Income Tax (Provision for Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 67,759	$ 119,057	$ 148,654	$ 310,562
Tax Adjustments, Settlements, and Unusual Provisions	664	0	(2,685)	0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(58,949)	0	(59,139)	0
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	7,537	(3,635)	8,795	(14,049)
Income Tax Reconciliation Foreign Income Tax Basis Differential	(2,371)	2,126	(9,264)	(14,633)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	(5,334)	(2,501)	5,357	11,627
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Amount	1,851	299	650	(873)
Income Tax Reconciliation Change In Foreign Enacted Tax Rate	(166)	(1,139)	30	(2,332)
Income Tax Reconciliation SubpartF	(99)	64	211	1,390
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	(544)	1,230	(1,003)	(834)
Effective Income Tax Rate Reconciliation Global Intangible Low Taxed Income	7,624	0	11,916	0
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	817	2,762	5,067	7,226	$ 10,500
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	4,213	452	4,108	133
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	94	(620)	(492)	(1,737)
Income Tax Expense (Benefit)	$ 21,462	$ 112,571	$ 102,071	$ 282,028
Effective Income Tax Rate Reconciliation, Percent	6.70%	33.10%	14.40%	31.80%