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Collaboration and Other Agreements - Provention (Details)		3 Months Ended		9 Months Ended
	May 31, 2018 USD ($) performance_obligation $ / shares shares	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Collaboration And Other Agreements [Line Items]
Revenues		$ 18,741,000	$ 20,798,000	$ 38,996,000	$ 44,327,000
Fair Value		$ 86,276,000		86,276,000
Provention
Collaboration And Other Agreements [Line Items]
Number of performance obligations | performance_obligation	2
Collaborative agreement transaction price	$ 6,100,000
Number of shares available under warrants (in shares) | shares	2,432,688
License Agreement | Provention | Provention PRV-3279
Collaboration And Other Agreements [Line Items]
Warrant to purchase shares of common stock, exercise price (in dollars per share) | $ / shares	$ 2.50
Potential development and regulatory milestone payments under agreement	$ 65,000,000.0
Potential commercial milestone payments under agreement	$ 225,000,000.0
Asset Purchase Agreement | Provention | Provention PRV-031
Collaboration And Other Agreements [Line Items]
Warrant to purchase shares of common stock, exercise price (in dollars per share) | $ / shares	$ 2.50
Potential development and regulatory milestone payments under agreement	$ 170,000,000.0
Potential commercial milestone payments under agreement	225,000,000.0
Potential milestone payments to third parties	$ 1,300,000
Revenues From License Agreements | Provention
Collaboration And Other Agreements [Line Items]
Revenues			$ 6,100,000
Warrant
Collaboration And Other Agreements [Line Items]
Increase in valuation				$ 20,500,000
Fair Value Measurements, Recurring Basis | Warrant
Collaboration And Other Agreements [Line Items]
Fair Value						$ 1,890,000

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