CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)/Income	Treasury Stock	Deferred Compensation Arrangements	Total
Balance at Dec. 31, 2020	$ 53,755	$ 1,025,163	$ 960,183	$ 62,077	$ (6,198)	$ 9,127	$ 2,104,107
Balance (in shares) at Dec. 31, 2020	53,593,127
Increase (Decrease) in Stockholders' Equity
Net income			189,694				189,694
Other comprehensive loss, net of tax				(112,704)			(112,704)
Dividends declared:
Common			(91,591)				(91,591)
Common stock activity under employee stock plans	$ 337	9,484					9,821
Common stock activity under employee stock plans (in shares)	337,822
Stock-based compensation		6,334					6,334
Distribution of stock under deferred compensation arrangements		323			694	(1,017)	0
Distribution of stock under deferred compensation arrangements (in shares)	18,089
Treasury stock purchased					(5,106)	252	(4,854)
Treasury stock purchased (in shares)	(70,991)
Balance at Dec. 31, 2021	$ 54,092	1,041,304	1,058,286	(50,627)	(10,610)	8,362	2,100,807
Balance (in shares) at Dec. 31, 2021	53,878,047
Increase (Decrease) in Stockholders' Equity
Net income			188,081				188,081
Other comprehensive loss, net of tax				(635,812)			(635,812)
Dividends declared:
Common			(93,915)				(93,915)
Common stock activity under employee stock plans	$ 98	1,086					1,184
Common stock activity under employee stock plans (in shares)	97,779
Stock-based compensation		7,738					7,738
Distribution of stock under deferred compensation arrangements		103			739	(842)	0
Distribution of stock under deferred compensation arrangements (in shares)	14,934
Treasury stock purchased					(16,614)	236	(16,378)
Treasury stock purchased (in shares)	(253,511)
Balance at Dec. 31, 2022	$ 54,190	1,050,231	1,152,452	(686,439)	(26,485)	7,756	1,551,705
Balance (in shares) at Dec. 31, 2022	53,737,249
Increase (Decrease) in Stockholders' Equity
Net income			131,924				131,924
Other comprehensive loss, net of tax				129,547			129,547
Dividends declared:
Common			(95,507)				(95,507)
Common stock activity under employee stock plans	$ 182	833					1,015
Common stock activity under employee stock plans (in shares)	182,091
Stock-based compensation		9,269					9,269
Distribution of stock under deferred compensation arrangements		(44)			1,126	(1,082)	0
Distribution of stock under deferred compensation arrangements (in shares)	19,264
Treasury stock purchased					(30,233)	217	(30,016)
Treasury stock purchased (in shares)	(611,544)
Balance at Dec. 31, 2023	$ 54,372	$ 1,060,289	$ 1,188,869	$ (556,892)	$ (55,592)	$ 6,891	$ 1,697,937
Balance (in shares) at Dec. 31, 2023	53,327,060