Convertible Senior Notes - Carrying Values of Notes Excluding the Discounts upon Original Issuance and Third Party Offering Costs (Detail) - Convertible Senior Notes Due 2020 [Member] - USD ($) $ in Thousands	May 05, 2018	Feb. 03, 2018	Jun. 30, 2015
Liability component
Principal	$ 300,000	$ 300,000
Less: Debt discount	(39,974)	(44,135)	$ (3,800)
Net carrying amount	260,026	255,865
Equity component	$ 84,003	$ 84,003