Commitments and Contingencies - Additional Information (Details)				1 Months Ended					3 Months Ended		6 Months Ended
	Apr. 02, 2020	Apr. 09, 2019	Jan. 01, 2017 USD ($)	Aug. 06, 2020 USD ($)	Sep. 30, 2019	Feb. 28, 2019 USD ($)	Apr. 30, 2018 ft²	Jul. 31, 2016 USD ($) ft²	Jun. 30, 2020 USD ($) ft² extensionOption	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft² extensionOption	Jun. 30, 2019 USD ($)	Aug. 10, 2020 USD ($)	Dec. 12, 2018 USD ($)
Commitments And Contingencies [Line Items]
Lessee, operating lease, residual value guarantee, description											The lease agreements do not contain residual value guarantees.
Lessee, operating lease, residual value guarantee											false
Operating lease, cost									$ 1,600,000	$ 1,600,000	$ 3,300,000	$ 3,300,000
Operating lease, payments									1,800,000	$ 1,700,000	3,500,000	3,400,000
Increase in excess inventory purchase commitments											$ 10,954,000	$ 0
Supply agreement description											The Esteve Agreement has an initial term of four years, beginning April 9, 2019 and ending April 9, 2023
Total remaining contract costs									23,200,000		$ 23,200,000
Contract cost incurred in research and development activities											68,100,000
Supply Agreement, Patheon Inc.
Commitments And Contingencies [Line Items]
Minimum purchase commitment									400,000		$ 400,000
Subsequent Event | Supply Agreement, Patheon Inc.
Commitments And Contingencies [Line Items]
Minimum purchase commitment				$ 1,300,000
BioVectra Inc
Commitments And Contingencies [Line Items]
Agreement expiration year											2026
Description of termination of agreement prior to contract term											The Company may terminate the BioVectra Agreement prior to the expiration of the contract term, which could result in early termination fee.
Cost of purchased minimum quantity product									127,000,000.0		$ 127,000,000.0
Preliminary fair value of the off-market element														$ 29,500,000
Increase in excess inventory purchase commitments									11,000,000.0
Inventory purchase commitments									41,500,000		41,500,000
Accretion expense											1,000,000.0
Siegfried Evionnaz SA
Commitments And Contingencies [Line Items]
Cost of purchased minimum quantity product									51,800,000		$ 51,800,000
Agreement expiration date											Dec. 31, 2021
Agreement renewal term termination											1 year
Agreement early termination											Dec. 31, 2021
Esteve Química, S.A
Commitments And Contingencies [Line Items]
Initial term of supply agreement		4 years
Minimum supply commitment									$ 13,600,000		$ 13,600,000
Esteve Química, S.A | Subsequent Event
Commitments And Contingencies [Line Items]
Minimum supply commitment													$ 23,900,000
STA Pharmaceutical Hong Kong Limited
Commitments And Contingencies [Line Items]
Minimum purchase commitment, initial term	4 years
Minimum purchase commitment through fourth quarter of 2021											$ 0
STA Pharmaceutical Hong Kong Limited | Subsequent Event
Commitments And Contingencies [Line Items]
Minimum purchase commitment through fourth quarter of 2021				$ 44,700,000
Minimum
Commitments And Contingencies [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term									5.91%		5.91%
Operating lease, remaining lease term									1 year 5 months 1 day		1 year 5 months 1 day
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									6 years 2 months 12 days		6 years 2 months 12 days
Keryx Biopharmaceuticals, Inc.
Commitments And Contingencies [Line Items]
Preliminary fair value of the off-market element														$ 29,510,000
Cambridge
Commitments And Contingencies [Line Items]
Area of property leased (in square feet) | ft²							65,167	45,362
Annual lease expense								$ 242,000
Monthly lease expense			$ 22,000
Operating lease payments commencement date			Jan. 01, 2017
Cambridge | Letter of Credit | Other current 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 payments commencement date							Feb. 28, 2019
Leased property delivered, date							2018-09
Leased property subject to annual rent escalations, commencement date							2019-09
Lease expiration date											Sep. 11, 2026
Lease period, number of extension options | extensionOption									1		1
Lease extension period									5 years		5 years
Cambridge | Lab Space
Commitments And Contingencies [Line Items]
Lease expiration date											Nov. 30, 2021
Lease period, number of extension options | extensionOption									1		1
Lease extension period									2 years		2 years
Boston | Keryx Biopharmaceuticals, Inc. | Letter of Credit | Other current assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease									$ 800,000		$ 800,000
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
Lease expiration month year											2023-02
Boston | Office Space | Keryx Biopharmaceuticals, Inc.
Commitments And Contingencies [Line Items]
Lease expiration date											Feb. 28, 2023
Lease period, number of extension options | extensionOption									1		1
Lease extension period									5 years		5 years
Operating sublease commencement date					Oct. 16, 2019
Sublease expiration date					Feb. 28, 2023
Sublease rental income									$ 500,000		$ 900,000