Revenue - Development and Collaboration Agreement (Details)	1 Months Ended			3 Months Ended								9 Months Ended	12 Months Ended
	Apr. 30, 2018 USD ($) plan	Feb. 28, 2018	Jan. 31, 2015	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Development and Collaboration Agreement
Total revenue				$ 18,730,000	$ 18,257,000	$ 15,008,000	$ 19,862,000	$ 29,499,000	$ 12,427,000	$ 26,150,000	$ 5,338,000		$ 71,857,000	$ 73,414,000	$ 60,370,000
Percentage of profit share		33.00%											35.00%
Alfasigma
Development and Collaboration Agreement
Deferred revenue				200,000									$ 200,000
Performance period (in years)													6 years
Number of performance obligations | plan	5
Viatris
Development and Collaboration Agreement
Transaction price				34,200,000									$ 34,200,000
Deferred revenue				$ 300,000									$ 300,000
Performance period (in years)			17 years										11 years
Percentage of profit share													65.00%
Number of performance obligations													2
Pfizer
Development and Collaboration Agreement
Number of performance obligations													2
Operating expenses
Development and Collaboration Agreement
Percentage of profit share												35.00%
Development and Collaboration Agreement | Alfasigma
Development and Collaboration Agreement
Collaboration transaction price	$ 11,000,000.0
Option exercise fee	10,000,000.0
Non-refundable reimbursement fee	$ 1,000,000.0
Maximum potential payments receivable															26,800,000
Development and Commercialization Agreement | Alfasigma
Development and Collaboration Agreement
Total revenue														$ 100,000	$ 10,700,000