Debt - Schedule of Debt Obligations (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total debt excluding financing lease liabilities	$ 1,232.9
Financing lease liabilities	9.6	$ 8.8
Total debt	1,242.5	673.5
Less current portion of long-term debt	8.3	7.2
Long-term debt, less current portion	1,124.4	660.6
Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Total debt excluding financing lease liabilities	575.0
Term Debt and Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Less unamortized discount on Term Debt and Convertible Senior Notes	95.5	1.2
Less unamortized debt issuance costs on Term Debt and Convertible Senior Notes	14.3	4.5
Term Debt [Member]
Debt Instrument [Line Items]
Total debt excluding financing lease liabilities	$ 657.9	$ 664.7

Debt instrument carrying amount and finance lease liability.

No definition available.

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- Definition

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.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, after accumulated amortization, of debt discount.

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

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- Definition

Amount of long-term debt and lease obligation, classified as noncurrent.

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Amount of long-term debt and lease obligation, classified as current.

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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