Net Loss Per Share - Reconciliation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss attributable to common stockholders	$ (55.6)	$ (21.0)	$ (104.6)	$ (57.5)
Denominator:
Weighted average common shares outstanding—basic (shares)	61,444,958	11,891,979	60,643,764	11,750,198
Weighted average common shares outstanding—diluted (shares)	61,444,958	11,891,979	60,643,764	11,750,198
Net loss per share attributable to common stockholders—basic (usd per share)	$ (0.90)	$ (1.77)	$ (1.72)	$ (4.89)
Net loss per share attributable to common stockholders—diluted (usd per share)	$ (0.90)	$ (1.77)	$ (1.72)	$ (4.89)