Reconciliation of Change in Value of Company's Warrants Liability (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended							12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Warrants and Rights Note Disclosure [Abstract]
Beginning balance			$ 9,006				$ 65,193	$ 9,006	$ 65,193	$ 5,446
Increase in value of warrants	(4,256)	3,784	3,251	(23,984)	17,160	1,945	26,906	2,779	22,027	91,938
Reclassification to stockholders' equity upon exercise of warrants								(11,785)	(78,214)	(32,191)
Ending balance				$ 9,006					$ 9,006	$ 65,193