Convertible Notes - Schedule of Components of Net Carrying Amount of Convertible Notes (Detail) - Convertible Senior Notes Due 2023 [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Nov. 30, 2020	Dec. 31, 2019	Oct. 31, 2018
Debt Instrument [Line Items]
5.00% convertible notes	$ 277,857	$ 197,143	$ 475,000	$ 475,000
Unamortized discount	(15,229)		(34,219)
Unamortized transaction costs	(4,839)		(10,571)
Net carrying amount	$ 257,789		$ 430,210

Face (par) amount of debt instrument at time of issuance.

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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, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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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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