Significant Component of Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Tax Assets [Line Items]
Net operating loss carryforwards	$ 66,209	$ 42,715
Start-up and organizational costs	41,529	44,262
Research and development credit carryforwards	25,058	18,388
Stock compensation	1,028	991
Capitalized acquisition costs	12,323	13,270
Deferred revenue	1,074	1,388
Depreciation	129	331
Other	1,254	998
Deferred Tax Assets Gross	148,604	122,343
Less valuation allowance	(148,604)	(122,343)
Net deferred tax assets