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

Nature of Operations and Summary of Significant Accounting Policies (Schedule of Changes in Deferred Revenues Relating to Warranty Commitments) (Details)

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Nature of Operations and Summary of Significant Accounting Policies (Schedule of Changes in Deferred Revenues Relating to Warranty Commitments) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Changes in deferred revenues      
Balance at beginning of year $ 17,555 $ 14,100 $ 15,939
Revenue deferred in the period 22,309 19,413  
Revenue recognized in the period (18,854) (21,252)  
Balance at end of year $ 17,555 $ 14,100