Derivative Instruments - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2013	Jun. 30, 2014
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
Common stock shares issued and sold		21,303,750
Warrant , Exercise Price		$ 1.43
Warrants expiration date		Dec. 16, 2018
Derivative warrant liability fair value		$ 7.2	$ 4.7