Stock Based Compensation - Components of Equity-Based Compensation (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 07, 2019	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 11.7		$ 45.1	$ 11.7	$ 10.8
Expected tax benefit	0.0		6.4	0.0	2.3
Restricted stock and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	11.7		3.1	0.0	9.6
Expected tax benefit	0.0		0.5	0.0	2.3
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.0	$ 20.0	23.0	0.0	0.0
Expected tax benefit	0.0		5.9	0.0	0.0
Incentive units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.0		19.0	11.7	0.0
Employee stock purchase plan ("ESPP")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0.0		$ 0.0	$ 0.0	$ 1.2