Strategic Alliances (Details) - USD ($)			1 Months Ended				12 Months Ended			27 Months Ended	60 Months Ended
	Oct. 21, 2019	Oct. 12, 2017	Jul. 31, 2018	May 31, 2016	Jan. 31, 2015	Dec. 31, 2010	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2019	Mar. 31, 2013
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Initial upfront payment		$ 6,000,000
Milestone revenue recognized										$ 0
Contract liability							$ 21,800,000	$ 91,100,000		21,800,000	$ 21,800,000
Deferred revenue, current							19,196,000	63,503,000		19,196,000	19,196,000
Deferred revenue, noncurrent							2,571,000	27,566,000		2,571,000	2,571,000
Vifor Fresenius Medical Care Pharma Ltd | Exclusive Option
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments, maximum				$ 555,000,000
Vifor Fresenius Medical Care Pharma Ltd | Launch and Sales-based Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments, maximum				195,000,000
Vifor Fresenius Medical Care Pharma Ltd | Regulatory Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payment			$ 2,000,000.0
Milestone payments, maximum				35,000,000
Vifor Fresenius Medical Care Pharma Ltd | Development and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from license fees received				$ 50,000,000
Pfizer | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue recognized											0
Milestone payments, maximum					$ 275,000,000.0
Non-refundable upfront payment					295,000,000.0		295,000,000.0
Additional milestone payment to be received					275,000,000.0
Contract liability							16,300,000			$ 16,300,000	$ 16,300,000
Tesaro
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments, maximum						$ 85,000,000.0
Milestone payment ranges						30,000,000.0
Upfront payment under license agreements						$ 6,000,000.0
Maximum period to receive royalties						12 years
Tesaro | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue recognized							$ 0	$ 0	$ 10,000,000.0
Pharmsynthez
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Ownership percentage							9.00%			9.00%	9.00%
RXi Pharmaceuticals Corporation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments												$ 50,000,000.0
Minimum | Pfizer | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment ranges					20,000,000.0
Maximum | Pfizer | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment ranges					$ 90,000,000.0
Phase Two Initiation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payments		6,000,000
Regulatory and Development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payments		31,000,000
Sales Revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payments		$ 75,000,000
Product | Pfizer
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual height velocity at point in time	12 months