Income Taxes (Deferred tax assets (liabilities) (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Deferred tax asset:
Net operating loss carryforwards	$ 31,398,000	$ 29,122,000
Accrued expenses	19,000	87,000
Amortization of definite lived intangible assets	0	10,000
Non-qualified stock option compensation	598,000	315,000
Depreciation	68,000	72,000
Deferred revenue	943,000	880,000
Other	1,000	139,000
Patents	0	(23,000)
Deferred gain on installment sale	(1,000)	0
State net operating loss carryforwards, net of federal tax benefit	929,000	579,000
Research tax credit carryforwards	2,433,000	2,274,000
Total deferred tax assets	36,388,000	33,455,000
Valuation allowance	(36,388,000)	(33,455,000)
Net deferred tax assets	$ 0	$ 0