Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 14,816	$ 12,435
Depreciation and amortization	2,900	2,300	$ 1,500
Lease and loaner instruments
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 1,500	$ 900