Commitments and Contingencies - Additional Information (Details)						1 Months Ended				3 Months Ended				9 Months Ended
	Feb. 10, 2021	Sep. 04, 2020	Apr. 02, 2020	Apr. 09, 2019	Jan. 01, 2017 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Feb. 28, 2019 USD ($)	Jul. 31, 2016 USD ($) ft²	Sep. 30, 2021 USD ($) ft² extensionOption	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) ft² extensionOption	Sep. 30, 2020 USD ($)	Nov. 30, 2020 ft²	Apr. 30, 2018 ft²
Commitments And Contingencies [Line Items]
Operating lease, cost										$ 1,700,000			$ 1,700,000	$ 5,000,000	$ 5,000,000
Operating lease, payments										1,800,000			1,800,000	5,300,000	5,300,000
Increase (decrease) in purchase commitments										(6,000,000.0)				15,376,000	10,304,000
Charge to cost of goods sold											$ 30,300,000
Total remaining contract costs										7,600,000				7,600,000
Contract cost incurred in research and development activities														244,400,000
Supply Agreement, Patheon Inc.
Commitments And Contingencies [Line Items]
Minimum purchase commitment										4,200,000				4,200,000
BioVectra Inc
Commitments And Contingencies [Line Items]
Long-term minimum purchase commitment renewal term		1 year
Cost of purchased minimum quantity product										82,900,000				82,900,000
Siegfried Evionnaz SA
Commitments And Contingencies [Line Items]
Cost of purchased minimum quantity product										$ 27,700,000				$ 27,700,000
Purchase commitment, option to extend, prior notice period														12 months
Esteve Química, S.A
Commitments And Contingencies [Line Items]
Initial term of supply agreement				4 years
Long-term minimum purchase commitment														$ 34,400,000
STA Pharmaceutical Hong Kong Limited
Commitments And Contingencies [Line Items]
Long-term minimum purchase commitment														$ 44,800,000
Minimum purchase commitment, initial term			4 years
WuXi STA
Commitments And Contingencies [Line Items]
Purchase commitment, option to extend, prior notice period	18 months
Minimum purchase commitment, initial term	4 years
Long-term purchase commitment, fixed price, period	12 months
Long-term purchase commitment, option to terminate, prior notice period (at least)	180 days
Minimum
Commitments And Contingencies [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term										6.22%				6.22%
Operating lease, remaining lease term										1 year 4 months 28 days				1 year 4 months 28 days
Maximum
Commitments And Contingencies [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term										6.94%				6.94%
Operating lease, remaining lease term										4 years 11 months 12 days				4 years 11 months 12 days
Keryx Biopharmaceuticals, Inc.
Commitments And Contingencies [Line Items]
Preliminary fair value of the off-market element							$ 55,800,000			$ 71,200,000				$ 71,200,000
Increase (decrease) in purchase commitments												$ (9,000,000)
Cambridge
Commitments And Contingencies [Line Items]
Area of property leased (in square feet) | ft²									45,362							65,167
Annual lease expense									$ 242,000
Monthly lease expense					$ 22,000
Cambridge | Letter of Credit | Other Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease										$ 1,600,000				$ 1,600,000
Cambridge | Office Space
Commitments And Contingencies [Line Items]
Area of property leased (in square feet) | ft²																	19,805
Monthly lease expense								$ 135,000
Operating lease, free monthly rent, period							2 months
Lease period, number of extension options | extensionOption										1				1
Lease extension period										5 years				5 years
Cambridge | Office Space | Scenario Forecast
Commitments And Contingencies [Line Items]
Monthly lease expense						$ 48,000
Boston | Keryx Biopharmaceuticals, Inc. | Letter of Credit | Other Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease										$ 400,000				$ 400,000
Boston | Office Space
Commitments And Contingencies [Line Items]
Area of property leased (in square feet) | ft²										27,300				27,300
Monthly lease expense														$ 136,000
Boston | Office Space | Keryx Biopharmaceuticals, Inc.
Commitments And Contingencies [Line Items]
Lease period, number of extension options | extensionOption										1				1
Lease extension period										5 years				5 years
Sublease rental income										$ 400,000			$ 400,000	$ 1,300,000	$ 1,300,000