Summary of Significant Accounting Policies - Potential Common Shares Excluded from Computations of Diluted Net Loss Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computations of net loss per share (in shares)	28,288	27,329	27,356
Stock options, restricted stock units and performance stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computations of net loss per share (in shares)	7,975	7,507	5,189
2019 Convertible Notes | Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computations of net loss per share (in shares)	18,966	18,966	18,966
2019 Convertible Notes potential make-whole shares | Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computations of net loss per share (in shares)	1,337	837	3,182
2014 Convertible Notes | Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computations of net loss per share (in shares)	10	19	19