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Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Allowance for Doubtful Accounts [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of period   $ 19 $ 136
Charged to costs & expenses     19
Deductions   19 136
Balance at end of period     19
Inventory Reserve [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of period $ 25,249 26,675 24,682
Charged to costs & expenses 6,406 3,303 2,225
Deductions 8,300 4,729 232
Balance at end of period 23,355 25,249 26,675
Warranty Liability [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of period 8,548 8,739 8,415
Charged to costs & expenses 6,951 8,561 2,998
Deductions 5,775 8,752 2,674
Balance at end of period 9,724 8,548 8,739
Deferred Tax Asset Valuation Allowance [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of period 6,149 7,250 7,463
Charged to costs & expenses 18 69 81
Deductions 161 1,170 294
Balance at end of period $ 6,006 $ 6,149 $ 7,250