Condensed Consolidating Financial Statements (Cash Flow) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net cash provided by operating activities	$ 288,937	$ 278,577
Cash flows from investing activities:
Capital expenditures	(49,463)	(37,402)
Return of capital from investees	5,908	347
Investment in and loans to investees	0	(87,488)
Payments for acquisition of a business, net of cash acquired	0	(34,879)
Increase (decrease) to investment in affiliates	0	0
Net cash used in investing activities	(43,555)	(159,422)
Cash flows from financing activities:
Deemed repurchases of restricted stock units	(23,019)	(15,734)
Purchase of treasury stock	(58,440)	(242,409)
Proceeds from stock option exercises	4,630	4,317
Principal payments on finance lease obligations	(2,590)	(2,625)
Distributions to noncontrolling interests	(10,129)	(6,967)
Proceeds from the issuance of long-term debt	0	0
Principal payments on long-term debt	(2,717)	0
Payments for financing costs		0
Net cash used in financing activities	(92,265)	(263,418)
Net increase (decrease) in cash and cash equivalents from operations	153,117	(144,263)
Effect of exchange rate changes on cash and cash equivalents	(1,661)	1,604
Cash and cash equivalents at beginning of period	554,886	558,783
Cash and cash equivalents at end of period	706,342	416,124
Eliminations
Cash flows from operating activities:
Net cash provided by operating activities	(394,915)	(433,038)
Cash flows from investing activities:
Capital expenditures	0	0
Return of capital from investees	0	0
Investment in and loans to investees	0	0
Payments for acquisition of a business, net of cash acquired	0	0
Increase (decrease) to investment in affiliates	265,383	701,129
Net cash used in investing activities	265,383	701,129
Cash flows from financing activities:
Deemed repurchases of restricted stock units	0	0
Purchase of treasury stock	0	0
Proceeds from stock option exercises	0	0
Principal payments on finance lease obligations	0	0
Distributions to noncontrolling interests	0	0
Proceeds from the issuance of long-term debt	0	0
Principal payments on long-term debt	0	0
Payments for financing costs		0
Net cash used in financing activities	0	0
Net increase (decrease) in cash and cash equivalents from operations	(129,532)	268,091
Effect of exchange rate changes on cash and cash equivalents	129,532	(268,091)
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Parent Company
Cash flows from operating activities:
Net cash provided by operating activities	273,682	296,928
Cash flows from investing activities:
Capital expenditures	0	0
Return of capital from investees	0	0
Investment in and loans to investees	0	0
Payments for acquisition of a business, net of cash acquired	0	0
Increase (decrease) to investment in affiliates	(221,104)	(46,945)
Net cash used in investing activities	(221,104)	(46,945)
Cash flows from financing activities:
Deemed repurchases of restricted stock units	(23,019)	(15,734)
Purchase of treasury stock	(58,440)	(242,409)
Proceeds from stock option exercises	4,630	4,317
Principal payments on finance lease obligations	0	0
Distributions to noncontrolling interests	0	0
Proceeds from the issuance of long-term debt	0	0
Principal payments on long-term debt	0	0
Payments for financing costs		0
Net cash used in financing activities	(76,829)	(253,826)
Net increase (decrease) in cash and cash equivalents from operations	(24,251)	(3,843)
Effect of exchange rate changes on cash and cash equivalents	24,223	6,408
Cash and cash equivalents at beginning of period	121	320
Cash and cash equivalents at end of period	93	2,885
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash provided by operating activities	400,444	852,314
Cash flows from investing activities:
Capital expenditures	(45,445)	(32,827)
Return of capital from investees	0	0
Investment in and loans to investees	0	0
Payments for acquisition of a business, net of cash acquired	0	0
Increase (decrease) to investment in affiliates	(44,279)	(1,550,189)
Net cash used in investing activities	(89,724)	(1,583,016)
Cash flows from financing activities:
Deemed repurchases of restricted stock units	0	0
Purchase of treasury stock	0	0
Proceeds from stock option exercises	0	0
Principal payments on finance lease obligations	(1,536)	(1,464)
Distributions to noncontrolling interests	0	0
Proceeds from the issuance of long-term debt	0	0
Principal payments on long-term debt	0	0
Payments for financing costs		0
Net cash used in financing activities	(1,536)	(1,464)
Net increase (decrease) in cash and cash equivalents from operations	309,184	(732,166)
Effect of exchange rate changes on cash and cash equivalents	(190,600)	584,331
Cash and cash equivalents at beginning of period	368,151	391,248
Cash and cash equivalents at end of period	486,735	243,413
Non- Guarantor Subsidiaries
Cash flows from operating activities:
Net cash provided by operating activities	9,726	(437,627)
Cash flows from investing activities:
Capital expenditures	(4,018)	(4,575)
Return of capital from investees	5,908	347
Investment in and loans to investees	0	(87,488)
Payments for acquisition of a business, net of cash acquired	0	(34,879)
Increase (decrease) to investment in affiliates	0	896,005
Net cash used in investing activities	1,890	769,410
Cash flows from financing activities:
Deemed repurchases of restricted stock units	0	0
Purchase of treasury stock	0	0
Proceeds from stock option exercises	0	0
Principal payments on finance lease obligations	(1,054)	(1,161)
Distributions to noncontrolling interests	(10,129)	(6,967)
Proceeds from the issuance of long-term debt	0	0
Principal payments on long-term debt	(2,717)	0
Payments for financing costs		0
Net cash used in financing activities	(13,900)	(8,128)
Net increase (decrease) in cash and cash equivalents from operations	(2,284)	323,655
Effect of exchange rate changes on cash and cash equivalents	35,184	(321,044)
Cash and cash equivalents at beginning of period	186,614	167,215
Cash and cash equivalents at end of period	$ 219,514	$ 169,826