Debt - Long-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Transaction costs - 2025 Notes	$ (5.4)	$ (6.8)
Total long-term debt		274.6
Convertible Debt
Debt Instrument [Line Items]
Convertible debt, interest rate	4.125%
Long-term debt, gross	$ 245.8	245.8
Revolving Credit Facility
Debt Instrument [Line Items]
Letters of credit outstanding, amount	14.5	14.4
Line of credit, remaining borrowing capacity	385.5	275.0
Revolving Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	$ 0.0	$ 35.6
LIBOR borrowings \| Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, interest rate	2.35%
Base rate borrowings \| Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, interest rate	4.50%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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The effective interest rate at the end of the reporting period.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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