Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 134,000	$ 145,000	$ 170,000
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Future amortization expense from patent assets held for 2017	129,000
Future amortization expense from patent assets held for 2018	113,000
Future amortization expense from patent assets held for 2019	106,000
Future amortization expense from patent assets held for 2020	102,000
Future amortization expense from patent assets held for 2021	$ 92,000