CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning 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	60,268			60,268
Other comprehensive income (loss), net of tax	(5,366)				(5,366)
Cash dividends declared	(21,963)			(21,963)
Treasury stock issued for restricted stock awards	0			(3,177)		3,177
Forfeitures of restricted stock awards	(302)			1,283		(1,585)
Recognition of restricted stock compensation expense	1,385		1,385
Ending Balance at Jun. 30, 2021	1,188,733	103,623	402,053	746,472	3,605	(67,020)
Beginning Balance at Mar. 31, 2021	1,168,278	103,623	401,353	731,718	1,061	(69,477)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	28,367			28,367
Other comprehensive income (loss), net of tax	2,544				2,544
Cash dividends declared	(10,989)			(10,989)
Treasury stock issued for restricted stock awards	0			(3,139)		3,139
Forfeitures of restricted stock awards	(167)			515		(682)
Recognition of restricted stock compensation expense	700		700
Ending Balance at Jun. 30, 2021	1,188,733	103,623	402,053	746,472	3,605	(67,020)
Beginning 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	58,001			58,001
Other comprehensive income (loss), net of tax	(60,081)				(60,081)
Cash dividends declared	(23,175)			(23,175)
Treasury stock issued for restricted stock awards	0			(135)		135
Forfeitures of restricted stock awards	(434)			1,294		(1,728)
Repurchase of S&T Stock	(4,153)					(4,153)
Recognition of restricted stock compensation expense	1,746		1,746
Ending Balance at Jun. 30, 2022	1,178,358	103,623	404,841	809,644	(67,171)	(72,579)
Beginning Balance at Mar. 31, 2022	1,184,950	103,623	403,841	791,345	(47,043)	(66,816)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	28,858			28,858
Other comprehensive income (loss), net of tax	(20,128)				(20,128)
Cash dividends declared	(11,791)			(11,791)
Forfeitures of restricted stock awards	(378)			1,232		(1,610)
Repurchase of S&T Stock	(4,153)					(4,153)
Recognition of restricted stock compensation expense	1,000		1,000
Ending Balance at Jun. 30, 2022	$ 1,178,358	$ 103,623	$ 404,841	$ 809,644	$ (67,171)	$ (72,579)