Reconciliation of Change in Value of Company's Warrants Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended			401 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Beginning balance				$ 65,193				$ 5,446	$ 65,193	$ 5,446	$ 39,111
Change in value of warrants	(23,984)	17,160	1,945	26,906	51,784	42,716	(13,488)	10,926	22,027	91,938	(33,022)	88,995
Ending balance	9,006				65,193				9,006	65,193	5,446	9,006
Warrant
Class of Warrant or Right [Line Items]
Reclassification to stockholders' equity upon exercise of warrants									$ (78,214)	$ (32,191)	$ (643)