Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Deferred revenue	$ 7,377,000	$ 7,490,000
Basis difference in equipment	(1,084,000)	(1,013,000)
Basis difference in intangibles	1,201,000	1,122,000
Accrued liabilities and other	550,000	1,563,000
R&D credit	11,589,000	11,138,000
AMT credit	79,000
Stock options	5,697,000	1,151,000
Net operating loss carry-forward	83,621,000	63,509,000
Gross, Deferred Tax Assets	109,030,000	84,960,000
Less: valuation allowance	(109,030,000)	(84,960,000)
Net of Valuation Allowance	$ 0	$ 0