CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance, shares at Dec. 31, 2020		54,145	3,558
Balance, beginning of period at Dec. 31, 2020	$ 2,079,095	$ 541	$ (98,075)	$ 1,513,787	$ 670,111	$ (7,269)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	63,071	0	0	0	63,071	0
Foreign currency translation adjustment	76	0	0	0	0	76
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	113	0	0	0	0	113
Postretirement medical liability adjustment	(158)	$ 0	$ 0	0	0
Stock based compensation, shares		93	17
Stock based compensation, value	2,242	$ 1	$ (970)	3,211	0
Stock Issued During Period, Value, Treasury Stock Reissued			$ 315
Issuance of shares, treasury stock			(12)
Issuance of shares		0
Issuance of shares, value	672	$ 0		357	0	0
Dividends on common stock	$ (31,124)	0	$ 0	0	(31,124)	0
Dividends per share	$ 0.62
Balance, end of period at Mar. 31, 2021	$ 2,113,835	$ 542	$ (98,730)	1,517,355	702,058	(7,390)
Balance, shares at Mar. 31, 2021		54,238	3,563
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
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	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
Stock Issued During Period, Value, Treasury Stock Reissued			$ 173
Issuance of shares, treasury stock			(6)
Issuance of shares
Issuance of shares, value	270			97	0
Dividends on common stock	$ (33,901)	0	$ 0	0	(33,901)	0
Dividends per share	$ 0.630
Balance, end of period at Mar. 31, 2022	$ 2,366,981	$ 577	$ (98,986)	$ 1,719,070	$ 753,677	$ (7,357)
Balance, shares at Mar. 31, 2022		57,693	3,556