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	135,504	0	0	0	135,504	0
Foreign currency translation adjustment	56	0	0	0	0	(56)
Reclassification of net losses on derivative instruments	339	0	0	0	0	339
Postretirement medical liability adjustment	(476)	$ 0	$ 0	0	0	(476)
Stock based compensation, shares		93	17
Stock based compensation, value	4,842	$ 1	$ (970)	5,811	0	0
Issuance of shares		1,919
Issuance of shares, treasury stock			(23)
Issuance of shares, value	122,433	$ 20	$ 621	121,792	0	0
Dividends on common stock	$ (95,148)	$ 0	$ 0	0	(95,148)	0
Dividends per share	$ 1.860
Balance, shares at Sep. 30, 2021		56,157	3,552
Balance, end of period at Sep. 30, 2021	$ 2,246,533	$ 562	$ (98,424)	1,641,390	710,467	(7,462)
Balance, shares at Jun. 30, 2021		55,118	3,558
Balance, beginning of period at Jun. 30, 2021	2,177,315	$ 551	$ (98,578)	1,575,159	707,598	(7,415)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	35,196	0	0	0	35,196	0
Foreign currency translation adjustment	1	0	0	0	0	1
Reclassification of net losses on derivative instruments	113	0	0	0	0	113
Postretirement medical liability adjustment	(159)	$ 0	$ 0	0	0	(159)
Stock based compensation, shares		0	0
Stock based compensation, value	1,301	$ 0	$ 0	1,301	0	0
Issuance of shares		1,039
Issuance of shares, treasury stock			(6)
Stock Issued During Period, Value, Treasury Stock Reissued			$ 154
Issuance of shares, value	65,095	$ 11		64,930	0	0
Dividends on common stock	$ (32,327)	$ 0	$ 0	0	(32,327)	0
Dividends per share	$ 0.620
Balance, shares at Sep. 30, 2021		56,157	3,552
Balance, end of period at Sep. 30, 2021	$ 2,246,533	$ 562	$ (98,424)	1,641,390	710,467	(7,462)
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	116,264	0	0	0	116,264	0
Foreign currency translation adjustment	5	0	0	0	0	5
Reclassification of net losses on derivative instruments	339	0	0	0	0	339
Postretirement medical liability adjustment	(474)	$ 0	$ 0	0	0	(474)
Stock based compensation, shares		87	16
Stock based compensation, value	5,146	$ 1	$ (911)	6,056	0	0
Issuance of shares		3,625
Issuance of shares, treasury stock			(21)
Issuance of shares, value	179,326	$ 36	$ 581	178,709	0	0
Dividends on common stock	$ (102,980)	$ 0	$ 0	0	(102,980)	0
Dividends per share	$ 1.89
Balance, shares at Sep. 30, 2022		61,318	3,541
Balance, end of period at Sep. 30, 2022	$ 2,537,329	$ 613	$ (98,578)	1,900,992	741,752	(7,450)
Balance, shares at Jun. 30, 2022		59,697	3,548
Balance, beginning of period at Jun. 30, 2022	2,464,520	$ 597	$ (98,765)	1,820,531	749,558	(7,401)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	27,368	0	0	0	27,368	0
Foreign currency translation adjustment	4	0	0	0	0	4
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		0	0
Stock based compensation, value	2,080	$ 0	$ 0	2,080	0	0
Issuance of shares		1,621
Issuance of shares, treasury stock			(7)
Stock Issued During Period, Value, Treasury Stock Reissued			$ 187
Issuance of shares, value	78,584	$ 16		78,381	0	0
Dividends on common stock	$ (35,174)	$ 0	$ 0	0	(35,174)	0
Dividends per share	$ 0.63
Balance, shares at Sep. 30, 2022		61,318	3,541
Balance, end of period at Sep. 30, 2022	$ 2,537,329	$ 613	$ (98,578)	$ 1,900,992	$ 741,752	$ (7,450)