Income Taxes - Income Tax Provision Related to Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
U.S. federal provision (benefit)
At statutory rate	$ (53,427)	$ (28,235)	$ (19,050)
Change in valuation allowance	51,981	22,210	11,831
Non-cash interest expense on liability related to sale of future royalties	6,899	7,217	7,311
Stock-based compensation	528	674	2,832
Foreign tax deduction	0	1,773	0
Research credits	(4,543)	(4,529)	(2,933)
Other	(562)	1,396	(503)
Provision (benefit) for income taxes	$ 876	$ 506	$ (512)