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, 2020	$ 553,519	$ 340	$ 642,887	$ 246,850	$ (336,558)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	34,110			34,110
Actuarially Determined Long-Term Liability Adjustments, Net of Tax	79,203				79,203
Investments in Available-for-Sale Securities (Net of $(23) Tax)	0
Interest Rate Hedge, Net of Tax	1,721				1,721
Comprehensive Income	115,034			34,110	80,924
Issuance of Common Stock	0	5	(5)
Amortization of Stock-Based Compensation Awards	6,632		6,632
Shares Withheld for Taxes	(2,303)		(2,303)
CCR Merger	(69)	0	(266)		197
Ending balance at Dec. 31, 2021	672,813	345	646,945	280,960	(255,437)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	466,979			466,979	0
Actuarially Determined Long-Term Liability Adjustments, Net of Tax	105,396			0	105,396
Investments in Available-for-Sale Securities (Net of $(23) Tax)	0
Interest Rate Hedge, Net of Tax	401			0	401
Comprehensive Income	572,776			466,979	105,797
Issuance of Common Stock	0	4	(4)
Repurchases of Common Stock	(7,988)	(2)	(2,333)	(5,653)
Amortization of Stock-Based Compensation Awards	7,890		7,890
Shares Withheld for Taxes	(6,261)		(6,261)
Dividends on Common Shares	(71,486)			(71,486)
Dividend Equivalents Earned on Stock-Based Compensation Awards	(1,918)			(1,918)
Ending balance at Dec. 31, 2022	1,165,826	347	646,237	668,882	(149,640)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	655,892			655,892
Actuarially Determined Long-Term Liability Adjustments, Net of Tax	500				500
Investments in Available-for-Sale Securities (Net of $(23) Tax)	80				80
Interest Rate Hedge, Net of Tax	0
Comprehensive Income	656,472			655,892	580
Issuance of Common Stock	0	4	(4)
Repurchases of Common Stock	(395,392)	(52)	(95,587)	(299,753)
Excise Tax on Repurchases of Common Stock	(3,729)			(3,729)
Amortization of Stock-Based Compensation Awards	10,046		10,046
Shares Withheld for Taxes	(12,831)		(12,831)
Dividends on Common Shares	(75,474)			(75,474)
Dividend Equivalents Earned on Stock-Based Compensation Awards	(1,476)			(1,476)
Ending balance at Dec. 31, 2023	$ 1,343,442	$ 299	$ 547,861	$ 944,342	$ (149,060)