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

Revenues (Shedule of Disaggregation of Revenues) (Details)

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Revenues (Shedule of Disaggregation of Revenues) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disaggregation of Revenue [Line Items]      
Total Revenues $ 663,237 $ 668,362 $ 672,458
Revenues recognized in point in time [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 587,477 594,817 599,634
Revenues recognized over time [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 75,760 73,545 72,824
Products [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 456,504 474,286 479,031
Products [Member] | Revenues recognized in point in time [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 456,504 474,286 479,031
Services [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 206,733 194,076 193,427
Services [Member] | Revenues recognized in point in time [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 130,973 120,531 120,603
Services [Member] | Revenues recognized over time [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 75,760 73,545 72,824
Americas [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 409,741 413,326 411,536
Americas [Member] | Products [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 251,589 263,212 257,547
Americas [Member] | Services [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 158,152 150,114 153,989
EMEA [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 147,162 148,279 137,924
EMEA [Member] | Products [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 119,151 123,616 117,074
EMEA [Member] | Services [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 28,011 24,663 20,850
Asia Pacific [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 106,334 106,757 122,998
Asia Pacific [Member] | Products [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues 85,764 87,458 104,410
Asia Pacific [Member] | Services [Member]      
Disaggregation of Revenue [Line Items]      
Total Revenues $ 20,570 $ 19,299 $ 18,588