Derivative Instruments - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended		1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended
	Aug. 31, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013 2013 Warrants	Sep. 30, 2014 2013 Warrants	Aug. 31, 2014 2014 Warrants	Sep. 30, 2014 2014 Warrants	Jul. 31, 2012 2022 Notes	Sep. 30, 2014 2022 Notes
Derivative [Line Items]
Percentage of convertible senior notes embedded derivatives								7.50%
Convertible senior notes due date								2022
2022 notes, conversion date								Jul. 01, 2017	Jul. 01, 2017
Common stock shares issued and sold	15,000,000	21,303,750		21,303,750
Warrant , Exercise Price			$ 1.18	$ 1.43		$ 0.85
Warrants expiration date					Dec. 16, 2018		Aug. 05, 2019
Common stock shares issued		68,492,894	99,592,898			30,000,000
Additional purchase of common stock shares						15,000,000
Derivative warrant liability fair value		$ 7,243	$ 2,877