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 (loss)	(4,450)			(4,450)
Actuarially determined long-term liability adjustments	1,525				1,525
Interest Rate Hedge, net	391				391
Comprehensive Income (Loss)	(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 (loss)	273,962
Actuarially determined long-term liability adjustments	4,574
Interest Rate Hedge, net	401
Investments in available-for-sale securities	0
Comprehensive Income (Loss)	278,937
Ending balance at Sep. 30, 2022	916,445	349	647,448	519,110	(250,462)
Beginning balance at Mar. 31, 2022	668,408	348	645,071	276,510	(253,521)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	126,291			126,291
Actuarially determined long-term liability adjustments	1,524				1,524
Interest Rate Hedge, net	224				224
Comprehensive Income (Loss)	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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	152,121			152,121
Actuarially determined long-term liability adjustments	1,525				1,525
Interest Rate Hedge, net	(214)				(214)
Investments in available-for-sale securities	0
Comprehensive Income (Loss)	153,432			152,121	1,311
Amortization of Stock-Based Compensation Awards	1,224		1,224
Shares Withheld for Taxes	7		7
Dividends on common shares	(34,871)			(34,871)
Dividend Equivalents Earned on Stock-Based Compensation Awards	(941)			(941)
Ending balance at Sep. 30, 2022	916,445	349	647,448	519,110	(250,462)
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 (loss)	230,377			230,377
Actuarially determined long-term liability adjustments	(901)				(901)
Investments in available-for-sale securities	212				212
Comprehensive Income (Loss)	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 (loss)	498,825
Actuarially determined long-term liability adjustments	(2,702)
Interest Rate Hedge, net	0
Investments in available-for-sale securities	(49)
Comprehensive Income (Loss)	496,074
Ending balance at Sep. 30, 2023	1,308,790	312	569,071	891,798	(152,391)
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 (loss)	167,723			167,723
Actuarially determined long-term liability adjustments	(900)				(900)
Investments in available-for-sale securities	(255)				(255)
Comprehensive Income (Loss)	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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	100,725			100,725
Actuarially determined long-term liability adjustments	(901)				(901)
Interest Rate Hedge, net	0
Investments in available-for-sale securities	(6)				(6)
Comprehensive Income (Loss)	99,818			100,725	(907)
Repurchases of common stock	(126,634)	(15)	(28,171)	(98,448)
Excise Tax on Repurchases of Common Stock	(1,265)			(1,265)
Amortization of Stock-Based Compensation Awards	1,676		1,676
Ending balance at Sep. 30, 2023	$ 1,308,790	$ 312	$ 569,071	$ 891,798	$ (152,391)