Stock-based Payments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	$ 5.9	$ 10.6	$ 12.2	$ 22.2
Time-Based Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	0.1	1.1	0.3	2.5
Unrecognized compensation cost related to non-vested time-based option awards	0.8		0.8
Performance-Based Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-IPO stock-based compensation	$ 0.0	$ 2.3	$ 0.0	$ 5.4