Debt - Schedule of Interest Expense (Details) - Senior Notes - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
2027 Notes
Debt Instrument [Line Items]
Contractual interest coupon	$ 8.4		$ 16.7
Amortization of issuance costs	0.3		0.6
Total	8.7		17.3
2022 Notes
Debt Instrument [Line Items]
Contractual interest coupon		$ 2.0		$ 13.8
Amortization of issuance costs		0.1		0.7
Total		2.1		14.5
2021 Notes
Debt Instrument [Line Items]
Contractual interest coupon	0.0	1.1	0.8	2.3
Amortization of debt discount	0.0	0.8	0.5	1.6
Amortization of issuance costs	0.0	0.1	0.1	0.2
Total	$ 0.0	$ 2.0	$ 1.4	$ 4.1