Parent Company Condensed Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
OPERATING ACTIVITIES
Net income	$ 134,230	$ 131,265	$ 144,781
Net Cash Provided by Operating Activities	133,616	173,367	171,749
FINANCING ACTIVITIES
Repayments on long-term borrowings	(81)	(38,381)	(5,464)
Repurchase of shares for taxes on restricted stock	(1,672)	(870)	(798)
Repurchase of common stock	(36,274)	0	(19,808)
Cash dividends paid to common shareholders	(52,887)	(50,974)	(49,708)
Net Cash Provided by (Used in) Financing Activities	99,800	(43,867)	296,073
Net (decrease) increase in cash and due from banks	(81,384)	11,208	23,603
Cash and due from banks at beginning of period	244,820	233,612	210,009
Cash and Due From Banks at End of Period	163,436	244,820	233,612
S&T
OPERATING ACTIVITIES
Net income	134,230	131,265	144,781
Equity in undistributed earnings of subsidiaries	(74,466)	(70,334)	(63,489)
Other	3,726	9,484	1,402
Net Cash Provided by Operating Activities	63,490	70,415	82,694
FINANCING ACTIVITIES
Repayments on long-term borrowings	0	0	(5,464)
Repurchase of shares for taxes on restricted stock	(1,672)	(870)	(798)
Repurchase of common stock	(36,273)	0	(19,808)
Cash dividends paid to common shareholders	(52,887)	(50,974)	(49,708)
Net Cash Provided by (Used in) Financing Activities	(90,832)	(51,844)	(75,778)
Net (decrease) increase in cash and due from banks	(27,342)	18,571	6,916
Cash and due from banks at beginning of period	39,304	20,733	13,817
Cash and Due From Banks at End of Period	$ 11,962	$ 39,304	$ 20,733