Convertible Senior Notes - Carrying Value of 2018 Convertible Notes (Detail) - 2018 Convertible Notes [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal amount	$ 35,815	$ 40,565
(Less): Unamortized debt discount (amortized through December 2018)	(412)	(2,101)
(Less): Debt issuance costs	(46)	(240)
Carrying value	$ 35,357	$ 38,224

Debt Instrument Carrying Amount Net Of Discount

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, after accumulated amortization, of debt discount.

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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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