CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive, Net Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interests [Member]	Total
Beginning balance at Dec. 31, 2018	$ 6,547	$ 823,347	$ (33,511)	$ 2,723,592	$ (306,788)	$ 3,114	$ 3,216,301
Beginning balance (in shares) at Dec. 31, 2018	65,472				(5,608)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	118	0	0	$ 1,838	0	1,956
Stock option exercises (in shares)	0				34
Issuance of stock for equity awards, net of forfeitures	$ 0	(1,912)	0	0	$ 1,912	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				34
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (2,023)	0	(2,023)
Tax withholdings on equity award vesting (in shares)	0				(30)
Amortization of unearned share-based compensation	$ 0	7,907	0	0	$ 0	0	7,907
Total comprehensive income (loss), net of taxes	0	0	6,544	91,583	0	314	98,441
Return of investment to noncontrolling interests	0	0	0	0	0	(410)	(410)
Ending balance at Jun. 30, 2019	$ 6,547	829,460	(26,967)	2,815,175	$ (305,061)	3,018	3,322,172
Ending balance (in shares) at Jun. 30, 2019	65,472				(5,570)
Beginning balance at Mar. 31, 2019	$ 6,547	827,497	(32,971)	2,767,888	$ (306,625)	3,072	3,265,408
Beginning balance (in shares) at Mar. 31, 2019	65,472				(5,599)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	66	0	0	$ 474	0	540
Stock option exercises (in shares)	0				9
Issuance of stock for equity awards, net of forfeitures	$ 0	(1,110)	0	0	$ 1,110	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				20
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (20)	0	(20)
Tax withholdings on equity award vesting (in shares)	0				0
Amortization of unearned share-based compensation	$ 0	3,007	0	0	$ 0	0	3,007
Total comprehensive income (loss), net of taxes	0	0	6,004	47,287	0	153	53,444
Return of investment to noncontrolling interests	0	0	0	0	0	(207)	(207)
Ending balance at Jun. 30, 2019	$ 6,547	829,460	(26,967)	2,815,175	$ (305,061)	3,018	3,322,172
Ending balance (in shares) at Jun. 30, 2019	65,472				(5,570)
Beginning balance at Dec. 31, 2019	$ 6,547	835,899	(37,799)	2,865,939	$ (301,963)	2,969	3,371,592
Beginning balance (in shares) at Dec. 31, 2019	65,472				(5,513)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	26	0	0	$ 327	0	353
Stock option exercises (in shares)	0				15
Issuance of stock for equity awards, net of forfeitures	$ 0	(5,703)	0	0	$ 5,703	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				103
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (3,191)	0	(3,191)
Tax withholdings on equity award vesting (in shares)	0				(39)
Amortization of unearned share-based compensation	$ 0	8,652	0	0	$ 0	0	8,652
Total comprehensive income (loss), net of taxes	0	0	(3,318)	(322,239)	0	539	(325,018)
Return of investment to noncontrolling interests	0	0	0	0	0	(404)	(404)
Ending balance at Jun. 30, 2020	$ 6,547	838,874	(41,117)	2,543,700	$ (299,124)	3,104	3,051,984
Ending balance (in shares) at Jun. 30, 2020	65,472				(5,434)
Beginning balance at Mar. 31, 2020	$ 6,547	837,879	(38,991)	2,518,698	$ (301,424)	3,045	3,025,754
Beginning balance (in shares) at Mar. 31, 2020	65,472				(5,475)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock for equity awards, net of forfeitures	$ 0	(2,326)	0	0	$ 2,326	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				42
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (26)	0	(26)
Tax withholdings on equity award vesting (in shares)	0				(1)
Amortization of unearned share-based compensation	$ 0	3,321	0	0	$ 0	0	3,321
Total comprehensive income (loss), net of taxes	0	0	(2,126)	25,002	0	261	23,137
Return of investment to noncontrolling interests	0	0	0	0	0	(202)	(202)
Ending balance at Jun. 30, 2020	$ 6,547	$ 838,874	$ (41,117)	$ 2,543,700	$ (299,124)	$ 3,104	$ 3,051,984
Ending balance (in shares) at Jun. 30, 2020	65,472				(5,434)