Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2009
Income Tax Contingency [Line Items]
Change in valuation allowance	$ 2,642,000	$ (195,000)
Expiry year of operating loss carry-forwards related to federal and state research and development activities	2021
Recorded capital loss carryover				4,000,000
Deferred tax asset	1,360,000	1,593,000		1,360,000
Deferred tax asset, expiration period	2014
Provision for (benefit from) income taxes	0
Unrecognized tax benefits	748,036	673,880
Accrued interest and penalties related to uncertain tax	0
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Operating loss carry-forwards	212,591,000
Expiry year of operating loss carry-forwards	2020
Tax credits related to federal and state research and development	2,371,000
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Tax credits related to federal and state research and development	794,000
California [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carry-forwards	$ 38,606,000
Expiry year of operating loss carry-forwards	2017