Nature of Organization and Operations - Additional Information (Details)		1 Months Ended			3 Months Ended	6 Months Ended	18 Months Ended
	Dec. 11, 2015 USD ($)	May 31, 2016 USD ($)	Jan. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Jun. 30, 2016 USD ($) shares	Jun. 30, 2016 USD ($) Patient	Jun. 30, 2016 USD ($) Underwritten_offering
Nature Of Organization And Operations [Line Items]
Cash and cash equivalents and available for sale securities				$ 138,454,000	$ 188,649,000	$ 188,649,000	$ 188,649,000
Cash and cash equivalents					188,600,000	188,600,000	188,600,000
Current accounts payable and accrued expenses					$ 20,900,000	$ 20,900,000	20,900,000
Cantor Fitzgerald & Co
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares					0
IPO
Nature Of Organization And Operations [Line Items]
Proceeds from issuance of initial public offering							$ 187,400,000
Number of underwritten public offerings | Underwritten_offering							3
Follow-on public offering
Nature Of Organization And Operations [Line Items]
Proceeds from issuance of initial public offering			$ 61,000,000
Sale of stock, price per share | $ / shares			$ 9.00
Follow-on public offering | Common Stock
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares			7,250,000
Minimum
Nature Of Organization And Operations [Line Items]
Expected to incur substantial losses (in years)						4 years
Maximum
Nature Of Organization And Operations [Line Items]
Expected to incur substantial losses (in years)						5 years
Maximum | Cantor Fitzgerald & Co
Nature Of Organization And Operations [Line Items]
Common stock sales agreement amount		$ 75,000,000
Phase 3 vadadustat program | Minimum
Nature Of Organization And Operations [Line Items]
Cost of program per patient						$ 80,000
Phase 3 vadadustat program | Maximum
Nature Of Organization And Operations [Line Items]
Cost of program per patient						$ 85,000
PRO2TECT
Nature Of Organization And Operations [Line Items]
Number of patients | Patient						3,100
INNO2VATE
Nature Of Organization And Operations [Line Items]
Number of patients | Patient						2,600
Development and Commercialize Collaboration Agreement
Nature Of Organization And Operations [Line Items]
Collaborative arrangement right description						In December 2015, the Company entered into a collaboration agreement with Mitsubishi Tanabe to develop and commercialize vadadustat in Japan and certain other countries in Asia for total milestone payments of up to $350.0 million, including up to $100.0 million in upfront and development payments, of which $40.0 million was received in January 2016. If Japanese patients are not included in either the global Phase 3 PRO2TECT or INNO2VATE programs, $20.0 million of the $40.0 million received would be used to fund further local development of vadadustat in Japan or be refunded to Mitsubishi. In addition, the Company will receive tiered double-digit royalty payments on sales of vadadustat.
Development and Commercialize Collaboration Agreement | Upfront
Nature Of Organization And Operations [Line Items]
Milestone revenue			$ 40,000,000
Milestone revenue refundable			$ 20,000,000
Development and Commercialize Collaboration Agreement | Maximum
Nature Of Organization And Operations [Line Items]
Milestone revenue				350,000,000
Development and Commercialize Collaboration Agreement | Maximum | Upfront
Nature Of Organization And Operations [Line Items]
Milestone revenue	$ 100,000,000			$ 100,000,000