Nature of Organization and Operations - Additional Information (Details)	1 Months Ended				12 Months Ended
	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) Patient shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares
Nature Of Organization And Operations [Line Items]
Proceeds from sale of stock					$ 373,100,000
Proceeds from issuance of public offering					114,580,000	$ 66,623,000	$ 82,750,000
Cash and cash equivalents and available for sale securities			$ 260,343,000		$ 317,792,000	$ 260,343,000
Number of months for operating plan sufficiently funded by cash resources					12 months
Otsuka Pharmaceutical Co. Ltd. and Mitsubishi Tanabe Pharma Corporation
Nature Of Organization And Operations [Line Items]
Minimum committed amount in cost share funding and license payments under collaboration agreements					$ 573,000,000
Amount received from cost-share funding and license payments					$ 272,000,000
Common Stock
Nature Of Organization And Operations [Line Items]
Issuance of common stock, net of issuance costs, shares | shares					8,672,270	7,865,293	10,083,070
Common Stock | Vifor Pharma
Nature Of Organization And Operations [Line Items]
Issuance of common stock, net of issuance costs, shares | shares					3,571,429
Follow-on public offering
Nature Of Organization And Operations [Line Items]
Proceeds from issuance of public offering					$ 292,600,000
Follow-on public offering | Cantor Fitzgerald & Co
Nature Of Organization And Operations [Line Items]
Proceeds from issuance of public offering					$ 30,500,000
Pro Two Tech And Inno Two Vate
Nature Of Organization And Operations [Line Items]
Number of patients | Patient					6,900
License Agreement | Vifor Pharma
Nature Of Organization And Operations [Line Items]
Proceeds from sale of stock					$ 50,000,000
Development and Commercialize Collaboration Agreement | Mitsubishi Tanabe Pharma Corporation
Nature Of Organization And Operations [Line Items]
Collaborative arrangement right description					In December 2015, the Company entered into a collaboration agreement with MTPC to develop and commercialize vadadustat in Japan and certain other countries in Asia, collectively, the MTPC Territory, for total payments of up to $245.0 million, comprised of a $20.0 million upfront payment, up to $50.0 million in specified development and regulatory milestones, and up to $175.0 million in specified commercial milestones, as well as tiered double-digit royalty payments up to 20% on sales of vadadustat in the MTPC Territory (Note 3).
Upfront cash payment received					$ 0	$ 40,000,000
Development and Commercialize Collaboration Agreement | Mitsubishi Tanabe Pharma Corporation | Maximum
Nature Of Organization And Operations [Line Items]
Milestone revenue				$ 245,000,000	265,000,000
Additional milestone payments development costs fund				$ 50,000,000
Royalty payment percentage				20.00%			20.00%
Development and Commercialize Collaboration Agreement | Mitsubishi Tanabe Pharma Corporation | Upfront
Nature Of Organization And Operations [Line Items]
Upfront cash payment received				$ 20,000,000	20,000,000
Development and Commercialize Collaboration Agreement | Mitsubishi Tanabe Pharma Corporation | Commercial Milestone Payments
Nature Of Organization And Operations [Line Items]
Milestone revenue				$ 175,000,000
Development and Commercialize Collaboration Agreement | Mitsubishi Tanabe Pharma Corporation | Commercial Milestone Payments | Maximum
Nature Of Organization And Operations [Line Items]
Milestone revenue					$ 175,000,000
Development and Commercialize Collaboration and License Agreement | Otsuka Pharmaceutical Company. Ltd. | Global Development Plan
Nature Of Organization And Operations [Line Items]
Reimbursement for Otsuka's share of costs previously incurred	$ 200,000	$ 33,800,000
Development and Commercialize Collaboration and License Agreement | Otsuka Pharmaceutical Company. Ltd. | Minimum | Global Development Plan
Nature Of Organization And Operations [Line Items]
Collaborative arrangements cost sharing payments	163,600,000		153,600,000
Development and Commercialize Collaboration and License Agreement | Otsuka Pharmaceutical Company. Ltd. | Upfront
Nature Of Organization And Operations [Line Items]
Upfront cash payment received	73,000,000		125,000,000
Development and Commercialize Collaboration and License Agreement | Otsuka Pharmaceutical Company. Ltd. | Commercial Milestone Payments | Maximum
Nature Of Organization And Operations [Line Items]
Milestone revenue	525,000,000		575,000,000
Development and Commercialize Collaboration and License Agreement | Otsuka Pharmaceutical Company. Ltd. | Potential Development and Commercialization Milestones | Maximum
Nature Of Organization And Operations [Line Items]
Milestone revenue	$ 132,000,000		$ 190,000,000