Net Loss Per Share - Securities Excluded from the Computations of Diluted Net Loss Per Share (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the computations of diluted net loss per share (in shares)	2.6	2.0	1.2
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the computations of diluted net loss per share (in shares)	2.4	1.5	0.3
Restricted stock awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the computations of diluted net loss per share (in shares)	0.1	0.4	0.9
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the computations of diluted net loss per share (in shares)	0.1	0.1	0.0