Liability Related to Sale of Future Royalties, net - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended			2 Months Ended	3 Months Ended		8 Months Ended
	Mar. 31, 2021 USD ($)	Aug. 31, 2020 USD ($) unit_of_accounting	Jun. 30, 2018 USD ($) unit_of_accounting $ / shares shares	Feb. 29, 2020 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Liability For Sale of Future Royalties [Line Items]
Proceeds from sale of common stock	$ 229,500			$ 282,833	$ 308,743	$ 283,333
Current obligation to perform R&D services	41,059				41,059		$ 41,059	$ 846
Noncurrent obligation to perform R&D services	$ 60,530				$ 60,530		$ 60,530	$ 932
RPI Agreement
Liability For Sale of Future Royalties [Line Items]
Units of accounting related to consideration received | unit_of_accounting			2
Transaction consideration allocated to liability			$ 106,047
Transaction consideration allocated to equity			43,953
Transaction costs			377
2018 RPI Funding Agreement
Liability For Sale of Future Royalties [Line Items]
Proceeds from royalty agreement			$ 100,000
Effective interest rate (percent)	27.00%				27.00%		27.00%
RPI Purchase Agreement
Liability For Sale of Future Royalties [Line Items]
Common stock issued (shares) | shares			1,111,111
Common stock sold, price per share (in dollars per share) | $ / shares			$ 45.00
Proceeds from sale of common stock			$ 50,000
2020 RPI Funding Agreement
Liability For Sale of Future Royalties [Line Items]
Units of accounting related to consideration received | unit_of_accounting		2
Transaction consideration allocated to liability		$ 147,876
Transaction costs		400
Effective interest rate (percent)	6.00%				6.00%		6.00%
Sales-based participation rights sold, value		$ 250,000
Percentage of global net sales of products containing zavegepant for basis of participation rights		3.00%
Percentage of global net sales of products containing rimegepant for basis of participation rights		0.40%
Proceeds from sale of sales-based participation rights	$ 100,000	$ 150,000
Period from closing for repurchase if change of control consummated		180 days
Buy-Back option factor		2.0
Success-based milestone payments based on first zavegepant regulatory approval, relative to funded amount		1.9
Time period for success-based milestone payments		10 years
Proceeds allocated to obligation to perform contractual services	100,000	$ 2,124					$ 102,124
Current obligation to perform R&D services	40,417				$ 40,417		40,417
Noncurrent obligation to perform R&D services	$ 59,583				59,583		$ 59,583
Reduction in research and development expenses					$ (190)
2020 RPI Funding Agreement | Minimum
Liability For Sale of Future Royalties [Line Items]
Success-based milestone payments based on regulatory approval, relative to funded amount		0.6
2020 RPI Funding Agreement | Maximum
Liability For Sale of Future Royalties [Line Items]
Success-based milestone payments based on regulatory approval, relative to funded amount		2.95