Tax Effects of Temporary Differences and Carry Forwards on Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Income Tax Asset [Line Items]
Net operating loss carry forwards	$ 48,591	$ 21,850
Capitalized start-up costs	9,931	9,189
Research and development credits	1,527	1,088
Stock compensation	5,522	3,314
Other	5,028	3,597
Total deferred tax assets	70,599	39,038
Valuation allowance	(69,571)	(38,625)
Deferred tax liability-fixed assets	(1,028)	(413)
Net deferred tax assets, after valuation allowance