Permanent and Temporary Equity Permanent and Temporary Equity (Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Foreign currency translation	$ (55,016)	$ (45,580)
Accumulated unrealized gain on marketable debt securities	15,746	802
Derivative instruments	19,688	9,658
Accumulated other comprehensive loss	$ (19,582)	$ (35,120)

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant