Debt - Schedule of Interest Expense (Details) - Senior Notes - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
2027 Notes
Debt Instrument [Line Items]
Contractual interest coupon	$ 8.3		$ 25.0
Amortization of issuance costs	0.3		0.9
Total	8.6		25.9
2022 Notes
Debt Instrument [Line Items]
Contractual interest coupon		$ 0.0		$ 13.8
Amortization of issuance costs		0.0		0.7
Total		0.0		14.5
2021 Notes
Debt Instrument [Line Items]
Contractual interest coupon	0.0	1.2	0.8	3.5
Amortization of debt discount	0.0	0.7	0.5	2.3
Amortization of issuance costs	0.0	0.2	0.1	0.4
Total	$ 0.0	$ 2.1	$ 1.4	$ 6.2