Stock Transactions - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended
	Feb. 29, 2012	Jun. 30, 2012	Jun. 30, 2011	Feb. 22, 2012	Jun. 30, 2012 Performance-based awards	Jun. 30, 2012 Certain employees and non-employees
Class of Stock [Line Items]
Underwritten public offering, common stock issued and sold				5,175,000
Underwritten public offering, common stock price per share				$ 5.25
Underwritten public offering, net proceeds from issuance	$ 25,388,000
Underwritten public offering, commissions and issuance costs	1,780,000
Common Stock issued in connection with exercise of options						1,117,249
Cash proceeds from exercise of options		1,086,000	259,000			1,055,000
Performance-based awards, vesting period					3 years
Performance-based awards, recorded expense		$ 3,759,000	$ 521,000		$ 3,500,000