Stock-Based Compensation Expense and Employee Benefit Plans - Stock Options (Additional Information) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Arrangements with Employees and Nonemployees [Abstract]
Unrecognized compensation cost related to unvested stock options	$ 9.0		$ 9.0		$ 25.1
Expense expected to be recognized over remaining weighted-average period			1 year 2 months 12 days	2 years 1 month 6 days
Cash received from stock options exercised			$ 62.1	$ 4.2
Class A common stock
Share-based Arrangements with Employees and Nonemployees [Abstract]
Granted options (in shares)	0	200,000	0	200,000
Granted (in dollars per share)		$ 7.30		$ 7.30
Employee Stock Option
Share-based Arrangements with Employees and Nonemployees [Abstract]
Allocated share-based compensation expense	$ 2.7	$ 4.4	$ 10.0	$ 14.9