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

Equity (Schedule of Accumulated other comprehensive income (loss) (Details)

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Equity (Schedule of Accumulated other comprehensive income (loss) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance as of January 1 $ (13,479) $ (10,774) $ (3,647)
Other comprehensive income loss before reclassifications 7,149 (2,265) (8,551)
Amounts reclassified from accumulated other comprehensive income loss (693) (440) 1,424
Other comprehensive income (loss) 6,456 (2,705) (7,127)
Balance as of December 31 (7,023) (13,479) (10,774)
Net unrealized gain (loss) on cash flow hedges [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance as of January 1 (24) (107) (1,243)
Other comprehensive income loss before reclassifications 1,315 523 (288)
Amounts reclassified from accumulated other comprehensive income loss (961) (440) 1,424
Other comprehensive income (loss) 354 83 1,136
Balance as of December 31 330 (24) (107)
Foreign currency translation adjustment [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance as of January 1 (13,455) (10,667) (2,404)
Other comprehensive income loss before reclassifications 5,834 (2,788) (8,263)
Amounts reclassified from accumulated other comprehensive income loss 268
Other comprehensive income (loss) 6,102 (2,788) (8,263)
Balance as of December 31 $ (7,353) $ (13,455) $ (10,667)