees are earned based on specific transactions or customer activity within the customers' deposit accounts. These are earned at the time the transaction or customer activity occurs. Debit and credit card services - Interchange fees are earned whenever debit and credit cards are processed through third-party card payment networks. ATM fees are based on transactions by our customers' and other customers' use of our ATMs or other ATMs. Debit and credit card revenue is recognized at a point in time when the transaction is settled. Our performance obligation to our customers is generally satisfied and the related revenue is recognized at a point in time when the service is provided. Third-party service contracts include annual volume and marketing incentives which are recognized over a period of twelve months when we meet thresholds as stated in the service contract. Wealth management services - Wealth management services are primarily comprised of fees earned from the management and administration of trusts, assets under administration and other financial advisory services. Generally, wealth management fees are earned over a period of time between monthly and annually, per the related fee schedules. Our performance obligations with our customers are generally satisfied when we provide the services as stated in the customers' agreements. The fees are based on a fixed amount or a scale based on the level of services provided or amount of assets under management. Other fee revenue - Other fee revenue includes a variety of other traditional banking services such as, electronic banking fees, letters of credit origination fees, wire transfer fees, money orders, treasury checks, checksale fees and transfer fees. Our performance obligations are generally satisfied at a point in time, while fee revenue is recognized when the services are provided or the transaction is settled.

Basis of Presentation Basis of

Basis of Presentation Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Schedule of Impact of ASU 2016-13	The following table details the impact of ASU 2016-13 and the reclassification of loans for the identification of new portfolio loan segments under CECL: 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 )

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Summary of Consideration, Assets Acquired and Liabilities Assumed	The following table presents the preliminary fair value adjustments and the measurement period adjustments as of the dates presented: November 30, 2019 March 31, 2020 As Recorded by DNB Preliminary Fair Value Adjustments (1) As Recorded by S&T Measurement Period Adjustments As Recorded by S&T Fair Value of Assets Acquired Cash and cash equivalents $ 64,119 $ — $ 64,119 $ — $ 64,119 Securities and other investments 108,715 183 108,898 — 108,898 Loans 917,127 (8,143 ) 908,984 (2,496 ) 906,488 Allowance for credit losses (6,487 ) 6,487 — — — Goodwill 15,525 (15,525 ) — — — Premises and equipment 6,782 8,090 14,872 — 14,872 Accrued interest receivable 4,138 — 4,138 — 4,138 Deferred income taxes 2,017 (3,298 ) (1,281 ) 311 (970 ) Core deposits and other intangible assets 269 (269 ) — — — Other assets 24,883 (4,278 ) 20,605 40 20,645 Total Assets Acquired 1,137,088 (16,753 ) 1,120,335 (2,145 ) 1,118,190 Fair Value of Liabilities Assumed Deposits 966,263 1,002 967,265 (12 ) 967,253 Borrowings 37,617 (276 ) 37,341 (257 ) 37,084 Accrued interest payable and other liabilities 11,157 (3,184 ) 7,973 (68 ) 7,905 Total Liabilities Assumed 1,015,037 (2,458 ) 1,012,579 (337 ) 1,012,242 Total Net Assets Acquired $ 122,051 $ (14,295 ) $ 107,756 $ (1,808 ) $ 105,948 Core Deposit Intangible Asset $ 7,288 $ — $ 7,288 Wealth Management Intangible Asset 1,772 — 1,772 Total Fair Value of Net Assets Acquired and Identified $ 116,816 $ (1,808 ) $ 115,008 Consideration Paid Cash $ 360 $ — $ 360 Common stock 200,631 — 200,631 Fair Value of Total Consideration $ 200,991 $ — $ 200,991 Goodwill $ 84,175 $ 1,808 $ 85,983 (1) Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, deferred and current income taxes until the final valuations are complete and final tax returns are filed. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerators and Denominators of Basic Earnings Per Share with Diluted Earnings Per Share	The following table reconciles the numerators and denominators of basic and diluted earnings per share calculations for the periods presented. Three Months Ended March 31, (in thousands, except share and per share data) 2020 2019 Numerator for Earnings per Share—Basic: Net income $ 13,231 $ 22,928 Less: Income allocated to participating shares 29 62 Net Income Allocated to Shareholders $ 13,202 $ 22,866 Numerator for Earnings per Share—Diluted: Net income $ 13,231 $ 22,928 Net Income Available to Shareholders $ 13,231 $ 22,928 Denominators for Earnings per Share: Weighted Average Shares Outstanding—Basic 39,271,540 34,414,555 Add: Potentially dilutive shares 108,116 128,256 Denominator for Treasury Stock Method—Diluted 39,379,656 34,542,811 Weighted Average Shares Outstanding—Basic 39,271,540 34,414,555 Add: Average participating shares outstanding 54,398 92,659 Denominator for Two-Class Method—Diluted 39,325,938 34,507,214 Earnings per share—basic $ 0.34 $ 0.67 Earnings per share—diluted $ 0.34 $ 0.66 Restricted stock considered anti-dilutive excluded from potentially dilutive shares 41 68,314

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present our assets and liabilities that are measured at fair value on a recurring basis by fair value hierarchy level at March 31, 2020 and December 31, 2019 . There were no transfers between Level 1 and Level 2 for items measured at fair value on a recurring basis during the periods presented. March 31, 2020 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Available-for-sale debt securities: U.S. Treasury securities $ — $ 10,372 $ — $ 10,372 Obligations of U.S. government corporations and agencies — 137,982 — 137,982 Collateralized mortgage obligations of U.S. government corporations and agencies — 189,472 — 189,472 Residential mortgage-backed securities of U.S. government corporations and agencies — 21,193 — 21,193 Commercial mortgage-backed securities of U.S. government corporations and agencies — 284,679 — 284,679 Corporate Bonds — 7,551 — 7,551 Obligations of states and political subdivisions — 144,717 — 144,717 Total Available-for-sale Debt Securities — 795,966 — 795,966 Marketable equity securities 3,504 62 — 3,566 Total Securities 3,504 796,028 — 799,532 Securities held in a deferred compensation plan 4,782 — — 4,782 Derivative financial assets: Interest rate swaps — 88,135 — 88,135 Interest rate lock commitments — 2,927 — 2,927 Total Assets $ 8,286 $ 887,090 $ — $ 895,376 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 87,989 $ — $ 87,989 Forward sale contracts — 1,292 — 1,292 Total Liabilities $ — $ 89,281 $ — $ 89,281 December 31, 2019 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Available-for-sale debt securities: U.S. Treasury securities $ — $ 10,040 $ — $ 10,040 Obligations of U.S. government corporations and agencies — 157,697 — 157,697 Collateralized mortgage obligations of U.S. government corporations and agencies — 189,348 — 189,348 Residential mortgage-backed securities of U.S. government corporations and agencies — 22,418 — 22,418 Commercial mortgage-backed securities of U.S. government corporations and agencies — 275,870 — 275,870 Corporate Bonds — 7,627 — 7,627 Obligations of states and political subdivisions — 116,133 — 116,133 Total Available-for-Sale Debt Securities — 779,133 — 779,133 Marketable equity securities 5,078 72 — 5,150 Total Securities 5,078 779,205 — 784,283 Securities held in a deferred compensation plan 5,987 — — 5,987 Derivative financial assets: Interest rate swaps — 25,647 — 25,647 Interest rate lock commitments — 321 — 321 Forward sale contracts — 1 — 1 Total Assets $ 11,065 $ 805,174 $ — $ 816,239 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 25,615 $ — $ 25,615 Total Liabilities $ — $ 25,615 $ — $ 25,615
Schedule of Assets Measured at Fair Value on Nonrecurring Basis by Significant Unobservable Inputs	For Level 3 assets measured at fair value on a nonrecurring basis as of March 31, 2020 and December 31, 2019, the significant unobservable inputs used in the fair value measurements were as follows: March 31, 2020 Valuation Technique(s) Significant Unobservable Inputs Range (dollars in thousands) Loans held for investment $ 20,926 Collateral Method Third party appraisal Costs to sell 0% - 17% Discounted cash flow method Discount rate Contractual loan rate 3.25% Other real estate owned 3,045 Collateral method Third party appraisal Costs to sell 7% Mortgage servicing rights 3,929 Discounted cash flow method Third party service provider Discount rate 9.39% - 12.54% Constant prepayment rates 7.46% - 12.74% Total Assets $ 27,900 December 31, 2019 Valuation Technique(s) Significant Unobservable Inputs Range (dollars in thousands) Impaired loans $ 38,697 Collateral Method Third party appraisal Costs to sell 0% - 20% Discounted cash flow method Discount rate Contractual loan rate 4.75% - 5.50% Other real estate owned 3,231 Collateral method Third party appraisal Costs to sell 7% Mortgage servicing rights 1,134 Discounted cash flow method Third party service provider Discount rate 9.39% - 12.54% Constant prepayment rates 7.46% - 12.74% Total Assets $ 43,062
Schedule of Carrying Values and Fair Values of Financial Instruments	The carrying values and fair values of our financial instruments at March 31, 2020 and December 31, 2019 are presented in the following tables: Carrying Value (1) Fair Value Measurements at March 31, 2020 (dollars in thousands) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 187,684 $ 187,684 $ 187,684 $ — $ — Securities 799,532 799,532 3,504 796,028 — Loans held for sale 7,309 7,309 — — 7,309 Portfolio loans, net 7,149,895 7,090,570 — — 7,090,570 Bank owned life insurance 80,978 80,798 — 80,798 — FHLB and other restricted stock 28,253 28,253 — — 28,253 Securities held in a deferred compensation plan 4,782 4,782 4,782 — — Mortgage servicing rights 3,979 3,982 — — 3,982 Interest rate swaps 88,135 88,135 — 88,135 — Interest rate lock commitments 2,927 2,927 — 2,927 — LIABILITIES Deposits $ 7,057,879 $ 7,065,896 $ 5,469,826 $ 1,596,070 $ — Securities sold under repurchase agreements 69,644 69,644 69,644 — — Short-term borrowings 410,240 410,240 410,240 — — Long-term borrowings 50,180 51,675 4,630 47,045 — Junior subordinated debt securities 64,038 64,038 64,038 — — Interest rate swaps 87,989 87,989 — 87,989 — Forward sales contracts 1,292 1,292 — 1,292 — (1) As reported in the Consolidated Balance Sheets Carrying Value (1) Fair Value Measurements at December 31, 2019 (dollars in thousands) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 197,823 $ 197,823 $ 197,823 $ — $ — Securities 784,283 784,283 5,078 779,205 — Loans held for sale 5,256 5,256 — — 5,256 Portfolio loans, net 7,074,928 6,940,875 — — 6,940,875 Bank owned life insurance 80,473 80,473 — 80,473 — FHLB and other restricted stock 22,977 22,977 — — 22,977 Securities held in a Deferred Compensation Plan 5,987 5,987 5,987 — — Mortgage servicing rights 4,662 4,650 — — 4,650 Interest rate swaps 25,647 25,647 — 25,647 — Interest rate lock commitments 321 321 — 321 — Forward sale contracts 1 1 — 1 — LIABILITIES Deposits $ 7,036,576 $ 7,034,595 $ 5,441,143 $ 1,593,452 $ — Securities sold under repurchase agreements 19,888 19,888 19,888 — — Short-term borrowings 281,319 281,319 281,319 — — Long-term borrowings 50,868 51,339 4,678 46,661 — Junior subordinated debt securities 64,277 64,277 64,277 — — Interest rate swaps 25,615 25,615 — 25,615 — (1) As reported in the Consolidated Balance Sheets

Securities (Tables)

Securities (Tables)	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Marketable Securities	The following table presents the fair values of our securities portfolio at the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Available-for-sale debt securities $ 795,966 $ 779,133 Marketable equity securities 3,566 5,150 Total Securities $ 799,532 $ 784,283
Schedule of Debt Securities, Available-for-Sale	The following tables present the amortized cost and fair value of available-for-sale debt securities as of the dates presented: March 31, 2020 December 31, 2019 (dollars in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 9,972 $ 400 $ — $ 10,372 $ 9,969 $ 71 $ — $ 10,040 Obligations of U.S. government corporations and agencies 132,938 5,044 — 137,982 155,969 1,773 (45 ) 157,697 Collateralized mortgage obligations of U.S. government corporations and agencies 180,682 8,790 — 189,472 186,879 2,773 (304 ) 189,348 Residential mortgage-backed securities of U.S. government corporations and agencies 20,391 802 — 21,193 22,120 321 (23 ) 22,418 Commercial mortgage-backed securities of U.S. government corporations and agencies 272,651 12,028 — 284,679 273,771 2,680 (581 ) 275,870 Corporate obligations 7,532 30 (11 ) 7,551 7,603 24 — 7,627 Obligations of states and political subdivisions 139,530 5,187 — 144,717 112,116 4,017 — 116,133 Total Available-for-Sale Debt Securities (1) $ 763,696 $ 32,281 $ (11 ) $ 795,966 $ 768,427 $ 11,659 $ (953 ) $ 779,133 (1) Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.
Schedule of Temporally Impaired Debt Securities	The following tables present the fair value and the age of gross unrealized losses on available-for-sale debt securities by investment category as of the dates presented: March 31, 2020 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized U.S. Treasury securities — $ — $ — — $ — $ — — $ — $ — Obligations of U.S. government corporations and agencies — — — — — — — — — Collateralized mortgage obligations of U.S. government corporations and agencies — — — — — — — — — Residential mortgage-backed securities of U.S. government corporations and agencies — — — — — — — — — Commercial mortgage-backed securities of U.S. government corporations and agencies — — — — — — — — — Corporate bonds 2 2,989 (11 ) — — — 2 2,989 (11 ) Obligations of states and political subdivisions — — — — — — — — — Total 2 $ 2,989 $ (11 ) — $ — $ — 2 $ 2,989 $ (11 ) December 31, 2019 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized Number of Securities Fair Value Unrealized U.S. Treasury securities — $ — $ — — $ — $ — — $ — $ — Obligations of U.S. government corporations and agencies 3 22,638 (45 ) — — — 3 22,638 (45 ) Collateralized mortgage obligations of U.S. government corporations and agencies 6 23,393 (73 ) 6 25,254 (231 ) 12 48,647 (304 ) Residential mortgage-backed securities of U.S. government corporations and agencies 1 982 (2 ) 1 2,534 (21 ) 2 3,516 (23 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 9 90,005 (581 ) — — — 9 90,005 (581 ) Corporate bonds 1 79 — — — — 1 79 — Obligations of states and political subdivisions — — — — — — — — — Total Temporarily Impaired Debt Securities 20 $ 137,097 $ (701 ) 7 $ 27,788 $ (252 ) 27 $ 164,885 $ (953 )
Schedule of Unrealized Gains and Losses, Net of Tax, of Debt Securities Available-for-Sale	The following table presents net unrealized gains and losses, net of tax, on available-for-sale debt securities included in accumulated other comprehensive income/(loss), for the periods presented: March 31, 2020 December 31, 2019 (dollars in thousands) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains/(Losses) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains/(Losses) Total unrealized gains/(losses) on available-for-sale debt securities $ 32,281 $ (11 ) $ 32,270 $ 11,659 $ (953 ) $ 10,706 Income tax (expense) benefit (6,873 ) 2 (6,871 ) (2,486 ) 203 (2,283 ) Net Unrealized Gains/(Losses), Net of Tax Included in Accumulated Other Comprehensive Income/(Loss) $ 25,408 $ (9 ) $ 25,399 $ 9,173 $ (750 ) $ 8,423
Schedule of Contractual Maturity of Debt Securities Available-for-Sale Securities	The amortized cost and fair value of available-for-sale debt securities at March 31, 2020 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. March 31, 2020 (dollars in thousands) Amortized Cost Fair Value Obligations of the U.S. Treasury, U.S. government corporations and agencies, and obligations of states and political subdivisions Due in one year or less $ 84,687 $ 85,259 Due after one year through five years 100,877 106,112 Due after five years through ten years 65,732 68,913 Due after ten years 31,144 32,786 Available-for-Sale Debt Securities With Maturities 282,440 293,070 Collateralized mortgage obligations of U.S. government corporations and agencies 180,682 189,473 Residential mortgage-backed securities of U.S. government corporations and agencies 20,391 21,193 Commercial mortgage-backed securities of U.S. government corporations and agencies 272,651 284,679 Corporate Securities 7,532 7,551 Total Available-for-Sale Debt Securities $ 763,696 $ 795,966
Schedule of Unrealized Gains and Losses on Marketable Equity Securities	The following table presents realized and unrealized net gains and losses for our marketable equity securities for the periods presented: Three Months Ended (dollars in thousands) 2020 2019 Marketable Equity Securities Net gains and losses recognized during the period on equity securities $ (1,585 ) $ (318 ) Less: Net gains and losses recognized during the period on equity securities sold during the period — — Unrealized Losses/Gains Recognized During the Reporting Period on Equity Securities Still Held at the Reporting Date $ (1,585 ) $ (318 )

Loans and Loans Held for Sale (

Loans and Loans Held for Sale (Tables)	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Schedule of Composition of Loans	The following table presents loans as of the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Commercial Commercial real estate $ 3,442,495 $ 3,416,518 Commercial and industrial 1,781,402 1,720,833 Commercial construction 396,518 375,445 Total Commercial Loans 5,620,415 5,512,796 Consumer Residential mortgage 988,816 998,585 Home Equity 544,405 538,348 Installment and other consumer 79,887 79,033 Consumer construction 13,222 8,390 Total Consumer Loans 1,626,330 1,624,356 Total Portfolio Loans 7,246,745 7,137,152 Loans held for sale 7,309 5,256 Total Loans (1) $ 7,254,054 $ 7,142,408 (1) Excludes interest receivable of $22.1 million at both March 31, 2020 and December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.
Schedule of Restructured Loans for Periods Presented	The following tables summarize restructured loans as of the dates presented: March 31, 2020 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 30 $ 28,973 $ 29,003 Commercial and industrial 4,566 4,665 9,231 Commercial construction 3,316 — 3,316 Business banking 1,524 352 1,876 Consumer real estate 5,749 2,064 7,813 Other consumer 4 — 4 Total (1) $ 15,189 $ 36,055 $ 51,243 (1) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. December 31, 2019 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 22,233 $ 6,713 $ 28,946 Commercial and industrial 6,909 695 7,604 Commercial construction 1,425 — 1,425 Residential mortgage 2,013 822 2,835 Home equity 4,371 678 5,049 Installment and other consumer 9 4 13 Total $ 36,960 $ 8,912 $ 45,872 The following tables present the restructured loans by portfolio segment and by type of concession for the three months ended March 31, 2020 and 2019: Three Months Ended March 31, 2020 (dollars in thousands) Number of Pre-Modification (1) Post-Modification (1) Total Difference Totals by Loan Segment Commercial Real Estate Principal deferral and maturity date extension 1 $ 2,210 $ 2,210 $ — Total Commercial Real Estate 1 2,210 2,210 — Commercial and Industrial Principal deferral and maturity date extension 5 3,780 3,780 — Total Commercial and Industrial 5 3,780 3,780 — Commercial Construction — Maturity date extension 1 1,891 1,891 — Total Commercial Construction 1 1,891 1,891 — Consumer Real Estate Consumer bankruptcy (2) 6 388 388 — Maturity date extension and reduction in payment 1 27 27 — Total Consumer Real Estate 7 415 415 — Totals by Concession Type Principal deferral and maturity date extension 6 5,991 5,991 — Maturity date extension 1 1,891 1,891 — Consumer bankruptcy (2) 6 388 388 — Maturity date extension and payment reduction 1 27 27 — Total (3) 14 $ 8,297 $ 8,297 $ — (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. (3) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Three Months Ended March 31, 2019 (dollars in thousands) Number of Pre-Modification ( 1) Post-Modification (1) Total Difference Totals by Loan Segment Commercial and Industrial Maturity date extension and interest rate reduction 1 $ 5,201 $ 5,201 $ — Principal deferral and maturity date extension — — — — Total Commercial and Industrial 1 5,201 5,201 — Residential Mortgage Consumer bankruptcy (2) 1 49 49 — Total Residential Mortgage 1 49 49 — Home Equity Consumer bankruptcy (2) 7 191 168 (23 ) Interest rate reduction 1 81 81 — Maturity date extension and reduction in payment — — — — Total Home Equity 8 272 249 (23 ) Totals by Concession Type Maturity date extension and interest rate reduction 1 5,201 5,201 — Consumer bankruptcy (2) 8 240 217 (23 ) Interest rate reduction 1 81 81 — Total 10 $ 5,522 $ 5,499 $ (23 ) (1) Excludes loans that were fully paid-off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed.
Schedule of Summary of Nonperforming Assets	The following table is a summary of nonperforming assets as of the dates presented: Nonperforming Assets (dollars in thousands) March 31, 2020 December 31, 2019 Nonperforming Assets Nonaccrual loans $ 37,744 $ 45,145 Nonaccrual TDRs 36,055 8,912 Total Nonaccrual Loans 73,799 54,057 OREO 3,389 3,525 Total Nonperforming Assets $ 77,188 $ 57,582 The following table presents loans on nonaccrual status and loans past due 90 days or more and still accruing by class of loan: As or for the Three Months Ended March 31, 2020 (dollars in thousands) Beginning of Period Nonaccrual End of Period Nonaccrual Nonaccrual With No Related Allowance Past Due 90+ Days Still Accruing Interest Income Recognized on Nonaccrual Commercial real estate $25,356 $ 46,533 $39,454 $ 700 $684 Commercial and industrial 10,911 4,505 4,054 2,615 64 Commercial construction 737 571 285 933 — Business banking 9,863 11,316 2,363 768 58 Consumer real estate 6,063 10,616 398 83 47 Other consumer 1,127 258 — 195 28 Total $54,057 $73,799 $46,554 $ 5,294 $881

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Schedule of Loans Credit Quality Indicators	The following table presents loan balances by year of origination and performing and nonperforming status for our portfolio segments as of March 31, 2020: (dollars in thousands) 2020 2019 2018 2017 2016 2015 and Prior Revolving Revolving-Term Total Commercial Real Estate Performing $ 169,367 $ 486,935 $ 453,673 $ 371,144 $ 431,919 $ 935,536 $ 59,882 $ — $ 2,908,456 Nonperforming — — — — 19,791 23,713 3,008 21 46,533 Total Commercial Real Estate 169,367 486,935 453,673 371,144 451,710 959,249 62,890 21 2,954,989 Commercial and Industrial Performing 75,969 252,166 171,093 108,269 76,593 303,745 531,881 — 1,519,716 Nonperforming — — 364 — 709 62 3,370 — 4,505 Total Commercial and Industrial 75,969 252,166 171,457 108,269 77,302 303,807 535,251 — 1,524,221 Commercial Construction Performing 23,004 179,956 117,527 18,055 18,986 20,020 12,083 — 389,631 Nonperforming — — — 108 — 463 — — 571 Total Commercial Construction 23,004 179,956 117,527 18,163 18,986 20,483 12,083 — 390,202 Business Banking Performing 40,952 181,576 151,933 107,176 94,230 355,259 128,022 — 1,059,148 Nonperforming — 110 1,093 1,272 882 7,779 180 — 11,316 Total Business Banking 40,952 181,686 153,026 108,448 95,112 363,038 128,202 — 1,070,464 Consumer Real Estate Performing 33,737 149,942 86,401 83,526 90,151 318,926 432,403 21,367 1,216,453 Nonperforming — 190 133 413 3,763 4,957 176 984 10,616 Total Consumer Real Estate 33,737 150,132 86,534 83,939 93,914 323,883 432,579 22,351 1,227,069 Other Consumer Performing 8,706 10,010 10,802 6,606 5,682 7,359 28,478 1,899 79,542 Nonperforming — — — — — 258 — — 258 Total Other Consumer 8,706 10,010 10,802 6,606 5,682 7,617 28,478 1,899 79,800 Performing 351,735 1,260,585 991,429 694,776 717,561 1,940,845 1,192,749 23,266 7,172,946 Nonperforming — 300 1,590 1,793 25,145 37,232 6,734 1,005 73,799 Total Loan Balance $ 351,735 $ 1,260,885 $ 993,019 $ 696,569 $ 742,706 $ 1,978,077 $ 1,199,483 $ 24,271 $ 7,246,745 The following table presents collateral-dependent loans by class of loan: March 31, 2020 Type of Collateral (dollars in thousands) Real Estate Blanket Lien Investment/Cash Other Commercial real estate $51,630 $— $— $— Commercial and industrial 4,686 4,545 40 — Commercial construction 3,602 — — — Business banking 2,322 876 — 689 Consumer real estate — — — — Other consumer 398 — — — Total $62,638 $5,421 $40 $689 The following table presents the recorded investment in commercial loan classes by internally assigned risk ratings as of December 31, 2019: December 31, 2019 (dollars in thousands) Commercial % of Commercial % of Commercial % of Total % of Pass $ 3,270,437 95.7 % $ 1,636,314 93.4 % $ 347,324 92.5 % $ 5,254,076 95.3 % Special mention 57,285 1.7 % 36,484 1.7 % 10,109 2.7 % 103,878 1.9 % Substandard 86,772 2.5 % 47,980 4.9 % 17,899 4.8 % 152,651 2.8 % Doubtful 2,023 — % 55 — % 133 — % 2,191 — % Total $ 3,416,518 100.0 % $ 1,720,833 100.0 % $ 375,445 100.0 % $ 5,512,796 100.0 % The following table presents loan balances by year of origination and internally assigned risk rating for our portfolio segments as of March 31, 2020: Risk Rating (dollars in thousands) 2020 2019 2018 2017 2016 2015 and Prior Revolving Revolving-Term Total Commercial Real Estate Pass $ 169,367 $ 483,699 $ 452,024 $ 359,553 $ 416,420 $ 882,326 $ 59,032 — $ 2,822,421 Special Mention — 3,236 187 11,591 10,005 26,575 850 — 52,444 Substandard — — 1,462 — 25,285 50,348 3,008 21 80,124 Total Commercial Real Estate 169,367 486,935 453,673 371,144 451,710 959,249 62,890 21 2,954,989 Commercial and Industrial Pass 75,969 240,261 165,631 103,537 73,798 282,138 486,045 — 1,427,379 Special Mention — 6,239 3,525 947 1,883 9,437 31,890 — 53,921 Substandard — 5,666 2,301 3,785 1,621 12,232 17,316 — 42,921 Total Commercial and Industrial 75,969 252,166 171,457 108,269 77,302 303,807 535,251 — 1,524,221 Commercial Construction Pass 23,004 179,956 117,527 17,122 18,986 11,586 11,992 — 380,173 Special Mention — — — — — 5,117 91 — 5,208 Substandard — — — 1,041 — 3,780 — — 4,821 Total Commercial Construction 23,004 179,956 117,527 18,163 18,986 20,483 12,083 — 390,202 Business Banking Pass 40,952 181,242 148,419 103,027 89,925 327,333 125,800 — 1,016,698 Special Mention — 62 1,496 1,775 1,181 7,902 737 — 13,153 Substandard — 382 3,111 3,646 4,006 27,803 1,665 — 40,613 Total Business Banking 40,952 181,686 153,026 108,448 95,112 363,038 128,202 — 1,070,464 Consumer Real Estate Pass 33,737 149,942 86,463 83,402 92,013 316,169 432,274 20,966 1,214,966 Special Mention — — — — 798 304 — — 1,102 Substandard — 190 71 537 1,103 7,410 305 1,385 11,001 Total Consumer Real Estate 33,737 150,132 86,534 83,939 93,914 323,883 432,579 22,351 1,227,069 Other consumer Pass 8,706 9,522 10,670 6,474 5,088 3,365 28,156 773 72,754 Special Mention — — — — — — — — — Substandard — 488 132 132 594 4,252 322 1,126 7,046 Total Other Consumer 8,706 10,010 10,802 6,606 5,682 7,617 28,478 1,899 79,800 Total Loan Balance $ 351,735 $ 1,260,885 $ 993,019 $ 696,569 $ 742,706 $ 1,978,077 $ 1,199,483 $ 24,271 $ 7,246,745
Schedule of Age Analysis of Past Due Loans Segregated by Class of Loans	The following tables present the age analysis of past due loans segregated by class of loans as of the dates presented: March 31, 2020 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days Past Due (1) Non - performing Total Past Due Loans Total Loans Commercial real estate $ 2,901,375 $ 6,381 $ — $ 700 $ 46,533 $ 53,614 $ 2,954,989 Commercial and industrial 1,516,639 463 — 2,615 4,505 7,582 1,524,221 Commercial construction 388,122 576 — 933 571 2,080 390,202 Business banking 1,048,241 6,758 3,381 768 11,316 22,223 1,070,464 Consumer real estate 1,211,865 3,859 646 83 10,616 15,203 1,227,069 Other consumer 79,083 174 91 195 258 717 79,800 Total $ 7,145,326 $ 18,211 $ 4,117 $ 5,294 $ 73,799 $ 101,419 $ 7,246,745 (1) Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument. December 31, 2019 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due 90 Days Past Due (1) Non - performing Total Past Total Loans Commercial real estate $ 3,025,505 $ 7,749 $ 71 $ 911 $ 25,356 $ 34,087 $ 3,059,592 Commercial and industrial 1,466,460 126 1,589 1,443 10,911 14,069 1,480,529 Commercial construction 367,204 956 1,163 — 737 2,856 370,060 Business banking 830,735 5,093 1,099 — 9,863 16,055 846,790 Consumer real estate 1,283,591 2,620 1,758 1,175 6,063 11,616 1,295,207 Other consumer 81,866 1,448 305 228 1,127 3,108 84,974 Total $ 7,055,361 $ 17,992 $ 5,985 $ 3,757 $ 54,057 $ 81,791 $ 7,137,152 (1) Represents acquired loans that were recorded at fair value at the acquisition date and remain performing at March 31, 2020 and December 31, 2019.
Schedule of Loans on Nonaccrual Status and Loans Past Due 90 days Or More	The following table is a summary of nonperforming assets as of the dates presented: Nonperforming Assets (dollars in thousands) March 31, 2020 December 31, 2019 Nonperforming Assets Nonaccrual loans $ 37,744 $ 45,145 Nonaccrual TDRs 36,055 8,912 Total Nonaccrual Loans 73,799 54,057 OREO 3,389 3,525 Total Nonperforming Assets $ 77,188 $ 57,582 The following table presents loans on nonaccrual status and loans past due 90 days or more and still accruing by class of loan: As or for the Three Months Ended March 31, 2020 (dollars in thousands) Beginning of Period Nonaccrual End of Period Nonaccrual Nonaccrual With No Related Allowance Past Due 90+ Days Still Accruing Interest Income Recognized on Nonaccrual Commercial real estate $25,356 $ 46,533 $39,454 $ 700 $684 Commercial and industrial 10,911 4,505 4,054 2,615 64 Commercial construction 737 571 285 933 — Business banking 9,863 11,316 2,363 768 58 Consumer real estate 6,063 10,616 398 83 47 Other consumer 1,127 258 — 195 28 Total $54,057 $73,799 $46,554 $ 5,294 $881
Schedule of Allowance for Credit Loss	The following table presents activity in the ACL for the three months ended March 31, 2020: Three Months Ended March 31, 2020 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Business Banking (1) Consumer Real Estate Other Consumer Total Loans Allowance for credit losses on loans: Balance at beginning of period $ 30,577 $ 15,681 $ 7,900 $ — $ 6,337 $ 1,729 $ 62,224 Impact of CECL adoption 4,810 7,853 (3,376 ) 12,898 4,525 642 27,352 Provision for credit losses on loans 7,639 6,196 2,309 1,194 472 620 18,430 Charge-offs (442 ) (9,879 ) (229 ) (460 ) (172 ) (248 ) (11,430 ) Recoveries 27 19 2 74 38 114 274 Net (Charge-offs)/Recoveries (415 ) (9,860 ) (227 ) (386 ) (134 ) (134 ) (11,156 ) Balance at End of Period $ 42,611 $ 19,870 $ 6,606 $ 13,706 $ 11,200 $ 2,857 $ 96,850 (1) 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. Our new segmentation breaks out business banking loans from our other loan segments: CRE, C&I , commercial construction, consumer real estate and other consumer. The business banking allowance balance at the beginning of period is included in the other segments and reclassified to business banking through the impact of CECL adoption line.
Schedule of Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status	The following table presents the recorded investment in consumer loan classes by performing and nonperforming status as of December 31, 2019: December 31, 2019 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and Other Consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 991,066 99.2 % $ 535,709 99.5 % $ 78,993 99.9 % $ 8,390 100.0 % $ 1,614,158 99.4 % Nonperforming 7,519 0.8 % 2,639 0.5 % 40 0.1 % — — % 10,198 0.6 % Total $ 998,585 100.0 % $ 538,348 100.0 % $ 79,033 100.0 % $ 8,390 100.0 % $ 1,624,356 100.0 %
Schedule of Investments in Loans Considered to be Impaired and Related Information on Impaired Loans	The following table presents average recorded investment and interest income recognized on impaired loans for the three months ended March 31, 2019: Three months ended March 31, 2019 (dollars in thousands) Average Recorded Investment Interest Income Recognized With a related allowance recorded: Commercial real estate $ 15,107 $ 144 Commercial and industrial 12,780 209 Commercial construction 2,319 140 Consumer real estate 8,846 417 Other consumer 4 — Total with a Related Allowance Recorded 39,056 910 Without a related allowance recorded: Commercial real estate 12,983 400 Commercial and industrial 980 35 Commercial construction 489 — Consumer real estate 14 1 Other consumer 10 1 Total without a Related Allowance Recorded 14,476 437 Total: Commercial real estate 28,090 544 Commercial and industrial 13,760 244 Commercial construction 2,808 140 Consumer real estate 8,860 418 Other consumer 14 1 Total $ 53,532 $ 1,347 The following table presents investments in loans considered to be impaired and related information on those impaired loans as of December 31, 2019: December 31, 2019 (dollars in thousands) Recorded Unpaid Related With a related allowance recorded: Commercial real estate $ 13,011 $ 14,322 $ 2,023 Commercial and industrial 10,001 10,001 55 Commercial construction 489 489 113 Consumer real estate — — — Other consumer 9 9 9 Total with a Related Allowance Recorded 23,510 24,821 2,200 Without a related allowance recorded: Commercial real estate 34,909 40,201 — Commercial and industrial 7,605 10,358 — Commercial construction 1,425 2,935 — Consumer real estate 7,884 8,445 — Other consumer 4 11 — Total without a Related Allowance Recorded 51,827 61,950 — Total: Commercial real estate 47,920 54,523 2,023 Commercial and industrial 17,606 20,359 55 Commercial construction 1,914 3,424 113 Consumer real estate 7,884 8,445 — Other consumer 13 20 9 Total $ 75,337 $ 86,771 $ 2,200
Schedule of Summary of Allowance for Loan Losses	Three Months Ended March 31, 2019 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of period $ 33,707 $ 11,596 $ 7,983 $ 6,187 $ 1,494 $ 6,996 Charge-offs (1 ) (5,477 ) — (162 ) (425 ) (6,023 ) Recoveries 122 417 — 148 169 787 Net (Charge-offs)/Recoveries 121 (5,060 ) — (14 ) (256 ) (5,236 ) Provision for credit losses 1,075 5,460 (1,226 ) 5 249 5,649 Balance at End of Period $ 34,903 $ 11,996 $ 6,757 $ 6,178 $ 1,487 $ 61,409
Schedule of Summary of Allowance for Loan Losses and Recorded Investments	The following tables present the allowance for loan losses and recorded investments in loans by category as of December 31,2019: December 31, 2019 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ 2,023 $ 28,554 $ 30,577 $ 47,920 $ 3,368,598 $ 3,416,518 Commercial and industrial 55 15,626 15,681 17,606 1,703,227 1,720,833 Commercial construction 113 7,787 7,900 1,914 373,531 375,445 Consumer real estate — 6,337 6,337 7,884 1,537,439 1,545,323 Other consumer 9 1,720 1,729 13 79,020 79,033 Total $ 2,200 $ 60,024 $ 62,224 $ 75,337 $ 7,061,815 $ 7,137,152

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Value of Derivative Assets and Derivative Liabilities	The following table indicates the amounts representing the value of derivative assets and derivative liabilities as of the dates presented: Derivatives Derivatives (included in Other Liabilities) (dollars in thousands) March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Derivatives not Designated as Hedging Instruments: Interest Rate Swap Contracts - Commercial Loans Fair value $ 88,135 $ 25,647 $ 87,989 $ 25,615 Notional amount 918,481 740,762 918,481 740,762 Collateral posted — — 86,720 26,127 Interest Rate Lock Commitments - Mortgage Loans Fair value 2,927 321 — — Notional amount 86,674 9,829 — — Forward Sale Contracts - Mortgage Loans Fair value — 1 1,292 — Notional amount $ — $ 12,750 $ 91,750 $ —
Schedule of Offsetting Derivative Assets	The following table indicates the gross amounts of commercial loan swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets as of the dates presented: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Derivatives not Designated as Hedging Instruments: Gross amounts recognized $ 90,723 $ 26,146 $ 90,577 $ 26,114 Gross amounts offset (2,588 ) (499 ) (2,588 ) (499 ) Net Amounts Presented in the Consolidated Balance Sheets 88,135 25,647 87,989 25,615 Gross amounts not offset (1) — — (86,720 ) (26,127 ) Net Amount $ 88,135 $ 25,647 $ 1,269 $ (512 ) (1) Amounts represent collateral posted for the periods presented.
Schedule of Offsetting Derivative Liabilities	The following table indicates the gross amounts of commercial loan swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets as of the dates presented: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Derivatives not Designated as Hedging Instruments: Gross amounts recognized $ 90,723 $ 26,146 $ 90,577 $ 26,114 Gross amounts offset (2,588 ) (499 ) (2,588 ) (499 ) Net Amounts Presented in the Consolidated Balance Sheets 88,135 25,647 87,989 25,615 Gross amounts not offset (1) — — (86,720 ) (26,127 ) Net Amount $ 88,135 $ 25,647 $ 1,269 $ (512 ) (1) Amounts represent collateral posted for the periods presented.
Schedule of Amount of Gain or Loss Recognized in Income on Derivatives	The following table indicates the gain or loss recognized in income on derivatives for the periods presented: Three Months Ended March 31, (dollars in thousands) 2020 2019 Derivatives not Designated as Hedging Instruments Interest rate swap contracts—commercial loans $ 114 $ (122 ) Interest rate lock commitments—mortgage loans 2,606 88 Forward sale contracts—mortgage loans (1,293 ) 33 Total Derivatives Gain/(Loss) $ 1,427 $ (1 )

Borrowings (Tables)

Borrowings (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Information Pertaining to Borrowings	Information pertaining to borrowings is summarized in the table below as of the dates presented: March 31, 2020 December 31, 2019 (dollars in thousands) Balance Weighted Balance Weighted Short-term Borrowings Securities sold under repurchase agreements $ 69,644 0.25 % $ 19,888 0.74 % Short-term borrowings 410,240 0.44 % 281,319 1.84 % Total Short-term Borrowings 479,884 0.41 % 301,207 1.76 % Long-term Borrowings Long-term borrowings 50,180 2.59 % 50,868 2.60 % Junior subordinated debt securities 64,038 3.63 % 64,277 3.59 % Total Long-term Borrowings 114,218 3.17 % 115,145 3.15 % Total Borrowings $ 594,102 0.94 % $ 416,352 2.14 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of Commitments and Letters of Credit	The following table sets forth our commitments and letters of credit as of the dates presented: (dollars in thousands) March 31, 2020 December 31, 2019 Commitments to extend credit $ 1,967,190 $ 1,910,805 Standby letters of credit 85,021 80,040 Total $ 2,052,211 $ 1,990,845
Unfunded Loan Commitments, Allowance For Credit Loss	The activity in the allowance for credit losses on unfunded loan commitments for the three months ended March 31, 2020 was as follows: (dollars in thousands) Total Three months ended March 31, 2020 Allowance for credit losses on unfunded loan commitments: Balance at beginning of period $ 3,112 Impact of adopting ASU 2016-13 1,349 January 1, 2020 4,461 Provision for credit losses 1,616 March 31, 2020 $ 6,077

Revenue From Contracts With C_2

Revenue From Contracts With Customers (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The information presented in the following table presents the point of revenue recognition for revenue from contracts with customers. Other revenue streams such as: interest income, net securities gains and losses, insurance, mortgage banking and other revenues that are accounted for under other generally accepted accounting principles are excluded. (dollars in thousands) Three Months Ended March 31, Revenue Streams Point of Revenue Recognition 2020 2019 Service charges on deposit accounts Over a period of time $ 484 $ 457 At a point in time 3,074 2,696 $ 3,558 $ 3,153 Debit and credit card Over a period of time $ 194 $ 185 At a point in time 3,287 2,789 $ 3,482 $ 2,974 Wealth management Over a period of time $ 345 $ 413 At a point in time 2,018 1,635 $ 2,362 $ 2,048 Other fee revenue At a point in time $ 919 $ 919

Other Comprehensive Income_(L_2

Other Comprehensive Income/(Loss) (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Tax Effects of Components of Other Comprehensive Loss	The following table presents the change in components of other comprehensive income/(loss) for the periods presented, net of tax effects. Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 (dollars in thousands) Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount Change in net unrealized gains/(losses) on available-for-sale debt securities (1) $ 21,568 $ (4,592 ) $ 16,976 $ 7,398 $ (1,578 ) $ 5,820 Adjustment to funded status of employee benefit plans 465 (99 ) 366 453 (97 ) 356 Other Comprehensive Income/(Loss) $ 22,033 $ (4,691 ) $ 17,342 $ 7,851 $ (1,675 ) $ 6,176 (1) Reclassification adjustments are comprised of realized security gains or losses. The realized gains or losses have been reclassified out of accumulated other comprehensive income/(loss) and have affected certain lines in the Consolidated Statements of Comprehensive Income as follows: the pre-tax amount is included in net gain on sale of securities, the tax expense amount is included in the provision for income taxes and the net of tax amount is included in net income. There were no reclassification adjustments for the three months ended March 31, 2020 or 2019.

Employee Benefits (Tables)

Employee Benefits (Tables)	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Schedule of Components of Net Periodic Pension Cost and Other Changes in Plan Assets and Benefit	The following table summarizes the components of net periodic pension cost for the periods presented: Three Months Ended March 31, (dollars in thousands) 2020 2019 Components of Net Periodic Pension Cost Interest cost on projected benefit obligation $ 891 $ 989 Expected return on plan assets (972 ) (1,180 ) Net amortization 384 394 Net Periodic Pension Expense $ 303 $ 203

Basis of Presentation - Schedul

Basis of Presentation - Schedule of Impact of ASU 2016-13 (Details) - USD ($) $ in Thousands		Mar. 31, 2020		Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		$ (96,850)		$ (62,224)	$ (62,224)
Total loans		7,254,054	[1]	7,074,928	7,142,408	[1]
Net deferred tax asset				13,206
Allowance for credit losses on unfunded loan commitments		6,077		3,113	3,112
Retained earnings		740,726		761,083	761,083
As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans				(89,577)
Total loans				7,047,575
Net deferred tax asset				19,317
Allowance for credit losses on unfunded loan commitments				4,462	4,461
Retained earnings				738,493
Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans				(27,353)	(27,352)
Total loans				(27,353)
Net deferred tax asset				6,111
Allowance for credit losses on unfunded loan commitments				1,349	1,349
Retained earnings				(22,590)
Commercial and industrial | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans				(9,900)
Commercial | Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				3,416,518
Allowance for credit losses on loans		(42,611)			(30,577)
Commercial | Commercial real estate | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				2,946,319
Commercial | Commercial real estate | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				(470,199)
Allowance for credit losses on loans					(4,810)
Commercial | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,720,833
Allowance for credit losses on loans		(19,870)			(15,681)
Commercial | Commercial and industrial | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,458,541
Commercial | Commercial and industrial | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				(262,292)
Allowance for credit losses on loans					(7,853)
Commercial | Commercial construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				375,445
Allowance for credit losses on loans		(6,606)			(7,900)
Commercial | Commercial construction | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				345,263
Commercial | Commercial construction | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				(30,182)
Allowance for credit losses on loans					3,376
Commercial | Business banking
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				0
Allowance for credit losses on loans	[2]	(13,706)			0
Commercial | Business banking | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,092,908
Commercial | Business banking | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,092,908
Allowance for credit losses on loans	[2]				(12,898)
Consumer | Consumer real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,545,323
Allowance for credit losses on loans		(11,200)			(6,337)
Consumer | Consumer real estate | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				1,235,352
Consumer | Consumer real estate | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				(309,971)
Allowance for credit losses on loans					(4,525)
Consumer | Other consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				79,033
Allowance for credit losses on loans		$ (2,857)			(1,729)
Consumer | Other consumer | As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				58,769
Consumer | Other consumer | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance				$ (20,264)
Allowance for credit losses on loans					$ (642)
[1]	Excludes interest receivable of $22.1 million at both March 31, 2020 and December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.
[2]	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. Our new segmentation breaks out business banking loans from our other loan segments: CRE, C&I , commercial construction, consumer real estate and other consumer. The business banking allowance balance at the beginning of period is included in the other segments and reclassified to business banking through the impact of CECL adoption line.

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to allowance for credit loss	$ 96,850	$ 62,224	$ 62,224
Retained earnings	(1,176,251)		(1,191,998)	$ (943,156)	$ (935,761)
Threshold for evaluation for expected credit loss of commercial loans	500
Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to allowance for credit loss		27,353	27,352
Impact of ASU 2016-13 Adoption | DNB
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to allowance for credit loss		9,300
Impact of ASU 2016-13 Adoption | S&T Legacy Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to allowance for credit loss		8,200
Impact of ASU 2016-13 Adoption | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to allowance for credit loss		9,900
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ (740,726)		$ (761,083)	$ (716,078)	$ (701,819)
Retained Earnings | Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 22,600

Business Combinations - Additio

Business Combinations - Additional Information (Details)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Nov. 30, 2019USD ($)banking_location$ / sharesshares		Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Business Acquisition [Line Items]
Goodwill	$ 374,270,000	$ 371,621,000			$ 374,270,000		$ 374,270,000	$ 371,621,000
Adjustments, Loans	10,900,000	$ 12,300,000
Merger related expenses					2,342,000	$ 0
Professional services and legal					1,048,000	$ 1,184,000
DNB
Business Acquisition [Line Items]
Number of banking locations | banking_location			14
Shares of S&T offered for each share of DNB (shares) | shares			1.22
Fair value of total consideration			$ 200,991,000
Cash			$ 360,000
S&T common shares issued (shares) | shares			5,318,964
S&T common shares issued, fair value (in dollars per share) | $ / shares			$ 37.72
Goodwill	85,983,000		$ 84,175,000		85,983,000		85,983,000
Preliminary estimates adjustments							1,808,000
Adjustments, Loans			8,143,000	[1]	(2,500,000)		2,496,000
Adjustments, Borrowings			276,000	[1]			257,000
Adjustments, Deferred income taxes			(3,298,000)	[1]			311,000
Carryover of allowance for credit losses	0		0		0		0
Fair value of loans acquired	906,488,000		908,984,000		906,488,000		906,488,000
Discount on loans acquired			$ 10,500,000
Direct costs related to merger	$ 13,700,000				13,700,000		$ 13,700,000
Merger related expenses					2,300,000			11,400,000
Professional services and legal					200,000			2,800,000
Severance payments					1,400,000			3,400,000
Data processing, contract termination, and conversion cost expenses					400,000			4,700,000
Other expenses					$ 300,000			$ 500,000
[1]	Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, deferred and current income taxes until the final valuations are complete and final tax returns are filed. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.

Business Combinations - Conside

Business Combinations - Consideration, Assets Acquired and Liabilities Assumed (Details) - USD ($)		Mar. 31, 2020	Dec. 31, 2019	Nov. 30, 2019		Mar. 31, 2020	Mar. 31, 2020
Fair Value of Assets Acquired
Adjustments, Loans		$ (10,900,000)	$ (12,300,000)
Goodwill		374,270,000	371,621,000			$ 374,270,000	$ 374,270,000
Fair Value of Liabilities Assumed
Goodwill		374,270,000	$ 371,621,000			374,270,000	374,270,000
As Recorded by DNB
Fair Value of Assets Acquired
Cash and cash equivalents				$ 64,119,000
Securities and other investments				108,715,000
Loans				917,127,000
Allowance for credit losses				(6,487,000)
Goodwill				15,525,000
Premises and equipment				6,782,000
Accrued interest receivable				4,138,000
Deferred income taxes				2,017,000
Core deposits and other intangible assets				269,000
Other assets				24,883,000
Total Assets Acquired				1,137,088,000
Fair Value of Liabilities Assumed
Deposits				966,263,000
Borrowings				37,617,000
Accrued interest payable and other liabilities				11,157,000
Total Liabilities Assumed				1,015,037,000
Total Net Assets Acquired				122,051,000
Identifiable Intangible Assets				269,000
Goodwill				15,525,000
DNB
Fair Value of Assets Acquired
Cash and cash equivalents		64,119,000		64,119,000		64,119,000	64,119,000
Adjustments, Cash and cash equivalents				0	[1]		0
Securities and other investments		108,898,000		108,898,000		108,898,000	108,898,000
Adjustments, Securities and other investments				183,000	[1]		0
Loans		906,488,000		908,984,000		906,488,000	906,488,000
Adjustments, Loans				(8,143,000)	[1]	2,500,000	(2,496,000)
Allowance for credit losses		0		0		0	0
Adjustments, Allowance for credit losses				6,487,000	[1]		0
Goodwill		85,983,000		84,175,000		85,983,000	85,983,000
Adjustments, Goodwill				(15,525,000)	[1]		1,808,000
Premises and equipment		14,872,000		14,872,000		14,872,000	14,872,000
Adjustments, Premises and equipment				8,090,000	[1]		0
Accrued interest receivable		4,138,000		4,138,000		4,138,000	4,138,000
Adjustments, Accrued interest receivable				0	[1]		0
Deferred income taxes		(970,000)		(1,281,000)		(970,000)	(970,000)
Adjustments, Deferred income taxes				(3,298,000)	[1]		311,000
Adjustments, Core deposits and other intangible assets	[1]			(269,000)
Other assets		20,645,000		20,605,000		20,645,000	20,645,000
Adjustments, Other assets				(4,278,000)	[1]		40,000
Total Assets Acquired		1,118,190,000		1,120,335,000		1,118,190,000	1,118,190,000
Adjustments, Total Assets Acquired				(16,753,000)	[1]		(2,145,000)
Fair Value of Liabilities Assumed
Deposits		967,253,000		967,265,000		967,253,000	967,253,000
Adjustments, Deposits				1,002,000	[1]		(12,000)
Borrowings		37,084,000		37,341,000		37,084,000	37,084,000
Adjustments, Borrowings				(276,000)	[1]		(257,000)
Accrued interest payable and other liabilities		7,905,000		7,973,000		7,905,000	7,905,000
Adjustments, Accrued interest payable and other liabilities				(3,184,000)	[1]		(68,000)
Total Liabilities Assumed		1,012,242,000		1,012,579,000		1,012,242,000	1,012,242,000
Adjustments, Total Liabilities Assumed				(2,458,000)	[1]		(337,000)
Total Net Assets Acquired		105,948,000		107,756,000		105,948,000	105,948,000
Adjustments, Total Net Assets Acquired				(14,295,000)	[1]		(1,808,000)
Total Fair Value of Net Assets Acquired and Identified		115,008,000		116,816,000		115,008,000	115,008,000
Adjustments, Total Fair Value of Net Assets Acquired and Identified							(1,808,000)
Cash				360,000
Common stock				200,631,000
Fair Value of Total Consideration				200,991,000
Goodwill		85,983,000		84,175,000		85,983,000	85,983,000
Core deposits | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets		7,288,000		7,288,000		7,288,000	7,288,000
Adjustments, Core deposits and other intangible assets							0
Fair Value of Liabilities Assumed
Identifiable Intangible Assets		7,288,000		7,288,000		7,288,000	7,288,000
Wealth management | DNB
Fair Value of Assets Acquired
Core deposits and other intangible assets		1,772,000		1,772,000		1,772,000	1,772,000
Adjustments, Core deposits and other intangible assets							0
Fair Value of Liabilities Assumed
Identifiable Intangible Assets		$ 1,772,000		$ 1,772,000		$ 1,772,000	$ 1,772,000
[1]	Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, deferred and current income taxes until the final valuations are complete and final tax returns are filed. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator for Earnings per Share Basic and Diluted:
Net income	$ 13,231	$ 22,928
Less: Income allocated to participating shares	29	62
Net Income Allocated to Shareholders	13,202	22,866
Net Income Available to Shareholders	$ 13,231	$ 22,928
Denominators for Earnings per Share:
Weighted Average Shares Outstanding—Basic (in shares)	39,271,540	34,414,555
Add: Potentially dilutive shares (in shares)	108,116	128,256
Denominator for Treasury Stock Method—Diluted (in shares)	39,379,656	34,542,811
Weighted Average Shares Outstanding—Basic (in shares)	39,271,540	34,414,555
Add: Average participating shares outstanding (in shares)	54,398	92,659
Denominator for Two-Class Method—Diluted (in shares)	39,325,938	34,507,214
Earnings per share—basic (in dollars per share)	$ 0.34	$ 0.67
Earnings per share—diluted (in dollars per share)	$ 0.34	$ 0.66
Restricted Stock
Denominators for Earnings per Share:
Anti-dilutive excluded from potentially dilutive shares (in shares)	41	68,314

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)		Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 to Level 2		$ 0	$ 0
ASSETS
Debt securities available-for-sale	[1]	795,966,000	779,133,000
Marketable equity securities		3,566,000	5,150,000
U.S. Treasury securities
ASSETS
Debt securities available-for-sale		10,372,000	10,040,000
Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		137,982,000	157,697,000
Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		189,472,000	189,348,000
Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		21,193,000	22,418,000
Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		284,679,000	275,870,000
Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale		144,717,000	116,133,000
Fair Value Measurements, Recurring
ASSETS
Debt securities available-for-sale		795,966,000	779,133,000
Marketable equity securities		3,566,000	5,150,000
Total securities		799,532,000	784,283,000
Securities held in a deferred compensation plan		4,782,000	5,987,000
Total Assets		895,376,000	816,239,000
LIABILITIES
Total Liabilities		89,281,000	25,615,000
Fair Value Measurements, Recurring | U.S. Treasury securities
ASSETS
Debt securities available-for-sale		10,372,000	10,040,000
Fair Value Measurements, Recurring | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		137,982,000	157,697,000
Fair Value Measurements, Recurring | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		189,472,000	189,348,000
Fair Value Measurements, Recurring | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		21,193,000	22,418,000
Fair Value Measurements, Recurring | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		284,679,000	275,870,000
Fair Value Measurements, Recurring | Corporate Bonds
ASSETS
Debt securities available-for-sale		7,551,000	7,627,000
Fair Value Measurements, Recurring | Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale		144,717,000	116,133,000
Fair Value Measurements, Recurring | Interest rate swaps
ASSETS
Derivative financial assets		88,135,000	25,647,000
LIABILITIES
Derivative financial liabilities		87,989,000	25,615,000
Fair Value Measurements, Recurring | Interest rate lock commitments
ASSETS
Derivative financial assets		2,927,000	321,000
Fair Value Measurements, Recurring | Forward sale contracts
ASSETS
Derivative financial assets			1,000
LIABILITIES
Derivative financial liabilities		1,292,000
Fair Value Measurements, Recurring | Level 1
ASSETS
Debt securities available-for-sale		0	0
Marketable equity securities		3,504,000	5,078,000
Total securities		3,504,000	5,078,000
Securities held in a deferred compensation plan		4,782,000	5,987,000
Total Assets		8,286,000	11,065,000
LIABILITIES
Total Liabilities		0	0
Fair Value Measurements, Recurring | Level 1 | U.S. Treasury securities
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Corporate Bonds
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 1 | Interest rate swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements, Recurring | Level 1 | Interest rate lock commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements, Recurring | Level 1 | Forward sale contracts
ASSETS
Derivative financial assets			0
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring | Level 2
ASSETS
Debt securities available-for-sale		795,966,000	779,133,000
Marketable equity securities		62,000	72,000
Total securities		796,028,000	779,205,000
Securities held in a deferred compensation plan		0	0
Total Assets		887,090,000	805,174,000
LIABILITIES
Total Liabilities		89,281,000	25,615,000
Fair Value Measurements, Recurring | Level 2 | U.S. Treasury securities
ASSETS
Debt securities available-for-sale		10,372,000	10,040,000
Fair Value Measurements, Recurring | Level 2 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		137,982,000	157,697,000
Fair Value Measurements, Recurring | Level 2 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		189,472,000	189,348,000
Fair Value Measurements, Recurring | Level 2 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		21,193,000	22,418,000
Fair Value Measurements, Recurring | Level 2 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		284,679,000	275,870,000
Fair Value Measurements, Recurring | Level 2 | Corporate Bonds
ASSETS
Debt securities available-for-sale		7,551,000	7,627,000
Fair Value Measurements, Recurring | Level 2 | Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale		144,717,000	116,133,000
Fair Value Measurements, Recurring | Level 2 | Interest rate swaps
ASSETS
Derivative financial assets		88,135,000	25,647,000
LIABILITIES
Derivative financial liabilities		87,989,000	25,615,000
Fair Value Measurements, Recurring | Level 2 | Interest rate lock commitments
ASSETS
Derivative financial assets		2,927,000	321,000
Fair Value Measurements, Recurring | Level 2 | Forward sale contracts
ASSETS
Derivative financial assets			1,000
LIABILITIES
Derivative financial liabilities		1,292,000
Fair Value Measurements, Recurring | Level 3
ASSETS
Debt securities available-for-sale		0	0
Marketable equity securities		0	0
Total securities		0	0
Securities held in a deferred compensation plan		0	0
Total Assets		0	0
LIABILITIES
Total Liabilities		0	0
Fair Value Measurements, Recurring | Level 3 | U.S. Treasury securities
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Corporate Bonds
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale		0	0
Fair Value Measurements, Recurring | Level 3 | Interest rate swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements, Recurring | Level 3 | Interest rate lock commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements, Recurring | Level 3 | Forward sale contracts
ASSETS
Derivative financial assets			$ 0
LIABILITIES
Derivative financial liabilities		$ 0
[1]	Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets Measured at Fair Value on Nonrecurring Basis by Significant Unobservable Inputs (Details) - Fair Value, Measurements, Nonrecurring	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on a nonrecurring basis	$ 0	$ 0
Level 3
ASSETS
Total Assets	27,900,000	43,062,000
Collateral Method | Level 3
ASSETS
Loans held for investment	20,926,000
Impaired loans		38,697,000
Other real estate owned	3,045,000	3,231,000
Discounted cash flow method | Level 3
ASSETS
Mortgage servicing rights	$ 3,929,000	$ 1,134,000
Costs to sell | Collateral Method | Level 3
ASSETS
Other real estate owned, measurement input	0.07	0.07
Contractual loan rate | Discounted cash flow method | Level 3
ASSETS
Loans held for investment, measurement input	0.0325
Minimum | Costs to sell | Collateral Method | Level 3
ASSETS
Loans held for investment, measurement input	0
Impaired loans, measurement input		0
Minimum | Contractual loan rate | Discounted cash flow method | Level 3
ASSETS
Impaired loans, measurement input		0.0475
Minimum | Discount rate | Discounted cash flow method | Level 3
ASSETS
Mortgage servicing rights, measurement input	0.0939	0.0939
Minimum | Constant prepayment rates | Discounted cash flow method | Level 3
ASSETS
Mortgage servicing rights, measurement input	0.0746	0.0746
Maximum | Costs to sell | Collateral Method | Level 3
ASSETS
Loans held for investment, measurement input	0.17
Impaired loans, measurement input		0.20
Maximum | Contractual loan rate | Discounted cash flow method | Level 3
ASSETS
Impaired loans, measurement input		0.0550
Maximum | Discount rate | Discounted cash flow method | Level 3
ASSETS
Mortgage servicing rights, measurement input	0.1254	0.1254
Maximum | Constant prepayment rates | Discounted cash flow method | Level 3
ASSETS
Mortgage servicing rights, measurement input	0.1274	0.1274

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
ASSETS
Securities, at fair value		$ 799,532	$ 784,283
Portfolio loans, net		7,149,895	7,074,928
FHLB and other restricted stock		28,253	22,977
LIABILITIES
Junior subordinated debt securities		64,038	64,277
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	[1]	187,684	197,823
Securities, at fair value	[1]	799,532	784,283
Loans held for sale	[1]	7,309	5,256
Portfolio loans, net	[1]	7,149,895	7,074,928
Bank owned life insurance	[1]	80,978	80,473
FHLB and other restricted stock	[1]	28,253	22,977
Securities held in a deferred compensation plan	[1]	4,782	5,987
Mortgage servicing rights	[1]	3,979	4,662
LIABILITIES
Deposits	[1]	7,057,879	7,036,576
Securities sold under repurchase agreements	[1]	69,644	19,888
Short-term borrowings	[1]	410,240	281,319
Long-term borrowings	[1]	50,180	50,868
Junior subordinated debt securities	[1]	64,038	64,277
Carrying Value | Interest rate swaps
ASSETS
Derivative financial assets	[1]	88,135	25,647
LIABILITIES
Derivative financial liabilities	[1]	87,989	25,615
Carrying Value | Interest rate lock commitments
ASSETS
Derivative financial assets	[1]	2,927	321
Carrying Value | Forward sale contracts
ASSETS
Derivative financial assets	[1]		1
LIABILITIES
Derivative financial liabilities	[1]	1,292
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits		187,684	197,823
Securities, at fair value		799,532	784,283
Loans held for sale		7,309	5,256
Portfolio loans, net		7,090,570	6,940,875
Bank owned life insurance		80,798	80,473
FHLB and other restricted stock		28,253	22,977
Securities held in a deferred compensation plan		4,782	5,987
Mortgage servicing rights		3,982	4,650
LIABILITIES
Deposits		7,065,896	7,034,595
Securities sold under repurchase agreements		69,644	19,888
Short-term borrowings		410,240	281,319
Long-term borrowings		51,675	51,339
Junior subordinated debt securities		64,038	64,277
Fair Value Measurements | Interest rate swaps
ASSETS
Derivative financial assets		88,135	25,647
LIABILITIES
Derivative financial liabilities		87,989	25,615
Fair Value Measurements | Interest rate lock commitments
ASSETS
Derivative financial assets		2,927	321
Fair Value Measurements | Forward sale contracts
ASSETS
Derivative financial assets			1
LIABILITIES
Derivative financial liabilities		1,292
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits		187,684	197,823
Securities, at fair value		3,504	5,078
Loans held for sale		0	0
Portfolio loans, net		0	0
Bank owned life insurance		0	0
FHLB and other restricted stock		0	0
Securities held in a deferred compensation plan		4,782	5,987
Mortgage servicing rights		0	0
LIABILITIES
Deposits		5,469,826	5,441,143
Securities sold under repurchase agreements		69,644	19,888
Short-term borrowings		410,240	281,319
Long-term borrowings		4,630	4,678
Junior subordinated debt securities		64,038	64,277
Fair Value Measurements | Level 1 | Interest rate swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 1 | Interest rate lock commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 1 | Forward sale contracts
ASSETS
Derivative financial assets			0
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements | Level 2
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities, at fair value			779,205
Loans held for sale		0	0
Portfolio loans, net		0	0
Bank owned life insurance		80,798	80,473
FHLB and other restricted stock		0	0
Securities held in a deferred compensation plan		0	0
Mortgage servicing rights		0	0
LIABILITIES
Deposits		1,596,070	1,593,452
Securities sold under repurchase agreements		0	0
Short-term borrowings		0	0
Long-term borrowings		47,045	46,661
Junior subordinated debt securities		0	0
Fair Value Measurements | Level 2 | Interest rate swaps
ASSETS
Derivative financial assets		88,135	25,647
LIABILITIES
Derivative financial liabilities		87,989	25,615
Fair Value Measurements | Level 2 | Interest rate lock commitments
ASSETS
Derivative financial assets		2,927	321
Fair Value Measurements | Level 2 | Forward sale contracts
ASSETS
Derivative financial assets			1
LIABILITIES
Derivative financial liabilities		1,292
Fair Value Measurements | Level 3
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities, at fair value		0	0
Loans held for sale		7,309	5,256
Portfolio loans, net		7,090,570	6,940,875
Bank owned life insurance		0	0
FHLB and other restricted stock		28,253	22,977
Securities held in a deferred compensation plan		0	0
Mortgage servicing rights		3,982	4,650
LIABILITIES
Deposits		0	0
Securities sold under repurchase agreements		0	0
Short-term borrowings		0	0
Long-term borrowings		0	0
Junior subordinated debt securities		0	0
Fair Value Measurements | Level 3 | Interest rate swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 3 | Interest rate lock commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 3 | Forward sale contracts
ASSETS
Derivative financial assets			$ 0
LIABILITIES
Derivative financial liabilities		$ 0
[1]	As reported in the Consolidated Balance Sheets

Securities - Fair Values and Am

Securities - Fair Values and Amortized Costs Securities (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	[1]	$ 763,696	$ 768,427
Debt Securities, Available-for-Sale, Gross Unrealized Gains	[1]	32,281	11,659
Debt Securities, Available-for-Sale, Gross Unrealized Losses	[1]	(11)	(953)
Debt Securities, Available-for-Sale, Fair Value	[1]	795,966	779,133
Marketable equity securities		3,566	5,150
Total Securities		799,532	784,283
Interest receivable		3,500	3,400
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		9,972	9,969
Debt Securities, Available-for-Sale, Gross Unrealized Gains		400	71
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0
Debt Securities, Available-for-Sale, Fair Value		10,372	10,040
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		132,938	155,969
Debt Securities, Available-for-Sale, Gross Unrealized Gains		5,044	1,773
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0	(45)
Debt Securities, Available-for-Sale, Fair Value		137,982	157,697
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		180,682	186,879
Debt Securities, Available-for-Sale, Gross Unrealized Gains		8,790	2,773
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0	(304)
Debt Securities, Available-for-Sale, Fair Value		189,472	189,348
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		20,391	22,120
Debt Securities, Available-for-Sale, Gross Unrealized Gains		802	321
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0	(23)
Debt Securities, Available-for-Sale, Fair Value		21,193	22,418
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		272,651	273,771
Debt Securities, Available-for-Sale, Gross Unrealized Gains		12,028	2,680
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0	(581)
Debt Securities, Available-for-Sale, Fair Value		284,679	275,870
Corporate obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		7,532	7,603
Debt Securities, Available-for-Sale, Gross Unrealized Gains		30	24
Debt Securities, Available-for-Sale, Gross Unrealized Losses		(11)	0
Debt Securities, Available-for-Sale, Fair Value		7,551	7,627
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost		139,530	112,116
Debt Securities, Available-for-Sale, Gross Unrealized Gains		5,187	4,017
Debt Securities, Available-for-Sale, Gross Unrealized Losses		0	0
Debt Securities, Available-for-Sale, Fair Value		$ 144,717	$ 116,133
[1]	Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.

Securities - Fair Value and Age

Securities - Fair Value and Age of Gross Unrealized Losses of Debt Securities (Details) $ in Thousands	Mar. 31, 2020USD ($)security	Dec. 31, 2019USD ($)security
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	2	20
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 2,989	$ 137,097
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ (11)	$ (701)
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	7
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 27,788
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ (252)
Temporarily Impaired Debt Securities, Number of Securities | security	2	27
Temporarily Impaired Debt Securities, Fair Value, Total	$ 2,989	$ 164,885
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (11)	$ (953)
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 0
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ 0
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	3
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 22,638
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ (45)
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, Number of Securities | security	0	3
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 22,638
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (45)
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	6
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 23,393
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ (73)
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	6
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 25,254
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ (231)
Temporarily Impaired Debt Securities, Number of Securities | security	0	12
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 48,647
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (304)
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	1
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 982
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ (2)
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	1
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 2,534
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ (21)
Temporarily Impaired Debt Securities, Number of Securities | security	0	2
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 3,516
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (23)
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	9
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 90,005
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ (581)
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, Number of Securities | security	0	9
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 90,005
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (581)
Corporate Bonds
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	2	1
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 2,989	$ 79
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ (11)	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, Number of Securities | security	2	1
Temporarily Impaired Debt Securities, Fair Value, Total	$ 2,989	$ 79
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (11)	$ 0
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Temporarily Impaired Debt Securities, Less Than 12 Months, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, Less Than 12 Months, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, Less Than 12 Months, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, 12 Months or More, Fair Value	$ 0	$ 0
Temporarily Impaired Debt Securities, 12 Months or More, Unrealized Losses	$ 0	$ 0
Temporarily Impaired Debt Securities, Number of Securities | security	0	0
Temporarily Impaired Debt Securities, Fair Value, Total	$ 0	$ 0
Temporarily Impaired Debt Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ 0

Securities - Additional Informa

Securities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2020USD ($)security	Dec. 31, 2019USD ($)security
Investments, Debt and Equity Securities [Abstract]
Number of debt securities in unrealized loss position | security		2	27
OTTI	$ 0
Securities pledged for regulatory and legal requirements		$ 298,400,000	$ 286,000,000

Securities - Unrealized Gains (

Securities - Unrealized Gains (Losses) of Debt Securities (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Total unrealized gains/(losses) on debt securities available-for-sale, Gross Unrealized Gains	[1]	$ 32,281	$ 11,659
Total unrealized gains/(losses) on debt securities available-for-sale, Gross Unrealized Losses	[1]	(11)	(953)
Total unrealized gains/(losses) on debt securities available-for-sale, Net Unrealized Gains/(Losses)		32,270	10,706
Income tax (expense) benefit, Gross Unrealized Gains		(6,873)	(2,486)
Income tax (expense) benefit, Gross Unrealized Losses		2	203
Income tax (expense) benefit, Net Unrealized Gains/(Losses)		(6,871)	(2,283)
Net Unrealized Gains/(Losses), Net of Tax Included in Accumulated Other Comprehensive Loss, Gross Unrealized Gains		25,408	9,173
Net Unrealized Gains/(Losses), Net of Tax Included in Accumulated Other Comprehensive Loss, Gross Unrealized Losses		(9)	(750)
Net Unrealized Gains/(Losses), Net of Tax Included in Accumulated Other Comprehensive Loss, Net Unrealized Gains/(Losses)		$ 25,399	$ 8,423
[1]	Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.

Securities - Contractual Maturi

Securities - Contractual Maturities of Debt Securities (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less		$ 84,687
Due after one year through five years		100,877
Due after five years through ten years		65,732
Due after ten years		31,144
Debt Securities Available-for-sale, Maturity, Amortized Cost		282,440
Debt Securities, Available-for-Sale, Amortized Cost	[1]	763,696	$ 768,427
Fair Value
Due in one year or less		85,259
Due after one year through five years		106,112
Due after five years through ten years		68,913
Due after ten years		32,786
Debt Securities Available-for-sale, Maturity, Fair Value		293,070
Debt Securities, Available-for-Sale, Fair Value	[1]	795,966	779,133
Collateralized mortgage obligations of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities		180,682
Debt Securities, Available-for-Sale, Amortized Cost		180,682	186,879
Fair Value
Available-for-Sale Debt Securities With Maturities		189,473
Debt Securities, Available-for-Sale, Fair Value		189,472	189,348
Residential mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities		20,391
Debt Securities, Available-for-Sale, Amortized Cost		20,391	22,120
Fair Value
Available-for-Sale Debt Securities With Maturities		21,193
Debt Securities, Available-for-Sale, Fair Value		21,193	22,418
Commercial mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities		272,651
Debt Securities, Available-for-Sale, Amortized Cost		272,651	273,771
Fair Value
Available-for-Sale Debt Securities With Maturities		284,679
Debt Securities, Available-for-Sale, Fair Value		284,679	$ 275,870
Corporate Securities
Amortized Cost
Available-for-Sale Debt Securities With Maturities		7,532
Fair Value
Available-for-Sale Debt Securities With Maturities		$ 7,551
[1]	Excludes interest receivable of $3.5 million at March 31, 2020 and $3.4 million at December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.

Securities - Unrealized Gains_2

Securities - Unrealized Gains (Losses) on Marketable Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Net gains and losses recognized during the period on equity securities	$ (1,585)	$ (318)
Less: Net gains and losses recognized during the period on equity securities sold during the period	0	0
Unrealized Losses/Gains Recognized During the Reporting Period on Equity Securities Still Held at the Reporting Date	$ (1,585)	$ (318)

Loans and Loans Held for Sale -

Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands		Mar. 31, 2020USD ($)loan	Dec. 31, 2019USD ($)	Mar. 31, 2020USD ($)noteloan		Mar. 31, 2019USD ($)loan	Dec. 31, 2019USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income		$ 5,000	$ 4,600	$ 5,000			$ 4,600
Purchase accounting fair value adjustments		$ 10,900	$ 12,300
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status				6 months
Restructured loans	[1]			$ 8,297	[2]	$ 5,499
Number of troubled debt restructuring loans returned to accruing status | loan				0		3
Amount of trouble debt restructuring loans returned to accruing status						$ 1,700
Number of commitments to lend additional funds on TDRs | loan		20		20
Commitments to lend additional funds on TDRs		$ 2,300		$ 2,300
Minimum period of loan payment defaults following restructure for TDRs to be in default				90 days
Number of defaulted TDRs that were restructured within the last twelve months prior to defaulting | loan				11		0
Amount of defaulted TDRs that were restructured within the last twelve months prior to defaulting				$ 21,100
Number of notes related to individual customer resulting in an increase in defaulted troubled debt restructuring loans due to Covid-19 | note				5
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of commercial loans in total portfolio loans		77.60%	77.20%	77.60%			77.20%
Commercial loans			$ 5,512,796				$ 5,512,796
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans	[1]			$ 2,210
Commercial real estate | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loans			3,416,518				3,416,518
CRE and commercial construction | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loans		$ 3,800,000	$ 3,800,000	$ 3,800,000			$ 3,800,000
Combined percentage of commercial real estate and commercial construction in total commercial loans		68.30%	68.80%	68.30%			68.80%
Combined percentage of commercial real estate and commercial construction in total portfolio loans		53.00%	53.10%	53.00%			53.10%
Concentration risk percentage of commercial real estate and commercial construction				0.00%			0.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of)		13.60%	11.00%	13.60%			11.00%
Out of market exposure of combined portfolio (percent)		5.40%	5.40%	5.40%			5.40%
Percentage of total loans out-of-state excluding contiguous states		2.80%	2.90%	2.80%			2.90%
Nonperforming TDRs | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans				$ 20,900
[1]	Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.
[2]	Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.

Loans and Loans Held for Sale_2

Loans and Loans Held for Sale - Composition of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020		Jan. 01, 2020	Dec. 31, 2019
Composition of the loans
Portfolio loans, net of unearned income	$ 7,246,745			$ 7,137,152
Loans held for sale	7,309			5,256
Total Loans	7,254,054	[1]	$ 7,074,928	7,142,408	[1]
Interest receivable	22,100			22,100
Commercial real estate
Composition of the loans
Portfolio loans, net of unearned income				3,416,518
Commercial and industrial
Composition of the loans
Portfolio loans, net of unearned income				1,720,833
Commercial construction
Composition of the loans
Portfolio loans, net of unearned income				375,445
Commercial
Composition of the loans
Portfolio loans, net of unearned income	5,620,415			5,512,796
Commercial | Commercial real estate
Composition of the loans
Portfolio loans, net of unearned income	3,442,495			3,416,518
Commercial | Commercial and industrial
Composition of the loans
Portfolio loans, net of unearned income	1,781,402			1,720,833
Commercial | Commercial construction
Composition of the loans
Portfolio loans, net of unearned income	396,518			375,445
Consumer
Composition of the loans
Portfolio loans, net of unearned income	1,626,330			1,624,356
Consumer | Residential Mortgage
Composition of the loans
Portfolio loans, net of unearned income	988,816			998,585
Consumer | Home equity
Composition of the loans
Portfolio loans, net of unearned income	544,405			538,348
Consumer | Installment and other consumer
Composition of the loans
Portfolio loans, net of unearned income	79,887			79,033
Consumer | Consumer construction
Composition of the loans
Portfolio loans, net of unearned income	$ 13,222			$ 8,390
[1]	Excludes interest receivable of $22.1 million at both March 31, 2020 and December 31, 2019. Interest receivable is included in other assets in the consolidated balance sheets.

Loans and Loans Held for Sale_3

Loans and Loans Held for Sale - Summary of Restructured Loans (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	$ 8,297	[2]	$ 5,499
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	2,210
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	3,780		5,201
Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	1,891
Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]	415
Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]			49
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans	[1]			$ 249
Performing TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		15,189	[3]		$ 36,960
Performing TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		30			22,233
Performing TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4,566			6,909
Performing TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		3,316			1,425
Performing TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		1,524
Performing TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		5,749
Performing TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					2,013
Performing TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					4,371
Performing TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4
Performing TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					9
Nonperforming TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		36,055	[3]		8,912
Nonperforming TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		28,973			6,713
Nonperforming TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		4,665			695
Nonperforming TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		0			0
Nonperforming TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		352
Nonperforming TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		2,064
Nonperforming TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					822
Nonperforming TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					678
Nonperforming TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		0
Nonperforming TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					4
Total TDRs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		51,243	[3]		45,872
Total TDRs | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		29,003			28,946
Total TDRs | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		9,231			7,604
Total TDRs | Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		3,316			1,425
Total TDRs | Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		1,876
Total TDRs | Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		7,813
Total TDRs | Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					2,835
Total TDRs | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					5,049
Total TDRs | Other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans		$ 4
Total TDRs | Installment and other consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Restructured loans					$ 13
[1]	Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.
[2]	Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.
[3]	Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.

Loans and Loans Held for Sale_4

Loans and Loans Held for Sale - Restructured Loans By Segment and Type of Concession (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020USD ($)loan		Mar. 31, 2019USD ($)loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		14	[1]	10
Pre-Modification Outstanding Recorded Investment	[2]	$ 8,297	[1]	$ 5,522
Post-Modification Outstanding Recorded Investment	[2]	8,297	[1]	5,499
Total Difference in Recorded Investment		$ 0	[1]	$ (23)
Principal deferral and maturity date extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		6
Pre-Modification Outstanding Recorded Investment	[2]	$ 5,991
Post-Modification Outstanding Recorded Investment	[2]	5,991
Total Difference in Recorded Investment		$ 0
Maturity date extension and interest rate reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				1
Pre-Modification Outstanding Recorded Investment	[2]			$ 5,201
Post-Modification Outstanding Recorded Investment	[2]			5,201
Total Difference in Recorded Investment				$ 0
Maturity date extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 1,891
Post-Modification Outstanding Recorded Investment	[2]	1,891
Total Difference in Recorded Investment		$ 0
Consumer bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	[3]	6		8
Pre-Modification Outstanding Recorded Investment	[2],[3]	$ 388		$ 240
Post-Modification Outstanding Recorded Investment	[2],[3]	388		217
Total Difference in Recorded Investment	[3]	$ 0		$ (23)
Interest rate reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				1
Pre-Modification Outstanding Recorded Investment	[2]			$ 81
Post-Modification Outstanding Recorded Investment	[2]			81
Total Difference in Recorded Investment				$ 0
Maturity date extension and payment reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 27
Post-Modification Outstanding Recorded Investment	[2]	27
Total Difference in Recorded Investment		$ 0
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 2,210
Post-Modification Outstanding Recorded Investment	[2]	2,210
Total Difference in Recorded Investment		$ 0
Commercial real estate | Principal deferral and maturity date extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 2,210
Post-Modification Outstanding Recorded Investment	[2]	2,210
Total Difference in Recorded Investment		$ 0
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		5		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 3,780		$ 5,201
Post-Modification Outstanding Recorded Investment	[2]	3,780		5,201
Total Difference in Recorded Investment		$ 0		$ 0
Commercial and industrial | Principal deferral and maturity date extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		5		0
Pre-Modification Outstanding Recorded Investment	[2]	$ 3,780		$ 0
Post-Modification Outstanding Recorded Investment	[2]	3,780		0
Total Difference in Recorded Investment		$ 0		$ 0
Commercial and industrial | Maturity date extension and interest rate reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				1
Pre-Modification Outstanding Recorded Investment	[2]			$ 5,201
Post-Modification Outstanding Recorded Investment	[2]			5,201
Total Difference in Recorded Investment				$ 0
Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 1,891
Post-Modification Outstanding Recorded Investment	[2]	1,891
Total Difference in Recorded Investment		$ 0
Commercial construction | Maturity date extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 1,891
Post-Modification Outstanding Recorded Investment	[2]	1,891
Total Difference in Recorded Investment		$ 0
Consumer real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		7
Pre-Modification Outstanding Recorded Investment	[2]	$ 415
Post-Modification Outstanding Recorded Investment	[2]	415
Total Difference in Recorded Investment		$ 0
Consumer real estate | Consumer bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	[3]	6
Pre-Modification Outstanding Recorded Investment	[2],[3]	$ 388
Post-Modification Outstanding Recorded Investment	[2],[3]	388
Total Difference in Recorded Investment	[3]	$ 0
Consumer real estate | Maturity date extension and payment reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan		1
Pre-Modification Outstanding Recorded Investment	[2]	$ 27
Post-Modification Outstanding Recorded Investment	[2]	27
Total Difference in Recorded Investment		$ 0
Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				1
Pre-Modification Outstanding Recorded Investment	[2]			$ 49
Post-Modification Outstanding Recorded Investment	[2]			49
Total Difference in Recorded Investment				$ 0
Residential Mortgage | Consumer bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	[3]			1
Pre-Modification Outstanding Recorded Investment	[2],[3]			$ 49
Post-Modification Outstanding Recorded Investment	[2],[3]			49
Total Difference in Recorded Investment	[3]			$ 0
Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				8
Pre-Modification Outstanding Recorded Investment	[2]			$ 272
Post-Modification Outstanding Recorded Investment	[2]			249
Total Difference in Recorded Investment				$ (23)
Home equity | Consumer bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	[3]			7
Pre-Modification Outstanding Recorded Investment	[2],[3]			$ 191
Post-Modification Outstanding Recorded Investment	[2],[3]			168
Total Difference in Recorded Investment	[3]			$ (23)
Home equity | Interest rate reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				1
Pre-Modification Outstanding Recorded Investment	[2]			$ 81
Post-Modification Outstanding Recorded Investment	[2]			81
Total Difference in Recorded Investment				$ 0
Home equity | Maturity date extension and payment reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan				0
Pre-Modification Outstanding Recorded Investment	[2]			$ 0
Post-Modification Outstanding Recorded Investment	[2]			0
Total Difference in Recorded Investment				$ 0
[1]	Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.
[2]	Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.
[3]	Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed.

Loans and Loans Held for Sale_5

Loans and Loans Held for Sale - Nonperforming Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Nonperforming Assets
Nonaccrual loans	$ 37,744	$ 45,145
Nonaccrual TDRs	36,055	8,912
Total Nonaccrual Loans	73,799	54,057
OREO	3,389	3,525
Total Nonperforming Assets	$ 77,188	$ 57,582

Allowance for Credit Losses - L

Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 351,735
2019	1,260,885
2018	993,019
2017	696,569
2016	742,706
2015 and Prior	1,978,077
Revolving	1,199,483
Revolving-Term	24,271
Total	7,246,745	$ 7,137,152
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	169,367
2019	486,935
2018	453,673
2017	371,144
2016	451,710
2015 and Prior	959,249
Revolving	62,890
Revolving-Term	21
Total	2,954,989
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	169,367
2019	483,699
2018	452,024
2017	359,553
2016	416,420
2015 and Prior	882,326
Revolving	59,032
Revolving-Term	0
Total	2,822,421
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	3,236
2018	187
2017	11,591
2016	10,005
2015 and Prior	26,575
Revolving	850
Revolving-Term	0
Total	52,444
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	1,462
2017	0
2016	25,285
2015 and Prior	50,348
Revolving	3,008
Revolving-Term	21
Total	80,124
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75,969
2019	252,166
2018	171,457
2017	108,269
2016	77,302
2015 and Prior	303,807
Revolving	535,251
Revolving-Term	0
Total	1,524,221
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75,969
2019	240,261
2018	165,631
2017	103,537
2016	73,798
2015 and Prior	282,138
Revolving	486,045
Revolving-Term	0
Total	1,427,379
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	6,239
2018	3,525
2017	947
2016	1,883
2015 and Prior	9,437
Revolving	31,890
Revolving-Term	0
Total	53,921
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	5,666
2018	2,301
2017	3,785
2016	1,621
2015 and Prior	12,232
Revolving	17,316
Revolving-Term	0
Total	42,921
Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	23,004
2019	179,956
2018	117,527
2017	18,163
2016	18,986
2015 and Prior	20,483
Revolving	12,083
Revolving-Term	0
Total	390,202
Commercial construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	23,004
2019	179,956
2018	117,527
2017	17,122
2016	18,986
2015 and Prior	11,586
Revolving	11,992
Revolving-Term	0
Total	380,173
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	5,117
Revolving	91
Revolving-Term	0
Total	5,208
Commercial construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	1,041
2016	0
2015 and Prior	3,780
Revolving	0
Revolving-Term	0
Total	4,821
Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,952
2019	181,686
2018	153,026
2017	108,448
2016	95,112
2015 and Prior	363,038
Revolving	128,202
Revolving-Term	0
Total	1,070,464
Business banking | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,952
2019	181,242
2018	148,419
2017	103,027
2016	89,925
2015 and Prior	327,333
Revolving	125,800
Revolving-Term	0
Total	1,016,698
Business banking | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	62
2018	1,496
2017	1,775
2016	1,181
2015 and Prior	7,902
Revolving	737
Revolving-Term	0
Total	13,153
Business banking | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	382
2018	3,111
2017	3,646
2016	4,006
2015 and Prior	27,803
Revolving	1,665
Revolving-Term	0
Total	40,613
Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	33,737
2019	150,132
2018	86,534
2017	83,939
2016	93,914
2015 and Prior	323,883
Revolving	432,579
Revolving-Term	22,351
Total	1,227,069
Consumer real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	33,737
2019	149,942
2018	86,463
2017	83,402
2016	92,013
2015 and Prior	316,169
Revolving	432,274
Revolving-Term	20,966
Total	1,214,966
Consumer real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	798
2015 and Prior	304
Revolving	0
Revolving-Term	0
Total	1,102
Consumer real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	190
2018	71
2017	537
2016	1,103
2015 and Prior	7,410
Revolving	305
Revolving-Term	1,385
Total	11,001
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,706
2019	10,010
2018	10,802
2017	6,606
2016	5,682
2015 and Prior	7,617
Revolving	28,478
Revolving-Term	1,899
Total	79,800
Other consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,706
2019	9,522
2018	10,670
2017	6,474
2016	5,088
2015 and Prior	3,365
Revolving	28,156
Revolving-Term	773
Total	72,754
Other consumer | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Revolving-Term	0
Total	0
Other consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	488
2018	132
2017	132
2016	594
2015 and Prior	4,252
Revolving	322
Revolving-Term	1,126
Total	$ 7,046

Allowance for Credit Losses - A

Allowance for Credit Losses - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment to allowance for credit loss	$ 96,850	$ 62,224	$ 62,224
ACL provision, COVID-19 assessment	14,900
ACL provision, COVID-19 assessment, revised forecast	11,200
ACL provision, COVID-19 assessment, changes in current conditions	$ 3,700
Impact of ASU 2016-13 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment to allowance for credit loss		27,353	$ 27,352
S&T Legacy Loans | Impact of ASU 2016-13 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment to allowance for credit loss		8,200
Commercial and industrial | Impact of ASU 2016-13 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment to allowance for credit loss		9,900
DNB | Impact of ASU 2016-13 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment to allowance for credit loss		$ 9,300

Allowance for Credit Losses -_2

Allowance for Credit Losses - Loan Balances by Year of Origination and Performing and Nonperforming Status (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 351,735
2019	1,260,885
2018	993,019
2017	696,569
2016	742,706
2015 and Prior	1,978,077
Revolving	1,199,483
Revolving-Term	24,271
Total	7,246,745	$ 7,137,152
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	351,735
2019	1,260,585
2018	991,429
2017	694,776
2016	717,561
2015 and Prior	1,940,845
Revolving	1,192,749
Revolving-Term	23,266
Total	7,172,946
Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	300
2018	1,590
2017	1,793
2016	25,145
2015 and Prior	37,232
Revolving	6,734
Revolving-Term	1,005
Total	73,799
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	169,367
2019	486,935
2018	453,673
2017	371,144
2016	451,710
2015 and Prior	959,249
Revolving	62,890
Revolving-Term	21
Total	2,954,989
Commercial real estate | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	169,367
2019	486,935
2018	453,673
2017	371,144
2016	431,919
2015 and Prior	935,536
Revolving	59,882
Revolving-Term	0
Total	2,908,456
Commercial real estate | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	19,791
2015 and Prior	23,713
Revolving	3,008
Revolving-Term	21
Total	46,533
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75,969
2019	252,166
2018	171,457
2017	108,269
2016	77,302
2015 and Prior	303,807
Revolving	535,251
Revolving-Term	0
Total	1,524,221
Commercial and industrial | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75,969
2019	252,166
2018	171,093
2017	108,269
2016	76,593
2015 and Prior	303,745
Revolving	531,881
Revolving-Term	0
Total	1,519,716
Commercial and industrial | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	364
2017	0
2016	709
2015 and Prior	62
Revolving	3,370
Revolving-Term	0
Total	4,505
Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	23,004
2019	179,956
2018	117,527
2017	18,163
2016	18,986
2015 and Prior	20,483
Revolving	12,083
Revolving-Term	0
Total	390,202
Commercial construction | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	23,004
2019	179,956
2018	117,527
2017	18,055
2016	18,986
2015 and Prior	20,020
Revolving	12,083
Revolving-Term	0
Total	389,631
Commercial construction | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	108
2016	0
2015 and Prior	463
Revolving	0
Revolving-Term	0
Total	571
Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,952
2019	181,686
2018	153,026
2017	108,448
2016	95,112
2015 and Prior	363,038
Revolving	128,202
Revolving-Term	0
Total	1,070,464
Business banking | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,952
2019	181,576
2018	151,933
2017	107,176
2016	94,230
2015 and Prior	355,259
Revolving	128,022
Revolving-Term	0
Total	1,059,148
Business banking | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	110
2018	1,093
2017	1,272
2016	882
2015 and Prior	7,779
Revolving	180
Revolving-Term	0
Total	11,316
Consumer real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	33,737
2019	150,132
2018	86,534
2017	83,939
2016	93,914
2015 and Prior	323,883
Revolving	432,579
Revolving-Term	22,351
Total	1,227,069
Consumer real estate | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	33,737
2019	149,942
2018	86,401
2017	83,526
2016	90,151
2015 and Prior	318,926
Revolving	432,403
Revolving-Term	21,367
Total	1,216,453
Consumer real estate | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	190
2018	133
2017	413
2016	3,763
2015 and Prior	4,957
Revolving	176
Revolving-Term	984
Total	10,616
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,706
2019	10,010
2018	10,802
2017	6,606
2016	5,682
2015 and Prior	7,617
Revolving	28,478
Revolving-Term	1,899
Total	79,800
Other consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,706
2019	10,010
2018	10,802
2017	6,606
2016	5,682
2015 and Prior	7,359
Revolving	28,478
Revolving-Term	1,899
Total	79,542
Other consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
2015 and Prior	258
Revolving	0
Revolving-Term	0
Total	$ 258

Allowance for Credit Losses -_3

Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Current		$ 7,145,326	$ 7,055,361
Past due		101,419	81,791
Non - performing		73,799	54,057
Total		7,246,745	7,137,152
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due		18,211	17,992
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due		4,117	5,985
90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	[1]	5,294	3,757
Commercial
Financing Receivable, Past Due [Line Items]
Total		5,620,415	5,512,796
Commercial | Commercial real estate
Financing Receivable, Past Due [Line Items]
Current		2,901,375	3,025,505
Past due		53,614	34,087
Non - performing		46,533	25,356
Total		2,954,989	3,059,592
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current		1,516,639	1,466,460
Past due		7,582	14,069
Non - performing		4,505	10,911
Total		1,524,221	1,480,529
Commercial | Commercial construction
Financing Receivable, Past Due [Line Items]
Current		388,122	367,204
Past due		2,080	2,856
Non - performing		571	737
Total		390,202	370,060
Commercial | Business banking
Financing Receivable, Past Due [Line Items]
Current		1,048,241	830,735
Past due		22,223	16,055
Non - performing		11,316	9,863
Total		1,070,464	846,790
Commercial | 30 to 59 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due		6,381	7,749
Commercial | 30 to 59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due		463	126
Commercial | 30 to 59 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Past due		576	956
Commercial | 30 to 59 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Past due		6,758	5,093
Commercial | 60 to 89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due		0	71
Commercial | 60 to 89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due		0	1,589
Commercial | 60 to 89 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Past due		0	1,163
Commercial | 60 to 89 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Past due		3,381	1,099
Commercial | 90 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Past due	[1]	700	911
Commercial | 90 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Past due	[1]	2,615	1,443
Commercial | 90 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Past due	[1]	933	0
Commercial | 90 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Past due	[1]	768	0
Consumer
Financing Receivable, Past Due [Line Items]
Total		1,626,330	1,624,356
Consumer | Consumer real estate
Financing Receivable, Past Due [Line Items]
Current		1,211,865	1,283,591
Past due		15,203	11,616
Non - performing		10,616	6,063
Total		1,227,069	1,295,207
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Current		79,083	81,866
Past due		717	3,108
Non - performing		258	1,127
Total		79,800	84,974
Consumer | 30 to 59 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Past due		3,859	2,620
Consumer | 30 to 59 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Past due		174	1,448
Consumer | 60 to 89 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Past due		646	1,758
Consumer | 60 to 89 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Past due		91	305
Consumer | 90 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Past due	[1]	83	1,175
Consumer | 90 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Past due	[1]	$ 195	$ 228
[1]	Represents acquired loans that were recorded at fair value at the acquisition date and remain performing at March 31, 2020 and December 31, 2019.

Allowance for Credit Losses -_4

Allowance for Credit Losses - Loans on Nonaccrual Status and Loans Past Due 90 Days or More and Still Accruing (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	$ 54,057
End of Period Nonaccrual	73,799
Nonaccrual With No Related Allowance	46,554
Past Due 90 Days Still Accruing	5,294
Interest Income Recognized on Nonaccrual	881
Commercial | Commercial real estate
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	25,356
End of Period Nonaccrual	46,533
Nonaccrual With No Related Allowance	39,454
Past Due 90 Days Still Accruing	700
Interest Income Recognized on Nonaccrual	684
Commercial | Commercial and industrial
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	10,911
End of Period Nonaccrual	4,505
Nonaccrual With No Related Allowance	4,054
Past Due 90 Days Still Accruing	2,615
Interest Income Recognized on Nonaccrual	64
Commercial | Commercial construction
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	737
End of Period Nonaccrual	571
Nonaccrual With No Related Allowance	285
Past Due 90 Days Still Accruing	933
Interest Income Recognized on Nonaccrual	0
Commercial | Business banking
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	9,863
End of Period Nonaccrual	11,316
Nonaccrual With No Related Allowance	2,363
Past Due 90 Days Still Accruing	768
Interest Income Recognized on Nonaccrual	58
Consumer | Consumer real estate
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	6,063
End of Period Nonaccrual	10,616
Nonaccrual With No Related Allowance	398
Past Due 90 Days Still Accruing	83
Interest Income Recognized on Nonaccrual	47
Consumer | Other consumer
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual	1,127
End of Period Nonaccrual	258
Nonaccrual With No Related Allowance	0
Past Due 90 Days Still Accruing	195
Interest Income Recognized on Nonaccrual	$ 28

Allowance for Credit Losses - C

Allowance for Credit Losses - Collateral Dependent Loans by Class of Loan (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020
Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	$ 62,638
Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	5,421
Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	40
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	689
Commercial | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans		$ 3,416,518
Commercial | Commercial real estate | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	51,630
Commercial | Commercial real estate | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial real estate | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial real estate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans		1,720,833
Commercial | Commercial and industrial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	4,686
Commercial | Commercial and industrial | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	4,545
Commercial | Commercial and industrial | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	40
Commercial | Commercial and industrial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans		375,445
Commercial | Commercial construction | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	3,602
Commercial | Commercial construction | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial construction | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Commercial construction | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Business banking
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans		$ 0
Commercial | Business banking | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	2,322
Commercial | Business banking | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	876
Commercial | Business banking | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Business banking | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	689
Commercial | Consumer real estate | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Consumer real estate | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Consumer real estate | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Consumer real estate | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Other consumer | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	398
Commercial | Other consumer | Blanket Lien
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Other consumer | Investment/Cash
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	0
Commercial | Other consumer | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Collateral dependent loans	$ 0

Allowance for Credit Losses -_5

Allowance for Credit Losses - Allowance for Credit Loss Activity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 62,224
Provision for credit losses on loans	18,430
Charge-offs	(11,430)
Recoveries	274
Net (Charge-offs)/Recoveries	(11,156)
Balance at End of Period	96,850
Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	30,577
Provision for credit losses on loans	7,639
Charge-offs	(442)
Recoveries	27
Net (Charge-offs)/Recoveries	(415)
Balance at End of Period	42,611
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	15,681
Provision for credit losses on loans	6,196
Charge-offs	(9,879)
Recoveries	19
Net (Charge-offs)/Recoveries	(9,860)
Balance at End of Period	19,870
Commercial | Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,900
Provision for credit losses on loans	2,309
Charge-offs	(229)
Recoveries	2
Net (Charge-offs)/Recoveries	(227)
Balance at End of Period	6,606
Commercial | Business banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	[1]
Provision for credit losses on loans	1,194	[1]
Charge-offs	(460)	[1]
Recoveries	74	[1]
Net (Charge-offs)/Recoveries	(386)	[1]
Balance at End of Period	13,706	[1]
Consumer | Consumer real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	6,337
Provision for credit losses on loans	472
Charge-offs	(172)
Recoveries	38
Net (Charge-offs)/Recoveries	(134)
Balance at End of Period	11,200
Consumer | Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,729
Provision for credit losses on loans	620
Charge-offs	(248)
Recoveries	114
Net (Charge-offs)/Recoveries	(134)
Balance at End of Period	2,857
Impact of CECL adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	27,352
Impact of CECL adoption | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	4,810
Impact of CECL adoption | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,853
Impact of CECL adoption | Commercial | Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	(3,376)
Impact of CECL adoption | Commercial | Business banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	12,898	[1]
Impact of CECL adoption | Consumer | Consumer real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	4,525
Impact of CECL adoption | Consumer | Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 642
[1]	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. Our new segmentation breaks out business banking loans from our other loan segments: CRE, C&I , commercial construction, consumer real estate and other consumer. The business banking allowance balance at the beginning of period is included in the other segments and reclassified to business banking through the impact of CECL adoption line.

Allowance for Credit Losses - R

Allowance for Credit Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial $ in Thousands	Dec. 31, 2019USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 5,512,796
Total percentage of recorded investment in commercial loan	100.00%
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 5,254,076
Total percentage of recorded investment in commercial loan	95.30%
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 103,878
Total percentage of recorded investment in commercial loan	1.90%
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 152,651
Total percentage of recorded investment in commercial loan	2.80%
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 2,191
Total percentage of recorded investment in commercial loan	0.00%
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 3,416,518
Total percentage of recorded investment in commercial loan	100.00%
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 3,270,437
Total percentage of recorded investment in commercial loan	95.70%
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 57,285
Total percentage of recorded investment in commercial loan	1.70%
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 86,772
Total percentage of recorded investment in commercial loan	2.50%
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 2,023
Total percentage of recorded investment in commercial loan	0.00%
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,720,833
Total percentage of recorded investment in commercial loan	100.00%
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,636,314
Total percentage of recorded investment in commercial loan	93.40%
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 36,484
Total percentage of recorded investment in commercial loan	1.70%
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 47,980
Total percentage of recorded investment in commercial loan	4.90%
Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 55
Total percentage of recorded investment in commercial loan	0.00%
Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 375,445
Total percentage of recorded investment in commercial loan	100.00%
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 347,324
Total percentage of recorded investment in commercial loan	92.50%
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 10,109
Total percentage of recorded investment in commercial loan	2.70%
Commercial construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 17,899
Total percentage of recorded investment in commercial loan	4.80%
Commercial construction | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 133
Total percentage of recorded investment in commercial loan	0.00%

Allowance for Credit Losses -_6

Allowance for Credit Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Details) - Consumer $ in Thousands	Dec. 31, 2019USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,624,356
Percentage of Total	100.00%
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,614,158
Percentage of Total	99.40%
Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 10,198
Percentage of Total	0.60%
Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 998,585
Percentage of Total	100.00%
Residential Mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 991,066
Percentage of Total	99.20%
Residential Mortgage | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 7,519
Percentage of Total	0.80%
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 538,348
Percentage of Total	100.00%
Home equity | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 535,709
Percentage of Total	99.50%
Home equity | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 2,639
Percentage of Total	0.50%
Installment and other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 79,033
Percentage of Total	100.00%
Installment and other consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 78,993
Percentage of Total	99.90%
Installment and other consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 40
Percentage of Total	0.10%
Consumer construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 8,390
Percentage of Total	100.00%
Consumer construction | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 8,390
Percentage of Total	100.00%
Consumer construction | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 0
Percentage of Total	0.00%

Allowance for Credit Losses - I

Allowance for Credit Losses - Investments in Loans Considered to be Impaired and Related Information on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		$ 23,510
With a related allowance recorded, Unpaid Principal Balance		24,821
Impaired financing receivable, Related Allowance		2,200
Without a related allowance recorded, Recorded Investment		51,827
Without a related allowance, Unpaid Principal Balance		61,950
Impaired Financing Receivable, Recorded Investment, Total		75,337
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		86,771
With a related allowance recorded, Average Recorded Investment	$ 39,056
With a related allowance recorded, Interest Income Recognized	910
Without a related allowance recorded, Average Recorded Investment	14,476
Without a related allowance recorded, Interest Income Recognized	437
Impaired financing receivable, Average Recorded Investment, Total	53,532
Impaired financing Receivable, Interest Income Recognized, Total	1,347
Commercial real estate
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		13,011
With a related allowance recorded, Unpaid Principal Balance		14,322
Impaired financing receivable, Related Allowance		2,023
Without a related allowance recorded, Recorded Investment		34,909
Without a related allowance, Unpaid Principal Balance		40,201
Impaired Financing Receivable, Recorded Investment, Total		47,920
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		54,523
With a related allowance recorded, Average Recorded Investment	15,107
With a related allowance recorded, Interest Income Recognized	144
Without a related allowance recorded, Average Recorded Investment	12,983
Without a related allowance recorded, Interest Income Recognized	400
Impaired financing receivable, Average Recorded Investment, Total	28,090
Impaired financing Receivable, Interest Income Recognized, Total	544
Commercial and industrial
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		10,001
With a related allowance recorded, Unpaid Principal Balance		10,001
Impaired financing receivable, Related Allowance		55
Without a related allowance recorded, Recorded Investment		7,605
Without a related allowance, Unpaid Principal Balance		10,358
Impaired Financing Receivable, Recorded Investment, Total		17,606
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		20,359
With a related allowance recorded, Average Recorded Investment	12,780
With a related allowance recorded, Interest Income Recognized	209
Without a related allowance recorded, Average Recorded Investment	980
Without a related allowance recorded, Interest Income Recognized	35
Impaired financing receivable, Average Recorded Investment, Total	13,760
Impaired financing Receivable, Interest Income Recognized, Total	244
Commercial construction
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		489
With a related allowance recorded, Unpaid Principal Balance		489
Impaired financing receivable, Related Allowance		113
Without a related allowance recorded, Recorded Investment		1,425
Without a related allowance, Unpaid Principal Balance		2,935
Impaired Financing Receivable, Recorded Investment, Total		1,914
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		3,424
With a related allowance recorded, Average Recorded Investment	2,319
With a related allowance recorded, Interest Income Recognized	140
Without a related allowance recorded, Average Recorded Investment	489
Without a related allowance recorded, Interest Income Recognized	0
Impaired financing receivable, Average Recorded Investment, Total	2,808
Impaired financing Receivable, Interest Income Recognized, Total	140
Consumer real estate
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		0
With a related allowance recorded, Unpaid Principal Balance		0
Impaired financing receivable, Related Allowance		0
Without a related allowance recorded, Recorded Investment		7,884
Without a related allowance, Unpaid Principal Balance		8,445
Impaired Financing Receivable, Recorded Investment, Total		7,884
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		8,445
With a related allowance recorded, Average Recorded Investment	8,846
With a related allowance recorded, Interest Income Recognized	417
Without a related allowance recorded, Average Recorded Investment	14
Without a related allowance recorded, Interest Income Recognized	1
Impaired financing receivable, Average Recorded Investment, Total	8,860
Impaired financing Receivable, Interest Income Recognized, Total	418
Other consumer
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment		9
With a related allowance recorded, Unpaid Principal Balance		9
Impaired financing receivable, Related Allowance		9
Without a related allowance recorded, Recorded Investment		4
Without a related allowance, Unpaid Principal Balance		11
Impaired Financing Receivable, Recorded Investment, Total		13
Impaired Financing Receivable, Total Unpaid Principal Balance, Total		$ 20
With a related allowance recorded, Average Recorded Investment	4
With a related allowance recorded, Interest Income Recognized	0
Without a related allowance recorded, Average Recorded Investment	10
Without a related allowance recorded, Interest Income Recognized	1
Impaired financing receivable, Average Recorded Investment, Total	14
Impaired financing Receivable, Interest Income Recognized, Total	$ 1

Allowance for Credit Losses - S

Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 6,996
Charge-offs	(6,023)
Recoveries	787
Net (Charge-offs)/Recoveries	(5,236)
Provision for credit losses	5,649
Balance at End of Period	61,409
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	33,707
Charge-offs	(1)
Recoveries	122
Net (Charge-offs)/Recoveries	121
Provision for credit losses	1,075
Balance at End of Period	34,903
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	11,596
Charge-offs	(5,477)
Recoveries	417
Net (Charge-offs)/Recoveries	(5,060)
Provision for credit losses	5,460
Balance at End of Period	11,996
Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,983
Charge-offs	0
Recoveries	0
Net (Charge-offs)/Recoveries	0
Provision for credit losses	(1,226)
Balance at End of Period	6,757
Consumer real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	6,187
Charge-offs	(162)
Recoveries	148
Net (Charge-offs)/Recoveries	(14)
Provision for credit losses	5
Balance at End of Period	6,178
Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,494
Charge-offs	(425)
Recoveries	169
Net (Charge-offs)/Recoveries	(256)
Provision for credit losses	249
Balance at End of Period	$ 1,487

Allowance for Credit Losses -_7

Allowance for Credit Losses - Summary of Allowance for Credit Losses and Recorded Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		$ 2,200
Allowance for Loan Losses, Collectively Evaluated for Impairment		60,024
Total Allowance for Loan Losses	$ 96,850	62,224	$ 61,409	$ 6,996
Portfolio Loans, Individually Evaluated for Impairment		75,337
Portfolio Loans, Collectively Evaluated for Impairment		7,061,815
Total	$ 7,246,745	7,137,152
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		2,023
Allowance for Loan Losses, Collectively Evaluated for Impairment		28,554
Total Allowance for Loan Losses		30,577
Portfolio Loans, Individually Evaluated for Impairment		47,920
Portfolio Loans, Collectively Evaluated for Impairment		3,368,598
Total		3,416,518
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		55
Allowance for Loan Losses, Collectively Evaluated for Impairment		15,626
Total Allowance for Loan Losses		15,681
Portfolio Loans, Individually Evaluated for Impairment		17,606
Portfolio Loans, Collectively Evaluated for Impairment		1,703,227
Total		1,720,833
Commercial construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		113
Allowance for Loan Losses, Collectively Evaluated for Impairment		7,787
Total Allowance for Loan Losses		7,900
Portfolio Loans, Individually Evaluated for Impairment		1,914
Portfolio Loans, Collectively Evaluated for Impairment		373,531
Total		375,445
Consumer real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		0
Allowance for Loan Losses, Collectively Evaluated for Impairment		6,337
Total Allowance for Loan Losses		6,337
Portfolio Loans, Individually Evaluated for Impairment		7,884
Portfolio Loans, Collectively Evaluated for Impairment		1,537,439
Total		1,545,323
Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment		9
Allowance for Loan Losses, Collectively Evaluated for Impairment		1,720
Total Allowance for Loan Losses		1,729
Portfolio Loans, Individually Evaluated for Impairment		13
Portfolio Loans, Collectively Evaluated for Impairment		79,020
Total		$ 79,033

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Period for commitments (in days)	60 days

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Other Assets
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	$ 88,135	$ 25,647
Other Assets | Interest rate swap contracts—commercial loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	88,135	25,647
Notional amount, Derivatives (included in Other Assets)	918,481	740,762
Collateral posted, Derivatives (included in Other Assets)	0	0
Other Assets | Interest rate lock commitments—mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	2,927	321
Notional amount, Derivatives (included in Other Assets)	86,674	9,829
Other Assets | Forward sale contracts—mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	0	1
Notional amount, Derivatives (included in Other Assets)	0	12,750
Other Liabilities
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	87,989	25,615
Other Liabilities | Interest rate swap contracts—commercial loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	87,989	25,615
Notional amount, Derivatives (included in Other Liabilities)	918,481	740,762
Collateral posted, Derivatives (included in Other Liabilities)	86,720	26,127
Other Liabilities | Interest rate lock commitments—mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	0	0
Notional amount, Derivatives (included in Other Liabilities)	0	0
Other Liabilities | Forward sale contracts—mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	1,292	0
Notional amount, Derivatives (included in Other Liabilities)	$ 91,750	$ 0

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Schedule of Gross Amounts of Derivative Assets and Derivative Liabilities (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Other Assets
Derivatives (included in Other Assets)
Gross amounts recognized		$ 90,723	$ 26,146
Gross amounts offset		(2,588)	(499)
Net Amounts Presented in the Consolidated Balance Sheets		88,135	25,647
Gross amounts not offset	[1]	0	0
Net Amount		88,135	25,647
Other Liabilities
Derivatives (included in Other Liabilities)
Gross amounts recognized		90,577	26,114
Gross amounts offset		(2,588)	(499)
Net Amounts Presented in the Consolidated Balance Sheets		87,989	25,615
Gross amounts not offset	[1]	(86,720)	(26,127)
Net Amount		$ 1,269	$ (512)
[1]	Amounts represent collateral posted for the periods presented.

Derivative Instruments and He_6

Derivative Instruments and Hedging Activities - Amount of Gain or Loss Recognized in Income on Derivatives (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain/(Loss)	$ 1,427	$ (1)
Interest rate swap contracts—commercial loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain/(Loss)	114	(122)
Interest rate lock commitments—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain/(Loss)	2,606	88
Forward sale contracts—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain/(Loss)	$ (1,293)	$ 33

Borrowings - Additional Informa

Borrowings - Additional Information (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Long Term And Short Term Debt [Line Items]
Total long-term debt outstanding at a fixed rate	$ 45,600,000
Total long-term debt outstanding at a variable rate	$ 67,100,000
Percentage of equity owned	100.00%
Federal Home Loan Bank Advance
Long Term And Short Term Debt [Line Items]
Total borrowings	$ 458,900,000	$ 532,900,000
Short-term borrowings	410,200,000
Long-term borrowings	50,200,000
Maximum borrowing capacity	3,100,000,000
Borrowing capacity utilized	698,100,000
Letter of credit to collateralize public funds	239,200,000
Remaining borrowing capacity	2,400,000,000
Mortgage Backed Securities
Long Term And Short Term Debt [Line Items]
Amortized cost of securities pledged as collateral	66,400,000	22,700,000
Carrying value of securities pledged as collateral	$ 70,000,000	$ 23,000,000

Borrowings - Summary of Informa

Borrowings - Summary of Information Pertaining to Borrowings (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Long Term And Short Term Debt [Line Items]
Short-term borrowings, Balance	$ 479,884	$ 301,207
Long-term borrowings, Balance	114,218	115,145
Total Borrowings, Balance	$ 594,102	$ 416,352
Short-term borrowings, Weighted Average Rate	0.41%	1.76%
Long-term borrowings, Weighted Average Rate	3.17%	3.15%
Total Borrowings, Weighted Average Rate	0.94%	2.14%
Securities sold under repurchase agreements
Long Term And Short Term Debt [Line Items]
Short-term borrowings, Balance	$ 69,644	$ 19,888
Short-term borrowings, Weighted Average Rate	0.25%	0.74%
Short-term borrowings
Long Term And Short Term Debt [Line Items]
Short-term borrowings, Balance	$ 410,240	$ 281,319
Short-term borrowings, Weighted Average Rate	0.44%	1.84%
Long-term borrowings
Long Term And Short Term Debt [Line Items]
Long-term borrowings, Balance	$ 50,180	$ 50,868
Long-term borrowings, Weighted Average Rate	2.59%	2.60%
Junior subordinated debt securities
Long Term And Short Term Debt [Line Items]
Long-term borrowings, Balance	$ 64,038	$ 64,277
Long-term borrowings, Weighted Average Rate	3.63%	3.59%

Commitments and Contingencies -

Commitments and Contingencies - Commitments and Letters of Credit (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Other Commitments [Line Items]
Commitments and letters of credit	$ 2,052,211	$ 1,990,845
Commitments to extend credit
Other Commitments [Line Items]
Commitments and letters of credit	1,967,190	1,910,805
Standby letters of credit
Other Commitments [Line Items]
Commitments and letters of credit	$ 85,021	$ 80,040

Commitments and Contingencies_2

Commitments and Contingencies - Allowance for Credit Losses for Unfunded Loan Commitments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Jan. 01, 2020
Other Commitments [Line Items]
Balance at beginning of period	$ 3,112
Allowance for credit losses on unfunded loan commitments	6,077	$ 3,113
Provision for credit losses	1,616
Balance at end of period	6,077
Impact of ASU 2016-13 Adoption
Other Commitments [Line Items]
Balance at beginning of period	1,349
Allowance for credit losses on unfunded loan commitments	1,349	1,349
As Reported Under ASU 2016-13
Other Commitments [Line Items]
Balance at beginning of period	4,461
Allowance for credit losses on unfunded loan commitments	$ 4,461	$ 4,462

Revenue From Contracts With C_3

Revenue From Contracts With Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Service charges on deposit accounts
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	$ 3,558	$ 3,153
Service charges on deposit accounts | Over a period of time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	484	457
Service charges on deposit accounts | At a point in time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	3,074	2,696
Debit and credit card
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	3,482	2,974
Debit and credit card | Over a period of time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	194	185
Debit and credit card | At a point in time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	3,287	2,789
Wealth management
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	2,362	2,048
Wealth management | Over a period of time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	345	413
Wealth management | At a point in time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	2,018	1,635
Other fee revenue | At a point in time
Disaggregation of Revenue [Line Items]
Revenues from contract with customers	$ 919	$ 919

Other Comprehensive Income_(L_3

Other Comprehensive Income/(Loss) (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount		$ 22,033,000	$ 7,851,000
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit		(4,691,000)	(1,675,000)
Net of Tax Amount
Other Comprehensive Income/(Loss), Net of Tax Amount		17,342,000	6,176,000
Accumulated Net Investment Gain (Loss) Attributable to Parent
Pre-Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	21,568,000	7,398,000
Tax (Expense) Benefit
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	(4,592,000)	(1,578,000)
Net of Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	[1]	16,976,000	5,820,000
Reclassifications	[1]	0	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount		465,000	453,000
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit		(99,000)	(97,000)
Net of Tax Amount
Other Comprehensive Income/(Loss), Net of Tax Amount		$ 366,000	$ 356,000
[1]	Reclassification adjustments are comprised of realized security gains or losses. The realized gains or losses have been reclassified out of accumulated other comprehensive income/(loss) and have affected certain lines in the Consolidated Statements of Comprehensive Income as follows: the pre-tax amount is included in securities gains/losses-net, the tax expense amount is included in the provision for income taxes and the net of tax amount is included in net income. There were no reclassification adjustments for the three months ended March 31, 2020 or 2019.

Employee Benefits - Additional

Employee Benefits - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Service costs included in net periodic pension expense	$ 0
Expected long-term rate of return on plan assets	3.50%	4.80%
Fixed Income Funds | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation (as a percentage)	85.00%
Fixed Income Funds | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation (as a percentage)	95.00%
Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation (as a percentage)	5.00%
Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation (as a percentage)	15.00%

Employee Benefits - Components

Employee Benefits - Components of Net Periodic Pension Cost and Other Changes in Plan Assets and Benefit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Components of Net Periodic Pension Cost
Interest cost on projected benefit obligation	$ 891	$ 989
Expected return on plan assets	(972)	(1,180)
Net amortization	384	394
Net Periodic Pension Expense	$ 303	$ 203

Qualified Affordable Housing (D

Qualified Affordable Housing (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Sep. 11, 2019
Schedule of Equity Method Investments [Line Items]
Investment in qualified affordable housing projects	$ 6,400,000			$ 4,800,000
Tax credits to offset amortization expense of investments in affordable housing projects	600,000	$ 700,000
New Qualified Affordable Housing Project
Schedule of Equity Method Investments [Line Items]
Investment in qualified affordable housing projects	3,600,000
New qualified affordable housing project commitment					$ 10,200,000
Forecast | New Qualified Affordable Housing Project
Schedule of Equity Method Investments [Line Items]
Amortization expense of investments in qualified affordable housing projects			$ 0
Tax credits to offset amortization expense of investments in affordable housing projects			$ 0
Noninterest Expense
Schedule of Equity Method Investments [Line Items]
Amortization expense of investments in qualified affordable housing projects	$ 600,000	$ 700,000

Share Repurchase Plan (Details)

Share Repurchase Plan (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Sep. 16, 2019
Equity, Class of Treasury Stock [Line Items]
Cost to repurchase common shares	$ 12,559,000	$ 12,287,000
September 16, 2019 Plan
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 50,000,000
Repurchased common shares (in shares)	411,430
Cost to repurchase common shares	$ 12,600,000
Cost to repurchase common shares (in dollars per share)	$ 30.52

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	May 05, 2020USD ($)loan	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Subsequent Event [Line Items]
Loans		$ 7,149,895	$ 7,074,928
CARES Act, Paycheck Protection Program Loans | Subsequent Event
Subsequent Event [Line Items]
Number of loans | loan	2,959
Loans	$ 548,000

Uncategorized Items - stba-2020

Label	Element	Value
Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 167,000
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	167,000
Accounting Standards Update 2016-13 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(22,590,000)
Accounting Standards Update 2016-13 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (22,590,000)