CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Paid In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance, net of tax at Dec. 31, 2020	$ 875,297	$ 47,419	$ 771,511	$ 111,208	$ (123,921)	$ 69,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,091			34,091
Other comprehensive income (loss)	(29,494)					(29,494)
Issuance of common stock for dividend reinvestment plan	332	11	321
Purchase of common stock	(15,213)				(15,213)
Stock compensation expense	674		674
Net issuance of common stock under employee stock plans	3,386		2,309	(41)	1,118
Cash dividends paid on common stock	(10,476)			(10,476)
Ending balance, net of tax at Mar. 31, 2021	858,597	47,430	774,815	134,782	(138,016)	39,586
Beginning balance, net of tax at Dec. 31, 2020	875,297	47,419	771,511	111,208	(123,921)	69,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	84,714
Other comprehensive income (loss)	(25,106)
Ending balance, net of tax at Sep. 30, 2021	877,866	47,450	778,600	163,809	(155,967)	43,974
Beginning balance, net of tax at Mar. 31, 2021	858,597	47,430	774,815	134,782	(138,016)	39,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,317			21,317
Other comprehensive income (loss)	25,301					25,301
Issuance of common stock for dividend reinvestment plan	330	9	321
Purchase of common stock	(3,497)				(3,497)
Stock compensation expense	686		686
Net issuance of common stock under employee stock plans	2,441		1,591	(47)	897
Cash dividends paid on common stock	(10,775)			(10,775)
Ending balance, net of tax at Jun. 30, 2021	894,400	47,439	777,413	145,277	(140,616)	64,887
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,306			29,306
Other comprehensive income (loss)	(20,913)					(20,913)
Issuance of common stock for dividend reinvestment plan	324	11	313
Purchase of common stock	(15,438)				(15,438)
Stock compensation expense	829		829
Net issuance of common stock under employee stock plans	64		45	(68)	87
Cash dividends paid on common stock	(10,706)			(10,706)
Ending balance, net of tax at Sep. 30, 2021	877,866	47,450	778,600	163,809	(155,967)	43,974
Beginning balance, net of tax at Dec. 31, 2021	912,172	47,461	780,501	179,813	(155,308)	59,705
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24,996			24,996
Other comprehensive income (loss)	(139,976)					(139,976)
Issuance of common stock for dividend reinvestment plan	322	10	312
Purchase of common stock	(3,358)				(3,358)
Stock compensation expense	819		819
Net issuance of common stock under employee stock plans	269		182	(67)	154
Cash dividends paid on common stock	(11,003)			(11,003)
Ending balance, net of tax at Mar. 31, 2022	784,241	47,471	781,814	193,739	(158,512)	(80,271)
Beginning balance, net of tax at Dec. 31, 2021	912,172	47,461	780,501	179,813	(155,308)	59,705
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	77,352
Other comprehensive income (loss)	(240,395)
Ending balance, net of tax at Sep. 30, 2022	707,636	47,490	783,803	224,142	(167,109)	(180,690)
Beginning balance, net of tax at Mar. 31, 2022	784,241	47,471	781,814	193,739	(158,512)	(80,271)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,405			25,405
Other comprehensive income (loss)	(59,064)					(59,064)
Issuance of common stock for dividend reinvestment plan	313	10	303
Purchase of common stock	(8,842)				(8,842)
Stock compensation expense	847		847
Net issuance of common stock under employee stock plans	(212)		(453)	(67)	308
Cash dividends paid on common stock	(10,906)			(10,906)
Ending balance, net of tax at Jun. 30, 2022	731,782	47,481	782,511	208,171	(167,046)	(139,335)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26,951			26,951
Other comprehensive income (loss)	(41,355)					(41,355)
Issuance of common stock for dividend reinvestment plan	278	9	269
Purchase of common stock	(309)				(309)
Stock compensation expense	760		760
Net issuance of common stock under employee stock plans	448		263	(61)	246
Cash dividends paid on common stock	(10,919)			(10,919)
Ending balance, net of tax at Sep. 30, 2022	$ 707,636	$ 47,490	$ 783,803	$ 224,142	$ (167,109)	$ (180,690)