Related-Party Transactions - Additional Information (Detail) - USD ($)		1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 28, 2017	Jun. 30, 2018	Dec. 31, 2017	Feb. 28, 2017	May 31, 2016	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2017	May 09, 2016
Related Party Transaction [Line Items]
Non refundable upfront payments received					$ 85,000,000.0
Non refundable upfront payment received in equity investment, shares					3,333,333
Performance obligations satisfied (or partially satisfied) in previous periods						$ 1,825,000		$ 39,502,000
Transaction price											$ 78,000,000.0
Upfront payments received					$ 78,000,000.0
Non refundable upfront payments allocated for issuance of common stock					$ 7,000,000.0
Issuance of common stock, per share value					$ 2.10
Collaboration and license revenue from related party						5,027,000	$ 10,581,000	60,165,000	$ 26,081,000
Avacopan Agreement [Member]
Related Party Transaction [Line Items]
Non refundable upfront payments received					$ 85,000,000.0
Non refundable upfront payment received in cash					60,000,000.0
Non refundable upfront payment received in equity investment					$ 25,000,000.0
Share price of common stock in equity investment					$ 7.50
Non refundable upfront payment received in equity investment, shares					3,333,333
Performance obligations satisfied (or partially satisfied) in previous periods			$ 50,000,000.0
Transaction price						153,000,000.0		153,000,000.0
Collaboration and license revenue from related party						2,900,000	8,800,000	9,900,000	20,900,000
Avacopan Agreement [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Potential milestone payments receivable								460,000,000.0
Avacopan Amendment [Member]
Related Party Transaction [Line Items]
Non refundable upfront payments received				$ 20,000,000.0
Upfront cash commitment				$ 20,000,000.0
Avacopan Letter Agreement [Member]
Related Party Transaction [Line Items]
Non refundable payment for expanded rights	$ 5,000,000.0	$ 5,000,000.0
CCX140 Agreement [Member]
Related Party Transaction [Line Items]
Non refundable payment for expanded rights		5,000,000.0						5,000,000.0		$ 50,000,000.0
Performance obligations satisfied (or partially satisfied) in previous periods								2,000,000.0
Transaction price						66,500,000		66,500,000
Upfront payments received								50,000,000.0
Collaboration and license revenue from related party						2,100,000	$ 1,800,000	$ 50,200,000	$ 5,200,000
Non refundable upfront commitment		$ 11,500,000
Deferred Revenue, Recognized						46,700,000
Other current liabilities to related party						6,200,000
Development Funding, Reduction						$ 47,200,000
Vifor [Member]
Related Party Transaction [Line Items]
Purchase of Common stock, shares								9,194,085
Vifor [Member] | CCX140 Agreement [Member]
Related Party Transaction [Line Items]
Development funding								$ 11,500,000