Changes in Initial Product Warranty Accrual and Expenses Under Initial and Extended Warranties (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accrued Warranty Liabilities [Line Items]
Initial warranty accrual, beginning balance	$ 1,025	$ 1,755	$ 1,096	$ 1,699
Provision for estimated warranty cost	461	23	609	360
Warranty expenditures	(231)	(260)	(450)	(541)
Initial warranty accrual, ending balance	1,255	1,518	1,255	1,518
Less warranty accrual, long-term	247		247
Total warranty accrual, current portion	$ 1,008	$ 1,518	$ 1,008	$ 1,518	$ 1,096