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)

v3.8.0.1
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, 2017
Dec. 31, 2016
Changes in deferred revenues    
Balance at beginning of year $ 17,555 $ 14,100
Revenue deferred in the period 18,454 22,309
Revenue recognized in the period (16,791) (18,854)
Balance at end of year $ 19,218 $ 17,555