Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
2027 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	12,321,900	12,321,900
Shares issuable upon exercise of stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	10,435,930	9,863,703
Non-vested shares under restricted stock grants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	3,385,821	4,964,544