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Collaboration and Other Agreements - Provention (Details)		3 Months Ended			6 Months Ended
	May 31, 2018 USD ($) performance_obligation $ / shares shares	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Collaboration And Other Agreements [Line Items]
Revenues		$ 10,593,000		$ 18,834,000	$ 20,255,000	$ 23,529,000
Fair Value		91,820,000			91,820,000
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
Common stock warrants
Collaboration And Other Agreements [Line Items]
Increase in valuation		19,600,000			20,500,000
Fair Value Measurements, Recurring Basis | Common stock warrants
Collaboration And Other Agreements [Line Items]
Fair Value		$ 22,356,000			$ 22,356,000		$ 1,890,000

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