0.25% Convertible Senior Notes, Convertible Note Hedge and Warrant - Schedule of Net Carrying Amount of Equity Component (Detail) - 0.25% Convertible Senior Notes Due 2022 as Equity Component [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt discount for conversion option	$ 106,006	$ 106,006
Issuance costs	(2,854)	(2,854)
Net carrying amount	$ 103,152	$ 103,152