Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common stock	Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Retained Earnings	Deferred Compensation	Treasury Stock at Cost	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2020	$ 681	$ 335,365	$ 108,714	$ 1,084,217	$ 8,292	$ (401,291)	$ 1,135,978
Shares, Outstanding, Beginning Balance at Dec. 31, 2020	45,142,580
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				73,012			73,012
Other comprehensive earnings (loss), net of tax			(44,747)				(44,747)
Deferred compensation					(366)	366
Share-based compensation		1,392					1,392
Share-based compensation (in shares)	60,858
Dividends and dividend equivalents				(10,849)			(10,849)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2021	$ 681	336,757	63,967	1,146,380	7,926	(400,925)	1,154,786
Shares, Outstanding, Ending Balance at Mar. 31, 2021	45,203,438
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2020	$ 681	335,365	108,714	1,084,217	8,292	(401,291)	1,135,978
Shares, Outstanding, Beginning Balance at Dec. 31, 2020	45,142,580
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)							184,070
Other comprehensive earnings (loss), net of tax							(41,810)
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2021	$ 682	340,868	66,904	1,234,801	8,330	(401,329)	1,250,256
Shares, Outstanding, Ending Balance at Sep. 30, 2021	45,244,505
Stockholders' Equity Attributable to Parent, Beginning Balance at Mar. 31, 2021	$ 681	336,757	63,967	1,146,380	7,926	(400,925)	1,154,786
Shares, Outstanding, Beginning Balance at Mar. 31, 2021	45,203,438
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				81,815			81,815
Other comprehensive earnings (loss), net of tax			15,177				15,177
Deferred compensation					325	(325)
Share-based compensation	$ 1	1,342					1,343
Share-based compensation (in shares)	19,905
Dividends and dividend equivalents				(11,318)			(11,318)
Stockholders' Equity Attributable to Parent, Ending Balance at Jun. 30, 2021	$ 682	338,099	79,144	1,216,877	8,251	(401,250)	1,241,803
Shares, Outstanding, Ending Balance at Jun. 30, 2021	45,223,343
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				29,243			29,243
Other comprehensive earnings (loss), net of tax			(12,240)				(12,240)
Deferred compensation					79	(79)
Share-based compensation		2,769					2,769
Share-based compensation (in shares)	21,162
Dividends and dividend equivalents				(11,319)			(11,319)
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2021	$ 682	340,868	66,904	1,234,801	8,330	(401,329)	1,250,256
Shares, Outstanding, Ending Balance at Sep. 30, 2021	45,244,505
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2021	$ 682	343,742	49,826	1,228,110	9,642	(402,641)	1,229,361
Shares, Outstanding, Beginning Balance at Dec. 31, 2021	45,289,337
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				47,923			47,923
Other comprehensive earnings (loss), net of tax			(115,581)				(115,581)
Deferred compensation					(973)	973
Share-based compensation		3,049					3,049
Share-based compensation (in shares)	26,605
Dividends and dividend equivalents				(11,330)			(11,330)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2022	$ 682	346,791	(65,755)	1,264,703	8,669	(401,668)	1,153,422
Shares, Outstanding, Ending Balance at Mar. 31, 2022	45,315,942
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2021	$ 682	343,742	49,826	1,228,110	9,642	(402,641)	1,229,361
Shares, Outstanding, Beginning Balance at Dec. 31, 2021	45,289,337
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)							485,577
Other comprehensive earnings (loss), net of tax							(294,392)
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2022	$ 683	352,129	(244,566)	1,678,746	9,047	(402,046)	1,393,993
Shares, Outstanding, Ending Balance at Sep. 30, 2022	45,378,171
Stockholders' Equity Attributable to Parent, Beginning Balance at Mar. 31, 2022	$ 682	346,791	(65,755)	1,264,703	8,669	(401,668)	1,153,422
Shares, Outstanding, Beginning Balance at Mar. 31, 2022	45,315,942
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				(2,239)			(2,239)
Other comprehensive earnings (loss), net of tax			(97,563)				(97,563)
Deferred compensation					276	(276)
Share-based compensation	$ 1	2,370					2,371
Share-based compensation (in shares)	52,862
Dividends and dividend equivalents				(11,803)			(11,803)
Stockholders' Equity Attributable to Parent, Ending Balance at Jun. 30, 2022	$ 683	349,161	(163,318)	1,250,661	8,945	(401,944)	1,044,188
Shares, Outstanding, Ending Balance at Jun. 30, 2022	45,368,804
Increase Decrease In Stockholders Equity Roll Forward
Net earnings (loss)				439,893			439,893
Other comprehensive earnings (loss), net of tax			(81,248)				(81,248)
Deferred compensation					102	(102)
Share-based compensation		2,968					2,968
Share-based compensation (in shares)	9,367
Dividends and dividend equivalents				(11,808)			(11,808)
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2022	$ 683	$ 352,129	$ (244,566)	$ 1,678,746	$ 9,047	$ (402,046)	$ 1,393,993
Shares, Outstanding, Ending Balance at Sep. 30, 2022	45,378,171