Debt - Schedule of Interest Expense (Details) - Senior Notes - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
2027 Notes
Debt Instrument [Line Items]
Contractual interest coupon	$ 8.3
Amortization of issuance costs	0.3
Total	8.6
2022 Notes
Debt Instrument [Line Items]
Contractual interest coupon		$ 11.8
Amortization of issuance costs		0.6
Total		12.4
2021 Notes
Debt Instrument [Line Items]
Contractual interest coupon	0.8	1.2
Amortization of debt discount	0.5	0.8
Amortization of issuance costs	0.1	0.1
Total	$ 1.4	$ 2.1

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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