Warrants and Warrant Derivative Liability - Additional Information (Detail) $ / shares in Units, $ in Thousands			6 Months Ended	12 Months Ended
	Feb. 27, 2015 shares	Oct. 16, 2009 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Derivative [Line Items]
Preferred stock issued under private placement, net | $			$ 52,149
Preferred stock issued under private placement, gross proceeds | $			$ 52,800
Warrants expiration date			Feb. 27, 2015
Warrants exercised			1,844,585
Proceed from exercise of warrants | $			$ 2,713
Warrants expired	6,242,803
Maximum
Derivative [Line Items]
Warrants outstanding				8,087,388
Prior To Agreement
Derivative [Line Items]
Warrants expiration date			Oct. 16, 2014
Warrants Issued October 2009
Derivative [Line Items]
Warrants outstanding			0
Warrants expiration date			Feb. 27, 2015
Warrants exercised			1,844,585
Proceed from exercise of warrants | $			$ 2,700
Warrants expired	6,242,803
Warrants Issued October 2009 | Maximum
Derivative [Line Items]
Warrants outstanding				8,087,388
Warrants Issued October 2009 | Prior To Agreement
Derivative [Line Items]
Warrants expiration date			Oct. 16, 2014
Warrants Issued July 2009
Derivative [Line Items]
Warrants outstanding			0	0
Warrants exercised				1,684,888
Proceed from exercise of warrants | $				$ 1,700
October 2009 Private Placement
Derivative [Line Items]
Preferred stock issued under private placement, net | $		$ 70,000
Preferred stock issued under private placement, gross proceeds | $		$ 62,300
Common stock issued under private placement, shares		66,400,000
Number of shares that each ADS represents		1
Preferred stock issued under private placement, price per share | $ / shares		$ 1.00
October 2009 Private Placement | Warrants issued to three former officers
Derivative [Line Items]
Number of warrants issued		900,000
October 2009 Private Placement | Bridge Loan
Derivative [Line Items]
Bridge notes converted in conjunction with the private placement, amount | $		$ 3,600
Common stock issued under private placement, shares		4,000,000
Number of shares that each ADS represents		1
Bridge notes converted in conjunction with the private placement, price per share | $ / shares		$ 0.90
October 2009 Private Placement | Warrants Issued October 2009
Derivative [Line Items]
Number of warrants issued		35,200,000
Description of pricing variability feature and classification of warrants			The warrants issued in connection with the October 2009 financing contained a pricing variability feature which provided for an increase to the exercise price if the exchange rate between the U.S. dollar and British pound adjusts such that the warrants could be exercised at a price less than the £0.5 par value of the common stock - that is, if the exchange rate exceeded U.S. $3.00 per £1.0 sterling. Due to the potential variable nature of the exercise price, the warrants are not considered to be indexed to the Company’s common stock. Accordingly, the warrants do not qualify for the exception to classify the warrants within equity and are classified as a derivative liability.
October 2009 Private Placement | Warrants Issued October 2009 | Maximum
Derivative [Line Items]
Warrants issued, number of shares called by the warrant		36,100,000
October 2009 Private Placement | Warrants Issued October 2009 | American Depositary Share
Derivative [Line Items]
Warrant term		5 years
Warrants issued, number of shares called by a warrant		0.5
Exercise price of the warrants | $ / shares		$ 1.50
October 2009 Private Placement | Warrants Issued October 2009 | Bridge Loan | American Depositary Share
Derivative [Line Items]
Warrant term		5 years
Warrants issued, number of shares called by a warrant		0.5
Exercise price of the warrants | $ / shares		$ 1.50