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0.25% Convertible Senior Notes, Convertible Note Hedge and Warrant - Schedule of Net Carrying Amount of Liability Component (Detail) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Net carrying amount $ 340,564 $ 318,782
0.25% Convertible Senior Notes Due 2022 as Liability Component [Member]    
Debt Instrument [Line Items]    
Principal 399,992 400,000
Unamortized debt discount (55,299) (75,575)
Unamortized issuance costs (4,129) (5,643)
Net carrying amount $ 340,564 $ 318,782