Interest Expense - Summary of Interest Expense by Cash and Non-Cash Components (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Debt Instrument [Line Items]
Cash interest expense	$ (324)	$ (417)	$ (696)	$ (881)
Non-cash interest expense
Non-cash interest expense			(99)	(78)
Loss on extinguishment of 2013 Notes			(8,331)
Non-cash capitalized interest expense	180	0	411	0
Total non-cash interest expense	57	(73)	(9,412)	(12,234)
Total interest expense	(267)	(490)	(10,108)	(13,115)
Convertible Notes [Member]
Non-cash interest expense
Non-cash interest expense	0	0	(1,250)	(9,204)
Debt issuance costs [Member]
Non-cash interest expense
Non-cash interest expense	(48)	(39)	(100)	(140)
Warrant and Derivative Related Debt Discounts [Member]
Non-cash interest expense
Non-cash interest expense	(75)	(34)	(142)	(2,890)
2013 Notes [Member]
Non-cash interest expense
Loss on extinguishment of 2013 Notes	$ 0	$ 0	$ (8,331)	$ 0