Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive (Loss) Income
Beginning balance at Dec. 31, 2021	$ 672,813	$ 345	$ 646,945	$ 280,960	$ (255,437)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	(4,450)			(4,450)
Actuarially determined long-term liability adjustments	1,525				1,525
Unrealized Gain on Cash Flow Hedges (Net of tax: $—, ($75), $—, ($205))	391				391
Comprehensive (Loss) Income	(2,534)			(4,450)	1,916
Issuance of Common Stock	0	3	(3)
Amortization of Stock-Based Compensation Awards	4,201		4,201
Shares Withheld for Taxes	(6,072)		(6,072)
Ending balance at Mar. 31, 2022	668,408	348	645,071	276,510	(253,521)
Beginning balance at Dec. 31, 2021	672,813	345	646,945	280,960	(255,437)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	121,841
Actuarially determined long-term liability adjustments	3,049
Unrealized Gain on Cash Flow Hedges (Net of tax: $—, ($75), $—, ($205))	615
Investments in available-for-sale securities	0
Comprehensive (Loss) Income	125,505
Ending balance at Jun. 30, 2022	797,594	349	646,217	402,801	(251,773)
Beginning balance at Mar. 31, 2022	668,408	348	645,071	276,510	(253,521)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	126,291			126,291
Actuarially determined long-term liability adjustments	1,524				1,524
Unrealized Gain on Cash Flow Hedges (Net of tax: $—, ($75), $—, ($205))	224				224
Investments in available-for-sale securities	0
Comprehensive (Loss) Income	128,039			126,291	1,748
Issuance of Common Stock	0	1	(1)
Amortization of Stock-Based Compensation Awards	1,269		1,269
Shares Withheld for Taxes	(122)		(122)
Ending balance at Jun. 30, 2022	797,594	349	646,217	402,801	(251,773)
Beginning balance at Dec. 31, 2022	1,165,826	347	646,237	668,882	(149,640)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	230,377			230,377
Actuarially determined long-term liability adjustments	(901)				(901)
Investments in available-for-sale securities	212				212
Comprehensive (Loss) Income	229,688			230,377	(689)
Issuance of Common Stock	0	3	(3)
Repurchases of common stock	(67,133)	(11)	(22,446)	(44,676)
Excise Tax on Repurchases of Common Stock	(478)			(478)
Amortization of Stock-Based Compensation Awards	4,792		4,792
Shares Withheld for Taxes	(12,708)		(12,708)
Dividends on common shares	(38,287)			(38,287)
Dividend Equivalents Earned on Stock-Based Compensation Awards	(803)			(803)
Ending balance at Mar. 31, 2023	1,280,897	339	615,872	815,015	(150,329)
Beginning balance at Dec. 31, 2022	1,165,826	347	646,237	668,882	(149,640)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	398,100
Actuarially determined long-term liability adjustments	(1,801)
Unrealized Gain on Cash Flow Hedges (Net of tax: $—, ($75), $—, ($205))	0
Investments in available-for-sale securities	(43)
Comprehensive (Loss) Income	396,256
Ending balance at Jun. 30, 2023	1,335,195	327	595,566	890,786	(151,484)
Beginning balance at Mar. 31, 2023	1,280,897	339	615,872	815,015	(150,329)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	167,723			167,723
Actuarially determined long-term liability adjustments	(900)				(900)
Unrealized Gain on Cash Flow Hedges (Net of tax: $—, ($75), $—, ($205))	0
Investments in available-for-sale securities	(255)				(255)
Comprehensive (Loss) Income	166,568			167,723	(1,155)
Repurchases of common stock	(75,627)	(12)	(22,261)	(53,354)
Excise Tax on Repurchases of Common Stock	(728)			(728)
Amortization of Stock-Based Compensation Awards	1,993		1,993
Shares Withheld for Taxes	(38)		(38)
Dividends on common shares	(37,187)			(37,187)
Dividend Equivalents Earned on Stock-Based Compensation Awards	(683)			(683)
Ending balance at Jun. 30, 2023	$ 1,335,195	$ 327	$ 595,566	$ 890,786	$ (151,484)