Convertible Notes - Schedule of Interest Expense Schedule of Interest Expense Related to Convertible Notes (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Amortization of discount	$ 1,653	$ 2,597
Convertible Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Contractual coupon interest	3,473	5,938
Amortization of discount	1,253	2,009
Amortization of transaction costs	401	588
Total	$ 5,127	$ 8,535

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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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.

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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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