Net Loss per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 15, 2020	Jun. 30, 2020	Apr. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Follow-on Public Offering [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Purchase common stock per share amount				$ 23.00		$ 23.00
Purchase of common stock value				$ 136,525
Restricted Stock Units [Member] | Executive Officers [Member] | Share-based Payment Arrangement, Employee [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive unvested restricted stock units outstanding					236,000
Restricted Stock Units [Member] | 2014 Equity Incentive Plan [Member] | Executive Officers [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive unvested restricted stock units outstanding					0
Common stock, shares issued		30,000	65,834
Restricted Stock Units [Member] | 2014 Equity Incentive Plan [Member] | Director [Member] | Share-based Payment Arrangement, Nonemployee [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, approved and granted					36,000
Employee Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents					5,265,642	4,575,454
Exclusive License Agreement [Member] | Vifor International Ltd. [Member] | Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued	2,939,552
Purchase common stock per share amount	$ 17.0094
Purchase of common stock value	$ 50,000