Annual report pursuant to Section 13 and 15(d)

Item 15 (Details)

v3.8.0.1
Item 15 (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Allowance for Doubtful Accounts [Member]        
Valuation and Qualifying Accounts Disclosure [Line Items]        
Valuation Allowances and Reserves, Balance $ 73 $ 87 $ 236 $ 57
Valuation Allowances and Reserves, Additions for Charges to Cost and Expense 133 87 179  
Valuation Allowances and Reserves, Additions for Charges to Other Accounts 27 0 0  
Valuation Allowances and Reserves, Deductions (174) (236) 0  
Warranty Reserves [Member]        
Valuation and Qualifying Accounts Disclosure [Line Items]        
Valuation Allowances and Reserves, Balance 941 860 157 60
Valuation Allowances and Reserves, Additions for Charges to Cost and Expense 492 335 193  
Valuation Allowances and Reserves, Additions for Charges to Other Accounts 122 489 37  
Valuation Allowances and Reserves, Deductions (533) (121) (133)  
Valuation Allowance of Deferred Tax Assets [Member]        
Valuation and Qualifying Accounts Disclosure [Line Items]        
Valuation Allowances and Reserves, Balance 84,561 100,284 98,535 $ 29,399
Valuation Allowances and Reserves, Additions for Charges to Cost and Expense (50,881) 0 69,136  
Valuation Allowances and Reserves, Additions for Charges to Other Accounts 35,158 8,410 0  
Valuation Allowances and Reserves, Deductions $ 0 $ (6,661) $ 0