License, Collaboration and Other Significant Agreements - International Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. Narrative (Details)		3 Months Ended	12 Months Ended			57 Months Ended
	Apr. 25, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2021 USD ($) performance_obligation	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues			$ 213,578,000	$ 295,307,000	$ 335,001,000
Deferred revenue			42,380,000			$ 42,380,000
Short-term deferred revenue			20,906,000	15,214,000		20,906,000
Deferred revenue, net of current portion			21,474,000	25,345,000		21,474,000
Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue			3,171,000	7,227,000	0	3,171,000
Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			4,309,000	1,722,000	0	4,309,000
Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			19,094,000	3,045,000	15,822,000	19,094,000
License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues			$ 71,362,000	166,406,000	223,882,000
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Estimate subsequent cost share payment receivable						244,600,000
Milestone or royalty payments received	$ 0
Collaboration agreement, notice period for termination			12 months
Number of performance obligations | performance_obligation			3
Transaction price			$ 317,700,000
Reimbursement for Otsuka's share of costs previously incurred			200,000
Deferred revenue			9,860,000			9,860,000
Short-term deferred revenue			5,467,000			5,467,000
Deferred revenue, net of current portion			4,393,000			4,393,000
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue			900,000			900,000
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			1,300,000			1,300,000
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable				0
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues			$ 16,449,000	$ 45,451,000	$ 75,614,000
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Maximum | Licensed HIF Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Eligible milestone payments, period			24 months
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Minimum | Licensed HIF Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Eligible milestone payments, period			12 months
Otsuka Pharmaceutical Co. Ltd. | Otsuka International Agreement | Global Development Plan
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reimbursement for Otsuka's share of costs previously incurred		$ 200,000
Otsuka Pharmaceutical Co. Ltd. | Up-front, Non-refundable and Non-creditable | Otsuka International Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment received			$ 73,000,000			73,000,000
Otsuka Pharmaceutical Co. Ltd. | Regulatory Milestone Payments | Otsuka International Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential developmental milestone revenue			17,000,000			$ 17,000,000
Otsuka Pharmaceutical Co. Ltd. | Commercial Milestone Payments | Otsuka International Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone revenue (up to)			$ 525,000,000