Mandatorily Redeemable Preferred Shares, net - Narrative (Details)	1 Months Ended	3 Months Ended
	Apr. 30, 2019 USD ($) closing $ / shares shares	Mar. 31, 2020 USD ($) shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 shares
Mandatorily Redeemable Preferred Shares
Interest expense		$ 5,561,000	$ 0
Settlement of derivative liability		$ 42,821,000
Series A Preferred Shares
Mandatorily Redeemable Preferred Shares
Number of shares sold in transaction (in shares) | shares	2,495
Issuance price per share (in dollars per share) | $ / shares	$ 50,100
Gross proceeds from transaction	$ 125,000,000
Payment for priority review voucher	$ 105,000,000
Number of additional closings per share agreement, maximum | closing	3
Aggregate value of additional closings available per share agreement	$ 75,000,000
Maximum fee per share agreement for nonissuance of shares	3,000,000
Fee required per share agreement if all shares issued	$ 0
Redemption relative to original purchase price upon optional redemption	2
Annual interest rate upon default of redemption (percent)	18.00%
Effective interest rate (percent)		18.00%
Mandatorily redeemable shares issued (in shares) | shares		2,495		2,495
Mandatorily redeemable shares outstanding (in shares) | shares		2,495		2,495
Series A Preferred Shares | Change of control
Mandatorily Redeemable Preferred Shares
Redemption relative to original purchase price upon required redemption	2
Series A Preferred Shares | FDA approval of rimegepant
Mandatorily Redeemable Preferred Shares
Redemption relative to original purchase price upon required redemption	2