Warrant Liability - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2008	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Class of Warrant or Right [Line Items]
Warrant registered direct offering	6,686,650
Net proceeds from warrant	$ 17,500,000
Number of shares of common stock in each unit	1
Number of shares of common stock issuable for each warrant	0.5
Price of common stock	$ 2.68
Common stock that can be acquired upon exercise of warrant		3,343,325		3,343,325
Exercise price		3.62		3.62
Change in fair value of warrant liability		(101,000)	1,304,000	0	1,237,000
Warrant liability		$ 368,000		$ 368,000		$ 368,000
Minimum
Class of Warrant or Right [Line Items]
Warrant exercise date				Jan. 31, 2009
Maximum
Class of Warrant or Right [Line Items]
Warrant exercise date				Jul. 31, 2013