Parent Company Condensed Financial Information - Statements of Net Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Condensed Income Statements, Captions [Line Items]
Total Interest and Dividend Income	$ 515,872	$ 477,901	$ 340,751
Interest expense on long-term debt	1,964	1,332	411
Income tax benefit	33,553	34,023	33,410
Equity in undistributed net income (distribution in excess of net income) of:
Net Income	131,265	144,781	135,520
S&T
Condensed Income Statements, Captions [Line Items]
Dividends from subsidiaries	66,775	86,950	61,426
Total Interest and Dividend Income	66,775	86,950	61,426
Interest expense on long-term debt	2,180	2,372	1,545
Other expenses	4,973	4,764	4,112
Total expense	7,153	7,136	5,657
Income before income tax and undistributed net income of subsidiaries	59,622	79,814	55,769
Income tax benefit	(1,309)	(1,478)	(1,208)
Income before undistributed net income of subsidiaries	60,931	81,292	56,977
Equity in undistributed net income (distribution in excess of net income) of:
Bank subsidiary	70,823	63,337	79,566
Nonbank subsidiaries	(489)	152	(1,023)
Net Income	$ 131,265	$ 144,781	$ 135,520