XML 11 R1.htm IDEA: XBRL DOCUMENT v3.19.2
Cover Page - shares
 6 Months Ended
Jun. 30, 2019
Jul. 30, 2019
Cover page.    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
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   34,309,170
Amendment Flag false  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0000719220  
Current Fiscal Year End Date --12-31