CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interests [Member]	Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standards | ASU 2018-02 [Member]	$ 0	$ 0	$ 0	$ (1,797)	$ 0	$ 0	$ (1,797)
Beginning balance at Dec. 31, 2017	$ 6,547	802,961	(32,405)	2,646,937	$ (313,220)	3,403	3,114,223
Beginning balance (in shares) at Dec. 31, 2017	65,472				(5,783)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	2,161	0	0	$ 11,149	0	13,310
Stock option exercises (in shares)	0				232
Issuance of stock for equity awards, net of forfeitures	$ 0	(966)	0	0	$ 966	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				17
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (4,821)	0	(4,821)
Tax withholdings on equity award vesting (in shares)	0				(61)
Amortization of unearned share-based compensation	$ 0	16,649	0	0	$ 0	0	16,649
Total comprehensive income, net of taxes	0	0	(7,139)	102,889	0	520	96,270
Return of investment to noncontrolling interests	0	0	0	0	0	(686)	(686)
Ending balance at Sep. 30, 2018	$ 6,547	820,805	(39,544)	2,748,029	$ (305,926)	3,237	3,233,148
Ending balance (in shares) at Sep. 30, 2018	65,472				(5,595)
Beginning balance at Jun. 30, 2018	$ 6,547	817,609	(39,922)	2,706,213	$ (306,097)	3,341	3,187,691
Beginning balance (in shares) at Jun. 30, 2018	65,472				(5,598)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	50	0	0	$ 226	0	276
Stock option exercises (in shares)	0				4
Issuance of stock for equity awards, net of forfeitures	$ 0	48	0	0	$ (48)	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				(1)
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (7)	0	(7)
Tax withholdings on equity award vesting (in shares)	0				0
Amortization of unearned share-based compensation	$ 0	3,098	0	0	$ 0	0	3,098
Total comprehensive income, net of taxes	0	0	378	41,816	0	134	42,328
Return of investment to noncontrolling interests	0	0	0	0	0	(238)	(238)
Ending balance at Sep. 30, 2018	$ 6,547	820,805	(39,544)	2,748,029	$ (305,926)	3,237	3,233,148
Ending balance (in shares) at Sep. 30, 2018	65,472				(5,595)
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	355	0	0	$ 3,263	0	3,618
Stock option exercises (in shares)	0				60
Issuance of stock for equity awards, net of forfeitures	$ 0	(1,889)	0	0	$ 1,889	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	$ (2,031)	0	(2,031)
Tax withholdings on equity award vesting (in shares)	0				(30)
Amortization of unearned share-based compensation	$ 0	11,079	0	0	$ 0	0	11,079
Total comprehensive income, net of taxes	0	0	6,098	139,570	0	477	146,145
Return of investment to noncontrolling interests	0	0	0	0	0	(614)	(614)
Ending balance at Sep. 30, 2019	$ 6,547	832,892	(27,413)	2,863,162	$ (303,667)	2,977	3,374,498
Ending balance (in shares) at Sep. 30, 2019	65,472				(5,544)
Beginning balance at Jun. 30, 2019	$ 6,547	829,460	(26,967)	2,815,175	$ (305,061)	3,018	3,322,172
Beginning balance (in shares) at Jun. 30, 2019	65,472				(5,570)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	$ 0	237	0	0	$ 1,425	0	1,662
Stock option exercises (in shares)	0				26
Issuance of stock for equity awards, net of forfeitures	$ 0	23	0	0	$ (23)	0	0
Issuance of stock for equity awards, net of forfeitures (in shares)	0				0
Tax withholdings on equity award vesting	$ 0	0	0	0	$ (8)	0	(8)
Tax withholdings on equity award vesting (in shares)	0				0
Amortization of unearned share-based compensation	$ 0	3,172	0	0	$ 0	0	3,172
Total comprehensive income, net of taxes	0	0	(446)	47,987	0	163	47,704
Return of investment to noncontrolling interests	0	0	0	0	0	(204)	(204)
Ending balance at Sep. 30, 2019	$ 6,547	$ 832,892	$ (27,413)	$ 2,863,162	$ (303,667)	$ 2,977	$ 3,374,498
Ending balance (in shares) at Sep. 30, 2019	65,472				(5,544)