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

Goodwill (Schedule of Changes in the Carrying Amount of Goodwill) (Details)

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Goodwill (Schedule of Changes in the Carrying Amount of Goodwill) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Goodwill [Abstract].      
Goodwill as of January 1 $ 383,853 $ 1,323,502  
Goodwill impairment charges (942,408) $ (102,470)
Goodwill acquired 5,400  
Translation differences 1,700 (2,700)  
Goodwill as of December 31 $ 385,629 $ 383,853 $ 1,323,502