Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands				1 Months Ended										3 Months Ended	12 Months Ended
	Aug. 31, 2019 USD ($) $ / shares	Jul. 29, 2019 USD ($) $ / shares shares	Jul. 23, 2018 USD ($) shares	Dec. 31, 2020 $ / shares shares	Oct. 31, 2020 shares	Jun. 30, 2020 shares	Dec. 31, 2019 $ / shares shares	Aug. 31, 2019 USD ($) $ / shares shares	May 31, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 $ / shares shares	Jul. 31, 2018 $ / shares shares	May 31, 2018 shares	Jun. 30, 2020 shares	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Apr. 04, 2019 USD ($)	Mar. 20, 2019 $ / shares
Sale Of Stock [Line Items]
Common stock, shares authorized				100,000,000			100,000,000								100,000,000	100,000,000
Common stock, par value | $ / shares				$ 0.001			$ 0.001								$ 0.001	$ 0.001
Preferred stock, shares authorized				5,000,000			5,000,000								5,000,000	5,000,000
Preferred stock, par value | $ / shares				$ 0.001			$ 0.001								$ 0.001	$ 0.001
Common stock, shares outstanding				49,872,213			46,720,225								49,872,213	46,720,225
Common stock, shares issued				49,872,213			46,720,225								49,872,213	46,720,225
Preferred stock, shares issued				0			0								0	0
Preferred Stock Shares Outstanding				0			0								0	0
Number of votes for each share of common stock | item															1
Restricted stock units vested shares											83,791
Unregistered common stock exchanged for consulting services | $																$ 197
2014 Equity Incentive Plan [Member] | Director [Member]
Sale Of Stock [Line Items]
Vesting period of awards granted															3 years
2014 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | Executive Officers [Member]
Sale Of Stock [Line Items]
Common stock, shares issued							36,666		74,166							36,666
2014 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | Executive Officers [Member] | February 2020 [Member]
Sale Of Stock [Line Items]
Restricted stock units, vested				36,750
Shareholder Consulting Agreement [Member]
Sale Of Stock [Line Items]
Number of shares of unregistered common stock exchanged for consulting services										10,195
Price per share | $ / shares																			$ 19.37
Consulting services performance period										6 months
Vifor International Ltd. [Member]
Sale Of Stock [Line Items]
Common stock, shares issued													1,174,827
General and Administrative [Member] | Restricted Stock Units [Member] | Director [Member]
Sale Of Stock [Line Items]
Compensation expense | $															$ 528	$ 287
General and Administrative [Member] | Restricted Stock Units [Member] | Executive Officers [Member]
Sale Of Stock [Line Items]
Compensation expense | $															$ 1,167	1,180	$ 1,217
General and Administrative [Member] | Shareholder Consulting Agreement [Member]
Sale Of Stock [Line Items]
Compensation expense | $																$ 197
Non-Exclusive License Agreement
Sale Of Stock [Line Items]
Upfront fee | $	$ 8,000							$ 8,000
Upfront fee payable, cash | $	4,000							4,000
Upfront fee payable, stock | $	$ 4,000							$ 4,000
Price per share | $ / shares	$ 23.42							$ 23.42
Share price average, Determination period								30 days
Percentage of payment, stock	50.00%
Exclusive License Agreement [Member] | Vifor International Ltd. [Member]
Sale Of Stock [Line Items]
Common stock, shares issued					2,939,552										2,939,552
Maximum [Member]
Sale Of Stock [Line Items]
Aggregate offering price of securities | $																		$ 300,000
Follow-on Public Offering [Member]
Sale Of Stock [Line Items]
Price per share | $ / shares							$ 23.00				$ 19.00					$ 23.00	$ 19.00
Common Stock [Member]
Sale Of Stock [Line Items]
Common stock, shares issued																6,325,000	5,175,000
Restricted stock units vested shares							36,666								156,584	110,832	83,791
Number of shares of unregistered common stock exchanged for consulting services																10,195
Common Stock [Member] | Director [Member]
Sale Of Stock [Line Items]
Vesting period of awards granted						1 year
Restricted stock units vested shares						24,000
Common Stock [Member] | Executive Officers [Member]
Sale Of Stock [Line Items]
Restricted stock units vested shares									74,166					95,834
Common Stock [Member] | Non-Exclusive License Agreement
Sale Of Stock [Line Items]
Common stock, shares issued								170,793
Upfront fee payable, stock | $	$ 4,000							$ 4,000
Common Stock [Member] | Follow-on Public Offering [Member]
Sale Of Stock [Line Items]
Common stock, shares issued		6,325,000
Common stock, shares issued												5,175,000
Price per share | $ / shares		$ 23.00										$ 19.00
Proceeds from issuance of common stock net of underwriting discounts, commissions and estimated offering expenses | $		$ 136,498
Proceeds from issuance of common stock net of underwriting discounts and offering costs | $			$ 92,063
Common Stock [Member] | Underwriter's Over-Allotment [Member]
Sale Of Stock [Line Items]
Common stock, shares issued		825,000	675,000
Underwriting discounts, commission and offering expenses | $		$ 8,977	$ 6,262