Long-term Debt - Summary of Long-term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Finance leases	$ 43.9	$ 45.6
Total debt, net of unamortized discount and deferred financing costs	467.2	624.3
Less: Amounts due within one year	(163.6)	(299.9)
Total long-term debt, net of unamortized discount and deferred financing costs	$ 303.6	324.4
Secured debt
Debt Instrument [Line Items]
Effective interest rate (as a percent)	1.83%
Term loan | Secured debt
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 288.8	308.5
Unamortized deferred financing costs	(0.9)	(1.4)
Senior Notes	$ 287.9	$ 307.1
2 1/4% Notes
Debt Instrument [Line Items]
Effective interest rate (as a percent)	5.80%	5.80%
2 1/4% Notes | Convertible Debt
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 145.9	$ 300.0
Unamortized deferred financing costs	(10.5)	(28.4)
Total convertible senior notes	135.4	$ 271.6
Less: Amounts due within one year	$ (135.4)
Debt instrument interest rate stated percentage	2.25%