Annual report pursuant to Section 13 and 15(d)

Schedule II Valuation and Qualifying Accounts (Details)

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Schedule II Valuation and Qualifying Accounts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Allowance for doubtful accounts      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period $ 35 $ 82 $ 247
Charged to (Reduction of) Cost and Expenses 240 202 (45)
Deductions (106) (249) (120)
Balance at End of Period 169 35 82
Inventory reserves      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 697 966 682
Charged to (Reduction of) Cost and Expenses 1,828 1,237 984
Deductions (1,849) (1,506) (700)
Balance at End of Period $ 676 $ 697 $ 966