CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income/(Loss)	Treasury Stock
Beginning balance at Dec. 31, 2019	$ 1,191,998	$ (22,590)	$ 103,623	$ 399,944	$ 761,083	$ (22,590)	$ (11,670)	$ (60,982)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,040				21,040
Other comprehensive income, net of tax	20,641						20,641
Cash dividends declared	(43,949)				(43,949)
Treasury stock issued for restricted stock awards	0				(7,361)			7,361
Forfeitures of restricted stock awards	(594)				1,838			(2,432)
Repurchase of S&T Stock	(12,559)							(12,559)
Recognition of restricted stock compensation expense	724			724
Ending balance at Dec. 31, 2020	1,154,711		103,623	400,668	710,061		8,971	(68,612)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	110,343				110,343
Other comprehensive income, net of tax	(16,061)						(16,061)
Cash dividends declared	(44,336)				(44,336)
Treasury stock issued for restricted stock awards	0				(4,163)			4,163
Forfeitures of restricted stock awards	(630)				1,754			(2,384)
Repurchase of S&T Stock	0
Recognition of restricted stock compensation expense	2,427			2,427
Ending balance at Dec. 31, 2021	1,206,454		103,623	403,095	773,659		(7,090)	(66,833)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	135,520				135,520
Other comprehensive income, net of tax	(105,035)						(105,035)
Cash dividends declared	(47,023)				(47,023)
Treasury stock issued for restricted stock awards	0				(135)			135
Forfeitures of restricted stock awards	(808)				1,927			(2,735)
Repurchase of S&T Stock	(7,637)							(7,637)
Recognition of restricted stock compensation expense	3,188			3,188
Ending balance at Dec. 31, 2022	$ 1,184,659		$ 103,623	$ 406,283	$ 863,948		$ (112,125)	$ (77,070)