Stock-based Payments - Summary of RSU Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	$ 4.5	$ 11.4	$ 16.7	$ 33.6
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	9.5	12.1	33.9	34.1
Unrecognized compensation expense related to RSUs	61.2		61.2
Time-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	8.8	11.4	31.0	32.5
Unrecognized compensation expense related to RSUs	50.8		50.8
Co-Investment RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	0.0	0.1	0.1	0.3
Unrecognized compensation expense related to RSUs	0.0		0.0
Performance-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	0.7	$ 0.6	2.8	$ 1.3
Unrecognized compensation expense related to RSUs	$ 10.4		$ 10.4