Debt - Schedule of Interest Expense Recognized Related to Convertible Notes (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Amortization of debt issuance costs and discount			$ 8,513	$ 8,067
Convertible Senior Notes Due in 2024 [Member]
Debt Instrument [Line Items]
Contractual interest expense	$ 143	$ 143	431	431
Amortization of debt issuance costs and discount	2,871	2,720	8,496	8,050
Total	$ 3,014	$ 2,863	$ 8,927	$ 8,481

Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

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Period Type:	duration