Intangible Assets - Schedule of Patent Cost and Other Asset (Detail) - Patents [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Patent costs	$ 2,427	$ 2,525
Accumulated amortization	(1,598)	(1,583)
Finite-lived intangible assets, net	$ 829	$ 942