Equity and Liability Components of Notes (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Principal amount of the Notes outstanding	$ 343,208	$ 344,490
Unamortized discount of liability component	(13,129)	(19,217)
Less: current portion	2,440	496
Long-term debt	327,639	324,777
Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount of the Notes outstanding	150,000	150,000
Unamortized discount of liability component	(12,235)	(15,399)
Net carrying amount of liability component	137,765	134,601
Less: current portion	0	0
Long-term debt	137,765	134,601
Carrying value of equity component, net of issuance costs	$ 20,993	$ 20,993
Remaining amortization period of discount on the liability component	2 years 6 months	3 years 3 months 18 days

Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Face (par) amount of debt instrument at time of issuance.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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