Debt - Schedule of Interest Expense Recognized Related to Notes (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Debt Disclosure [Abstract]
Contractual interest expense	$ 0.4	$ 0.4
Amortization of debt discount	12.0	5.5
Amortization of transaction costs	1.2	0.7
Total	$ 13.6	$ 6.6

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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- Definition

Amount of amortization expense attributable to debt issuance costs.

+ References

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No definition available.

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- Definition

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

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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