Nature of Organization and Operations - Additional Information (Details)			1 Months Ended			12 Months Ended
	Mar. 25, 2014 USD ($) $ / shares shares	Mar. 06, 2014	Jan. 31, 2016 USD ($) $ / shares shares	Aug. 31, 2015 USD ($)	Apr. 30, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) Patient shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 shares
Nature Of Organization And Operations [Line Items]
Convertible redeemable preferred stock converted into common stock | shares	12,115,183						0
Common stock, shares authorized | shares	175,000,000					175,000,000	175,000,000
Preferred stock, shares authorized | shares	25,000,000					25,000,000	25,000,000
Cash and cash equivalents and available for sale securities						$ 138,454,000	$ 108,918,000
Stock split, conversion ratio		1.75
Entity incorporation date						Feb. 27, 2007
Cantor Fitzgerald & Co
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares						1,719,434
Proceeds from sale of common stock, net of commissions						$ 18,400,000
Issuance of additional common stock, shares | shares						0
IPO
Nature Of Organization And Operations [Line Items]
Sale of stock, price per share | $ / shares	$ 17.00
Proceeds from issuance of initial public offering	$ 104,400,000
Convertible redeemable preferred stock converted into common stock | shares	12,115,183
Follow-on public offering
Nature Of Organization And Operations [Line Items]
Sale of stock, price per share | $ / shares					$ 8.25
Proceeds from issuance of initial public offering					$ 64,600,000
Follow-on public offering | Subsequent Event
Nature Of Organization And Operations [Line Items]
Sale of stock, price per share | $ / shares			$ 9.00
Proceeds from issuance of initial public offering			$ 61,000,000
Common Stock
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares						10,083,070	6,762,000	176,717
Common Stock | IPO
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares	6,762,000
Common Stock | Overallotment option granted to underwriters
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares	879,647				1,090,909
Common Stock | Follow-on public offering
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares					8,363,636
Common Stock | Follow-on public offering | Subsequent Event
Nature Of Organization And Operations [Line Items]
Issuance of common stock, shares | shares			7,250,000
Maximum | Cantor Fitzgerald & Co
Nature Of Organization And Operations [Line Items]
Common stock sales agreement amount				$ 50,000,000
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, we 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 million, including up to $100 million in upfront and development payments, of which $40.0 million was received in January 2016. Of the $40.0 million received, $20.0 million is subject to refund to Mitsubishi depending on the outcome of discussions with the Japanese regulator about the global trial design. In addition, we will receive tiered double-digit royalty payments on sales of vadadustat.
Development and Commercialize Collaboration Agreement | Subsequent Event | 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