CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Deferred Compensation Arrangements	Total
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			135,551				135,551
Other comprehensive loss, net of tax				(695,754)			(695,754)
Dividends declared:
Common			(70,196)				(70,196)
Common stock activity under employee stock plans	$ 96	990					1,086
Common stock activity under employee stock plans (in shares)	95,586
Stock-based compensation		6,047					6,047
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					(16,378)		(16,378)
Treasury stock purchased (in shares)	(250,000)
Treasury stock issued to benefit plans, net					(177)	177	0
Treasury stock issued to benefit plans, net (in shares)	(2,551)
Balance at Sep. 30, 2022	$ 54,188	1,048,444	1,123,641	(746,381)	(26,426)	7,697	1,461,163
Balance (in shares) at Sep. 30, 2022	53,736,016
Balance at Jun. 30, 2022	$ 54,185	1,046,303	1,098,664	(518,727)	(26,369)	7,640	1,661,696
Balance (in shares) at Jun. 30, 2022	53,734,027
Increase (Decrease) in Stockholders' Equity
Net income			48,691				48,691
Other comprehensive loss, net of tax				(227,654)			(227,654)
Dividends declared:
Common			(23,714)				(23,714)
Common stock activity under employee stock plans	$ 3	284					287
Common stock activity under employee stock plans (in shares)	2,892
Stock-based compensation		1,857					1,857
Treasury stock issued to benefit plans, net					(57)	57	0
Treasury stock issued to benefit plans, net (in shares)	(903)
Balance at Sep. 30, 2022	$ 54,188	1,048,444	1,123,641	(746,381)	(26,426)	7,697	1,461,163
Balance (in shares) at Sep. 30, 2022	53,736,016
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			98,218				98,218
Other comprehensive loss, net of tax				(5,254)			(5,254)
Dividends declared:
Common			(71,474)				(71,474)
Common stock activity under employee stock plans	$ 174	537					711
Common stock activity under employee stock plans (in shares)	173,610
Stock-based compensation		6,709					6,709
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					(25,676)		(25,676)
Treasury stock purchased (in shares)	(500,000)
Treasury stock issued to benefit plans, net					(163)	163	0
Treasury stock issued to benefit plans, net (in shares)	(3,134)
Balance at Sep. 30, 2023	$ 54,364	1,057,433	1,179,196	(691,693)	(51,198)	6,837	1,554,939
Balance (in shares) at Sep. 30, 2023	53,426,989
Balance at Jun. 30, 2023	$ 54,364	1,054,871	1,159,126	(611,702)	(46,038)	6,785	1,617,406
Balance (in shares) at Jun. 30, 2023	53,528,090
Increase (Decrease) in Stockholders' Equity
Net income			44,129				44,129
Other comprehensive loss, net of tax				(79,991)			(79,991)
Dividends declared:
Common			(24,059)				(24,059)
Common stock activity under employee stock plans	$ 0	47					47
Common stock activity under employee stock plans (in shares)	71
Stock-based compensation		2,515					2,515
Treasury stock purchased					(5,108)		(5,108)
Treasury stock purchased (in shares)	(100,000)
Treasury stock issued to benefit plans, net					(52)	52	0
Treasury stock issued to benefit plans, net (in shares)	(1,172)
Balance at Sep. 30, 2023	$ 54,364	$ 1,057,433	$ 1,179,196	$ (691,693)	$ (51,198)	$ 6,837	$ 1,554,939
Balance (in shares) at Sep. 30, 2023	53,426,989