Selected Quarterly Financial Data - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
	Nov. 09, 2016	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interim Reporting [Line Items]
Net revenue - collaboration					$ 250	$ 171,965
(Loss) gain on extinguishment of debt					(1,611)	72,024	$ (1,049)
Net revenue - commercial product sales		$ 1,200			$ 9,192	1,895
License and Collaboration Agreement with Sanofi
Interim Reporting [Line Items]
(Loss) gain on extinguishment of debt	$ 500
License and Collaboration Agreement with Sanofi | Sanofi-Aventis Deutschland GmbH
Interim Reporting [Line Items]
Net revenue - collaboration			$ 10,200	$ 161,800		$ 172,000
(Loss) gain on extinguishment of debt			$ 72,000