Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Net loss				$ (75,760)	$ (108,947)
Accumulated deficit		$ (1,363,228)		(1,363,228)		$ (1,287,468)
Total revenues		18,189	$ 13,281	46,501	37,407
Cash and cash equivalents		$ 188,217	$ 204,491	$ 188,217	$ 204,491	$ 176,225	$ 262,252
Number of months Capital resources meets capital expenditures				12 months
Product
Total revenues				$ 0
Subsequent event | Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. | Upfront payment
Upfront payments received under collaboration agreement	$ 40,000
Open Market Sale Offer | Subsequent event
Consideration received from sale of common stock	$ 54,000