Long-term Debt - Additional Information (Detail)	1 Months Ended		3 Months Ended
	Jul. 31, 2015 USD ($) Tranche	Jun. 30, 2014 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Convertible Note Warrant
Debt Instrument [Line Items]
Proceeds from issuance of warrants		$ 27,600,000
PDL BioPharma
Debt Instrument [Line Items]
Proceeds from collaborators	$ 50,000,000		$ 2,300,000
Future maximum royalty payments, current year	20,000,000
Future maximum royalty payments, year two	20,000,000
Future maximum royalty payments, year three	$ 20,000,000
Percentage of royalty rate payable on net sales, current	2.50%
Percentage of royalty rate payable on net sales, year two	5.00%
Percentage of royalty rate payable on net sales, year three	5.00%
Percentage of royalty rate payable on net sales, year four	6.50%
Internal rate of return (as percent)			10.00%
Interest expense, debt			$ 900,000
PDL BioPharma | Put And Call Options
Debt Instrument [Line Items]
Internal rate of return (as percent)	10.00%
PDL BioPharma | Put And Call Options | Period 1
Debt Instrument [Line Items]
Option exercise price as percentage of paid amount (as percent)			115.00%
PDL BioPharma | Put And Call Options | Period 2
Debt Instrument [Line Items]
Option exercise price as percentage of paid amount (as percent)			120.00%
PDL BioPharma | Put And Call Options | There After
Debt Instrument [Line Items]
Option exercise price as percentage of paid amount (as percent)			130.00%
PDL BioPharma | Maximum
Debt Instrument [Line Items]
Royalty guarantees, commitments, amount	$ 150,000,000
PDL BioPharma | Scenario 1
Debt Instrument [Line Items]
Contract amount	$ 50,000,000
Period to receive additional payment	1 year
PDL BioPharma | Scenario 2
Debt Instrument [Line Items]
Contract amount	$ 100,000,000
PDL BioPharma | Scenario 2 | Minimum
Debt Instrument [Line Items]
Period to receive additional payment	6 months
Number of tranches | Tranche	1
PDL BioPharma | Scenario 2 | Maximum
Debt Instrument [Line Items]
Period to receive additional payment	12 months
Number of tranches | Tranche	2
PDL BioPharma | Scenario 3 | Maximum
Debt Instrument [Line Items]
Maximum royalty payment rate (as a percent)	7.50%
Convertible notes
Debt Instrument [Line Items]
Amount of debt issued		$ 200,000,000.0	$ 200,000,000		$ 200,000,000
Debt instrument, interest rate (as percent)		3.625%
Proceeds from issuance of debt		$ 192,900,000
Debt instrument, fee amount		6,000,000
Expenses from debt issuance		$ 1,100,000
Debt instrument, term		5 years
Interest expense, debt			$ 4,009,000	$ 3,856,000
Convertible notes | Convertible note hedge
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 43,200,000
Convertible notes | Liability Component
Debt Instrument [Line Items]
Effective interest rate (as percent)			9.625%