Quarterly Results of Operations (Unaudited) - Schedule of Selected Financial Data for Each Quarter (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended								12 Months Ended
	Oct. 31, 2020	May 31, 2018	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues			$ 112,089	$ 9,266	$ 5,634	$ 8,093	$ 4,511	$ 5,785	$ 5,208	$ 4,382	$ 135,082	$ 19,886	$ 13,469
Operating expenses			33,799	26,286	31,518	38,094	34,481	40,218	29,350	27,516	129,697	131,565	90,851
Net income (loss) - Basic and Diluted			$ 78,909	$ (16,509)	$ (25,068)	$ (28,922)	$ (28,611)	$ (32,842)	$ (22,960)	$ (21,960)	$ 8,410	$ (106,373)	$ (74,013)
Basic			$ 1.60	$ (0.35)	$ (0.54)	$ (0.62)					$ 0.18	$ (2.49)	$ (2.06)
Diluted			$ 1.59	$ (0.35)	$ (0.54)	$ (0.62)					0.18	$ (2.49)	$ (2.06)
Basic - sum measured on a quarterly basis											0.09
Diluted- sum measured on a quarterly basis											$ 0.08
Loss per share - Basic and Diluted							$ (0.61)	$ (0.74)	$ (0.58)	$ (0.56)
Vifor International Ltd. [Member]
Stock Issued During Period Shares New Issues		1,174,827
Exclusive License Agreement [Member] | Vifor International Ltd. [Member]
Stock Issued During Period Shares New Issues	2,939,552										2,939,552
License and Milestone Fees
Revenues											$ 134,439	$ 19,746	$ 13,436
License and Milestone Fees | Vifor Agreement [Member]
Revenues			$ 111,551								$ 111,551