Equity and Liability Components of Notes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Principal amount of the Notes outstanding	$ 239,097	$ 323,548
Unamortized discount and fees of liability component	(3,164)	(11,052)
Less: current portion	(2,468)	(37,611)
Long-term debt	233,465	274,885
Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount of the Notes outstanding	48,951	131,000
Unamortized discount and fees of liability component	(2,183)	(9,888)
Net carrying amount of liability component	46,768	121,112
Less: current portion	0	(35,165)
Long-term debt	46,768	85,947
Carrying value of equity component, net of issuance costs	$ (3,971)	$ 15,810
Remaining amortization period of discount on the liability component	1 year 3 months 18 days	2 years 3 months 18 days