Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Segment	Dec. 31, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Contractual term of the warrants			2 years
Risk free interest rate			0.25%
Volatility			53.00%
Estimated total enterprise value			$ 106,900,000
Realized gains or losses from sale of marketable securities		0	0	0
Restricted cash current, standby letters of credit	205,000	205,000	205,000
Property and equipment, estimated useful lives		3 years
Intangible asset, Amortization expense		111,000	111,000	111,000
Deferred offering costs	2,803,000	2,803,000	0
Clinical trial expenses	657,000
Number of operating segment		1
Intellectual Property And know-how
Summary Of Significant Accounting Policies [Line Items]
Intangible asset, acquired value	1,000,000	1,000,000
Intangible asset, estimated useful life		9 years
Intangible asset, Amortization expense		$ 100,000	$ 100,000	$ 100,000
Impaired Intangible Asset, Description		Company's intellectual property was fully amortized.
Maximum | Cash and Cash Equivalents
Summary Of Significant Accounting Policies [Line Items]
Highly liquid investments maturity period		90 days
Convertible Preferred Stock Warrant Liability
Summary Of Significant Accounting Policies [Line Items]
Estimated fair value		$ 8.00
Contractual term of the warrants		2 years 9 months 18 days
Risk free interest rate		0.36%
Volatility		55.00%
Subsequent Event
Summary Of Significant Accounting Policies [Line Items]
Reverse stock split ratio		3.56147
Reverse stock split		1-for-3.56147 reverse split of our issued and outstanding capital stock which became effective on January 15, 2013