Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Abstract]
Capital loss carry-forwards	$ 11,343	$ 16,564
Foreign provision for income taxes	64,252	25,139	$ 64,139
Undistributed earnings	466,000
Unrecognized deferred tax liability related to temporary differences	8,600
Earnings retained by subsidiaries and equity accounted investments	469,000	450,000	411,000
Gross unrecognized tax benefits	25,910	19,262	$ 15,904
Unrecognized tax benefits that would impact effective tax rate	13,737	9,227
Accrued interest and penalties	3,677	$ 2,695
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	9,734
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit)	(10,070)
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Liability	$ 336