Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 19	$ 136	$ 130
Charged to costs & expenses		19	23
Deductions	19	136	17
Balance at end of period		19	136
Inventory Reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	26,675	24,682	22,993
Charged to costs & expenses	3,303	2,225	2,549
Deductions	4,729	232	860
Balance at end of period	25,249	26,675	24,682
Warranty Liability [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	8,739	8,415	8,977
Charged to costs & expenses	8,561	2,998	3,103
Deductions	8,752	2,674	3,665
Balance at end of period	8,548	8,739	8,415
Deferred Tax Asset Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	7,250	7,463	8,842
Charged to costs & expenses	69	81	283
Deductions	1,170	294	1,662
Balance at end of period	$ 6,149	$ 7,250	$ 7,463