Subsequent Events	12 Months Ended
Dec. 31, 2025
Subsequent Events [Abstract]
Subsequent Event	NOTE 25. SUBSEQUENT EVENTS On January 21, 2026, the Board of Directors of S&T Bancorp, Inc. authorized a new $100 million share repurchase program. The new program replaced the existing share repurchase program effective January 26, 2026, and is set to expire February 1, 2027. The remaining capacity of $13.8 million under the existing share repurchase program was terminated. The new program authorizes the share repurchase of S&T's common stock from time to time through a combination of open market and privately negotiated transactions up to the authorized $100 million aggregate value of S&T's common stock. 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 the common stock, applicable securities laws and other legal and contractual requirements, as well as S&T’s financial performance. The repurchase program does not obligate S&T to repurchase any particular number of shares and may be extended, modified or discontinued at any time. As of February 25, 2026, 856,900 shares were repurchased under the new plan, at an average price of $43.45 per share, for $37.2 million excluding excise tax and commissions. As of February 25, 2026, there was $62.8 million in capacity remaining under the plan.

Subsequent Events

12 Months Ended

Dec. 31, 2025

NOTE 25. SUBSEQUENT EVENTS

On January 21, 2026, the Board of Directors of S&T Bancorp, Inc. authorized a new $100 million share repurchase program. The new program replaced the existing share repurchase program effective January 26, 2026, and is set to expire February 1, 2027. The remaining capacity of $13.8 million under the existing share repurchase program was terminated. The new program authorizes the share repurchase of S&T's common stock from time to time through a combination of open market and privately negotiated transactions up to the authorized $100 million aggregate value of S&T's common stock. 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 the common stock, applicable securities laws and other legal and contractual requirements, as well as S&T’s financial performance. The repurchase program does not obligate S&T to repurchase any particular number of shares and may be extended, modified or discontinued at any time. As of February 25, 2026, 856,900 shares were repurchased under the new plan, at an average price of $43.45 per share, for $37.2 million excluding excise tax and commissions. As of February 25, 2026, there was $62.8 million in capacity remaining under the plan.