Income Taxes - Schedule of Deferred Tax Assets and (Liabilities) (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Operating loss carryforwards	$ 44,120,000	$ 37,642,000	$ 28,972,000
Accrued expenses	8,861,000	8,576,000	7,778,000
Tax credit carryforwards	3,186,000	2,921,000	2,537,000
Intellectual property	4,846,000	3,377,000	1,604,000
Outside tax basis difference in affiliate	2,825,000	1,616,000	1,378,000
Equipment	388,000	237,000	156,000
Other		4,000	4,000
Total deferred tax assets	64,226,000	54,373,000	42,429,000
Deferred tax liabilities
Net deferred tax asset	64,226,000	54,373,000	42,429,000
Valuation allowance	(64,226,000)	(54,373,000)	(42,429,000)
Total deferred tax assets (liabilities)