Debt - Long-Term Debt from Royalty-Bearing Instrument-December 2012 Financing - Additional Information (Detail) - USD ($)		12 Months Ended
	Dec. 06, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Line Items]
Gain (loss) on change in fair value of derivative liabilities			$ 8,170,000	$ (1,106,000)
Long-term debt from royalty-bearing instrument, carrying amount net of unamortized discount		$ 92,403,000	93,592,000
Interest expense, non-cash		2,332,000	7,783,000	$ 8,258,000
CPPIB
Debt Disclosure [Line Items]
Maximum repayment of future revenue and receivables		109,100,000
Repayment under agreement		16,500,000
Future minimum repayment under agreement		5,300,000
BioPharma Debt
Debt Disclosure [Line Items]
Amount received at the closing of the agreement	$ 100,000,000
Maximum repayment of future revenue and receivables	150,000,000
Royalty-Bearing Debt
Debt Disclosure [Line Items]
Fair value of embedded derivative liability	$ 14,600,000
Gain (loss) on change in fair value of derivative liabilities		0	5,500,000
Long-term debt from royalty-bearing instrument, carrying amount net of unamortized discount		92,400,000	93,600,000
Royalty-Bearing Debt | Cash
Debt Disclosure [Line Items]
Interest expense, contractual coupon interest		6,400,000	6,700,000
Royalty-Bearing Debt | Non Cash
Debt Disclosure [Line Items]
Interest expense, non-cash		$ 2,100,000	$ 2,100,000