Summary of Carrying Values Estimated Fair Values of Notes and Facility Financing Obligation and Sanofi Loan Facility (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Sanofi-Aventis Deutschland GmbH
Convertible Debt [Line Items]
Carrying value	$ 44,500	$ 3,000
Estimated fair value	36,500	3,000
Senior convertible notes due August 15, 2018
Convertible Debt [Line Items]
Carrying value	27,613
Senior convertible notes due August 15, 2018 | Convertible Debt Securities
Convertible Debt [Line Items]
Carrying value	27,600
Estimated fair value	21,300
Facility financing obligation
Convertible Debt [Line Items]
Carrying value	74,600	73,000
Estimated fair value	$ 78,400	75,100
Senior convertible notes due August 15, 2015
Convertible Debt [Line Items]
Carrying value		99,355
Senior convertible notes due August 15, 2015 | Convertible Debt Securities
Convertible Debt [Line Items]
Carrying value		99,400
Estimated fair value		$ 102,900