CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock, Common	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance, shares at Dec. 31, 2021		57,606	3,546
Balance, beginning of period at Dec. 31, 2021	$ 2,339,713	$ 576	$ (98,248)	$ 1,716,227	$ 728,468	$ (7,310)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	59,110	0	0	0	59,110	0
Foreign currency translation adjustment	2	0	0	0	0	2
Reclassification of net losses on derivative instruments	113	0	0	0	0	113
Postretirement medical liability adjustment	(158)	$ 0	$ 0	0	0	(158)
Stock based compensation, shares		87	16
Stock based compensation, value	1,836	$ 1	$ (911)	2,746	0	0
Issuance of shares		0
Issuance of shares, treasury stock			(6)
Stock Issued During Period, Value, Treasury Stock Reissued			$ 173
Issuance of shares, value	270	$ 0		97	0	0
Dividends on common stock	$ (33,901)	$ 0	$ 0	0	(33,901)	0
Dividends per share	$ 0.63
Balance, shares at Mar. 31, 2022		57,693	3,556
Balance, end of period at Mar. 31, 2022	$ 2,366,981	$ 577	$ (98,986)	1,719,070	753,677	(7,357)
Balance, shares at Dec. 31, 2022		63,278	3,534
Balance, beginning of period at Dec. 31, 2022	2,665,183	$ 633	$ (98,392)	1,999,376	771,414	(7,848)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	62,530	0	0	0	62,530	0
Foreign currency translation adjustment	2	0	0	0	0	2
Reclassification of net losses on derivative instruments	113	0	0	0	0	113
Postretirement medical liability adjustment	(167)	$ 0	$ 0	0	0	(167)
Stock based compensation, shares		48	0
Stock based compensation, value	3,215	$ 0	$ (79)	3,294	0	0
Issuance of shares		0
Issuance of shares, treasury stock			(1)
Stock Issued During Period, Value, Treasury Stock Reissued			$ 0
Issuance of shares, value	169	$ 0		169	0	0
Dividends on common stock	$ (38,041)	$ 0	$ 0	0	(38,041)	0
Dividends per share	$ 0.64
Balance, shares at Mar. 31, 2023		63,326	3,533
Balance, end of period at Mar. 31, 2023	$ 2,693,000	$ 633	$ (98,471)	$ 2,002,839	$ 795,903	$ (7,904)