Notes Payable - Estimated Fair Value of Warrants (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2013 Immediately Before [Member] Amended and Restated August 2009 Warrants [Member]	Dec. 31, 2013 Immediately Before [Member] Amended and Restated June 2010 Warrants [Member]	Dec. 31, 2013 Immediately Before [Member] Amended and Restated August 2010 Warrants [Member]	Dec. 31, 2013 Immediately Before [Member] Amended and Restated July 2011 Warrants [Member]	Dec. 31, 2012 Immediately After [Member] Amended and Restated August 2009 Warrants [Member]	Dec. 31, 2012 Immediately After [Member] Amended and Restated June 2010 Warrants [Member]	Dec. 31, 2012 Immediately After [Member] Amended and Restated August 2010 Warrants [Member]	Dec. 31, 2012 Immediately After [Member] Amended and Restated July 2011 Warrants [Member]	Dec. 31, 2012 Immediately After [Member] MHR Restructuring Warrants [Member]
Estimated Fair Value Of Warrants [Line Items]
Fair value of warrants	$ 10,000,000	$ 445,000	$ 152,000	$ 570,000	$ 696,000	$ 768,000	$ 294,000	$ 741,000	$ 783,000	$ 2,058,000