Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]	Total
Balance at Dec. 31, 2020	$ 497	$ 578,082	$ 749,056	$ 417	$ (140,434)	$ 1,187,618
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	80,142	0	0	80,142
Cash dividends	0	0	(23,476)	0	0	(23,476)
Purchase of treasury shares	0	0	0	0	(9,871)	(9,871)
Net issuance of shares to employee and other stock plans	0	(4,606)	0	0	1,702	(2,904)
Stock-based compensation	0	3,256	0	0	0	3,256
Other comprehensive income (loss)	0	0	0	(9,709)	0	(9,709)
Balance at Jun. 30, 2021	497	576,732	805,722	(9,292)	(148,603)	1,225,056
Balance at Mar. 31, 2021	497	578,597	777,170	(16,699)	(148,584)	1,190,981
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	40,296	0	0	40,296
Cash dividends	0	0	(11,744)	0	0	(11,744)
Purchase of treasury shares	0	0	0	0	(851)	(851)
Net issuance of shares to employee and other stock plans	0	(2,453)	0	0	832	(1,621)
Stock-based compensation	0	588	0	0	0	588
Other comprehensive income (loss)	0	0	0	7,407	0	7,407
Balance at Jun. 30, 2021	497	576,732	805,722	(9,292)	(148,603)	1,225,056
Balance at Dec. 31, 2021	497	576,976	856,203	(23,344)	(159,879)	1,250,453
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	76,901	0	0	76,901
Cash dividends	0	0	(24,075)	0	0	(24,075)
Purchase of treasury shares	0	0	0	0	(14,713)	(14,713)
Net issuance of shares to employee and other stock plans	0	(2,910)	0	0	1,058	(1,852)
Stock-based compensation	0	3,279	0	0	0	3,279
Other comprehensive income (loss)	0	0	0	(101,437)	0	(101,437)
Balance at Jun. 30, 2022	497	577,345	909,029	(124,781)	(173,534)	1,188,556
Balance at Mar. 31, 2022	497	577,374	883,246	(91,375)	(167,492)	1,202,250
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	37,775	0	0	37,775
Cash dividends	0	0	(11,992)	0	0	(11,992)
Purchase of treasury shares	0	0	0	0	(6,561)	(6,561)
Net issuance of shares to employee and other stock plans	0	(836)	0	0	519	(317)
Stock-based compensation	0	807	0	0	0	807
Other comprehensive income (loss)	0	0	0	(33,406)	0	(33,406)
Balance at Jun. 30, 2022	$ 497	$ 577,345	$ 909,029	$ (124,781)	$ (173,534)	$ 1,188,556