Parent Company Condensed Financial Information - Statements of Net Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, Captions [Line Items]
Total Interest and Dividend Income	$ 477,901	$ 340,751	$ 289,262
Interest expense on long-term debt	1,332	411	458
Income tax benefit	34,023	33,410	25,325
Equity in undistributed net income (distribution in excess of net income) of:
Net Income	144,781	135,520	110,343
S&T
Condensed Income Statements, Captions [Line Items]
Dividends from subsidiaries	86,950	61,426	62,333
Investment income	0	0	0
Total Interest and Dividend Income	86,950	61,426	62,333
Interest expense on long-term debt	2,372	1,545	1,400
Other expenses	4,764	4,112	3,947
Tax expense	7,136	5,657	5,347
Income before income tax and undistributed net income of subsidiaries	79,814	55,769	56,986
Income tax benefit	(1,478)	(1,208)	(1,140)
Income before undistributed net income of subsidiaries	81,292	56,977	58,126
Equity in undistributed net income (distribution in excess of net income) of:
Bank subsidiary	63,337	79,566	57,025
Nonbank subsidiaries	152	(1,023)	(4,808)
Net Income	$ 144,781	$ 135,520	$ 110,343