Net Loss per Share - Reconciliation (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss attributable to common stockholders — basic	$ (236.9)	$ (297.8)	$ (241.3)
Net loss attributable to common stockholders — diluted	$ (236.9)	$ (297.8)	$ (241.3)
Denominator:
Weighted average common shares outstanding — basic (in shares)	69,658,912	64,921,524	61,224,433
Weighted average common shares outstanding — diluted (in shares)	69,658,912	64,921,524	61,224,433
Net loss per share attributable to common stockholders — basic (usd per share)	$ (3.40)	$ (4.59)	$ (3.94)
Net loss per share attributable to common stockholders — diluted (usd per share)	$ (3.40)	$ (4.59)	$ (3.94)