Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Income Taxes (Schedule of Unrecognized Tax Benefits) (Details)

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Income Taxes (Schedule of Unrecognized Tax Benefits) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]      
Balance at beginning of year $ 18,000 $ 13,930 $ 8,552
Additions for tax positions related to the current year 8,777 4,039 4,116
Foreign currency fluctuation 1,242
Additions for tax positions related to previous years 129 1,987
Subtractions for tax positions related to previous years (687)
Reduction of reserve for statute expirations (15) (98) (725)
Balance at end of year $ 28,037 $ 18,000 $ 13,930