Derivative Instruments - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2012	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Percentage of convertible senior notes embedded derivatives	7.50%
Convertible senior notes due date	2022
Convertible notes, conversion date	Jul. 01, 2017	Jul. 01, 2017
Common stock shares issued and sold			21,303,750
Warrant , Exercise Price			$ 1.85
Warrants expiration date			Dec. 16, 2018
Derivative warrant liability fair value		$ 6.0	$ 7.2