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Guarantees (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Product Warranty [Abstract]    
Period of warranty 12 months  
Change in warranty accrual [Roll Forward]    
Beginning accrued product warranty $ 133,000 $ 251,000
Accruals for warranties issued 289,000 125,000
Adjustments related to pre-existing warranties including expirations and changes in estimates 87,000 (150,000)
Cost of warranty repair (273,000) (93,000)
Ending accrued product warranty $ 236,000 $ 133,000