Annual report pursuant to Section 13 and 15(d)

Item 15 (Details)

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Item 15 (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
SEC Schedule, 12-09, Allowance, Credit Loss [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
Allowances for Doubtful Accounts $ 46 $ 73 $ 87 $ 236
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense 0 133 87  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account 0 27 0  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction (27) (174) (236)  
SEC Schedule, 12-09, Reserve, Warranty [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
Allowances for Doubtful Accounts 519 941 860 157
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense (414) 492 335  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account 0 122 489  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction (8) (533) (121)  
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]        
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]        
Allowances for Doubtful Accounts 79,196 84,560 100,284 $ 98,535
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense (5,761) (50,881) 0  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account 397 35,157 8,410  
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction $ 0 $ 0 $ (6,661)