Nature of the Business and Basis of Presentation (Details) - USD ($)		1 Months Ended			2 Months Ended	9 Months Ended
	Aug. 10, 2020	Sep. 30, 2020	Feb. 29, 2020	Jan. 31, 2020	Feb. 29, 2020	Sep. 30, 2020	Sep. 30, 2019	Aug. 31, 2020
Nature of business [Line Items]
Proceeds from issuance of common shares					$ 282,833,000	$ 283,333,000	$ 303,221,000
Other offering expenses						$ 2,300,000	$ 1,150,000
Sixth Street Financing Agreement | Senior secured debt
Nature of business [Line Items]
Credit agreement term	5 years
Credit facility capacity								$ 500,000,000
2020 RPI Funding Agreement
Nature of business [Line Items]
Sales-based participation rights sold, value								$ 250,000,000
Public Offering
Nature of business [Line Items]
Common stock issued (shares)				4,830,917
Issuance price per share (in dollars per share)				$ 51.75
Proceeds from issuance of common shares				$ 245,877,000
Underwriting discounts and commissions				3,623,000
Other offering expenses				$ 500,000
Over-Allotment Option
Nature of business [Line Items]
Common stock issued (shares)			724,637
Proceeds from issuance of common shares			$ 36,956,000
Underwriting discounts and commissions			$ 543,000
RPI Preferred Share Purchase Agreement | Series B preferred shares
Nature of business [Line Items]
Consideration on sale of shares receivable in installments	$ 200,000,000
BioShin Preferred Shares | Series A preferred shares
Nature of business [Line Items]
Proceeds from shares issued		$ 60,000,000